Programs & Examples On #Slot

Best way to "push" into C# array

Your question is a little off the mark. In particular, you say "that the element needs to be added into the first empty slot in an array, lie (sic) a Java push function would do."

  1. Java's Array does not have a push operation - JavaScript does. Java and JavaScript are two very different languages
  2. JavaScript's push function does not behave as you describe. When you "push" a value into a JavaScript array, the array is extended by one element, and that new element is assigned the pushed value, see: Mozilla's Array.prototype.push function docs

The verb "Push" is not something that is used with an Array in any language that I know of except JavaScript. I suspect that it's only in JavaScript because it could be there (since JavaScript is a completely dynamic language). I'm pretty sure it wasn't designed in intentionally.

A JavaScript-style Push operation in C# could be written in this somewhat inefficient manner:

int [] myArray = new int [] {1, 2, 3, 4};
var tempList = myArray.ToList();
tempList.Add(5);
myArray = tempList.ToArray();   //equiv: myArray.Push(5);

"Push" is used in some types of containers, particularly Stacks, Queues and Deques (which get two pushes - one from the front, one from the back). I urge you not to include Push as a verb in your explanation of arrays. It adds nothing to a CS student's vocabulary.

In C#, as in most traditional procedural languages, an array is a collection of elements of a single type, contained in a fixed length contiguous block of memory. When you allocate an array, the space for every array element is allocated (and, in C# those elements are initialized to the default value of the type, null for reference types).

In C#, arrays of reference types are filled with object references; arrays of value types are filled with instances of that value type. As a result, an array of 4 strings uses the same memory as an array of 4 instance of your application class (since they are both reference types). But, an array of 4 DateTime instances is significantly longer that of an array of 4 short integers.

In C#, an instance of an array is an instance of System.Array, a reference type. Arrays have a few properties and methods (like the Length property). Otherwise, there isn't much you can do with an array: you can read (or write) from (or to) individual elements using an array index. Arrays of type T also implement IEnumerable<T>, so you can iterate through the elements of an array.

Arrays are mutable (the values in an array can be written to), but they have a fixed length - they can't be extended or shortened. They are ordered, and they can't be re-arranged (except by swizzling the values manually).

C# arrays are covariant. If you were to ask the C# language designers, this would be the feature they regret the most. It's one of the few ways you can break C# type safety. Consider this code (assuming that Cat and Dog classes inherit from Animal):

Cat[] myCats = new Cat[]{myCat, yourCat, theirCat};
Animal[] animals = (Animal[]) myCats;     //legal but dangerous
animals[1] = new Dog();                   //heading off the cliff
myCats[1].Speak();                        //Woof!

That "feature" is the result of the lack of generic types and explicit covariance/contravariance in the initial version of the .NET Framework and the urge to copy a Java "feature".

Arrays do show up in many core .NET APIs (for example, System.Reflection). They are there, again, because the initial release did not support generic collections.

In general, an experienced C# programmer will not use many arrays in his applications, preferring to use more capable collections such as List<T>, Dictionary<TKey, TValue>, HashSet<T> and friends. In particular, that programmer will tend to pass collections around using IEnumerable<T> an interface that all collections implement. The big advantage of using IEnumerable<T> as parameters and return types (where possible and logical) is that collections accessed via IEnumerable<T> references are immutable. It's kinda-sorta like using const correctly in C++.

One thing you might consider adding in to your lectures on arrays - after everyone has mastered the basics - is the new Span<T> type. Spans may make C# arrays useful.

Finally, LINQ (Language Integrated Query) introduced a lot of functionality to collections (by adding Extension Methods to IEnumerable<T>). Make sure your student do not have a using System.Linq; statement up at the top of their code - mixing LINQ in to a beginning student's class on arrays would bewilder him or her.

BTW: what kind of class is it you teach? At what level?

Is the server running on host "localhost" (::1) and accepting TCP/IP connections on port 5432?

I often encounter this problem on windows,the way I solved the problem is Service - Click PostgreSQL Database Server 8.3 - Click the second tab "log in" - choose the first line "the local system account".

Delete item from state array in react

It's Very Simple First You Define a value

state = {
  checked_Array: []
}

Now,

fun(index) {
  var checked = this.state.checked_Array;
  var values = checked.indexOf(index)
  checked.splice(values, 1);
  this.setState({checked_Array: checked});
  console.log(this.state.checked_Array)
}

New warnings in iOS 9: "all bitcode will be dropped"

If you are using CocoaPods and you want to disable Bitcode for all libraries, use the following command in the Podfile

post_install do |installer|
    installer.pods_project.targets.each do |target|
        target.build_configurations.each do |config|
            config.build_settings['ENABLE_BITCODE'] = 'NO'
        end
    end
end

AngularJs - ng-model in a SELECT

However, ngOptions provides some benefits such as reducing memory and increasing speed by not creating a new scope for each repeated instance. angular docs

Alternative solution is use ng-init directive. You can specify function that will be initialize your default data.

$scope.init = function(){
            angular.forEach($scope.units, function(item){
                if(item.id === $scope.data.unit){
                    $scope.data.unit = item;
                }
            });
        } 

See jsfiddle

iOS how to set app icon and launch images

This is a very frustrating part of XCode. Like many, I wasted hours on this when I switched to a newer version of xcode (version 8). The solution for me was to open the properties for my project and under the "App Icons and Launch Images" choose the "migrate" option for the icons. This made absolutely no sense to me as I already had all my icons there, but it worked! Unfortunately I now seem to have two copies of my launcher icons in the project though.

Container is running beyond memory limits

Running yarn on Windows Linux subsystem with Ubunto OS, error "running beyond virtual memory limits, Killing container" I resolved it by disabling virtual memory check in the file yarn-site.xml

<property> <name>yarn.nodemanager.vmem-check-enabled</name> <value>false</value> </property> 

React.js: Wrapping one component into another

In addition to Sophie's answer, I also have found a use in sending in child component types, doing something like this:

var ListView = React.createClass({
    render: function() {
        var items = this.props.data.map(function(item) {
            return this.props.delegate({data:item});
        }.bind(this));
        return <ul>{items}</ul>;
    }
});

var ItemDelegate = React.createClass({
    render: function() {
        return <li>{this.props.data}</li>
    }
});

var Wrapper = React.createClass({    
    render: function() {
        return <ListView delegate={ItemDelegate} data={someListOfData} />
    }
});

ImportError: No module named PytQt5

If you are on ubuntu, just install pyqt5 with apt-get command:

    sudo apt-get install python3-pyqt5   # for python3

or

    sudo apt-get install python-pyqt5    # for python2

However, on Ubuntu 14.04 the python-pyqt5 package is left out [source] and need to be installed manually [source]

Mock functions in Go

Personally, I don't use gomock (or any mocking framework for that matter; mocking in Go is very easy without it). I would either pass a dependency to the downloader() function as a parameter, or I would make downloader() a method on a type, and the type can hold the get_page dependency:

Method 1: Pass get_page() as a parameter of downloader()

type PageGetter func(url string) string

func downloader(pageGetterFunc PageGetter) {
    // ...
    content := pageGetterFunc(BASE_URL)
    // ...
}

Main:

func get_page(url string) string { /* ... */ }

func main() {
    downloader(get_page)
}

Test:

func mock_get_page(url string) string {
    // mock your 'get_page()' function here
}

func TestDownloader(t *testing.T) {
    downloader(mock_get_page)
}

Method2: Make download() a method of a type Downloader:

If you don't want to pass the dependency as a parameter, you could also make get_page() a member of a type, and make download() a method of that type, which can then use get_page:

type PageGetter func(url string) string

type Downloader struct {
    get_page PageGetter
}

func NewDownloader(pg PageGetter) *Downloader {
    return &Downloader{get_page: pg}
}

func (d *Downloader) download() {
    //...
    content := d.get_page(BASE_URL)
    //...
}

Main:

func get_page(url string) string { /* ... */ }

func main() {
    d := NewDownloader(get_page)
    d.download()
}

Test:

func mock_get_page(url string) string {
    // mock your 'get_page()' function here
}

func TestDownloader() {
    d := NewDownloader(mock_get_page)
    d.download()
}

Converting String Array to an Integer Array

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

class MultiArg {

    Scanner sc;
    int n;
    String as;
    List<Integer> numList = new ArrayList<Integer>();

    public void fun() {
        sc = new Scanner(System.in);
        System.out.println("enter value");
        while (sc.hasNextInt())
            as = sc.nextLine();
    }

    public void diplay() {
        System.out.println("x");
        Integer[] num = numList.toArray(new Integer[numList.size()]);
        System.out.println("show value " + as);
        for (Integer m : num) {
            System.out.println("\t" + m);
        }
    }
}

but to terminate the while loop you have to put any charecter at the end of input.

ex. input:

12 34 56 78 45 67 .

output:

12 34 56 78 45 67

Qt: How do I handle the event of the user pressing the 'X' (close) button?

If you have a QMainWindow you can override closeEvent method.

#include <QCloseEvent>
void MainWindow::closeEvent (QCloseEvent *event)
{
    QMessageBox::StandardButton resBtn = QMessageBox::question( this, APP_NAME,
                                                                tr("Are you sure?\n"),
                                                                QMessageBox::Cancel | QMessageBox::No | QMessageBox::Yes,
                                                                QMessageBox::Yes);
    if (resBtn != QMessageBox::Yes) {
        event->ignore();
    } else {
        event->accept();
    }
}


If you're subclassing a QDialog, the closeEvent will not be called and so you have to override reject():

void MyDialog::reject()
{
    QMessageBox::StandardButton resBtn = QMessageBox::Yes;
    if (changes) {
        resBtn = QMessageBox::question( this, APP_NAME,
                                        tr("Are you sure?\n"),
                                        QMessageBox::Cancel | QMessageBox::No | QMessageBox::Yes,
                                        QMessageBox::Yes);
    }
    if (resBtn == QMessageBox::Yes) {
        QDialog::reject();
    }
}

Uncaught ReferenceError: function is not defined with onclick

I was receiving the error (I'm using Vue) and I switched my onclick="someFunction()" to @click="someFunction" and now they are working.

How to get column by number in Pandas?

One is a column (aka Series), while the other is a DataFrame:

In [1]: df = pd.DataFrame([[1,2], [3,4]], columns=['a', 'b'])

In [2]: df
Out[2]:
   a  b
0  1  2
1  3  4

The column 'b' (aka Series):

In [3]: df['b']
Out[3]:
0    2
1    4
Name: b, dtype: int64

The subdataframe with columns (position) in [1]:

In [4]: df[[1]]
Out[4]:
   b
0  2
1  4

Note: it's preferable (and less ambiguous) to specify whether you're talking about the column name e.g. ['b'] or the integer location, since sometimes you can have columns named as integers:

In [5]: df.iloc[:, [1]]
Out[5]:
   b
0  2
1  4

In [6]: df.loc[:, ['b']]
Out[6]:
   b
0  2
1  4

In [7]: df.loc[:, 'b']
Out[7]:
0    2
1    4
Name: b, dtype: int64

How does it work - requestLocationUpdates() + LocationRequest/Listener

You are implementing LocationListener in your activity MainActivity. The call for concurrent location updates will therefor be like this:

mLocationClient.requestLocationUpdates(mLocationRequest, this);

Be sure that the LocationListener you're implementing is from the google api, that is import this:

import com.google.android.gms.location.LocationListener;

and not this:

import android.location.LocationListener;

and it should work just fine.

It's also important that the LocationClient really is connected before you do this. I suggest you don't call it in the onCreate or onStart methods, but in onResume. It is all explained quite well in the tutorial for Google Location Api: https://developer.android.com/training/location/index.html

Trying to create a file in Android: open failed: EROFS (Read-only file system)

If anyone getting this in unit/instrumentation testing, make sure you call getFilesDir() on the app context, not the test context. i.e. use:

Context appContext = getInstrumentation().getTargetContext().getApplicationContext();

not

Context appContext = InstrumentationRegistry.getContext;

Linker Error C++ "undefined reference "

Your error shows you are not compiling file with the definition of the insert function. Update your command to include the file which contains the definition of that function and it should work.

"Field has incomplete type" error

You are using a forward declaration for the type MainWindowClass. That's fine, but it also means that you can only declare a pointer or reference to that type. Otherwise the compiler has no idea how to allocate the parent object as it doesn't know the size of the forward declared type (or if it actually has a parameterless constructor, etc.)

So, you either want:

// forward declaration, details unknown
class A;

class B {
  A *a;  // pointer to A, ok
};

Or, if you can't use a pointer or reference....

// declaration of A
#include "A.h"

class B {
  A a;  // ok, declaration of A is known
};

At some point, the compiler needs to know the details of A.

If you are only storing a pointer to A then it doesn't need those details when you declare B. It needs them at some point (whenever you actually dereference the pointer to A), which will likely be in the implementation file, where you will need to include the header which contains the declaration of the class A.

// B.h
// header file

// forward declaration, details unknown
class A;

class B {
public: 
    void foo();
private:
  A *a;  // pointer to A, ok
};

// B.cpp
// implementation file

#include "B.h"
#include "A.h"  // declaration of A

B::foo() {
    // here we need to know the declaration of A
    a->whatever();
}

Heroku "psql: FATAL: remaining connection slots are reserved for non-replication superuser connections"

See Heroku “psql: FATAL: remaining connection slots are reserved for non-replication superuser connections”:

Heroku sometimes has a problem with database load balancing.

André Laszlo, markshiz and me all reported dealing with that in comments on the question.

To save you the support call, here's the response I got from Heroku Support for a similar issue:

Hello,

One of the limitations of the hobby tier databases is unannounced maintenance. Many hobby databases run on a single shared server, and we will occasionally need to restart that server for hardware maintenance purposes, or migrate databases to another server for load balancing. When that happens, you'll see an error in your logs or have problems connecting. If the server is restarting, it might take 15 minutes or more for the database to come back online.

Most apps that maintain a connection pool (like ActiveRecord in Rails) can just open a new connection to the database. However, in some cases an app won't be able to reconnect. If that happens, you can heroku restart your app to bring it back online.

This is one of the reasons we recommend against running hobby databases for critical production applications. Standard and Premium databases include notifications for downtime events, and are much more performant and stable in general. You can use pg:copy to migrate to a standard or premium plan.

If this continues, you can try provisioning a new database (on a different server) with heroku addons:add, then use pg:copy to move the data. Keep in mind that hobby tier rules apply to the $9 basic plan as well as the free database.

Thanks, Bradley

How to use QTimer

mytimer.h:

    #ifndef MYTIMER_H
    #define MYTIMER_H

    #include <QTimer>

    class MyTimer : public QObject
    {
        Q_OBJECT
    public:
        MyTimer();
        QTimer *timer;

    public slots:
        void MyTimerSlot();
    };

    #endif // MYTIME

mytimer.cpp:

#include "mytimer.h"
#include <QDebug>

MyTimer::MyTimer()
{
    // create a timer
    timer = new QTimer(this);

    // setup signal and slot
    connect(timer, SIGNAL(timeout()),
          this, SLOT(MyTimerSlot()));

    // msec
    timer->start(1000);
}

void MyTimer::MyTimerSlot()
{
    qDebug() << "Timer...";
}

main.cpp:

#include <QCoreApplication>
#include "mytimer.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    // Create MyTimer instance
    // QTimer object will be created in the MyTimer constructor
    MyTimer timer;

    return a.exec();
}

If we run the code:

Timer...
Timer...
Timer...
Timer...
Timer...
...

resources

How can I get the external SD card path for Android 4.0+?

 String path = Environment.getExternalStorageDirectory()
                        + File.separator + Environment.DIRECTORY_PICTURES;
                File dir = new File(path);

C# windows application Event: CLR20r3 on application start

Have been fighting this all morning and now have it solved and why it happened. Posting with the hope it helps others

I installed the Krypton.Toolkit which added the tools to the Visual studio toolbox automatically. I then added the tools to the designer, which automatically added the dll to the projrect references, however the toolkit was marked as CopyLocal=false

I built an installer, using all dlls in the release build folder (of course the above dll wasn't there).

Setting copylocal=true, then rebuilding the installer, everything worked fine.

Error: expected type-specifier before 'ClassName'

For future people struggling with a similar problem, the situation is that the compiler simply cannot find the type you are using (even if your Intelisense can find it).

This can be caused in many ways:

  • You forgot to #include the header that defines it.
  • Your inclusion guards (#ifndef BLAH_H) are defective (your #ifndef BLAH_H doesn't match your #define BALH_H due to a typo or copy+paste mistake).
  • Your inclusion guards are accidentally used twice (two separate files both using #define MYHEADER_H, even if they are in separate directories)
  • You forgot that you are using a template (eg. new Vector() should be new Vector<int>())
  • The compiler is thinking you meant one scope when really you meant another (For example, if you have NamespaceA::NamespaceB, AND a <global scope>::NamespaceB, if you are already within NamespaceA, it'll look in NamespaceA::NamespaceB and not bother checking <global scope>::NamespaceB) unless you explicitly access it.
  • You have a name clash (two entities with the same name, such as a class and an enum member).

To explicitly access something in the global namespace, prefix it with ::, as if the global namespace is a namespace with no name (e.g. ::MyType or ::MyNamespace::MyType).

How do I line up 3 divs on the same row?

I'm surprised that nobody gave CSS table layout as a solution:

_x000D_
_x000D_
.Row {_x000D_
    display: table;_x000D_
    width: 100%; /*Optional*/_x000D_
    table-layout: fixed; /*Optional*/_x000D_
    border-spacing: 10px; /*Optional*/_x000D_
}_x000D_
.Column {_x000D_
    display: table-cell;_x000D_
    background-color: red; /*Optional*/_x000D_
}
_x000D_
<div class="Row">_x000D_
    <div class="Column">C1</div>_x000D_
    <div class="Column">C2</div>_x000D_
    <div class="Column">C3</div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

Works in IE8+

Check out a JSFiddle Demo

Java using enum with switch statement

This should work in the way that you describe. What error are you getting? If you could pastebin your code that would help.

http://download.oracle.com/javase/tutorial/java/javaOO/enum.html

EDIT: Are you sure you want to define a static enum? That doesn't sound right to me. An enum is much like any other object. If your code compiles and runs but gives incorrect results, this would probably be why.

Convert int to a bit array in .NET

To convert the int 'x'

int x = 3;

One way, by manipulation on the int :

string s = Convert.ToString(x, 2); //Convert to binary in a string

int[] bits= s.PadLeft(8, '0') // Add 0's from left
             .Select(c => int.Parse(c.ToString())) // convert each char to int
             .ToArray(); // Convert IEnumerable from select to Array

Alternatively, by using the BitArray class-

BitArray b = new BitArray(new byte[] { x });
int[] bits = b.Cast<bool>().Select(bit => bit ? 1 : 0).ToArray();

accessing a file using [NSBundle mainBundle] pathForResource: ofType:inDirectory:

Are you attempting to do this inside of an XCTest and on the verge of smashing your laptop? This is the thread for you: Why can't code inside unit tests find bundle resources?

How do I get an empty array of any size in python?

x=[]
for i in range(0,5):
    x.append(i)
    print(x[i])

How to convert minutes to hours/minutes and add various time values together using jQuery?

As the above answer of ConnorLuddy can be slightly improved, there are a minor change to formula to convert minutes to hours:mins format

const convertMinsToHrsMins = (mins) => {
  let h = Math.floor(mins / 60);
  let m = Math.round(mins % 60);
  h = (h < 10) ? ('0' + h) : (h);
  m = (m < 10) ? ('0' + m) : (m);
  return `${h}:${m}`;
}

My theory is that we can not predict that `mins` value will always be an integer.
The added `Math.round` to function will correct the output.
For example: when the minutes=125.3245, the output will be 02:05 with this fix, and 02:05.3245000000000005 without the fix.

Hope that someone need this!

How can I make a horizontal ListView in Android?

My app uses a ListView in portraint mode which is simply switches to Gallery in landscape mode. Both of them use one BaseAdapter. This looks like shown below.

       setContentView(R.layout.somelayout);
       orientation = getResources().getConfiguration().orientation;

       if ( orientation == Configuration.ORIENTATION_LANDSCAPE )
       {

            Gallery gallery = (Gallery)findViewById( R.id.somegallery );

            gallery.setAdapter( someAdapter );

            gallery.setOnItemClickListener( new OnItemClickListener() {
            @Override
            public void onItemClick( AdapterView<?> parent, View view,
                    int position, long id ) {

                onClick( position );
            }
        });
       }
       else
       {
            setListAdapter( someAdapter );

            getListView().setOnScrollListener(this);
       }    

To handle scrolling events I've inherited my own widget from Gallery and override onFling(). Here's the layout.xml:

    <view 
    class="package$somegallery"
    android:id="@+id/somegallery" 
    android:layout_height="fill_parent" 
    android:layout_width="fill_parent">
    </view>

and code:

    public static class somegallery extends Gallery
    {
        private Context mCtx;

        public somegallery(Context context, AttributeSet attrs)
        {
            super(context, attrs);
            mCtx = context;
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {

            ( (CurrentActivity)mCtx ).onScroll();

            return super.onFling(e1, e2, velocityX, velocityY);
        }
   }

"No such file or directory" error when executing a binary

Old question, but hopefully this'll help someone else.

In my case I was using a toolchain on Ubuntu 12.04 that was built on Ubuntu 10.04 (requires GCC 4.1 to build). As most of the libraries have moved to multiarch dirs, it couldn't find ld.so. So, make a symlink for it.

Check required path:

$ readelf -a arm-linux-gnueabi-gcc | grep interpreter:
      [Requesting program interpreter: /lib/ld-linux-x86-64.so.2]

Create symlink:

$ sudo ln -s /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 /lib/ld-linux-x86-64.so.2

If you're on 32bit, it'll be i386-linux-gnu and not x86_64-linux-gnu.

Quickest way to find missing number in an array of numbers

simple solution with test data :

class A{

  public static void main(String[] args){
    int[] array = new int[200];
    for(int i=0;i<100;i++){
      if(i != 51){
        array[i] = i;  
      }
    }

    for(int i=100;i<200;i++){
      array[i] = i;  
    }

    int temp = 0;
    for(int i=0;i<200;i++){
      temp ^= array[i];
    }

    System.out.println(temp);
  }
} 

Usage of __slots__?

In Python, what is the purpose of __slots__ and what are the cases one should avoid this?

TLDR:

The special attribute __slots__ allows you to explicitly state which instance attributes you expect your object instances to have, with the expected results:

  1. faster attribute access.
  2. space savings in memory.

The space savings is from

  1. Storing value references in slots instead of __dict__.
  2. Denying __dict__ and __weakref__ creation if parent classes deny them and you declare __slots__.

Quick Caveats

Small caveat, you should only declare a particular slot one time in an inheritance tree. For example:

class Base:
    __slots__ = 'foo', 'bar'

class Right(Base):
    __slots__ = 'baz', 

class Wrong(Base):
    __slots__ = 'foo', 'bar', 'baz'        # redundant foo and bar

Python doesn't object when you get this wrong (it probably should), problems might not otherwise manifest, but your objects will take up more space than they otherwise should. Python 3.8:

>>> from sys import getsizeof
>>> getsizeof(Right()), getsizeof(Wrong())
(56, 72)

This is because the Base's slot descriptor has a slot separate from the Wrong's. This shouldn't usually come up, but it could:

>>> w = Wrong()
>>> w.foo = 'foo'
>>> Base.foo.__get__(w)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: foo
>>> Wrong.foo.__get__(w)
'foo'

The biggest caveat is for multiple inheritance - multiple "parent classes with nonempty slots" cannot be combined.

To accommodate this restriction, follow best practices: Factor out all but one or all parents' abstraction which their concrete class respectively and your new concrete class collectively will inherit from - giving the abstraction(s) empty slots (just like abstract base classes in the standard library).

See section on multiple inheritance below for an example.

Requirements:

  • To have attributes named in __slots__ to actually be stored in slots instead of a __dict__, a class must inherit from object.

  • To prevent the creation of a __dict__, you must inherit from object and all classes in the inheritance must declare __slots__ and none of them can have a '__dict__' entry.

There are a lot of details if you wish to keep reading.

Why use __slots__: Faster attribute access.

The creator of Python, Guido van Rossum, states that he actually created __slots__ for faster attribute access.

It is trivial to demonstrate measurably significant faster access:

import timeit

class Foo(object): __slots__ = 'foo',

class Bar(object): pass

slotted = Foo()
not_slotted = Bar()

def get_set_delete_fn(obj):
    def get_set_delete():
        obj.foo = 'foo'
        obj.foo
        del obj.foo
    return get_set_delete

and

>>> min(timeit.repeat(get_set_delete_fn(slotted)))
0.2846834529991611
>>> min(timeit.repeat(get_set_delete_fn(not_slotted)))
0.3664822799983085

The slotted access is almost 30% faster in Python 3.5 on Ubuntu.

>>> 0.3664822799983085 / 0.2846834529991611
1.2873325658284342

In Python 2 on Windows I have measured it about 15% faster.

Why use __slots__: Memory Savings

Another purpose of __slots__ is to reduce the space in memory that each object instance takes up.

My own contribution to the documentation clearly states the reasons behind this:

The space saved over using __dict__ can be significant.

SQLAlchemy attributes a lot of memory savings to __slots__.

To verify this, using the Anaconda distribution of Python 2.7 on Ubuntu Linux, with guppy.hpy (aka heapy) and sys.getsizeof, the size of a class instance without __slots__ declared, and nothing else, is 64 bytes. That does not include the __dict__. Thank you Python for lazy evaluation again, the __dict__ is apparently not called into existence until it is referenced, but classes without data are usually useless. When called into existence, the __dict__ attribute is a minimum of 280 bytes additionally.

In contrast, a class instance with __slots__ declared to be () (no data) is only 16 bytes, and 56 total bytes with one item in slots, 64 with two.

For 64 bit Python, I illustrate the memory consumption in bytes in Python 2.7 and 3.6, for __slots__ and __dict__ (no slots defined) for each point where the dict grows in 3.6 (except for 0, 1, and 2 attributes):

       Python 2.7             Python 3.6
attrs  __slots__  __dict__*   __slots__  __dict__* | *(no slots defined)
none   16         56 + 272†   16         56 + 112† | †if __dict__ referenced
one    48         56 + 272    48         56 + 112
two    56         56 + 272    56         56 + 112
six    88         56 + 1040   88         56 + 152
11     128        56 + 1040   128        56 + 240
22     216        56 + 3344   216        56 + 408     
43     384        56 + 3344   384        56 + 752

So, in spite of smaller dicts in Python 3, we see how nicely __slots__ scale for instances to save us memory, and that is a major reason you would want to use __slots__.

Just for completeness of my notes, note that there is a one-time cost per slot in the class's namespace of 64 bytes in Python 2, and 72 bytes in Python 3, because slots use data descriptors like properties, called "members".

>>> Foo.foo
<member 'foo' of 'Foo' objects>
>>> type(Foo.foo)
<class 'member_descriptor'>
>>> getsizeof(Foo.foo)
72

Demonstration of __slots__:

To deny the creation of a __dict__, you must subclass object:

class Base(object): 
    __slots__ = ()

now:

>>> b = Base()
>>> b.a = 'a'
Traceback (most recent call last):
  File "<pyshell#38>", line 1, in <module>
    b.a = 'a'
AttributeError: 'Base' object has no attribute 'a'

Or subclass another class that defines __slots__

class Child(Base):
    __slots__ = ('a',)

and now:

c = Child()
c.a = 'a'

but:

>>> c.b = 'b'
Traceback (most recent call last):
  File "<pyshell#42>", line 1, in <module>
    c.b = 'b'
AttributeError: 'Child' object has no attribute 'b'

To allow __dict__ creation while subclassing slotted objects, just add '__dict__' to the __slots__ (note that slots are ordered, and you shouldn't repeat slots that are already in parent classes):

class SlottedWithDict(Child): 
    __slots__ = ('__dict__', 'b')

swd = SlottedWithDict()
swd.a = 'a'
swd.b = 'b'
swd.c = 'c'

and

>>> swd.__dict__
{'c': 'c'}

Or you don't even need to declare __slots__ in your subclass, and you will still use slots from the parents, but not restrict the creation of a __dict__:

class NoSlots(Child): pass
ns = NoSlots()
ns.a = 'a'
ns.b = 'b'

And:

>>> ns.__dict__
{'b': 'b'}

However, __slots__ may cause problems for multiple inheritance:

class BaseA(object): 
    __slots__ = ('a',)

class BaseB(object): 
    __slots__ = ('b',)

Because creating a child class from parents with both non-empty slots fails:

>>> class Child(BaseA, BaseB): __slots__ = ()
Traceback (most recent call last):
  File "<pyshell#68>", line 1, in <module>
    class Child(BaseA, BaseB): __slots__ = ()
TypeError: Error when calling the metaclass bases
    multiple bases have instance lay-out conflict

If you run into this problem, You could just remove __slots__ from the parents, or if you have control of the parents, give them empty slots, or refactor to abstractions:

from abc import ABC

class AbstractA(ABC):
    __slots__ = ()

class BaseA(AbstractA): 
    __slots__ = ('a',)

class AbstractB(ABC):
    __slots__ = ()

class BaseB(AbstractB): 
    __slots__ = ('b',)

class Child(AbstractA, AbstractB): 
    __slots__ = ('a', 'b')

c = Child() # no problem!

Add '__dict__' to __slots__ to get dynamic assignment:

class Foo(object):
    __slots__ = 'bar', 'baz', '__dict__'

and now:

>>> foo = Foo()
>>> foo.boink = 'boink'

So with '__dict__' in slots we lose some of the size benefits with the upside of having dynamic assignment and still having slots for the names we do expect.

When you inherit from an object that isn't slotted, you get the same sort of semantics when you use __slots__ - names that are in __slots__ point to slotted values, while any other values are put in the instance's __dict__.

Avoiding __slots__ because you want to be able to add attributes on the fly is actually not a good reason - just add "__dict__" to your __slots__ if this is required.

You can similarly add __weakref__ to __slots__ explicitly if you need that feature.

Set to empty tuple when subclassing a namedtuple:

The namedtuple builtin make immutable instances that are very lightweight (essentially, the size of tuples) but to get the benefits, you need to do it yourself if you subclass them:

from collections import namedtuple
class MyNT(namedtuple('MyNT', 'bar baz')):
    """MyNT is an immutable and lightweight object"""
    __slots__ = ()

usage:

>>> nt = MyNT('bar', 'baz')
>>> nt.bar
'bar'
>>> nt.baz
'baz'

And trying to assign an unexpected attribute raises an AttributeError because we have prevented the creation of __dict__:

>>> nt.quux = 'quux'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'MyNT' object has no attribute 'quux'

You can allow __dict__ creation by leaving off __slots__ = (), but you can't use non-empty __slots__ with subtypes of tuple.

Biggest Caveat: Multiple inheritance

Even when non-empty slots are the same for multiple parents, they cannot be used together:

class Foo(object): 
    __slots__ = 'foo', 'bar'
class Bar(object):
    __slots__ = 'foo', 'bar' # alas, would work if empty, i.e. ()

>>> class Baz(Foo, Bar): pass
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Error when calling the metaclass bases
    multiple bases have instance lay-out conflict

Using an empty __slots__ in the parent seems to provide the most flexibility, allowing the child to choose to prevent or allow (by adding '__dict__' to get dynamic assignment, see section above) the creation of a __dict__:

class Foo(object): __slots__ = ()
class Bar(object): __slots__ = ()
class Baz(Foo, Bar): __slots__ = ('foo', 'bar')
b = Baz()
b.foo, b.bar = 'foo', 'bar'

You don't have to have slots - so if you add them, and remove them later, it shouldn't cause any problems.

Going out on a limb here: If you're composing mixins or using abstract base classes, which aren't intended to be instantiated, an empty __slots__ in those parents seems to be the best way to go in terms of flexibility for subclassers.

To demonstrate, first, let's create a class with code we'd like to use under multiple inheritance

class AbstractBase:
    __slots__ = ()
    def __init__(self, a, b):
        self.a = a
        self.b = b
    def __repr__(self):
        return f'{type(self).__name__}({repr(self.a)}, {repr(self.b)})'

We could use the above directly by inheriting and declaring the expected slots:

class Foo(AbstractBase):
    __slots__ = 'a', 'b'

But we don't care about that, that's trivial single inheritance, we need another class we might also inherit from, maybe with a noisy attribute:

class AbstractBaseC:
    __slots__ = ()
    @property
    def c(self):
        print('getting c!')
        return self._c
    @c.setter
    def c(self, arg):
        print('setting c!')
        self._c = arg

Now if both bases had nonempty slots, we couldn't do the below. (In fact, if we wanted, we could have given AbstractBase nonempty slots a and b, and left them out of the below declaration - leaving them in would be wrong):

class Concretion(AbstractBase, AbstractBaseC):
    __slots__ = 'a b _c'.split()

And now we have functionality from both via multiple inheritance, and can still deny __dict__ and __weakref__ instantiation:

>>> c = Concretion('a', 'b')
>>> c.c = c
setting c!
>>> c.c
getting c!
Concretion('a', 'b')
>>> c.d = 'd'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Concretion' object has no attribute 'd'

Other cases to avoid slots:

  • Avoid them when you want to perform __class__ assignment with another class that doesn't have them (and you can't add them) unless the slot layouts are identical. (I am very interested in learning who is doing this and why.)
  • Avoid them if you want to subclass variable length builtins like long, tuple, or str, and you want to add attributes to them.
  • Avoid them if you insist on providing default values via class attributes for instance variables.

You may be able to tease out further caveats from the rest of the __slots__ documentation (the 3.7 dev docs are the most current), which I have made significant recent contributions to.

Critiques of other answers

The current top answers cite outdated information and are quite hand-wavy and miss the mark in some important ways.

Do not "only use __slots__ when instantiating lots of objects"

I quote:

"You would want to use __slots__ if you are going to instantiate a lot (hundreds, thousands) of objects of the same class."

Abstract Base Classes, for example, from the collections module, are not instantiated, yet __slots__ are declared for them.

Why?

If a user wishes to deny __dict__ or __weakref__ creation, those things must not be available in the parent classes.

__slots__ contributes to reusability when creating interfaces or mixins.

It is true that many Python users aren't writing for reusability, but when you are, having the option to deny unnecessary space usage is valuable.

__slots__ doesn't break pickling

When pickling a slotted object, you may find it complains with a misleading TypeError:

>>> pickle.loads(pickle.dumps(f))
TypeError: a class that defines __slots__ without defining __getstate__ cannot be pickled

This is actually incorrect. This message comes from the oldest protocol, which is the default. You can select the latest protocol with the -1 argument. In Python 2.7 this would be 2 (which was introduced in 2.3), and in 3.6 it is 4.

>>> pickle.loads(pickle.dumps(f, -1))
<__main__.Foo object at 0x1129C770>

in Python 2.7:

>>> pickle.loads(pickle.dumps(f, 2))
<__main__.Foo object at 0x1129C770>

in Python 3.6

>>> pickle.loads(pickle.dumps(f, 4))
<__main__.Foo object at 0x1129C770>

So I would keep this in mind, as it is a solved problem.

Critique of the (until Oct 2, 2016) accepted answer

The first paragraph is half short explanation, half predictive. Here's the only part that actually answers the question

The proper use of __slots__ is to save space in objects. Instead of having a dynamic dict that allows adding attributes to objects at anytime, there is a static structure which does not allow additions after creation. This saves the overhead of one dict for every object that uses slots

The second half is wishful thinking, and off the mark:

While this is sometimes a useful optimization, it would be completely unnecessary if the Python interpreter was dynamic enough so that it would only require the dict when there actually were additions to the object.

Python actually does something similar to this, only creating the __dict__ when it is accessed, but creating lots of objects with no data is fairly ridiculous.

The second paragraph oversimplifies and misses actual reasons to avoid __slots__. The below is not a real reason to avoid slots (for actual reasons, see the rest of my answer above.):

They change the behavior of the objects that have slots in a way that can be abused by control freaks and static typing weenies.

It then goes on to discuss other ways of accomplishing that perverse goal with Python, not discussing anything to do with __slots__.

The third paragraph is more wishful thinking. Together it is mostly off-the-mark content that the answerer didn't even author and contributes to ammunition for critics of the site.

Memory usage evidence

Create some normal objects and slotted objects:

>>> class Foo(object): pass
>>> class Bar(object): __slots__ = ()

Instantiate a million of them:

>>> foos = [Foo() for f in xrange(1000000)]
>>> bars = [Bar() for b in xrange(1000000)]

Inspect with guppy.hpy().heap():

>>> guppy.hpy().heap()
Partition of a set of 2028259 objects. Total size = 99763360 bytes.
 Index  Count   %     Size   % Cumulative  % Kind (class / dict of class)
     0 1000000  49 64000000  64  64000000  64 __main__.Foo
     1     169   0 16281480  16  80281480  80 list
     2 1000000  49 16000000  16  96281480  97 __main__.Bar
     3   12284   1   987472   1  97268952  97 str
...

Access the regular objects and their __dict__ and inspect again:

>>> for f in foos:
...     f.__dict__
>>> guppy.hpy().heap()
Partition of a set of 3028258 objects. Total size = 379763480 bytes.
 Index  Count   %      Size    % Cumulative  % Kind (class / dict of class)
     0 1000000  33 280000000  74 280000000  74 dict of __main__.Foo
     1 1000000  33  64000000  17 344000000  91 __main__.Foo
     2     169   0  16281480   4 360281480  95 list
     3 1000000  33  16000000   4 376281480  99 __main__.Bar
     4   12284   0    987472   0 377268952  99 str
...

This is consistent with the history of Python, from Unifying types and classes in Python 2.2

If you subclass a built-in type, extra space is automatically added to the instances to accomodate __dict__ and __weakrefs__. (The __dict__ is not initialized until you use it though, so you shouldn't worry about the space occupied by an empty dictionary for each instance you create.) If you don't need this extra space, you can add the phrase "__slots__ = []" to your class.

How do I return multiple values from a function?

I vote for the dictionary.

I find that if I make a function that returns anything more than 2-3 variables I'll fold them up in a dictionary. Otherwise I tend to forget the order and content of what I'm returning.

Also, introducing a 'special' structure makes your code more difficult to follow. (Someone else will have to search through the code to find out what it is)

If your concerned about type look up, use descriptive dictionary keys, for example, 'x-values list'.

def g(x):
  y0 = x + 1
  y1 = x * 3
  y2 = y0 ** y3
  return {'y0':y0, 'y1':y1 ,'y2':y2 }

Options for HTML scraping?

In the .NET world, I recommend the HTML Agility Pack. Not near as simple as some of the above options (like HTMLSQL), but it's very flexible. It lets you maniuplate poorly formed HTML as if it were well formed XML, so you can use XPATH or just itereate over nodes.

http://www.codeplex.com/htmlagilitypack

Object of class mysqli_result could not be converted to string in

The query() function returns an object, you'll want fetch a record from what's returned from that function. Look at the examples on this page to learn how to print data from mysql

Why can't I declare static methods in an interface?

Java 8 Had changed the world you can have static methods in interface but it forces you to provide implementation for that.

public interface StaticMethodInterface {
public static int testStaticMethod() {
    return 0;
}

/**
 * Illegal combination of modifiers for the interface method
 * testStaticMethod; only one of abstract, default, or static permitted
 * 
 * @param i
 * @return
 */
// public static abstract int testStaticMethod(float i);

default int testNonStaticMethod() {
    return 1;
}

/**
 * Without implementation.
 * 
 * @param i
 * @return
 */
int testNonStaticMethod(float i);

}

Unique device identification

It looks like the phoneGap plugin will allow you to get the device's uid.

http://docs.phonegap.com/en/3.0.0/cordova_device_device.md.html#device.uuid

Update: This is dependent on running native code. We used this solution writing javascript that was being compiled to native code for a native phone application we were creating.

Where can I find the API KEY for Firebase Cloud Messaging?

Enter here:

https: //console.firebase.google.com/project/your-project-name/overview

(replace your-project with your project-name) and click in "Add firebase in your web app"(the red circle icon) this action show you a dialog with:

  • apiKey
  • authDomain
  • databaseURL
  • storageBucket
  • messagingSenderId

How to pass multiple checkboxes using jQuery ajax post

This would be better and easy

var arr = $('input[name="user_ids[]"]').map(function(){
  return $(this).val();
}).get();

console.log(arr);

How to add browse file button to Windows Form using C#

These links explain it with examples

http://dotnetperls.com/openfiledialog

http://www.geekpedia.com/tutorial67_Using-OpenFileDialog-to-open-files.html

private void button1_Click(object sender, EventArgs e)
{
    int size = -1;
    DialogResult result = openFileDialog1.ShowDialog(); // Show the dialog.
    if (result == DialogResult.OK) // Test result.
    {
       string file = openFileDialog1.FileName;
       try
       {
          string text = File.ReadAllText(file);
          size = text.Length;
       }
       catch (IOException)
       {
       }
    }
    Console.WriteLine(size); // <-- Shows file size in debugging mode.
    Console.WriteLine(result); // <-- For debugging use.
}

Use jQuery to get the file input's selected filename without the path

Get the first file from the control and then get the name of the file, it will ignore the file path on Chrome, and also will make correction of path for IE browsers. On saving the file, you have to use System.io.Path.GetFileName method to get the file name only for IE browsers

var fileUpload    = $("#ContentPlaceHolder1_FileUpload_mediaFile").get(0); 
var files         =  fileUpload.files; 
var mediafilename = ""; 

for (var i = 0; i < files.length; i++) { 
  mediafilename = files[i].name; 
} 

UnicodeDecodeError: 'utf8' codec can't decode byte 0x9c

Just in case of someone has the same problem. I'am using vim with YouCompleteMe, failed to start ycmd with this error message, what I did is: export LC_CTYPE="en_US.UTF-8", the problem is gone.

Eclipse count lines of code

The first thing to do is to determine your definition of "line of code" (LOC). In both your question

It counts a line with just one } as a line and he doesn't want that to count as "its not a line, its a style choice"

and in the answers, e.g.,

You can adjust the Lines of Code metrics by ignoring blank and comment-only lines or exclude Javadoc if you want

you can tell that people have different opinions as to what constitutes a line of code. In particular, people are often imprecise about whether they really want the number of lines of code or the number of statements. For example, if you have the following really long line filled with statements, what do you want to report, 1 LOC or hundreds of statements?

{ a = 1; b = 2; if (a==c) b++; /* etc. for another 1000 characters */ }

And when somebody asks you what you are calling a LOC, make sure you can answer, even if it is just "my definition of a LOC is Metrics2's definition". In general, for most commonly formatted code (unlike my example), the popular tools will give numbers fairly similar, so Metrics2, SonarQube, etc. should all be fine, as long as you use them consistently. In other words, don't count the LOC of some code using one tool and compare that value to a later version of that code that was measured with a different tool.

bower proxy configuration

I struggled with this from behind a proxy so I thought I should post what I did. Below one is worked for me.

-> "export HTTPS_PROXY=(yourproxy)"

What is the point of "Initial Catalog" in a SQL Server connection string?

If the user name that is in the connection string has access to more then one database you have to specify the database you want the connection string to connect to. If your user has only one database available then you are correct that it doesn't matter. But it is good practice to put this in your connection string.

java.sql.SQLException: Exhausted Resultset

When there is no records returned from Database for a particular condition and When I tried to access the rs.getString(1); I got this error "exhausted resultset".

Before the issue, my code was:

rs.next();
sNr= rs.getString(1);

After the fix:

while (rs.next()) {
    sNr = rs.getString(1);
}

React won't load local images

Best way to load local images in react is as follows

For example, Keep all your images(or any assets like videos, fonts) in the public folder as shown below.

enter image description here

Simply write <img src='/assets/images/Call.svg' /> to access the Call.svg image from any of your react component

Note: Keeping your assets in public folder ensures that, you can access it from anywhere from the project, by just giving '/path_to_image' and no need for any path traversal '../../' like this

ERROR: ld.so: object LD_PRELOAD cannot be preloaded: ignored

The linker takes some environment variables into account. one is LD_PRELOAD

from man 8 ld-linux:

LD_PRELOAD
          A whitespace-separated list of additional,  user-specified,  ELF
          shared  libraries  to  be loaded before all others.  This can be
          used  to  selectively  override  functions   in   other   shared
          libraries.   For  setuid/setgid  ELF binaries, only libraries in
          the standard search directories that are  also  setgid  will  be
          loaded.

Therefore the linker will try to load libraries listed in the LD_PRELOAD variable before others are loaded.

What could be the case that inside the variable is listed a library that can't be pre-loaded. look inside your .bashrc or .bash_profile environment where the LD_PRELOAD is set and remove that library from the variable.

How to convert entire dataframe to numeric while preserving decimals?

Using dplyr (a bit like sapply..)

df2 <- mutate_all(df1, function(x) as.numeric(as.character(x)))

which gives:

glimpse(df2)
Observations: 4
Variables: 2
$ a <dbl> 0.01, 0.02, 0.03, 0.04
$ b <dbl> 2, 4, 5, 7

from your df1 which was:

glimpse(df1)
Observations: 4
Variables: 2
$ a <fctr> 0.01, 0.02, 0.03, 0.04
$ b <dbl> 2, 4, 5, 7

Unable to run Java GUI programs with Ubuntu

I would check with another Java implementation/vendor. Preferrably Oracle/Sun Java: http://www.java.com/en/ . The open-source implementations unfortunately differ in weird ways.

Make a div into a link

To make thepeer's answer work in IE 7 and forward, it needs a few tweaks.

  1. IE will not honour z-index if the element is has no background-color, so the link will not overlap parts of the containig div that has content, only the blank parts. To fix this a background is added with opacity 0.

  2. For some reason IE7 and various compatibility modes completely fail when using the span in a link approach. However if the link itself is given the style it works just fine.

.blockLink  
{  
    position:absolute;  
    top:0;  
    left: 0;  
    width:100%;  
    height:100%;  
    z-index: 1;  
    background-color:#ffffff;   
    -ms-filter:"progid:DXImageTransform.Microsoft.Alpha(Opacity=0)";  
    filter: alpha(opacity=0);  
    opacity:0;  
}
<div style="position:relative">  
    <some content>  
    <a href="somepage" class="blockLink" />  
<div>

How can I check if a string is null or empty in PowerShell?

You guys are making this too hard. PowerShell handles this quite elegantly e.g.:

> $str1 = $null
> if ($str1) { 'not empty' } else { 'empty' }
empty

> $str2 = ''
> if ($str2) { 'not empty' } else { 'empty' }
empty

> $str3 = ' '
> if ($str3) { 'not empty' } else { 'empty' }
not empty

> $str4 = 'asdf'
> if ($str4) { 'not empty' } else { 'empty' }
not empty

> if ($str1 -and $str2) { 'neither empty' } else { 'one or both empty' }
one or both empty

> if ($str3 -and $str4) { 'neither empty' } else { 'one or both empty' }
neither empty

How does HttpContext.Current.User.Identity.Name know which usernames exist?

The HttpContext.Current.User.Identity.Name returns null

This depends on whether the authentication mode is set to Forms or Windows in your web.config file.

For example, if I write the authentication like this:

<authentication mode="Forms"/>

Then because the authentication mode="Forms", I will get null for the username. But if I change the authentication mode to Windows like this:

<authentication mode="Windows"/>

I can run the application again and check for the username, and I will get the username successfully.

For more information, see System.Web.HttpContext.Current.User.Identity.Name Vs System.Environment.UserName in ASP.NET.

Opacity of background-color, but not the text

I use an alpha-transparent PNG for that:

div.semi-transparent {
  background: url('semi-transparent.png');
}

For IE6, you'd need to use a PNG fix (1, 2), though.

How do you scroll up/down on the console of a Linux VM

It seems as though this is not easily possible: The Arch Linux Wiki lists no way to do this on the console (while easily possible on the virtual terminal).

You could use tmux scrolling:

Ctrl-b then [ then you can use your normal navigation keys to scroll around (eg. Up Arrow or PgDn). Press q to quit scroll mode.

Alternatively you can press Ctrl-b PgUp to go directly into copy mode and scroll one page up (which is what it sounds like you will want most of the time)

Call a VBA Function into a Sub Procedure

Procedures in a Module start being useful and generic when you pass in arguments.

For example:

Public Function DoSomethingElse(strMessage As String)  
    MsgBox strMessage
End Function

Can now display any message that is passed in with the string variable called strMessage.

use "netsh wlan set hostednetwork ..." to create a wifi hotspot and the authentication can't work correctly

It's a bit of a guess but could the quotes around happy be the problem? There have been some problems in the past where Android would either add or not recognize quotes around an SSID. Try setting up the hosted network connection again, but without the quotes that we see in the output for netsh wlan show hostednetwork.

Changing the resolution of a VNC session in linux

I think that depends on your window manager.

I'm a windows user, so this might be a wrong guess, but: Isn't there something called X-Server running on linux machines - at least on ones that might be interesting targets for VNC - that you can connect to with "X-Clients"?

VNC just takes everything that's on the screen and "tunnels it through your network". If I'm not totally wrong then the "X" protocol should give you the chance to use your client's desktop resolution.

Give X-Server on Wikipedia a try, that might give you a rough overview.

Twitter Bootstrap Use collapse.js on table cells [Almost Done]

If you're using Angular's ng-repeat to populate the table hackel's jquery snippet will not work by placing it in the document load event. You'll need to run the snippet after angular has finished rendering the table.

To trigger an event after ng-repeat has rendered try this directive:

var app = angular.module('myapp', [])
.directive('onFinishRender', function ($timeout) {
return {
    restrict: 'A',
    link: function (scope, element, attr) {
        if (scope.$last === true) {
            $timeout(function () {
                scope.$emit('ngRepeatFinished');
            });
        }
    }
}
});

Complete example in angular: http://jsfiddle.net/ADukg/6880/

I got the directive from here: Use AngularJS just for routing purposes

Turning Sonar off for certain code

You can annotate a class or a method with SuppressWarnings

@java.lang.SuppressWarnings("squid:S00112")

squid:S00112 in this case is a Sonar issue ID. You can find this ID in the Sonar UI. Go to Issues Drilldown. Find an issue you want to suppress warnings on. In the red issue box in your code is there a Rule link with a definition of a given issue. Once you click that you will see the ID at the top of the page.

IndexError: index 1 is out of bounds for axis 0 with size 1/ForwardEuler

The problem is with your line

x=np.array ([x0*n])

Here you define x as a single-item array of -200.0. You could do this:

x=np.array ([x0,]*n)

or this:

x=np.zeros((n,)) + x0

Note: your imports are quite confused. You import numpy modules three times in the header, and then later import pylab (that already contains all numpy modules). If you want to go easy, with one single

from pylab import *

line in the top you could use all the modules you need.

How do I calculate power-of in C#?

The function you want is Math.Pow in System.Math.

How do I get started with Node.js

You can follow these tutorials to get started

Tutorials

Developer Sites

Videos

Screencasts

Books

Courses

Blogs

Podcasts

JavaScript resources

Node.js Modules

Other

What does the "undefined reference to varName" in C mean?

You need to link both a.o and b.o:

gcc -o program a.c b.c

If you have a main() in each file, you cannot link them together.

However, your a.c file contains a reference to doSomething() and expects to be linked with a source file that defines doSomething() and does not define any function that is defined in a.c (such as main()).

You cannot call a function in Process B from Process A. You cannot send a signal to a function; you send signals to processes, using the kill() system call.

The signal() function specifies which function in your current process (program) is going to handle the signal when your process receives the signal.

You have some serious work to do understanding how this is going to work - how ProgramA is going to know which process ID to send the signal to. The code in b.c is going to need to call signal() with dosomething as the signal handler. The code in a.c is simply going to send the signal to the other process.

How to use color picker (eye dropper)?

Currently, the eyedropper tool is not working in my version of Chrome (as described above), though it worked for me in the past. I hear it is being updated in the latest version of Chrome.

However, I'm able to grab colors easily in Firefox.

  1. Open page in Firefox
  2. Hamburger Menu -> Web Developer -> Eyedropper
  3. Drag eyedropper tool over the image... Click.
    Color is copied to your clipboard, and eyedropper tool goes away.
  4. Paste color code

In case you cannot get the eyedropper tool to work in Chrome, this is a good work around.
I also find it easier to access :-)

Fixed footer in Bootstrap

You can do this by wrapping the page contents in a div with the following id styling applied:

<style>
#wrap {
   min-height: 100%;
   height: auto !important;
   height: 100%;
   margin: 0 auto -60px;
}
</style>

<div id="wrap">
    <!-- Your page content here... -->
</div>

Worked for me.

CSS3 transform not working

In webkit-based browsers(Safari and Chrome), -webkit-transform is ignored on inline elements.. Set display: inline-block; to make it work. For demonstration/testing purposes, you may also want to use a negative angle or a transformation-origin lest the text is rotated out of the visible area.

Insert default value when parameter is null

Don't specify the column or value when inserting and the DEFAULT constaint's value will be substituted for the missing value.

I don't know how this would work in a single column table. I mean: it would, but it wouldn't be very useful.

Youtube iframe wmode issue

Adding ?wmode=opaque to the URL seems to solve this problem for me, although I have not tested it in IE yet.

For those of you having troubles with the previously proposed solution, note that an inital ampersand will only work if you are already supplying other arguments to the URL. The first argument must have an initial question mark: http://www.example.com?first=foo&second=bar

Saving data to a file in C#

One liner:

System.IO.File.WriteAllText(@"D:\file.txt", content);

It creates the file if it doesn't exist and overwrites it if it exists. Make sure you have appropriate privileges to write to the location, otherwise you will get an exception.

https://msdn.microsoft.com/en-us/library/ms143375%28v=vs.110%29.aspx?f=255&MSPPError=-2147217396

Write string to text file and ensure it always overwrites the existing content.

Right pad a string with variable number of spaces

Whammo blammo (for leading spaces):

SELECT 
    RIGHT(space(60) + cust_name, 60),
    RIGHT(space(60) + cust_address, 60)

OR (for trailing spaces)

SELECT
    LEFT(cust_name + space(60), 60),
    LEFT(cust_address + space(60), 60),

Getting the last revision number in SVN?

The posted solutions don't handle the case when externals are being used.

If I have a URL or a working copy with the svn:externals property set, the externals may change and thus the subversion server's latest revision will change. But the latest revision of the working copy or URL will only report the revision number when the svn:externals propty was change or any item lower in the URL path, which is expected behavior.

So you either get the svn:externals property and iterate over the URLs and pick the heights revision or query the base URL from the subversion server. The version reported from the base URL will contain the latest revision for EVERYTHING on the server.

So, if you are using externals, it's best to use svn info BASE_URL where BASE_URL is the root URL for all paths on the subversion server.

How do I execute a program from Python? os.system fails due to spaces in path

subprocess.call will avoid problems with having to deal with quoting conventions of various shells. It accepts a list, rather than a string, so arguments are more easily delimited. i.e.

import subprocess
subprocess.call(['C:\\Temp\\a b c\\Notepad.exe', 'C:\\test.txt'])

How to create border in UIButton?

And in swift, you don't need to import "QuartzCore/QuartzCore.h"

Just use:

button.layer.borderWidth = 0.8
button.layer.borderColor = (UIColor( red: 0.5, green: 0.5, blue:0, alpha: 1.0 )).cgColor

or

button.layer.borderWidth = 0.8
button.layer.borderColor = UIColor.grayColor().cgColor

How to achieve function overloading in C?

As already stated, overloading in the sense that you mean isn't supported by C. A common idiom to solve the problem is making the function accept a tagged union. This is implemented by a struct parameter, where the struct itself consists of some sort of type indicator, such as an enum, and a union of the different types of values. Example:

#include <stdio.h>

typedef enum {
    T_INT,
    T_FLOAT,
    T_CHAR,
} my_type;

typedef struct {
    my_type type;
    union {
        int a; 
        float b; 
        char c;
    } my_union;
} my_struct;

void set_overload (my_struct *whatever) 
{
    switch (whatever->type) 
    {
        case T_INT:
            whatever->my_union.a = 1;
            break;
        case T_FLOAT:
            whatever->my_union.b = 2.0;
            break;
        case T_CHAR:
            whatever->my_union.c = '3';
    }
}

void printf_overload (my_struct *whatever) {
    switch (whatever->type) 
    {
        case T_INT:
            printf("%d\n", whatever->my_union.a);
            break;
        case T_FLOAT:
            printf("%f\n", whatever->my_union.b);
            break;
        case T_CHAR:
            printf("%c\n", whatever->my_union.c);
            break;
    }

}

int main (int argc, char* argv[])
{
    my_struct s;

    s.type=T_INT;
    set_overload(&s);
    printf_overload(&s);

    s.type=T_FLOAT;
    set_overload(&s);
    printf_overload(&s);

    s.type=T_CHAR;
    set_overload(&s);
    printf_overload(&s); 
}

Horizontal line using HTML/CSS

you could also do it this way, in my case i use it before and after an h1 (brute force it ehehehe)

.titleImage::before {
content: "--------";
letter-spacing: -3px;
}

.titreImage::after {
content: "--------";
letter-spacing: -3px;
}

If the letter spacing makes it so the line get in the text just use a margin to push it away!

App.Config change value

when use "ConfigurationUserLevel.None" your code is right run when you click in nameyourapp.exe in debug folder. .
but when your do developing app on visual stdio not right run!! because "vshost.exe" is run.

following parameter solve this problem : "Application.ExecutablePath"

try this : (Tested in VS 2012 Express For Desktop)

Configuration config = ConfigurationManager.OpenExeConfiguration(Application.ExecutablePath);
config.AppSettings.Settings["PortName"].Value = "com3";
config.Save(ConfigurationSaveMode.Minimal);

my english not good , i am sorry.

How do I retrieve query parameters in Spring Boot?

To accept both @PathVariable and @RequestParam in the same /user endpoint:

@GetMapping(path = {"/user", "/user/{data}"})
public void user(@PathVariable(required=false,name="data") String data,
                 @RequestParam(required=false) Map<String,String> qparams) {
    qparams.forEach((a,b) -> {
        System.out.println(String.format("%s -> %s",a,b));
    }
  
    if (data != null) {
        System.out.println(data);
    }
}

Testing with curl:

  • curl 'http://localhost:8080/user/books'
  • curl 'http://localhost:8080/user?book=ofdreams&name=nietzsche'

How do I get the command-line for an Eclipse run configuration?

You'll find the junit launch commands in .metadata/.plugins/org.eclipse.debug.core/.launches, assuming your Eclipse works like mine does. The files are named {TestClass}.launch.

You will probably also need the .classpath file in the project directory that contains the test class.

Like the run configurations, they're XML files (even if they don't have an xml extension).

jQuery: Count number of list elements?

I think this should do it:

var ct = $('#mylist').children().size(); 

Visual Studio build fails: unable to copy exe-file from obj\debug to bin\debug

None of the other answers worked for me but closing all open tabs in Visual Studio appears to have solved the problem.

How to encode URL to avoid special characters in Java?

URL construction is tricky because different parts of the URL have different rules for what characters are allowed: for example, the plus sign is reserved in the query component of a URL because it represents a space, but in the path component of the URL, a plus sign has no special meaning and spaces are encoded as "%20".

RFC 2396 explains (in section 2.4.2) that a complete URL is always in its encoded form: you take the strings for the individual components (scheme, authority, path, etc.), encode each according to its own rules, and then combine them into the complete URL string. Trying to build a complete unencoded URL string and then encode it separately leads to subtle bugs, like spaces in the path being incorrectly changed to plus signs (which an RFC-compliant server will interpret as real plus signs, not encoded spaces).

In Java, the correct way to build a URL is with the URI class. Use one of the multi-argument constructors that takes the URL components as separate strings, and it'll escape each component correctly according to that component's rules. The toASCIIString() method gives you a properly-escaped and encoded string that you can send to a server. To decode a URL, construct a URI object using the single-string constructor and then use the accessor methods (such as getPath()) to retrieve the decoded components.

Don't use the URLEncoder class! Despite the name, that class actually does HTML form encoding, not URL encoding. It's not correct to concatenate unencoded strings to make an "unencoded" URL and then pass it through a URLEncoder. Doing so will result in problems (particularly the aforementioned one regarding spaces and plus signs in the path).

Direct casting vs 'as' operator?

I would like to attract attention to the following specifics of the as operator:

https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/as

Note that the as operator performs only reference conversions, nullable conversions, and boxing conversions. The as operator can't perform other conversions, such as user-defined conversions, which should instead be performed by using cast expressions.

How can I use a JavaScript variable as a PHP variable?

I had the same problem a few weeks ago like yours; but I invented a brilliant solution for exchanging variables between PHP and JavaScript. It worked for me well:

  1. Create a hidden form on a HTML page

  2. Create a Textbox or Textarea in that hidden form

  3. After all of your code written in the script, store the final value of your variable in that textbox

  4. Use $_REQUEST['textbox name'] line in your PHP to gain access to value of your JavaScript variable.

I hope this trick works for you.

Why use pip over easy_install?

Another—as of yet unmentioned—reason for favoring pip is because it is the new hotness and will continue to be used in the future.

The infographic below—from the Current State of Packaging section in the The Hitchhiker's Guide to Packaging v1.0—shows that setuptools/easy_install will go away in the future.

enter image description here

Here's another infographic from distribute's documentation showing that Setuptools and easy_install will be replaced by the new hotness—distribute and pip. While pip is still the new hotness, Distribute merged with Setuptools in 2013 with the release of Setuptools v0.7.

enter image description here

Git Pull is Not Possible, Unmerged Files

Assuming you want to throw away any changes you have, first check the output of git status. For any file that says "unmerged" next to it, run git add <unmerged file>. Then follow up with git reset --hard. That will git rid of any local changes except for untracked files.

How to debug JavaScript / jQuery event bindings with Firebug or similar tools?

Looks like FireBug crew is working on an EventBug extension. It will add another panel to FireBug - Events.

"The events panel will list all of the event handlers on the page grouped by event type. For each event type you can open up to see the elements the listeners are bound to and summary of the function source." EventBug Rising

Although they cannot say right now when it will be released.

Is there a difference between x++ and ++x in java?

I landed here from one of its recent dup's, and though this question is more than answered, I couldn't help decompiling the code and adding "yet another answer" :-)

To be accurate (and probably, a bit pedantic),

int y = 2;
y = y++;

is compiled into:

int y = 2;
int tmp = y;
y = y+1;
y = tmp;

If you javac this Y.java class:

public class Y {
    public static void main(String []args) {
        int y = 2;
        y = y++;
    }
}

and javap -c Y, you get the following jvm code (I have allowed me to comment the main method with the help of the Java Virtual Machine Specification):

public class Y extends java.lang.Object{
public Y();
  Code:
   0:   aload_0
   1:   invokespecial  #1; //Method java/lang/Object."<init>":()V
   4:   return

public static void main(java.lang.String[]);
  Code:
   0:   iconst_2 // Push int constant `2` onto the operand stack. 

   1:   istore_1 // Pop the value on top of the operand stack (`2`) and set the
                 // value of the local variable at index `1` (`y`) to this value.

   2:   iload_1  // Push the value (`2`) of the local variable at index `1` (`y`)
                 // onto the operand stack

   3:   iinc  1, 1 // Sign-extend the constant value `1` to an int, and increment
                   // by this amount the local variable at index `1` (`y`)

   6:   istore_1 // Pop the value on top of the operand stack (`2`) and set the
                 // value of the local variable at index `1` (`y`) to this value.
   7:   return

}

Thus, we finally have:

0,1: y=2
2: tmp=y
3: y=y+1
6: y=tmp

How to declare an array of objects in C#

You are creating an array of null references. You should do something like:

for (int i = 0; i < houses.Count; i++)
{
    houses[i] = new GameObject();
}

Pass Method as Parameter using C#

In order to provide a clear and complete answer, I'm going to start from the very beginning before coming up with three possible solutions.


A brief introduction

All languages that run on top of the CLR (Common Language Runtime), such as C#, F#, and Visual Basic, work under a VM that runs higher level code than machine code, which native languages like C and C++ are compiled to. It follows that methods aren't Assembly subroutines, nor are they values, unlike JavaScript as well as most functional languages; rather, they're definitions that CLR recognizes. Thus, you cannot think to pass a method as a parameter, because methods don't produce any values themselves, as they're not expressions but statements, which are stored in the generated assemblies. At this point, you'll face delegates.


What's a delegate?

A delegate represents a handle to a method (the term handle is to be preferred over pointer as it is implementation–dependent.) As I said above, a method is not a value, hence there's a special class in CLR languages, namely Delegate, which wraps up any method.

Look at the following example:

static void MyMethod()
{
    Console.WriteLine("I was called by the Delegate special class!");
}

static void CallAnyMethod(Delegate yourMethod)
{
    yourMethod.DynamicInvoke(new object[] { /*Array of arguments to pass*/ });
}

static void Main()
{
    CallAnyMethod(MyMethod);
}

Three different solutions, the same underlying concept:

  • The type–unsafe way
    Using the Delegate special class directly the same way as the example above. The drawback here is your code being type–unsafe, allowing arguments to be passed dynamically, with no constraints.

  • The custom way
    Besides the Delegate special class, the concept of delegates spreads to custom delegates, which are declarations of methods preceded by the delegate keyword. They are type–checked the same as method declarations, leading to flawlessly safe code.

    Here's an example:

    delegate void PrintDelegate(string prompt);
    
    static void PrintSomewhere(PrintDelegate print, string prompt)
    {
        print(prompt);
    }
    
    static void PrintOnConsole(string prompt)
    {
        Console.WriteLine(prompt);
    }
    
    static void PrintOnScreen(string prompt)
    {
        MessageBox.Show(prompt);
    }
    
    static void Main()
    {
        PrintSomewhere(PrintOnConsole, "Press a key to get a message");
        Console.Read();
        PrintSomewhere(PrintOnScreen, "Hello world");
    }
    
  • The standard library's way
    Alternatively, you can use a delegate that's part of the .NET Standard:

    • Action wraps up a parameterless void method.
    • Action<T1> wraps up a void method with one parameter of type T1.
    • Action<T1, T2> wraps up a void method with two parameters of types T1 and T2, respectively.
    • And so forth...
    • Func<TR> wraps up a parameterless function with TR return type.
    • Func<T1, TR> wraps up a function with TR return type and with one parameter of type T1.
    • Func<T1, T2, TR> wraps up a function with TR return type and with two parameters of types T1 and T2, respectively.
    • And so forth...

    However, bear in mind that using predefined delegates like these, parameter names won't describe what they have to be passed in, nor is the delegate name meaningful on what it's supposed to do. Therefore, be cautious about when to use these delegates and refrain from using them in contexts where their purpose is not absolutely self–evident.

The latter solution is the one most people posted. I'm still mentioning it in my answer for the sake of completeness.

How to get last inserted id?

INSERT INTO aspnet_GameProfiles(UserId,GameId) VALUES(@UserId, @GameId)"; then you can just access to the last id by ordering the table in desc way.

SELECT TOP 1 UserId FROM aspnet_GameProfiles ORDER BY UserId DESC.

Android Studio 3.0 Flavor Dimension Issue

Here you can resolve this issue, you need to add flavorDimension with productFlavors's name and need to define dimension as well, see below example and for more information see here https://developer.android.com/studio/build/gradle-plugin-3-0-0-migration.html

flavorDimensions 'yourAppName' //here defined dimensions
productFlavors {
    production {
        dimension 'yourAppName' //you just need to add this line
        //here you no need to write applicationIdSuffix because by default it will point to your app package which is also available inside manifest.xml file.

    }

    staging {
        dimension 'yourAppName' //added here also
        applicationIdSuffix ".staging"//(.staging) will be added after your default package name.
        //or you can also use applicationId="your_package_name.staging" instead of applicationIdSuffix but remember if you are using applicationId then You have to mention full package name.
        //versionNameSuffix "-staging"

    }

    develop {
        dimension 'yourAppName' //add here too
        applicationIdSuffix ".develop"
        //versionNameSuffix "-develop"

    }

What is AF_INET, and why do I need it?

The primary purpose of AF_INET was to allow for other possible network protocols or address families (AF is for address family; PF_INET is for the (IPv4) internet protocol family). For example, there probably are a few Netware SPX/IPX networks around still; there were other network systems like DECNet, StarLAN and SNA, not to mention the ill-begotten ISO OSI (Open Systems Interconnection), and these did not necessarily use the now ubiquitous IP address to identify the peer host in network connections.

The ubiquitous alternative to AF_INET (which, in retrospect, should have been named AF_INET4) is AF_INET6, for the IPv6 address family. IPv4 uses 32-bit addresses; IPv6 uses 128-bit addresses.

You may see some other values - but they are unusual. It is there to allow for alternatives and future directions. The sockets interface is actually very general indeed - which is one of the reasons it has thrived where other networking interfaces have withered.

Life has (mostly) gotten simpler - be grateful.

Redirecting to another page in ASP.NET MVC using JavaScript/jQuery

You are not subscribing to any success callback in your $.post AJAX call. Meaning that the request is executed, but you do nothing with the results. If you want to do something useful with the results, try:

$.post('/Branch/Details/' + id, function(result) {
    // Do something with the result like for example inject it into
    // some placeholder and update the DOM.
    // This obviously assumes that your controller action returns
    // a partial view otherwise you will break your markup
});

On the other hand if you want to redirect, you absolutely do not need AJAX. You use AJAX only when you want to stay on the same page and update only a portion of it.

So if you only wanted to redirect the browser:

function foo(id) {
    window.location.href = '/Branch/Details/' + id;
}

As a side note: You should never be hardcoding urls like this. You should always be using url helpers when dealing with urls in an ASP.NET MVC application. So:

function foo(id) {
    var url = '@Url.Action("Details", "Branch", new { id = "__id__" })';
    window.location.href = url.replace('__id__', id);
}

git submodule tracking latest

Edit (2020.12.28): GitHub change default master branch to main branch since October 2020. See https://github.com/github/renaming


Update March 2013

Git 1.8.2 added the possibility to track branches.

"git submodule" started learning a new mode to integrate with the tip of the remote branch (as opposed to integrating with the commit recorded in the superproject's gitlink).

# add submodule to track master branch
git submodule add -b master [URL to Git repo];

# update your submodule
git submodule update --remote 

If you had a submodule already present you now wish would track a branch, see "how to make an existing submodule track a branch".

Also see Vogella's tutorial on submodules for general information on submodules.

Note:

git submodule add -b . [URL to Git repo];
                    ^^^

See git submodule man page:

A special value of . is used to indicate that the name of the branch in the submodule should be the same name as the current branch in the current repository.


See commit b928922727d6691a3bdc28160f93f25712c565f6:

submodule add: If --branch is given, record it in .gitmodules

This allows you to easily record a submodule.<name>.branch option in .gitmodules when you add a new submodule. With this patch,

$ git submodule add -b <branch> <repository> [<path>]
$ git config -f .gitmodules submodule.<path>.branch <branch>

reduces to

$ git submodule add -b <branch> <repository> [<path>]

This means that future calls to

$ git submodule update --remote ...

will get updates from the same branch that you used to initialize the submodule, which is usually what you want.

Signed-off-by: W. Trevor King [email protected]


Original answer (February 2012):

A submodule is a single commit referenced by a parent repo.
Since it is a Git repo on its own, the "history of all commits" is accessible through a git log within that submodule.

So for a parent to track automatically the latest commit of a given branch of a submodule, it would need to:

  • cd in the submodule
  • git fetch/pull to make sure it has the latest commits on the right branch
  • cd back in the parent repo
  • add and commit in order to record the new commit of the submodule.

gitslave (that you already looked at) seems to be the best fit, including for the commit operation.

It is a little annoying to make changes to the submodule due to the requirement to check out onto the correct submodule branch, make the change, commit, and then go into the superproject and commit the commit (or at least record the new location of the submodule).

Other alternatives are detailed here.

Howto? Parameters and LIKE statement SQL

Your visual basic code would look something like this:

Dim cmd as New SqlCommand("SELECT * FROM compliance_corner WHERE (body LIKE '%' + @query + '%') OR (title LIKE '%' + @query + '%')")

cmd.Parameters.Add("@query", searchString)

Multiple WHERE Clauses with LINQ extension methods

Just use the && operator like you would with any other statement that you need to do boolean logic.

if (useAdditionalClauses)
{
  results = results.Where(
                  o => o.OrderStatus == OrderStatus.Open 
                  && o.CustomerID == customerID)     
}

What is the best way to test for an empty string in Go?

I think the best way is to compare with blank string

BenchmarkStringCheck1 is checking with blank string

BenchmarkStringCheck2 is checking with len zero

I check with the empty and non-empty string checking. You can see that checking with a blank string is faster.

BenchmarkStringCheck1-4     2000000000           0.29 ns/op        0 B/op          0 allocs/op
BenchmarkStringCheck1-4     2000000000           0.30 ns/op        0 B/op          0 allocs/op


BenchmarkStringCheck2-4     2000000000           0.30 ns/op        0 B/op          0 allocs/op
BenchmarkStringCheck2-4     2000000000           0.31 ns/op        0 B/op          0 allocs/op

Code

func BenchmarkStringCheck1(b *testing.B) {
    s := "Hello"
    b.ResetTimer()
    for n := 0; n < b.N; n++ {
        if s == "" {

        }
    }
}

func BenchmarkStringCheck2(b *testing.B) {
    s := "Hello"
    b.ResetTimer()
    for n := 0; n < b.N; n++ {
        if len(s) == 0 {

        }
    }
}

How to select date from datetime column?

You can format the datetime to the Y-M-D portion:

DATE_FORMAT(datetime, '%Y-%m-%d')

Syntax error due to using a reserved word as a table or column name in MySQL

The Problem

In MySQL, certain words like SELECT, INSERT, DELETE etc. are reserved words. Since they have a special meaning, MySQL treats it as a syntax error whenever you use them as a table name, column name, or other kind of identifier - unless you surround the identifier with backticks.

As noted in the official docs, in section 10.2 Schema Object Names (emphasis added):

Certain objects within MySQL, including database, table, index, column, alias, view, stored procedure, partition, tablespace, and other object names are known as identifiers.

...

If an identifier contains special characters or is a reserved word, you must quote it whenever you refer to it.

...

The identifier quote character is the backtick ("`"):

A complete list of keywords and reserved words can be found in section 10.3 Keywords and Reserved Words. In that page, words followed by "(R)" are reserved words. Some reserved words are listed below, including many that tend to cause this issue.

  • ADD
  • AND
  • BEFORE
  • BY
  • CALL
  • CASE
  • CONDITION
  • DELETE
  • DESC
  • DESCRIBE
  • FROM
  • GROUP
  • IN
  • INDEX
  • INSERT
  • INTERVAL
  • IS
  • KEY
  • LIKE
  • LIMIT
  • LONG
  • MATCH
  • NOT
  • OPTION
  • OR
  • ORDER
  • PARTITION
  • RANK
  • REFERENCES
  • SELECT
  • TABLE
  • TO
  • UPDATE
  • WHERE

The Solution

You have two options.

1. Don't use reserved words as identifiers

The simplest solution is simply to avoid using reserved words as identifiers. You can probably find another reasonable name for your column that is not a reserved word.

Doing this has a couple of advantages:

  • It eliminates the possibility that you or another developer using your database will accidentally write a syntax error due to forgetting - or not knowing - that a particular identifier is a reserved word. There are many reserved words in MySQL and most developers are unlikely to know all of them. By not using these words in the first place, you avoid leaving traps for yourself or future developers.

  • The means of quoting identifiers differs between SQL dialects. While MySQL uses backticks for quoting identifiers by default, ANSI-compliant SQL (and indeed MySQL in ANSI SQL mode, as noted here) uses double quotes for quoting identifiers. As such, queries that quote identifiers with backticks are less easily portable to other SQL dialects.

Purely for the sake of reducing the risk of future mistakes, this is usually a wiser course of action than backtick-quoting the identifier.

2. Use backticks

If renaming the table or column isn't possible, wrap the offending identifier in backticks (`) as described in the earlier quote from 10.2 Schema Object Names.

An example to demonstrate the usage (taken from 10.3 Keywords and Reserved Words):

mysql> CREATE TABLE interval (begin INT, end INT);
ERROR 1064 (42000): You have an error in your SQL syntax.
near 'interval (begin INT, end INT)'

mysql> CREATE TABLE `interval` (begin INT, end INT); Query OK, 0 rows affected (0.01 sec)

Similarly, the query from the question can be fixed by wrapping the keyword key in backticks, as shown below:

INSERT INTO user_details (username, location, `key`)
VALUES ('Tim', 'Florida', 42)";               ^   ^

Inline for loop

q  = [1, 2, 3, 4, 1, 2, 5, 1, 2, 3, 4, 5]
vm = [-1, -1, -1, -1,1,2,3,1]

p = []
for v in vm:
    if v in q:
        p.append(q.index(v))
    else:
        p.append(99999)

print p
p = [q.index(v) if v in q else 99999 for v in vm]
print p

Output:

[99999, 99999, 99999, 99999, 0, 1, 2, 0]
[99999, 99999, 99999, 99999, 0, 1, 2, 0]

Instead of using append() in the list comprehension you can reference the p as direct output, and use q.index(v) and 99999 in the LC.

Not sure if this is intentional but note that q.index(v) will find just the first occurrence of v, even tho you have several in q. If you want to get the index of all v in q, consider using a enumerator and a list of already visited indexes

Something in those lines(pseudo-code):

visited = []
for i, v in enumerator(vm):
   if i not in visited:
       p.append(q.index(v))
   else:
       p.append(q.index(v,max(visited))) # this line should only check for v in q after the index of max(visited)
   visited.append(i)

How to read integer value from the standard input in Java

This causes headaches so I updated a solution that will run using the most common hardware and software tools available to users in December 2014. Please note that the JDK/SDK/JRE/Netbeans and their subsequent classes, template libraries compilers, editors and debuggerz are free.

This program was tested with Java v8 u25. It was written and built using
Netbeans IDE 8.0.2, JDK 1.8, OS is win8.1 (apologies) and browser is Chrome (double-apologies) - meant to assist UNIX-cmd-line OG's deal with modern GUI-Web-based IDEs at ZERO COST - because information (and IDEs) should always be free. By Tapper7. For Everyone.

code block:

    package modchk; //Netbeans requirement.
    import java.util.Scanner;
    //import java.io.*; is not needed Netbeans automatically includes it.           
    public class Modchk {
        public static void main(String[] args){
            int input1;
            int input2;

            //Explicity define the purpose of the .exe to user:
            System.out.println("Modchk by Tapper7. Tests IOStream and basic bool modulo fxn.\n"
            + "Commented and coded for C/C++ programmers new to Java\n");

            //create an object that reads integers:
            Scanner Cin = new Scanner(System.in); 

            //the following will throw() if you don't do you what it tells you or if 
            //int entered == ArrayIndex-out-of-bounds for your system. +-~2.1e9
            System.out.println("Enter an integer wiseguy: ");
            input1 = Cin.nextInt(); //this command emulates "cin >> input1;"

            //I test like Ernie Banks played hardball: "Let's play two!"
            System.out.println("Enter another integer...anyday now: ");
            input2 = Cin.nextInt(); 

            //debug the scanner and istream:
            System.out.println("the 1st N entered by the user was " + input1);
            System.out.println("the 2nd N entered by the user was " + input2);

            //"do maths" on vars to make sure they are of use to me:
            System.out.println("modchk for " + input1);
            if(2 % input1 == 0){
                System.out.print(input1 + " is even\n"); //<---same output effect as *.println
                }else{
                System.out.println(input1 + " is odd");
            }//endif input1

            //one mo' 'gain (as in istream dbg chk above)
            System.out.println("modchk for " + input2);
            if(2 % input2 == 0){
                System.out.print(input2 + " is even\n");
                }else{
                System.out.println(input2 + " is odd");
            }//endif input2
        }//end main
    }//end Modchk

How to display a date as iso 8601 format with PHP

Here is the good function for pre PHP 5: I added GMT difference at the end, it's not hardcoded.

function iso8601($time=false) {
    if ($time === false) $time = time();
    $date = date('Y-m-d\TH:i:sO', $time);
    return (substr($date, 0, strlen($date)-2).':'.substr($date, -2));
}

How can I convert a .jar to an .exe?

If your program is "publicly available non-commercial in nature" and has "a publicly available Web site that meets the basic quality standards", then you can try and get a free license of Excelsior. If its not then it's expensive, but still a viable option.

Program: https://www.excelsiorjet.com

As a side note: Here's a study of all existing Jar to EXE programs, which is a bit depressing - https://www.excelsior-usa.com/articles/java-to-exe.html

Auto height div with overflow and scroll when needed

You can do this assignment easily by using jquery. In this way, you can define number of row limitation. Furthermore, you can regular breakpoints height that want adding vertical scrolling. I must say that more than 3 rows get modify class and also height is 76px.

_x000D_
_x000D_
$(document).ready(function() {_x000D_
  var length = $(this).find('li').length;_x000D_
  if (length > 3) {_x000D_
    $(".parent").addClass('modify');_x000D_
  }_x000D_
})
_x000D_
/*for beauty*/_x000D_
_x000D_
ul {_x000D_
  margin: 0 auto;_x000D_
  width: 50%;_x000D_
  border: 1px solid #ccc;_x000D_
  padding: 3px;_x000D_
}_x000D_
_x000D_
ul li {_x000D_
  padding: 3px;_x000D_
  background: #ccc;_x000D_
  margin: 2px 0;_x000D_
  list-style: none;_x000D_
}_x000D_
_x000D_
/*main class*/_x000D_
_x000D_
.modify {_x000D_
  overflow-y: scroll;_x000D_
  height: 76px;_x000D_
}
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>_x000D_
_x000D_
<ul class="parent">_x000D_
  <li>item 1</li>_x000D_
  <li>item 2</li>_x000D_
  <li>item 3</li>_x000D_
  <li>item 4</li>_x000D_
</ul>
_x000D_
_x000D_
_x000D_

error: expected declaration or statement at end of input in c

Try to place a

return 0;

on the end of your code or just erase the

void

from your main function I hope that I helped

AWK: Access captured group from line pattern

With gawk, you can use the match function to capture parenthesized groups.

gawk 'match($0, pattern, ary) {print ary[1]}' 

example:

echo "abcdef" | gawk 'match($0, /b(.*)e/, a) {print a[1]}' 

outputs cd.

Note the specific use of gawk which implements the feature in question.

For a portable alternative you can achieve similar results with match() and substr.

example:

echo "abcdef" | awk 'match($0, /b[^e]*/) {print substr($0, RSTART+1, RLENGTH-1)}'

outputs cd.

'module' object has no attribute 'DataFrame'

I have faced similar problem, 'int' object has no attribute 'DataFrame',

This was because i have mistakenly used pd as a variable in my code and assigned an integer to it, while using the same pd as my pandas dataframe object by declaring - import pandas as pd.

I realized this, and changed my variable to something else, and fixed the error.

Export and Import all MySQL databases at one time

Export all databases in Ubuntu

1 - mysqldump -u root -p --databases database1 database2 > ~/Desktop/databases_1_2.sql

OR

2 - mysqldump -u root -p --all_databases > ~/Desktop/all_databases.sql

enter image description here

Creating Accordion Table with Bootstrap

In the accepted answer you get annoying spacing between the visible rows when the expandable row is hidden. You can get rid of that by adding this to css:

.collapse-row.collapsed + tr {
     display: none;
}

'+' is adjacent sibling selector, so if you want your expandable row to be the next row, this selects the next tr following tr named collapse-row.

Here is updated fiddle: http://jsfiddle.net/Nb7wy/2372/

Static extension methods

In short, no, you can't.

Long answer, extension methods are just syntactic sugar. IE:

If you have an extension method on string let's say:

public static string SomeStringExtension(this string s)
{
   //whatever..
}

When you then call it:

myString.SomeStringExtension();

The compiler just turns it into:

ExtensionClass.SomeStringExtension(myString);

So as you can see, there's no way to do that for static methods.

And another thing just dawned on me: what would really be the point of being able to add static methods on existing classes? You can just have your own helper class that does the same thing, so what's really the benefit in being able to do:

Bool.Parse(..)

vs.

Helper.ParseBool(..);

Doesn't really bring much to the table...

how to call url of any other website in php

use curl php library: http://php.net/manual/en/book.curl.php

direct example: CURL_EXEC:

<?php
// create a new cURL resource
$ch = curl_init();

// set URL and other appropriate options
curl_setopt($ch, CURLOPT_URL, "http://www.example.com/");
curl_setopt($ch, CURLOPT_HEADER, 0);

// grab URL and pass it to the browser
curl_exec($ch);

// close cURL resource, and free up system resources
curl_close($ch);
?>

How can I reference a commit in an issue comment on GitHub?

Answer above is missing an example which might not be obvious (it wasn't to me).

Url could be broken down into parts

https://github.com/liufa/Tuplinator/commit/f36e3c5b3aba23a6c9cf7c01e7485028a23c3811
                  \_____/\________/       \_______________________________________/
                   |        |                              |
            Account name    |                      Hash of revision
                        Project name              

Hash can be found here (you can click it and will get the url from browser).

enter image description here

Hope this saves you some time.

What is the difference between AF_INET and PF_INET in socket programming?

Checking the header file solve's the problem. One can check for there system compiler.

For my system , AF_INET == PF_INET

AF == Address Family And PF == Protocol Family

Protocol families, same as address families.

enter image description here

resource error in android studio after update: No Resource Found

First of all,

Try to check your SDK folder, for me, it was mydocuments/appdata/sdk.... etc. So basically my sdk folder was not fully downloaded, the source of this problem mainly. You have to either use another fully downloaded android sdk(including Tools section and extras that you really need) or use the eclipse sdk that you may downloaded earlier for your Eclipse android developments. Then build->clean your project once again.

Worth to try.

405 method not allowed Web API

Another possible issue which causes the same behavior is the default parameters in the routing. In my case the controller was located and instantiated correctly, but the POST was blocked because of default Get action specified:

config.Routes.MapHttpRoute(
    name: "GetAllRoute",
    routeTemplate: "api/{controller}.{ext}"/*,
    defaults: new { action = "Get" }*/ // this was causing the issue
);

How to make a DIV always float on the screen in top right corner?

Use position:fixed, as previously stated, IE6 doesn't recognize position:fixed, but with some css magic you can get IE6 to behave:

html, body {
    height: 100%;
    overflow:auto;
}
body #fixedElement {
    position:fixed !important;
    position: absolute; /*ie6 */
    bottom: 0;
}

The !important flag makes it so you don't have to use a conditional comment for IE. This will have #fixedElement use position:fixed in all browsers but IE, and in IE, position:absolute will take effect with bottom:0. This will simulate position:fixed for IE6

How do SO_REUSEADDR and SO_REUSEPORT differ?

Welcome to the wonderful world of portability... or rather the lack of it. Before we start analyzing these two options in detail and take a deeper look how different operating systems handle them, it should be noted that the BSD socket implementation is the mother of all socket implementations. Basically all other systems copied the BSD socket implementation at some point in time (or at least its interfaces) and then started evolving it on their own. Of course the BSD socket implementation was evolved as well at the same time and thus systems that copied it later got features that were lacking in systems that copied it earlier. Understanding the BSD socket implementation is the key to understanding all other socket implementations, so you should read about it even if you don't care to ever write code for a BSD system.

There are a couple of basics you should know before we look at these two options. A TCP/UDP connection is identified by a tuple of five values:

{<protocol>, <src addr>, <src port>, <dest addr>, <dest port>}

Any unique combination of these values identifies a connection. As a result, no two connections can have the same five values, otherwise the system would not be able to distinguish these connections any longer.

The protocol of a socket is set when a socket is created with the socket() function. The source address and port are set with the bind() function. The destination address and port are set with the connect() function. Since UDP is a connectionless protocol, UDP sockets can be used without connecting them. Yet it is allowed to connect them and in some cases very advantageous for your code and general application design. In connectionless mode, UDP sockets that were not explicitly bound when data is sent over them for the first time are usually automatically bound by the system, as an unbound UDP socket cannot receive any (reply) data. Same is true for an unbound TCP socket, it is automatically bound before it will be connected.

If you explicitly bind a socket, it is possible to bind it to port 0, which means "any port". Since a socket cannot really be bound to all existing ports, the system will have to choose a specific port itself in that case (usually from a predefined, OS specific range of source ports). A similar wildcard exists for the source address, which can be "any address" (0.0.0.0 in case of IPv4 and :: in case of IPv6). Unlike in case of ports, a socket can really be bound to "any address" which means "all source IP addresses of all local interfaces". If the socket is connected later on, the system has to choose a specific source IP address, since a socket cannot be connected and at the same time be bound to any local IP address. Depending on the destination address and the content of the routing table, the system will pick an appropriate source address and replace the "any" binding with a binding to the chosen source IP address.

By default, no two sockets can be bound to the same combination of source address and source port. As long as the source port is different, the source address is actually irrelevant. Binding socketA to ipA:portA and socketB to ipB:portB is always possible if ipA != ipB holds true, even when portA == portB. E.g. socketA belongs to a FTP server program and is bound to 192.168.0.1:21 and socketB belongs to another FTP server program and is bound to 10.0.0.1:21, both bindings will succeed. Keep in mind, though, that a socket may be locally bound to "any address". If a socket is bound to 0.0.0.0:21, it is bound to all existing local addresses at the same time and in that case no other socket can be bound to port 21, regardless which specific IP address it tries to bind to, as 0.0.0.0 conflicts with all existing local IP addresses.

Anything said so far is pretty much equal for all major operating system. Things start to get OS specific when address reuse comes into play. We start with BSD, since as I said above, it is the mother of all socket implementations.

BSD

SO_REUSEADDR

If SO_REUSEADDR is enabled on a socket prior to binding it, the socket can be successfully bound unless there is a conflict with another socket bound to exactly the same combination of source address and port. Now you may wonder how is that any different than before? The keyword is "exactly". SO_REUSEADDR mainly changes the way how wildcard addresses ("any IP address") are treated when searching for conflicts.

Without SO_REUSEADDR, binding socketA to 0.0.0.0:21 and then binding socketB to 192.168.0.1:21 will fail (with error EADDRINUSE), since 0.0.0.0 means "any local IP address", thus all local IP addresses are considered in use by this socket and this includes 192.168.0.1, too. With SO_REUSEADDR it will succeed, since 0.0.0.0 and 192.168.0.1 are not exactly the same address, one is a wildcard for all local addresses and the other one is a very specific local address. Note that the statement above is true regardless in which order socketA and socketB are bound; without SO_REUSEADDR it will always fail, with SO_REUSEADDR it will always succeed.

To give you a better overview, let's make a table here and list all possible combinations:

SO_REUSEADDR       socketA        socketB       Result
---------------------------------------------------------------------
  ON/OFF       192.168.0.1:21   192.168.0.1:21    Error (EADDRINUSE)
  ON/OFF       192.168.0.1:21      10.0.0.1:21    OK
  ON/OFF          10.0.0.1:21   192.168.0.1:21    OK
   OFF             0.0.0.0:21   192.168.1.0:21    Error (EADDRINUSE)
   OFF         192.168.1.0:21       0.0.0.0:21    Error (EADDRINUSE)
   ON              0.0.0.0:21   192.168.1.0:21    OK
   ON          192.168.1.0:21       0.0.0.0:21    OK
  ON/OFF           0.0.0.0:21       0.0.0.0:21    Error (EADDRINUSE)

The table above assumes that socketA has already been successfully bound to the address given for socketA, then socketB is created, either gets SO_REUSEADDR set or not, and finally is bound to the address given for socketB. Result is the result of the bind operation for socketB. If the first column says ON/OFF, the value of SO_REUSEADDR is irrelevant to the result.

Okay, SO_REUSEADDR has an effect on wildcard addresses, good to know. Yet that isn't it's only effect it has. There is another well known effect which is also the reason why most people use SO_REUSEADDR in server programs in the first place. For the other important use of this option we have to take a deeper look on how the TCP protocol works.

A socket has a send buffer and if a call to the send() function succeeds, it does not mean that the requested data has actually really been sent out, it only means the data has been added to the send buffer. For UDP sockets, the data is usually sent pretty soon, if not immediately, but for TCP sockets, there can be a relatively long delay between adding data to the send buffer and having the TCP implementation really send that data. As a result, when you close a TCP socket, there may still be pending data in the send buffer, which has not been sent yet but your code considers it as sent, since the send() call succeeded. If the TCP implementation was closing the socket immediately on your request, all of this data would be lost and your code wouldn't even know about that. TCP is said to be a reliable protocol and losing data just like that is not very reliable. That's why a socket that still has data to send will go into a state called TIME_WAIT when you close it. In that state it will wait until all pending data has been successfully sent or until a timeout is hit, in which case the socket is closed forcefully.

At most, the amount of time the kernel will wait before it closes the socket, regardless if it still has data in flight or not, is called the Linger Time. The Linger Time is globally configurable on most systems and by default rather long (two minutes is a common value you will find on many systems). It is also configurable per socket using the socket option SO_LINGER which can be used to make the timeout shorter or longer, and even to disable it completely. Disabling it completely is a very bad idea, though, since closing a TCP socket gracefully is a slightly complex process and involves sending forth and back a couple of packets (as well as resending those packets in case they got lost) and this whole close process is also limited by the Linger Time. If you disable lingering, your socket may not only lose data in flight, it is also always closed forcefully instead of gracefully, which is usually not recommended. The details about how a TCP connection is closed gracefully are beyond the scope of this answer, if you want to learn more about, I recommend you have a look at this page. And even if you disabled lingering with SO_LINGER, if your process dies without explicitly closing the socket, BSD (and possibly other systems) will linger nonetheless, ignoring what you have configured. This will happen for example if your code just calls exit() (pretty common for tiny, simple server programs) or the process is killed by a signal (which includes the possibility that it simply crashes because of an illegal memory access). So there is nothing you can do to make sure a socket will never linger under all circumstances.

The question is, how does the system treat a socket in state TIME_WAIT? If SO_REUSEADDR is not set, a socket in state TIME_WAIT is considered to still be bound to the source address and port and any attempt to bind a new socket to the same address and port will fail until the socket has really been closed, which may take as long as the configured Linger Time. So don't expect that you can rebind the source address of a socket immediately after closing it. In most cases this will fail. However, if SO_REUSEADDR is set for the socket you are trying to bind, another socket bound to the same address and port in state TIME_WAIT is simply ignored, after all its already "half dead", and your socket can bind to exactly the same address without any problem. In that case it plays no role that the other socket may have exactly the same address and port. Note that binding a socket to exactly the same address and port as a dying socket in TIME_WAIT state can have unexpected, and usually undesired, side effects in case the other socket is still "at work", but that is beyond the scope of this answer and fortunately those side effects are rather rare in practice.

There is one final thing you should know about SO_REUSEADDR. Everything written above will work as long as the socket you want to bind to has address reuse enabled. It is not necessary that the other socket, the one which is already bound or is in a TIME_WAIT state, also had this flag set when it was bound. The code that decides if the bind will succeed or fail only inspects the SO_REUSEADDR flag of the socket fed into the bind() call, for all other sockets inspected, this flag is not even looked at.

SO_REUSEPORT

SO_REUSEPORT is what most people would expect SO_REUSEADDR to be. Basically, SO_REUSEPORT allows you to bind an arbitrary number of sockets to exactly the same source address and port as long as all prior bound sockets also had SO_REUSEPORT set before they were bound. If the first socket that is bound to an address and port does not have SO_REUSEPORT set, no other socket can be bound to exactly the same address and port, regardless if this other socket has SO_REUSEPORT set or not, until the first socket releases its binding again. Unlike in case of SO_REUESADDR the code handling SO_REUSEPORT will not only verify that the currently bound socket has SO_REUSEPORT set but it will also verify that the socket with a conflicting address and port had SO_REUSEPORT set when it was bound.

SO_REUSEPORT does not imply SO_REUSEADDR. This means if a socket did not have SO_REUSEPORT set when it was bound and another socket has SO_REUSEPORT set when it is bound to exactly the same address and port, the bind fails, which is expected, but it also fails if the other socket is already dying and is in TIME_WAIT state. To be able to bind a socket to the same addresses and port as another socket in TIME_WAIT state requires either SO_REUSEADDR to be set on that socket or SO_REUSEPORT must have been set on both sockets prior to binding them. Of course it is allowed to set both, SO_REUSEPORT and SO_REUSEADDR, on a socket.

There is not much more to say about SO_REUSEPORT other than that it was added later than SO_REUSEADDR, that's why you will not find it in many socket implementations of other systems, which "forked" the BSD code before this option was added, and that there was no way to bind two sockets to exactly the same socket address in BSD prior to this option.

Connect() Returning EADDRINUSE?

Most people know that bind() may fail with the error EADDRINUSE, however, when you start playing around with address reuse, you may run into the strange situation that connect() fails with that error as well. How can this be? How can a remote address, after all that's what connect adds to a socket, be already in use? Connecting multiple sockets to exactly the same remote address has never been a problem before, so what's going wrong here?

As I said on the very top of my reply, a connection is defined by a tuple of five values, remember? And I also said, that these five values must be unique otherwise the system cannot distinguish two connections any longer, right? Well, with address reuse, you can bind two sockets of the same protocol to the same source address and port. That means three of those five values are already the same for these two sockets. If you now try to connect both of these sockets also to the same destination address and port, you would create two connected sockets, whose tuples are absolutely identical. This cannot work, at least not for TCP connections (UDP connections are no real connections anyway). If data arrived for either one of the two connections, the system could not tell which connection the data belongs to. At least the destination address or destination port must be different for either connection, so that the system has no problem to identify to which connection incoming data belongs to.

So if you bind two sockets of the same protocol to the same source address and port and try to connect them both to the same destination address and port, connect() will actually fail with the error EADDRINUSE for the second socket you try to connect, which means that a socket with an identical tuple of five values is already connected.

Multicast Addresses

Most people ignore the fact that multicast addresses exist, but they do exist. While unicast addresses are used for one-to-one communication, multicast addresses are used for one-to-many communication. Most people got aware of multicast addresses when they learned about IPv6 but multicast addresses also existed in IPv4, even though this feature was never widely used on the public Internet.

The meaning of SO_REUSEADDR changes for multicast addresses as it allows multiple sockets to be bound to exactly the same combination of source multicast address and port. In other words, for multicast addresses SO_REUSEADDR behaves exactly as SO_REUSEPORT for unicast addresses. Actually, the code treats SO_REUSEADDR and SO_REUSEPORT identically for multicast addresses, that means you could say that SO_REUSEADDR implies SO_REUSEPORT for all multicast addresses and the other way round.


FreeBSD/OpenBSD/NetBSD

All these are rather late forks of the original BSD code, that's why they all three offer the same options as BSD and they also behave the same way as in BSD.


macOS (MacOS X)

At its core, macOS is simply a BSD-style UNIX named "Darwin", based on a rather late fork of the BSD code (BSD 4.3), which was then later on even re-synchronized with the (at that time current) FreeBSD 5 code base for the Mac OS 10.3 release, so that Apple could gain full POSIX compliance (macOS is POSIX certified). Despite having a microkernel at its core ("Mach"), the rest of the kernel ("XNU") is basically just a BSD kernel, and that's why macOS offers the same options as BSD and they also behave the same way as in BSD.

iOS / watchOS / tvOS

iOS is just a macOS fork with a slightly modified and trimmed kernel, somewhat stripped down user space toolset and a slightly different default framework set. watchOS and tvOS are iOS forks, that are stripped down even further (especially watchOS). To my best knowledge they all behave exactly as macOS does.


Linux

Linux < 3.9

Prior to Linux 3.9, only the option SO_REUSEADDR existed. This option behaves generally the same as in BSD with two important exceptions:

  1. As long as a listening (server) TCP socket is bound to a specific port, the SO_REUSEADDR option is entirely ignored for all sockets targeting that port. Binding a second socket to the same port is only possible if it was also possible in BSD without having SO_REUSEADDR set. E.g. you cannot bind to a wildcard address and then to a more specific one or the other way round, both is possible in BSD if you set SO_REUSEADDR. What you can do is you can bind to the same port and two different non-wildcard addresses, as that's always allowed. In this aspect Linux is more restrictive than BSD.

  2. The second exception is that for client sockets, this option behaves exactly like SO_REUSEPORT in BSD, as long as both had this flag set before they were bound. The reason for allowing that was simply that it is important to be able to bind multiple sockets to exactly to the same UDP socket address for various protocols and as there used to be no SO_REUSEPORT prior to 3.9, the behavior of SO_REUSEADDR was altered accordingly to fill that gap. In that aspect Linux is less restrictive than BSD.

Linux >= 3.9

Linux 3.9 added the option SO_REUSEPORT to Linux as well. This option behaves exactly like the option in BSD and allows binding to exactly the same address and port number as long as all sockets have this option set prior to binding them.

Yet, there are still two differences to SO_REUSEPORT on other systems:

  1. To prevent "port hijacking", there is one special limitation: All sockets that want to share the same address and port combination must belong to processes that share the same effective user ID! So one user cannot "steal" ports of another user. This is some special magic to somewhat compensate for the missing SO_EXCLBIND/SO_EXCLUSIVEADDRUSE flags.

  2. Additionally the kernel performs some "special magic" for SO_REUSEPORT sockets that isn't found in other operating systems: For UDP sockets, it tries to distribute datagrams evenly, for TCP listening sockets, it tries to distribute incoming connect requests (those accepted by calling accept()) evenly across all the sockets that share the same address and port combination. Thus an application can easily open the same port in multiple child processes and then use SO_REUSEPORT to get a very inexpensive load balancing.


Android

Even though the whole Android system is somewhat different from most Linux distributions, at its core works a slightly modified Linux kernel, thus everything that applies to Linux should apply to Android as well.


Windows

Windows only knows the SO_REUSEADDR option, there is no SO_REUSEPORT. Setting SO_REUSEADDR on a socket in Windows behaves like setting SO_REUSEPORT and SO_REUSEADDR on a socket in BSD, with one exception:

Prior to Windows 2003, a socket with SO_REUSEADDR could always been bound to exactly the same source address and port as an already bound socket, even if the other socket did not have this option set when it was bound. This behavior allowed an application "to steal" the connected port of another application. Needless to say that this has major security implications!

Microsoft realized that and added another important socket option: SO_EXCLUSIVEADDRUSE. Setting SO_EXCLUSIVEADDRUSE on a socket makes sure that if the binding succeeds, the combination of source address and port is owned exclusively by this socket and no other socket can bind to them, not even if it has SO_REUSEADDR set.

This default behavior was changed first in Windows 2003, Microsoft calls that "Enhanced Socket Security" (funny name for a behavior that is default on all other major operating systems). For more details just visit this page. There are three tables: The first one shows the classic behavior (still in use when using compatibility modes!), the second one shows the behavior of Windows 2003 and up when the bind() calls are made by the same user, and the third one when the bind() calls are made by different users.


Solaris

Solaris is the successor of SunOS. SunOS was originally based on a fork of BSD, SunOS 5 and later was based on a fork of SVR4, however SVR4 is a merge of BSD, System V, and Xenix, so up to some degree Solaris is also a BSD fork, and a rather early one. As a result Solaris only knows SO_REUSEADDR, there is no SO_REUSEPORT. The SO_REUSEADDR behaves pretty much the same as it does in BSD. As far as I know there is no way to get the same behavior as SO_REUSEPORT in Solaris, that means it is not possible to bind two sockets to exactly the same address and port.

Similar to Windows, Solaris has an option to give a socket an exclusive binding. This option is named SO_EXCLBIND. If this option is set on a socket prior to binding it, setting SO_REUSEADDR on another socket has no effect if the two sockets are tested for an address conflict. E.g. if socketA is bound to a wildcard address and socketB has SO_REUSEADDR enabled and is bound to a non-wildcard address and the same port as socketA, this bind will normally succeed, unless socketA had SO_EXCLBIND enabled, in which case it will fail regardless the SO_REUSEADDR flag of socketB.


Other Systems

In case your system is not listed above, I wrote a little test program that you can use to find out how your system handles these two options. Also if you think my results are wrong, please first run that program before posting any comments and possibly making false claims.

All that the code requires to build is a bit POSIX API (for the network parts) and a C99 compiler (actually most non-C99 compiler will work as well as long as they offer inttypes.h and stdbool.h; e.g. gcc supported both long before offering full C99 support).

All that the program needs to run is that at least one interface in your system (other than the local interface) has an IP address assigned and that a default route is set which uses that interface. The program will gather that IP address and use it as the second "specific address".

It tests all possible combinations you can think of:

  • TCP and UDP protocol
  • Normal sockets, listen (server) sockets, multicast sockets
  • SO_REUSEADDR set on socket1, socket2, or both sockets
  • SO_REUSEPORT set on socket1, socket2, or both sockets
  • All address combinations you can make out of 0.0.0.0 (wildcard), 127.0.0.1 (specific address), and the second specific address found at your primary interface (for multicast it's just 224.1.2.3 in all tests)

and prints the results in a nice table. It will also work on systems that don't know SO_REUSEPORT, in which case this option is simply not tested.

What the program cannot easily test is how SO_REUSEADDR acts on sockets in TIME_WAIT state as it's very tricky to force and keep a socket in that state. Fortunately most operating systems seems to simply behave like BSD here and most of the time programmers can simply ignore the existence of that state.

Here's the code (I cannot include it here, answers have a size limit and the code would push this reply over the limit).

How do I select child elements of any depth using XPath?

You're almost there. Simply use:

//form[@id='myform']//input[@type='submit']

The // shortcut can also be used inside an expression.

how to use free cloud database with android app?

Now there are a lot of cloud providers , providing solutions like MBaaS (Mobile Backend as a Service). Some only give access to cloud database, some will do the user management for you, some let you place code around cloud database and there are facilities of access control, push notifications, analytics, integrated image and file hosting etc.

Here are some providers which have a "free-tier" (may change in future):

  1. Firebase (Google) - https://firebase.google.com/
  2. AWS Mobile (Amazon) - https://aws.amazon.com/mobile/
  3. Azure Mobile (Microsoft) - https://azure.microsoft.com/en-in/services/app-service/mobile/
  4. MongoDB Realm (MongoDB) - https://www.mongodb.com/realm
  5. Back4app (Popular) - https://www.back4app.com/

Open source solutions:

  1. Parse - http://parseplatform.org/
  2. Apache User Grid - https://usergrid.apache.org/
  3. SupaBase (under development) - https://supabase.io/

"Warning: iPhone apps should include an armv6 architecture" even with build config set

An ios 6 update

Changes in Xcode 4.5.x for ios 6

  1. Xcode 4.5.x (and later) does not support generating armv6 binaries.
  2. Now includes iPhone 5/armv7s support.
  3. The minimum supported deployment target with Xcode 4.5.x or later is iOS 4.3.

MVC3 DropDownListFor - a simple example?

I think this will help : In Controller get the list items and selected value

public ActionResult Edit(int id)
{
    ItemsStore item = itemStoreRepository.FindById(id);
    ViewBag.CategoryId = new SelectList(categoryRepository.Query().Get(), 
                                        "Id", "Name",item.CategoryId);

    // ViewBag to pass values to View and SelectList
    //(get list of items,valuefield,textfield,selectedValue)

    return View(item);
}

and in View

@Html.DropDownList("CategoryId",String.Empty)

How to assert two list contain the same elements in Python?

As of Python 3.2 unittest.TestCase.assertItemsEqual(doc) has been replaced by unittest.TestCase.assertCountEqual(doc) which does exactly what you are looking for, as you can read from the python standard library documentation. The method is somewhat misleadingly named but it does exactly what you are looking for.

a and b have the same elements in the same number, regardless of their order

Here a simple example which compares two lists having the same elements but in a different order.

  • using assertCountEqual the test will succeed
  • using assertListEqual the test will fail due to the order difference of the two lists

Here a little example script.

import unittest


class TestListElements(unittest.TestCase):
    def setUp(self):
        self.expected = ['foo', 'bar', 'baz']
        self.result = ['baz', 'foo', 'bar']

    def test_count_eq(self):
        """Will succeed"""
        self.assertCountEqual(self.result, self.expected)

    def test_list_eq(self):
        """Will fail"""
        self.assertListEqual(self.result, self.expected)

if __name__ == "__main__":
    unittest.main()

Side Note : Please make sure that the elements in the lists you are comparing are sortable.

WPF MVVM: How to close a window

For small apps, I use my own Application Controller for showing, closing and disposing windows and DataContexts. It's a central point in UI of an application.

It's something like this:

//It is singleton, I will just post 2 methods and their invocations
public void ShowNewWindow(Window window, object dataContext = null, bool dialog = true)
{
    window.DataContext = dataContext;
    addToWindowRegistry(dataContext, window);

    if (dialog)
        window.ShowDialog();
    else
        window.Show();

}

public void CloseWindow(object dataContextSender)
{
    var correspondingWindows = windowRegistry.Where(c => c.DataContext.Equals(dataContextSender)).ToList();
    foreach (var pair in correspondingWindows)
    {
        pair.Window.Close();              
    }
}

and their invocations from ViewModels:

// Show new Window with DataContext
ApplicationController.Instance.ShowNewWindow(
                new ClientCardsWindow(),
                new ClientCardsVM(),
                false);

// Close Current Window from viewModel
ApplicationController.Instance.CloseWindow(this);

Of course you can find some restrictions in my solution. Again: I use it for small projects, and it's enough. If you're interested, I can post full code here or somewhere else/

Difference between staticmethod and classmethod

tldr;

A staticmethod is essentially a function bound to a class (and consequently its instances)

A classmethod is essentially an inheritable staticmethod.

For details, see the excellent answers by others.

adb shell su works but adb root does not

You need to replace the adbd binary in the boot.img/sbin/ folder to one that is su capable. You will also have to make some default.prop edits too.

Samsung seems to make this more difficult than other vendors. I have some adbd binaries you can try but it will require the knowledge of de-compiling and re-compiling the boot.img with the new binary. Also, if you have a locked bootloader... this is not gonna happen.

Also Chainfire has an app that will grant adbd root permission in the play store: https://play.google.com/store/apps/details?id=eu.chainfire.adbd&hl=en

Lastly, if you are trying to write a windows script with SU permissions you can do this buy using the following command style... However, you will at least need to grant (on the phone) SU permissions the frist time its ran...

adb shell "su -c ls" <-list working directory with su rights. adb shell "su -c echo anytext > /data/test.file"

These are just some examples. If you state specifically what you are trying to accomplish I may be able to give more specific advice

-scosler

Python to print out status bar and percentage

As described in Mark Rushakoff's solution, you can output the carriage return character, sys.stdout.write('\r'), to reset the cursor to the beginning of the line. To generalize that solution, while also implementing Python 3's f-Strings, you could use

from time import sleep
import sys

n_bar = 50
iterable = range(33)  # for demo purposes
n_iter = len(iterable)
for i, item in enumerate(iterable):
    j = (i + 1) / n_iter

    sys.stdout.write('\r')
    sys.stdout.write(f"[{'=' * int(n_bar * j):{n_bar}s}] {int(100 * j)}%")
    sys.stdout.flush()

    sleep(0.05)  
    # do something with <item> here

Python: Writing to and Reading from serial port

a piece of code who work with python to read rs232 just in case somedoby else need it

ser = serial.Serial('/dev/tty.usbserial', 9600, timeout=0.5)
ser.write('*99C\r\n')
time.sleep(0.1)
ser.close()

no sqljdbc_auth in java.library.path

For easy fix follow these steps:

  1. goto: https://docs.microsoft.com/en-us/sql/connect/jdbc/building-the-connection-url#Connectingintegrated
  2. Download the JDBC file and extract to your preferred location
  3. open the auth folder matching your OS x64 or x86
  4. copy sqljdbc_auth.dll file
  5. paste in: C:\Program Files\Java\jdk_version\bin
  6. restart either eclipse or netbeans

SQL query for getting data for last 3 months

Last 3 months

SELECT DATEADD(dd,DATEDIFF(dd,0,DATEADD(mm,-3,GETDATE())),0)

Today

SELECT DATEADD(dd,DATEDIFF(dd,0,GETDATE()),0)

What is the difference between g++ and gcc?

What is the difference between g++ and gcc?

gcc has evolved from a single language "GNU C Compiler" to be a multi-language "GNU Compiler Collection". The term "GNU C Compiler" is still used sometimes in the context of C programming.

The g++ is the C++ compiler for the GNU Compiler Collection. Like gnat is the Ada compiler for gcc. see Using the GNU Compiler Collection (GCC)

For example, the Ubuntu 16.04 and 18.04 man g++ command returns the GCC(1) manual page.

The Ubuntu 16.04 and 18.04 man gcc states that ...

g++ accepts mostly the same options as gcc

and that the default ...

... use of gcc does not add the C++ library. g++ is a program that calls GCC and automatically specifies linking against the C++ library. It treats .c, .h and .i files as C++ source files instead of C source files unless -x is used. This program is also useful when precompiling a C header file with a .h extension for use in C++ compilations.

Search the gcc man pages for more details on the option variances between gcc and g++.

Which one should be used for general c++ development?

Technically, either gcc or g++ can be used for general C++ development with applicable option settings. However, the g++ default behavior is naturally aligned to a C++ development.

The Ubuntu 18.04 'gcc' man page added, and Ubuntu 20.04 continues to have, the following paragraph:

The usual way to run GCC is to run the executable called gcc, or machine-gcc when cross-compiling, or machine-gcc-version to run a specific version of GCC. When you compile C++ programs, you should invoke GCC as g++ instead.

Change default icon

Your application icon shows in the taskbar. The icon on the topleft (window) is the form-icon. Go to your form and fill the property "icon" with the same icon; problem solved. You don't need to put the icon in the outputfolder (that's just for setups).

UPDATE with CASE and IN - Oracle

You said that budgetpost is alphanumeric. That means it is looking for comparisons against strings. You should try enclosing your parameters in single quotes (and you are missing the final THEN in the Case expression).

UPDATE tab1   
SET budgpost_gr1=   CASE  
                        WHEN (budgpost in ('1001','1012','50055'))  THEN 'BP_GR_A'   
                        WHEN (budgpost in ('5','10','98','0'))  THEN 'BP_GR_B'  
                        WHEN (budgpost in ('11','876','7976','67465')) THEN 'What?'
                        ELSE 'Missing' 
                        END 

Html5 Full screen video

You can use html5 video player which has full screen playback option. This is a very good html5 player to have a look.
http://sublimevideo.net/

jQuery .attr("disabled", "disabled") not working in Chrome

For me, none of these answers worked, but I finally found one that did.

I needed this for IE-

$('input:text').attr("disabled", 'disabled');

I also had to add this for Chrome and Firefox -

$('input:text').AddClass("notactive");

and this -

<style type="text/css">
    .notactive {
        pointer-events: none;
        cursor: default;
    }
 </style>

What requests do browsers' "F5" and "Ctrl + F5" refreshes generate?

It is up to the browser but they behave in similar ways.

I have tested FF, IE7, Opera and Chrome.

F5 usually updates the page only if it is modified. The browser usually tries to use all types of cache as much as possible and adds an "If-modified-since" header to the request. Opera differs by sending a "Cache-Control: no-cache".

CTRL-F5 is used to force an update, disregarding any cache. IE7 adds an "Cache-Control: no-cache", as does FF, which also adds "Pragma: no-cache". Chrome does a normal "If-modified-since" and Opera ignores the key.

If I remember correctly it was Netscape which was the first browser to add support for cache-control by adding "Pragma: No-cache" when you pressed CTRL-F5.

Edit: Updated table

The table below is updated with information on what will happen when the browser's refresh-button is clicked (after a request by Joel Coehoorn), and the "max-age=0" Cache-control-header.

Updated table, 27 September 2010

+------------------------------------------------------------+
¦  UPDATED   ¦                Firefox 3.x                    ¦
¦27 SEP 2010 ¦  +--------------------------------------------¦
¦            ¦  ¦             MSIE 8, 7                      ¦
¦ Version 3  ¦  ¦  +-----------------------------------------¦
¦            ¦  ¦  ¦          Chrome 6.0                     ¦
¦            ¦  ¦  ¦  +--------------------------------------¦
¦            ¦  ¦  ¦  ¦       Chrome 1.0                     ¦
¦            ¦  ¦  ¦  ¦  +-----------------------------------¦
¦            ¦  ¦  ¦  ¦  ¦    Opera 10, 9                    ¦
¦            ¦  ¦  ¦  ¦  ¦  +--------------------------------¦
¦            ¦  ¦  ¦  ¦  ¦  ¦                                ¦
+------------+--+--+--+--+--+--------------------------------¦
¦          F5¦IM¦I ¦IM¦IM¦C ¦                                ¦
¦    SHIFT-F5¦- ¦- ¦CP¦IM¦- ¦ Legend:                        ¦
¦     CTRL-F5¦CP¦C ¦CP¦IM¦- ¦ I = "If-Modified-Since"        ¦
¦      ALT-F5¦- ¦- ¦- ¦- ¦*2¦ P = "Pragma: No-cache"         ¦
¦    ALTGR-F5¦- ¦I ¦- ¦- ¦- ¦ C = "Cache-Control: no-cache"  ¦
+------------+--+--+--+--+--¦ M = "Cache-Control: max-age=0" ¦
¦      CTRL-R¦IM¦I ¦IM¦IM¦C ¦ - = ignored                    ¦
¦CTRL-SHIFT-R¦CP¦- ¦CP¦- ¦- ¦                                ¦
+------------+--+--+--+--+--¦                                ¦
¦       Click¦IM¦I ¦IM¦IM¦C ¦ With 'click' I refer to a      ¦
¦ Shift-Click¦CP¦I ¦CP¦IM¦C ¦ mouse click on the browsers    ¦
¦  Ctrl-Click¦*1¦C ¦CP¦IM¦C ¦ refresh-icon.                  ¦
¦   Alt-Click¦IM¦I ¦IM¦IM¦C ¦                                ¦
¦ AltGr-Click¦IM¦I ¦- ¦IM¦- ¦                                ¦
+------------------------------------------------------------+

Versions tested:

  • Firefox 3.1.6 and 3.0.6 (WINXP)
  • MSIE 8.0.6001 and 7.0.5730.11 (WINXP)
  • Chrome 6.0.472.63 and 1.0.151.48 (WINXP)
  • Opera 10.62 and 9.61 (WINXP)

Notes:

  1. Version 3.0.6 sends I and C, but 3.1.6 opens the page in a new tab, making a normal request with only "I".

  2. Version 10.62 does nothing. 9.61 might do C unless it was a typo in my old table.

Note about Chrome 6.0.472: If you do a forced reload (like CTRL-F5) it behaves like the url is internally marked to always do a forced reload. The flag is cleared if you go to the address bar and press enter.

How to set image on QPushButton?

You can do this in QtDesigner. Just click on your button then go to icon property and then choose your image file.

Difference between Ctrl+Shift+F and Ctrl+I in Eclipse

Reformat affects the whole source code and may rebreak your lines, while Correct Indentation only affects the whitespace at the beginning of the lines.

Download File Using Javascript/jQuery

These functions are used in stacktrace.js:

/**
 * Try XHR methods in order and store XHR factory.
 *
 * @return <Function> XHR function or equivalent
 */
var createXMLHTTPObject = function() {
    var xmlhttp, XMLHttpFactories = [
        function() {
            return new XMLHttpRequest();
        }, function() {
            return new ActiveXObject('Msxml2.XMLHTTP');
        }, function() {
            return new ActiveXObject('Msxml3.XMLHTTP');
        }, function() {
            return new ActiveXObject('Microsoft.XMLHTTP');
        }
    ];
    for (var i = 0; i < XMLHttpFactories.length; i++) {
        try {
            xmlhttp = XMLHttpFactories[i]();
            // Use memoization to cache the factory
            createXMLHTTPObject = XMLHttpFactories[i];
            return xmlhttp;
        } catch (e) {
        }
    }
}

/**
 * @return the text from a given URL
 */
function ajax(url) {
    var req = createXMLHTTPObject();
    if (req) {
        try {
            req.open('GET', url, false);
            req.send(null);
            return req.responseText;
        } catch (e) {
        }
    }
    return '';
}

convert string array to string

string[] test = new string[2];

test[0] = "Hello ";
test[1] = "World!";

string.Join("", test);

FIFO class in Java

You're looking for any class that implements the Queue interface, excluding PriorityQueue and PriorityBlockingQueue, which do not use a FIFO algorithm.

Probably a LinkedList using add (adds one to the end) and removeFirst (removes one from the front and returns it) is the easiest one to use.

For example, here's a program that uses a LinkedList to queue and retrieve the digits of PI:

import java.util.LinkedList;

class Test {
    public static void main(String args[]) {
        char arr[] = {3,1,4,1,5,9,2,6,5,3,5,8,9};
        LinkedList<Integer> fifo = new LinkedList<Integer>();

        for (int i = 0; i < arr.length; i++)
            fifo.add (new Integer (arr[i]));

        System.out.print (fifo.removeFirst() + ".");
        while (! fifo.isEmpty())
            System.out.print (fifo.removeFirst());
        System.out.println();
    }
} 

Alternatively, if you know you only want to treat it as a queue (without the extra features of a linked list), you can just use the Queue interface itself:

import java.util.LinkedList;
import java.util.Queue;

class Test {
    public static void main(String args[]) {
        char arr[] = {3,1,4,1,5,9,2,6,5,3,5,8,9};
        Queue<Integer> fifo = new LinkedList<Integer>();

        for (int i = 0; i < arr.length; i++)
            fifo.add (new Integer (arr[i]));

        System.out.print (fifo.remove() + ".");
        while (! fifo.isEmpty())
            System.out.print (fifo.remove());
        System.out.println();
    }
}

This has the advantage of allowing you to replace the underlying concrete class with any class that provides the Queue interface, without having to change the code too much.

The basic changes are to change the type of fifo to a Queue and to use remove() instead of removeFirst(), the latter being unavailable for the Queue interface.

Calling isEmpty() is still okay since that belongs to the Collection interface of which Queue is a derivative.

Regular expression to match any character being repeated more than 10 times

A slightly more generic powershell example. In powershell 7, the match is highlighted including the last space (can you highlight in stack?).

'a b c d e f ' | select-string '([a-f] ){6,}'

a b c d e f 

How can I rollback a git repository to a specific commit?

Another way:

Checkout the branch you want to revert, then reset your local working copy back to the commit that you want to be the latest one on the remote server (everything after it will go bye-bye). To do this, in SourceTree, I right-clicked on the and selected "Reset BRANCHNAME to this commit".

Then navigate to your repository's local directory and run this command:

git -c diff.mnemonicprefix=false -c core.quotepath=false push -v -f -- tags REPOSITORY_NAME BRANCHNAME:BRANCHNAME 

This will erase all commits after the current one in your local repository but only for that one branch.

How to specify the bottom border of a <tr>?

What I want to say here is like some kind of add-on on @Suciu Lucian's answer.

The weird situation I ran into is that when I apply the solution of @Suciu Lucian in my file, it works in Chrome but not in Safari (and did not try in Firefox). After I studied the guide of styling table border published by w3.org, I found something alternative:

table.myTable{
  border-spacing: 0;
}

table.myTable td{
  border-bottom:1px solid red;
}

Yes you have to style the td instead of the tr.

How to check if directory exists in %PATH%?

You can also use substring replacement to test for the presence of a substring. Here I remove quotes to create PATH_NQ, then I remove "c:\mydir" from the PATH_NQ and compare it to the original to see if anything changed:

set PATH_NQ=%PATH:"=%
if not "%PATH_NQ%"=="%PATH_NQ:c:\mydir=%" goto already_in_path
set PATH=%PATH%;c:\mydir
:already_in_path

SQL server stored procedure return a table

Here's an example of a SP that both returns a table and a return value. I don't know if you need the return the "Return Value" and I have no idea about MATLAB and what it requires.

CREATE PROCEDURE test
AS 
BEGIN

    SELECT * FROM sys.databases

    RETURN 27
END

--Use this to test
DECLARE @returnval int

EXEC @returnval = test 

SELECT @returnval

How to split a string with angularJS

You can try something like this:

$scope.test = "test1,test2";
{{test.split(',')[0]}}

now you will get "test1" while you try {{test.split(',')[0]}}

and you will get "test2" while you try {{test.split(',')[1]}}

here is my plnkr:

http://plnkr.co/edit/jaXOrZX9UO9kmdRMImdN?p=preview

input() error - NameError: name '...' is not defined

Good contributions the previous ones.

import sys; print(sys.version)

def ingreso(nombre):
    print('Hi ', nombre, type(nombre))

def bienvenida(nombre):
    print("Hi "+nombre+", bye ")

nombre = raw_input("Enter your name: ")

ingreso(nombre)
bienvenida(nombre)

#Works in Python 2 and 3:
try: input = raw_input
except NameError: pass
print(input("Your name: "))
Enter your name: Joe
('Hi ', 'Joe', <type 'str'>)
Hi Joe, bye 

Your name: Joe
Joe

Thanks!

How to sort an array of ints using a custom comparator?

By transforming your int array into an Integer one and then using public static <T> void Arrays.sort(T[] a, Comparator<? super T> c) (the first step is only needed as I fear autoboxing may bot work on arrays).

Mocking HttpClient in unit tests

One alternative would be to setup a stub HTTP server that returns canned responses based on pattern matching the request url, meaning you test real HTTP requests not mocks. Historically this would have taken significant develoment effort and would have been far to slow to be considered for unit testing, however OSS library WireMock.net is easy to use and fast enough to be run with lots of tests so may be worth considering. Setup is a few lines of code:

var server = FluentMockServer.Start();
server.Given(
      Request.Create()
      .WithPath("/some/thing").UsingGet()
   )
   .RespondWith(
       Response.Create()
       .WithStatusCode(200)
       .WithHeader("Content-Type", "application/json")
       .WithBody("{'attr':'value'}")
   );

You can find a more details and guidance on using wiremock in tests here.

How to get the last characters in a String in Java, regardless of String size

E.g : "abcd: efg: 1006746" "bhddy: nshhf36: 1006754" "hfquv: nd: 5894254"

-Step 1: String firstString = "abcd: efg: 1006746";

-Step 2: String lastSevenNumber = firstString.substring(firstString.lastIndexOf(':'), firstString.length()).trim();

Paste Excel range in Outlook

Often this question is asked in the context of Ron de Bruin's RangeToHTML function, which creates an HTML PublishObject from an Excel.Range, extracts that via FSO, and inserts the resulting stream HTML in to the email's HTMLBody. In doing so, this removes the default signature (the RangeToHTML function has a helper function GetBoiler which attempts to insert the default signature).

Unfortunately, the poorly-documented Application.CommandBars method is not available via Outlook:

wdDoc.Application.CommandBars.ExecuteMso "PasteExcelTableSourceFormatting"

It will raise a runtime 6158:

enter image description here

But we can still leverage the Word.Document which is accessible via the MailItem.GetInspector method, we can do something like this to copy & paste the selection from Excel to the Outlook email body, preserving your default signature (if there is one).

Dim rng as Range
Set rng = Range("A1:F10") 'Modify as needed

With OutMail
    .To = "[email protected]"
    .BCC = ""
    .Subject = "Subject"
    .Display
    Dim wdDoc As Object     '## Word.Document
    Dim wdRange As Object   '## Word.Range
    Set wdDoc = OutMail.GetInspector.WordEditor
    Set wdRange = wdDoc.Range(0, 0)
    wdRange.InsertAfter vbCrLf & vbCrLf
    'Copy the range in-place
    rng.Copy
    wdRange.Paste
End With

Note that in some cases this may not perfectly preserve the column widths or in some instances the row heights, and while it will also copy shapes and other objects in the Excel range, this may also cause some funky alignment issues, but for simple tables and Excel ranges, it is very good:

enter image description here

Simple example of threading in C++

#include <thread>
#include <iostream>
#include <vector>
using namespace std;

void doSomething(int id) {
    cout << id << "\n";
}

/**
 * Spawns n threads
 */
void spawnThreads(int n)
{
    std::vector<thread> threads(n);
    // spawn n threads:
    for (int i = 0; i < n; i++) {
        threads[i] = thread(doSomething, i + 1);
    }

    for (auto& th : threads) {
        th.join();
    }
}

int main()
{
    spawnThreads(10);
}

angularjs to output plain text instead of html

You want to use the built-in browser HTML strip for that instead of applying yourself a regexp. It is more secure since the ever green browser does the work for you.

angular.module('myApp.filters', []).
  filter('htmlToPlaintext', function() {
    return function(text) {
      return stripHtml(text);
    };
  }
);

var stripHtml = (function () {
  var tmpEl = $document[0].createElement("DIV");
  function strip(html) {
    if (!html) {
      return "";
    }
    tmpEl.innerHTML = html;
    return tmpEl.textContent || tmpEl.innerText || "";
  }
  return strip;
}());

The reason for wrapping it in an self-executing function is for reusing the element creation.

javascript regular expression to not match a word

This can be done in 2 ways:

if (str.match(/abc|def/)) {
                       ...
                    }


if (/abc|def/.test(str)) {
                        ....
                    } 

Very Simple Image Slider/Slideshow with left and right button. No autoplay

Very simple code to make jquery slider Here is two div first is the slider viewer and second is the image list container. Just copy paste the code and customise with css.

    <div class="featured-image" style="height:300px">
     <img id="thumbnail" src="01.jpg"/>
    </div>

    <div class="post-margin" style="margin:10px 0px; padding:0px;" id="thumblist">
    <img src='01.jpg'>
    <img src='02.jpg'>
    <img src='03.jpg'>
    <img src='04.jpg'>
    </div>

    <script type="text/javascript">
            function changeThumbnail()
            {
            $("#thumbnail").fadeOut(200);
            var path=$("#thumbnail").attr('src');
            var arr= new Array(); var i=0;
            $("#thumblist img").each(function(index, element) {
               arr[i]=$(this).attr('src');
               i++;
            });
            var index= arr.indexOf(path);
            if(index==(arr.length-1))
            path=arr[0];
            else
            path=arr[index+1];
            $("#thumbnail").attr('src',path).fadeIn(200);
            setTimeout(changeThumbnail, 5000);  
            }
            setTimeout(changeThumbnail, 5000);
    </script>

new Date() is working in Chrome but not Firefox

One situation I've run into was when dealing with milliseconds. FF and IE will not parse this date string correctly when trying to create a new date. "2014/11/24 17:38:20.177Z" They do not know how to handle .177Z. Chrome will work though.

JavaScript string with new line - but not using \n

The reason it is not working is because javascript strings must be terminated before the next newline character (not a \n obviously). The reason \n exists is to allow developers an easy way to put the newline character (ASCII: 10) into their strings.

When you have a string which looks like this:

//Note lack of terminating double quote
var foo = "Bob 

Your code will have a syntax error at that point and cease to run.

If you wish to have a string which spans multiple lines, you may insert a backslash character '\' just before you terminate the line, like so:

//Perfectly valid code
var foo = "Bob \
is \
cool.";

However that string will not contain \n characters in the positions where the string was broken into separate lines. The only way to insert a newline into a string is to insert a character with a value of 10, the easiest way of which is the \n escape character.

var foo = "Bob\nis\ncool.";

How to set label size in Bootstrap

You'll have to do 2 things to make a Bootstrap label (or anything really) adjust sizes based on screen size:

  • Use a media query per display size range to adjust the CSS.
  • Override CSS sizing set by Bootstrap. You do this by making your CSS rules more specific than Bootstrap's. By default, Bootstrap sets .label { font-size: 75% }. So any extra selector on your CSS rule will make it more specific.

Here's an example CSS listing to accomplish what you are asking, using the default 4 sizes in Bootstrap:

@media (max-width: 767) {
    /* your custom css class on a parent will increase specificity */
    /* so this rule will override Bootstrap's font size setting */
    .autosized .label { font-size: 14px; }
}

@media (min-width: 768px) and (max-width: 991px) {
    .autosized .label { font-size: 16px; }
}

@media (min-width: 992px) and (max-width: 1199px) {
    .autosized .label { font-size: 18px; }
}

@media (min-width: 1200px) {
    .autosized .label { font-size: 20px; }
}

Here is how it could be used in the HTML:

<!-- any ancestor could be set to autosized -->
<div class="autosized">
    ...
        ...
            <span class="label label-primary">Label 1</span>
</div>

Select single item from a list

You can use IEnumerable.First() or IEnumerable.FirstOrDefault().

The difference is that First() will throw if no element is found (or if no element matches the conditions, if you use the conditions). FirstOrDefault() will return default(T) (null if it's a reference type).

Parsing CSV / tab-delimited txt file with Python

Start by turning the text into a list of lists. That will take care of the parsing part:

lol = list(csv.reader(open('text.txt', 'rb'), delimiter='\t'))

The rest can be done with indexed lookups:

d = dict()
key = lol[6][0]      # cell A7
value = lol[6][3]    # cell D7
d[key] = value       # add the entry to the dictionary
 ...

Angular.js vs Knockout.js vs Backbone.js

It depends on the nature of your application. And, since you did not describe it in great detail, it is an impossible question to answer. I find Backbone to be the easiest, but I work in Angular all day. Performance is more up to the coder than the framework, in my opinion.

Are you doing heavy DOM manipulation? I would use jQuery and Backbone.

Very data driven app? Angular with its nice data binding.

Game programming? None - direct to canvas; maybe a game engine.

How to list imported modules?

If you want to do this from outside the script:

Python 2

from modulefinder import ModuleFinder
finder = ModuleFinder()
finder.run_script("myscript.py")
for name, mod in finder.modules.iteritems():
    print name

Python 3

from modulefinder import ModuleFinder
finder = ModuleFinder()
finder.run_script("myscript.py")
for name, mod in finder.modules.items():
    print(name)

This will print all modules loaded by myscript.py.

How to get input textfield values when enter key is pressed in react js?

Use onKeyDown event, and inside that check the key code of the key pressed by user. Key code of Enter key is 13, check the code and put the logic there.

Check this example:

_x000D_
_x000D_
class CartridgeShell extends React.Component {_x000D_
_x000D_
   constructor(props) {_x000D_
      super(props);_x000D_
      this.state = {value:''}_x000D_
_x000D_
      this.handleChange = this.handleChange.bind(this);_x000D_
      this.keyPress = this.keyPress.bind(this);_x000D_
   } _x000D_
 _x000D_
   handleChange(e) {_x000D_
      this.setState({ value: e.target.value });_x000D_
   }_x000D_
_x000D_
   keyPress(e){_x000D_
      if(e.keyCode == 13){_x000D_
         console.log('value', e.target.value);_x000D_
         // put the login here_x000D_
      }_x000D_
   }_x000D_
_x000D_
   render(){_x000D_
      return(_x000D_
         <input value={this.state.value} onKeyDown={this.keyPress} onChange={this.handleChange} fullWidth={true} />_x000D_
      )_x000D_
    }_x000D_
}_x000D_
_x000D_
ReactDOM.render(<CartridgeShell/>, document.getElementById('app'))
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>_x000D_
_x000D_
_x000D_
<div id = 'app' />
_x000D_
_x000D_
_x000D_

Note: Replace the input element by Material-Ui TextField and define the other properties also.

How to get the selected radio button’s value?

Here is an Example for Radios where no Checked="checked" attribute is used

function test() {
var radios = document.getElementsByName("radiotest");
var found = 1;
for (var i = 0; i < radios.length; i++) {       
    if (radios[i].checked) {
        alert(radios[i].value);
        found = 0;
        break;
    }
}
   if(found == 1)
   {
     alert("Please Select Radio");
   }    
}

DEMO : http://jsfiddle.net/ipsjolly/hgdWp/2/ [Click Find without selecting any Radio]

Source : http://bloggerplugnplay.blogspot.in/2013/01/validateget-checked-radio-value-in.html

How to convert rdd object to dataframe in spark

SparkSession has a number of createDataFrame methods that create a DataFrame given an RDD. I imagine one of these will work for your context.

For example:

def createDataFrame(rowRDD: RDD[Row], schema: StructType): DataFrame

Creates a DataFrame from an RDD containing Rows using the given schema.

ListAGG in SQLSERVER

MySQL

SELECT FieldA
     , GROUP_CONCAT(FieldB ORDER BY FieldB SEPARATOR ',') AS FieldBs
  FROM TableName
 GROUP BY FieldA
 ORDER BY FieldA;

Oracle & DB2

SELECT FieldA
     , LISTAGG(FieldB, ',') WITHIN GROUP (ORDER BY FieldB) AS FieldBs
  FROM TableName
 GROUP BY FieldA
 ORDER BY FieldA;

PostgreSQL

SELECT FieldA
     , STRING_AGG(FieldB, ',' ORDER BY FieldB) AS FieldBs
  FROM TableName
 GROUP BY FieldA
 ORDER BY FieldA;

SQL Server

SQL Server ≥ 2017 & Azure SQL

SELECT FieldA
     , STRING_AGG(FieldB, ',') WITHIN GROUP (ORDER BY FieldB) AS FieldBs
  FROM TableName
 GROUP BY FieldA
 ORDER BY FieldA;

SQL Server ≤ 2016 (CTE included to encourage the DRY principle)

  WITH CTE_TableName AS (
       SELECT FieldA, FieldB
         FROM TableName)
SELECT t0.FieldA
     , STUFF((
       SELECT ',' + t1.FieldB
         FROM CTE_TableName t1
        WHERE t1.FieldA = t0.FieldA
        ORDER BY t1.FieldB
          FOR XML PATH('')), 1, LEN(','), '') AS FieldBs
  FROM CTE_TableName t0
 GROUP BY t0.FieldA
 ORDER BY FieldA;

SQLite

Ordering requires a CTE or subquery

  WITH CTE_TableName AS (
       SELECT FieldA, FieldB
         FROM TableName
        ORDER BY FieldA, FieldB)
SELECT FieldA
     , GROUP_CONCAT(FieldB, ',') AS FieldBs
  FROM CTE_TableName
 GROUP BY FieldA
 ORDER BY FieldA;

Without ordering

SELECT FieldA
     , GROUP_CONCAT(FieldB, ',') AS FieldBs
  FROM TableName
 GROUP BY FieldA
 ORDER BY FieldA;

Decimal to Hexadecimal Converter in Java

A better solution to convert Decimal To HexaDecimal and this one is less complex

import java.util.Scanner;
public class DecimalToHexa
{
    public static void main(String ar[])
    {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter a Decimal number: ");
        int n=sc.nextInt();
        if(n<0)
        {
            System.out.println("Enter a positive integer");
            return;
        }
        int i=0,d=0;
        String hx="",h="";
        while(n>0)
        {
            d=n%16;`enter code here`
            n/=16;
            if(d==10)h="A";
            else if(d==11)h="B";
            else if(d==12)h="C";
            else if(d==13)h="D";
            else if(d==14)h="E";
            else if(d==15)h="F";
            else h=""+d;            
            hx=""+h+hx;
        }
        System.out.println("Equivalent HEXA: "+hx);
    }
}        

Django: TemplateSyntaxError: Could not parse the remainder

Template Syntax Error: is due to many reasons one of them is {{ post.date_posted|date: "F d, Y" }} is the space between colon(:) and quote (") if u remove the space then it work like this ..... {{ post.date_posted|date:"F d, Y" }}

How can I add a string to the end of each line in Vim?

One option is:

:g/$/s//*

This will find every line end anchor and substitute it with *. I say "substitute" but, in actual fact, it's more of an append since the anchor is a special thing rather than a regular character. For more information, see Power of g - Examples.

Recover sa password

The best way is to simply reset the password by connecting with a domain/local admin (so you may need help from your system administrators), but this only works if SQL Server was set up to allow local admins (these are now left off the default admin group during setup).

If you can't use this or other existing methods to recover / reset the SA password, some of which are explained here:

Then you could always backup your important databases, uninstall SQL Server, and install a fresh instance.

You can also search for less scrupulous ways to do it (e.g. there are password crackers that I am not enthusiastic about sharing).

As an aside, the login properties for sa would never say Windows Authentication. This is by design as this is a SQL Authentication account. This does not mean that Windows Authentication is disabled at the instance level (in fact it is not possible to do so), it just doesn't apply for a SQL auth account.

I wrote a tip on using PSExec to connect to an instance using the NT AUTHORITY\SYSTEM account (which works < SQL Server 2012), and a follow-up that shows how to hack the SqlWriter service (which can work on more modern versions):

And some other resources:

How to change a PG column to NULLABLE TRUE?

From the fine manual:

ALTER TABLE mytable ALTER COLUMN mycolumn DROP NOT NULL;

There's no need to specify the type when you're just changing the nullability.

Input button target="_blank" isn't causing the link to load in a new window/tab

you will need to do it like this...

<a type="button" href="http://www.facebook.com/" value="facebook" target="_blank" class="button"></a>

and add the basic css if you want it to look like a btn.. like this

    .button {
    width:100px;
    height:50px;
    -moz-box-shadow:inset 0 1px 0 0 #fff;
    -webkit-box-shadow:inset 0 1px 0 0 #fff;
    box-shadow:inset 0 1px 0 0 #fff;
    background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #ffffff), color-stop(1, #d1d1d1) );
    background:-moz-linear-gradient( center top, #ffffff 5%, #d1d1d1 100% );
 filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#d1d1d1');
    background-color:#fff;
    -moz-border-radius:6px;
    -webkit-border-radius:6px;
    border-radius:6px;
    border:1px solid #dcdcdc;
    display:inline-block;
    color:#777;
    font-family:Helvetica;
    font-size:15px;
    font-weight:700;
    padding:6px 24px;
    text-decoration:none;
    text-shadow:1px 1px 0 #fff
}



  .button:hover {
    background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #d1d1d1), color-stop(1, #ffffff) );
    background:-moz-linear-gradient( center top, #d1d1d1 5%, #ffffff 100% );
 filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#d1d1d1', endColorstr='#ffffff');
    background-color:#d1d1d1
}
.button:active {
    position:relative;
    top:1px
}

target works only with href tags..

Check status of one port on remote host

In Bash, you can use pseudo-device files which can open a TCP connection to the associated socket. The syntax is /dev/$tcp_udp/$host_ip/$port.

Here is simple example to test whether Memcached is running:

</dev/tcp/localhost/11211 && echo Port open || echo Port closed

Here is another test to see if specific website is accessible:

$ echo "HEAD / HTTP/1.0" > /dev/tcp/example.com/80 && echo Connection successful.
Connection successful.

For more info, check: Advanced Bash-Scripting Guide: Chapter 29. /dev and /proc.

Related: Test if a port on a remote system is reachable (without telnet) at SuperUser.

For more examples, see: How to open a TCP/UDP socket in a bash shell (article).

How to parse this string in Java?

public class Test {
    public static void main(String args[]) {
    String s = "pre/fix/dir1/dir2/dir3/dir4/..";
    String prefix = "pre/fix";
    String[] tokens = s.substring(prefix.length()).split("/");
    for (int i=0; i<tokens.length; i++) {
        System.out.println(tokens[i]);
    }
    }

}

PHP output showing little black diamonds with a question mark

Using the same charset (as suggested here) in both the database and the HTML has not worked for me... So remembering that the code is generated as HTML, I chose to use the &quot;(HTML code) or the &#34; (ISO Latin-1 code) in my database text where quotes were used. This solved the problem while providing me a quotation mark. It is odd to note that prior to this solution, only some of the quotation marks and apostrophes did not display correctly while others did, however, the special code did work in all instances.

Python, Matplotlib, subplot: How to set the axis range?

Using axes objects is a great approach for this. It helps if you want to interact with multiple figures and sub-plots. To add and manipulate the axes objects directly:

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(12,9))

signal_axes = fig.add_subplot(211)
signal_axes.plot(xs,rawsignal)

fft_axes = fig.add_subplot(212)
fft_axes.set_title("FFT")
fft_axes.set_autoscaley_on(False)
fft_axes.set_ylim([0,1000])
fft = scipy.fft(rawsignal)
fft_axes.plot(abs(fft))

plt.show()

Mock HttpContext.Current in Test Init Method

If your application third party redirect internally, so it is better to mock HttpContext in below way :

HttpWorkerRequest initWorkerRequest = new SimpleWorkerRequest("","","","",new StringWriter(CultureInfo.InvariantCulture));
System.Web.HttpContext.Current = new HttpContext(initWorkerRequest);
System.Web.HttpContext.Current.Request.Browser = new HttpBrowserCapabilities();
System.Web.HttpContext.Current.Request.Browser.Capabilities = new Dictionary<string, string> { { "requiresPostRedirectionHandling", "false" } };

How to check if activity is in foreground or in visible background?

One possible solution might be setting a flag while showing the system-dialog and then in the onStop method of the activity life-cycle, check for the flag, if true, finish the activity.

For example, if the system dialog is triggered by some buttonclick, then the onclick listener might be like

private OnClickListener btnClickListener = new OnClickListener() {

    @Override
    public void onClick(View v) {           
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_SEND);
        intent.setType("text/plain");
        CheckActivity.this.startActivity(Intent.createChooser(intent, "Complete action using"));
        checkFlag = true;  //flag used to check

    }
};

and in onstop of activity:

@Override
protected void onStop() {
    if(checkFlag){
        finish();
    }
    super.onStop();
}

How can I rename a project folder from within Visual Studio?

There is another way doing this, using the *.sol, *csproj files.

  1. Open your solution file.
  2. Search for the *.csproj you would like to change.
  3. It will be like this (relative to the *.sol file):

    Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Shani.Commands.Impl", "Shani.Commands.Impl\Shani.Commands.Impl.csproj", "{747CFA4B-FC83-419A-858E-5E2DE2B948EE}"

  4. And just change the first part to the new diretory for example:

    Impl\Shani.Commands.Impl\Shani.Commands.Impl.csproj

  5. Of course, don't forget to move the whole project to that directory.

How to set URL query params in Vue with Vue-Router

To set/remove multiple query params at once I've ended up with the methods below as part of my global mixins (this points to vue component):

    setQuery(query){
        let obj = Object.assign({}, this.$route.query);

        Object.keys(query).forEach(key => {
            let value = query[key];
            if(value){
                obj[key] = value
            } else {
                delete obj[key]
            }
        })
        this.$router.replace({
            ...this.$router.currentRoute,
            query: obj
        })
    },

    removeQuery(queryNameArray){
        let obj = {}
        queryNameArray.forEach(key => {
            obj[key] = null
        })
        this.setQuery(obj)
    },

What is the difference between a string and a byte string?

From What is Unicode:

Fundamentally, computers just deal with numbers. They store letters and other characters by assigning a number for each one.

......

Unicode provides a unique number for every character, no matter what the platform, no matter what the program, no matter what the language.

So when a computer represents a string, it finds characters stored in the computer of the string through their unique Unicode number and these figures are stored in memory. But you can't directly write the string to disk or transmit the string on network through their unique Unicode number because these figures are just simple decimal number. You should encode the string to byte string, such as UTF-8. UTF-8 is a character encoding capable of encoding all possible characters and it stores characters as bytes (it looks like this). So the encoded string can be used everywhere because UTF-8 is nearly supported everywhere. When you open a text file encoded in UTF-8 from other systems, your computer will decode it and display characters in it through their unique Unicode number. When a browser receive string data encoded UTF-8 from network, it will decode the data to string (assume the browser in UTF-8 encoding) and display the string.

In python3, you can transform string and byte string to each other:

>>> print('??'.encode('utf-8'))
b'\xe4\xb8\xad\xe6\x96\x87'
>>> print(b'\xe4\xb8\xad\xe6\x96\x87'.decode('utf-8'))
?? 

In a word, string is for displaying to humans to read on a computer and byte string is for storing to disk and data transmission.

How to Store Historical Data

Another option is to archive the operational data on a [daily|hourly|whatever] basis. Most database engines support the extraction of the data into an archive.

Basically, the idea is to create a scheduled Windows or CRON job that

  1. determines the current tables in the operational database
  2. selects all data from every table into a CSV or XML file
  3. compresses the exported data to a ZIP file, preferably with the timestamp of the generation in the file name for easier archiving.

Many SQL database engines come with a tool that can be used for this purpose. For example, when using MySQL on Linux, the following command can be used in a CRON job to schedule the extraction:

mysqldump --all-databases --xml --lock-tables=false -ppassword | gzip -c | cat > /media/bak/servername-$(date +%Y-%m-%d)-mysql.xml.gz

hardcoded string "row three", should use @string resource

A good practice is write text inside String.xml

example:

String.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="yellow">Yellow</string>
</resources>

and inside layout:

<TextView android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:text="@string/yellow" />

Print a list in reverse order with range()?

because range(n) produces an iterable there are all sorts of nice things you can do which will produce the result you desire, such as:

range(n)[::-1]

if loops are ok, we can make sort of a queue:

a = []
for i in range(n):
    a.insert(0,a)
return a

or maybe use the reverse() method on it:

reverse(range(n))

How do I resolve "Cannot find module" error using Node.js?

For TypeScript users, if you are importing a built-in Node module (such as http, path or url) and you are getting an error such as "Cannot find module "x" then the error can be fixed by running

npm install @types/node --save-dev

The command will import the NodeJS TypeScript definitions into your project, allowing you to use Node's built-in modules.

Convert a CERT/PEM certificate to a PFX certificate

openssl pkcs12 -inkey bob_key.pem -in bob_cert.cert -export -out bob_pfx.pfx

Is there a way to make mv create the directory to be moved to if it doesn't exist?

You can even use brace extensions:

mkdir -p directory{1..3}/subdirectory{1..3}/subsubdirectory{1..2}      
  • which creates 3 directories (directory1, directory2, directory3),
    • and in each one of them two subdirectories (subdirectory1, subdirectory2),
      • and in each of them two subsubdirectories (subsubdirectory1 and subsubdirectory2).

You have to use bash 3.0 or newer.

Understanding the Linux oom-killer's logs

This webpage have an explanation and a solution.

The solution is:

To fix this problem the behavior of the kernel has to be changed, so it will no longer overcommit the memory for application requests. Finally I have included those mentioned values into the /etc/sysctl.conf file, so they get automatically applied on start-up:

vm.overcommit_memory = 2

vm.overcommit_ratio = 80

How do I force a vertical scrollbar to appear?

Give your body tag an overflow: scroll;

body {
    overflow: scroll;
}

or if you only want a vertical scrollbar use overflow-y

body {
    overflow-y: scroll;
}

Unix command-line JSON parser?

Anyone mentioned Jshon or JSON.sh?

https://github.com/keenerd/jshon

pipe json to it, and it traverses the json objects and prints out the path to the current object (as a JSON array) and then the object, without whitespace.

http://kmkeen.com/jshon/
Jshon loads json text from stdin, performs actions, then displays the last action on stdout and also was made to be part of the usual text processing pipeline.

How to add a custom right-click menu to a webpage?

<html>
<head>
<style>
.rightclick {
    /* YOUR CONTEXTMENU'S CSS */
    visibility: hidden;
    background-color: white;
    border: 1px solid grey;
    width: 200px;
    height: 300px;
}
</style>
</head>
<body>
  <div class="rightclick" id="ya">
    <p onclick="alert('choc-a-late')">I like chocolate</p><br><p onclick="awe-so-me">I AM AWESOME</p>
  </div>
  <p>Right click to get sweet results!</p>
</body>
<script>
    document.onclick = noClick;
    document.oncontextmenu = rightClick;
    function rightClick(e) {
        e = e || window.event;
        e.preventDefault();
        document.getElementById("ya").style.visibility = "visible";
        console.log("Context Menu v1.3.0 by IamGuest opened.");
   }
function noClick() {
    document.getElementById("ya").style.visibility = "hidden";
    console.log("Context Menu v1.3.0 by IamGuest closed.");
}
</script>
<!-- Coded by IamGuest. Thank you for using this code! -->
</html>

You can tweak and modify this code to make a better looking, more efficient contextmenu. As for modifying an existing contextmenu, I'm not sure how to do that... Check out this fiddle for an organized point of view. Also, try clicking the items in my contextmenu. They should alert you a few awesome messages. If they don't work, try something more... complex.

How to remove title bar from the android activity?

Add this two line in your style.xml

<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>

How to change a <select> value from JavaScript

If you would like it to go back to first option try this:

   document.getElementById("select").selectedIndex = 0;

Installing specific laravel version with composer create-project

To install specific version of laravel try this & simply command on terminal

composer create-project --prefer-dist laravel/laravel:5.5.0 {dir-name}

Equivalent of typedef in C#

C# supports some inherited covariance for event delegates, so a method like this:

void LowestCommonHander( object sender, EventArgs e ) { ... } 

Can be used to subscribe to your event, no explicit cast required

gcInt.MyEvent += LowestCommonHander;

You can even use lambda syntax and the intellisense will all be done for you:

gcInt.MyEvent += (sender, e) =>
{
    e. //you'll get correct intellisense here
};

Documentation for using JavaScript code inside a PDF file

Probably you are looking for JavaScript™ for Acrobat® API Reference.

This reference should be the most complete. But, as @Orbling said, not all PDF viewers might support all of the API.

EDIT:

It turns out there are newer versions of the reference in Acrobat SDK (thanks to @jss).

Acrobat Developer Center contains links to different versions of documentation. Current version of JavaScript reference from Acrobat DC SDK is available there too.

Android Webview gives net::ERR_CACHE_MISS message

For anything related to the internet, your app must have the internet permission in ManifestFile. I solved this issue by adding permission in AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET" />

receiving error: 'Error: SSL Error: SELF_SIGNED_CERT_IN_CHAIN' while using npm

As of February 27, 2014, npm no longer supports its self-signed certificates. The following options, as recommended by npm, is to do one of the following:

Upgrade your version of npm

npm install npm -g --ca=""

-- OR --

Tell your current version of npm to use known registrars

npm config set ca ""

Update: npm has posted More help with SELF_SIGNED_CERT_IN_CHAIN and npm with more solutions particular to different environments



You may or may not need to prepend sudo to the recommendations.


Other options

It seems that people are having issues using npm's recommendations, so here are some other potential solutions.

Upgrade Node itself
Receiving this error may suggest you have an older version of node, which naturally comes with an older version of npm. One solution is to upgrade your version of Node. This is likely the best option as it brings you up to date and fixes existing bugs and vulnerabilities.

The process here depends on how you've installed Node, your operating system, and otherwise.

Update npm
Being that you probably got here while trying to install a package, it is possible that npm install npm -g might fail with the same error. If this is the case, use update instead. As suggested by Nisanth Sojan:

npm update npm -g

Update npm alternative
One way around the underlying issue is to use known registrars, install, and then stop using known registrars. As suggested by jnylen:

npm config set ca ""
npm install npm -g
npm config delete ca

Most efficient way to see if an ArrayList contains an object in Java

Given your constraints, you're stuck with brute force search (or creating an index if the search will be repeated). Can you elaborate any on how the ArrayList is generated--perhaps there is some wiggle room there.

If all you're looking for is prettier code, consider using the Apache Commons Collections classes, in particular CollectionUtils.find(), for ready-made syntactic sugar:

ArrayList haystack = // ...
final Object needleField1 = // ...
final Object needleField2 = // ...

Object found = CollectionUtils.find(haystack, new Predicate() {
   public boolean evaluate(Object input) {
      return needleField1.equals(input.field1) && 
             needleField2.equals(input.field2);
   }
});

running a command as a super user from a python script

The safest way to do this is to prompt for the password beforehand and then pipe it into the command. Prompting for the password will avoid having the password saved anywhere in your code and it also won't show up in your bash history. Here's an example:

from getpass import getpass
from subprocess import Popen, PIPE

password = getpass("Please enter your password: ")
# sudo requires the flag '-S' in order to take input from stdin
proc = Popen("sudo -S apach2ctl restart".split(), stdin=PIPE, stdout=PIPE, stderr=PIPE)
# Popen only accepts byte-arrays so you must encode the string
proc.communicate(password.encode())

Bootstrap 3 panel header with buttons wrong position

I'm a little late to the game here, but the simple answer is to move the H4 AFTER the button div. This is a common issue when floating, always have your floats defined BEFORE the rest of the contents or you'll have that extra line-break problem.

<div class="panel-heading">
    <div class="btn-group pull-right">
        <a href="#" class="btn btn-default btn-sm">## Lock</a>
        <a href="#" class="btn btn-default btn-sm">## Delete</a>
        <a href="#" class="btn btn-default btn-sm">## Move</a>
    </div>
    <h4>Panel header</h4>
</div>

The issue here is that when your floats are defined after other items, the float's top will start at the last line-position of the element immediately before it. So, if the previous item wraps to line 3, your float will start at line 3 too.

Moving the float to the TOP of the list eliminates the issue because there are no previous elements to push it down and anything after the float will be rendered at the top line (assuming there is room on the line for all items)

Example of correct and incorrect ordering and the effects: http://www.bootply.com/HkDlNIKv9g

How to match letters only using java regex, matches method?

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.regex.*;

/* Write an application that prompts the user for a String that contains at least
 * five letters and at least five digits. Continuously re-prompt the user until a
 * valid String is entered. Display a message indicating whether the user was
 * successful or did not enter enough digits, letters, or both.
 */
public class FiveLettersAndDigits {

  private static String readIn() { // read input from stdin
    StringBuilder sb = new StringBuilder();
    int c = 0;
    try { // do not use try-with-resources. We don't want to close the stdin stream
      BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
      while ((c = reader.read()) != 0) { // read all characters until null
        // We don't want new lines, although we must consume them.
        if (c != 13 && c != 10) {
          sb.append((char) c);
        } else {
          break; // break on new line (or else the loop won't terminate)
        }
      }
      // reader.readLine(); // get the trailing new line
    } catch (IOException ex) {
      System.err.println("Failed to read user input!");
      ex.printStackTrace(System.err);
    }

    return sb.toString().trim();
  }

  /**
   * Check the given input against a pattern
   *
   * @return the number of matches
   */
  private static int getitemCount(String input, String pattern) {
    int count = 0;

    try {
      Pattern p = Pattern.compile(pattern);
      Matcher m = p.matcher(input);
      while (m.find()) { // count the number of times the pattern matches
        count++;
      }
    } catch (PatternSyntaxException ex) {
      System.err.println("Failed to test input String \"" + input + "\" for matches to pattern \"" + pattern + "\"!");
      ex.printStackTrace(System.err);
    }

    return count;
  }

  private static String reprompt() {
    System.out.print("Entered input is invalid! Please enter five letters and five digits in any order: ");

    String in = readIn();

    return in;
  }

  public static void main(String[] args) {
    int letters = 0, digits = 0;
    String in = null;
    System.out.print("Please enter five letters and five digits in any order: ");
    in = readIn();
    while (letters < 5 || digits < 5) { // will keep occuring until the user enters sufficient input
      if (null != in && in.length() > 9) { // must be at least 10 chars long in order to contain both
        // count the letters and numbers. If there are enough, this loop won't happen again.
        letters = getitemCount(in, "[A-Za-z]");
        digits = getitemCount(in, "[0-9]");

        if (letters < 5 || digits < 5) {
          in = reprompt(); // reset in case we need to go around again.
        }
      } else {
        in = reprompt();
      }
    }
  }

}

How to stop mongo DB in one command

From the given commands I think you're on Linux.

Start MongoDB:

$ sudo service mongod start
mongod start/running, process XXXXX 

Check the Status:

$ sudo service mongod status
mongod start/running, process XXXXX 

Stop MongoDB:

$ sudo service mongod stop
mongod stop/waiting 

How to use performSelector:withObject:afterDelay: with primitive types in Cocoa?

Here is what I used to call something I couldn't change using NSInvocation:

SEL theSelector = NSSelectorFromString(@"setOrientation:animated:");
NSInvocation *anInvocation = [NSInvocation
            invocationWithMethodSignature:
            [MPMoviePlayerController instanceMethodSignatureForSelector:theSelector]];

[anInvocation setSelector:theSelector];
[anInvocation setTarget:theMovie];
UIInterfaceOrientation val = UIInterfaceOrientationPortrait;
BOOL anim = NO;
[anInvocation setArgument:&val atIndex:2];
[anInvocation setArgument:&anim atIndex:3];

[anInvocation performSelector:@selector(invoke) withObject:nil afterDelay:1];

How to show Bootstrap table with sort icon

BOOTSTRAP 4

you can use a combination of

  • fa-chevron-down, fa-chevron-up

  • fa-sort-down, fa-sort-up

<th class="text-center">
    <div class="btn-group" role="group">
        <button type="button" class="btn btn-xs btn-link py-0 pl-0 pr-1">
             Some Text OR icon
        </button>
        <div class="btn-group-vertical">
            <a href="?sort=asc" class="btn btn-xs btn-link p-0">
                <i class="fas fa-sort-up"></i>
            </a>
            <a href="?sort=desc" class="btn btn-xs btn-link p-0">
                <i class="fas fa-sort-down"></i>
            </a>
        </div>
    </div>
</th>

Url decode UTF-8 in Python

The data is UTF-8 encoded bytes escaped with URL quoting, so you want to decode, with urllib.parse.unquote(), which handles decoding from percent-encoded data to UTF-8 bytes and then to text, transparently:

from urllib.parse import unquote

url = unquote(url)

Demo:

>>> from urllib.parse import unquote
>>> url = 'example.com?title=%D0%BF%D1%80%D0%B0%D0%B2%D0%BE%D0%B2%D0%B0%D1%8F+%D0%B7%D0%B0%D1%89%D0%B8%D1%82%D0%B0'
>>> unquote(url)
'example.com?title=????????+??????'

The Python 2 equivalent is urllib.unquote(), but this returns a bytestring, so you'd have to decode manually:

from urllib import unquote

url = unquote(url).decode('utf8')

How can I bind a background color in WPF/XAML?

Important:

Make sure you're using System.Windows.Media.Brush and not System.Drawing.Brush

They're not compatible and you'll get binding errors.

The color enumeration you need to use is also different

System.Windows.Media.Colors.Aquamarine (class name is Colors) <--- use this one System.Drawing.Color.Aquamarine (class name is Color)

If in doubt use Snoop and inspect the element's background property to look for binding errors - or just look in your debug log.

Function in JavaScript that can be called only once

try this

var fun = (function() {
  var called = false;
  return function() {
    if (!called) {
      console.log("I  called");
      called = true;
    }
  }
})()

Change status bar color with AppCompat ActionBarActivity

I'm not sure I understand the problem.

I you want to change the status bar color programmatically (and provided the device has Android 5.0) then you can use Window.setStatusBarColor(). It shouldn't make a difference whether the activity is derived from Activity or ActionBarActivity.

Just try doing:

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    Window window = getWindow();
    window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
    window.setStatusBarColor(Color.BLUE);
}

Just tested this with ActionBarActivity and it works alright.


Note: Setting the FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS flag programmatically is not necessary if your values-v21 styles file has it set already, via:

    <item name="android:windowDrawsSystemBarBackgrounds">true</item>

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException Error

NullPointerExceptions are among the easier exceptions to diagnose, frequently. Whenever you get an exception in Java and you see the stack trace ( that's what your second quote-block is called, by the way ), you read from top to bottom. Often, you will see exceptions that start in Java library code or in native implementations methods, for diagnosis you can just skip past those until you see a code file that you wrote.

Then you like at the line indicated and look at each of the objects ( instantiated classes ) on that line -- one of them was not created and you tried to use it. You can start by looking up in your code to see if you called the constructor on that object. If you didn't, then that's your problem, you need to instantiate that object by calling new Classname( arguments ). Another frequent cause of NullPointerExceptions is accidentally declaring an object with local scope when there is an instance variable with the same name.

In your case, the exception occurred in your constructor for Workshop on line 75. <init> means the constructor for a class. If you look on that line in your code, you'll see the line

denimjeansButton.addItemListener(this);

There are fairly clearly two objects on this line: denimjeansButton and this. this is synonymous with the class instance you are currently in and you're in the constructor, so it can't be this. denimjeansButton is your culprit. You never instantiated that object. Either remove the reference to the instance variable denimjeansButton or instantiate it.

How to post JSON to PHP with curl

You need to set a few extra flags so that curl sends the data as JSON.

command

$ curl -H "Content-Type: application/json" \
       -X POST \
       -d '{"JSON": "HERE"}' \
       http://localhost:3000/api/url

flags

  • -H: custom header, next argument is expected to be header
  • -X: custom HTTP verb, next argument is expected to be verb
  • -d: sends the next argument as data in an HTTP POST request

resources

pull out p-values and r-squared from a linear regression

Extension of @Vincent 's answer:

For lm() generated models:

summary(fit)$coefficients[,4]   ##P-values 
summary(fit)$r.squared          ##R squared values

For gls() generated models:

summary(fit)$tTable[,4]         ##P-values
##R-squared values are not generated b/c gls uses max-likelihood not Sums of Squares

To isolate an individual p-value itself, you'd add a row number to the code:

For example to access the p-value of the intercept in both model summaries:

summary(fit)$coefficients[1,4]
summary(fit)$tTable[1,4]  
  • Note, you can replace the column number with the column name in each of the above instances:

    summary(fit)$coefficients[1,"Pr(>|t|)"]  ##lm 
    summary(fit)$tTable[1,"p-value"]         ##gls 
    

If you're still unsure of how to access a value form the summary table use str() to figure out the structure of the summary table:

str(summary(fit))

Insert node at a certain position in a linked list C++

For inserting at a particular position k, you need to traverse the list till the position k-1 and then do the insert.

[You need not create a new node to traverse to that position as you did in your code] You should traverse from the head node.

How to insert a row in an HTML table body in JavaScript

Add rows:

_x000D_
_x000D_
<html>_x000D_
    <script>_x000D_
        function addRow() {_x000D_
            var table = document.getElementById('myTable');_x000D_
            //var row = document.getElementById("myTable");_x000D_
            var x = table.insertRow(0);_x000D_
            var e = table.rows.length-1;_x000D_
            var l = table.rows[e].cells.length;_x000D_
            //x.innerHTML = "&nbsp;";_x000D_
_x000D_
            for (var c=0, m=l; c < m; c++) {_x000D_
                table.rows[0].insertCell(c);_x000D_
                table.rows[0].cells[c].innerHTML = "&nbsp;&nbsp;";_x000D_
            }_x000D_
        }_x000D_
_x000D_
        function addColumn() {_x000D_
            var table = document.getElementById('myTable');_x000D_
            for (var r = 0, n = table.rows.length; r < n; r++) {_x000D_
                table.rows[r].insertCell(0);_x000D_
                table.rows[r].cells[0].innerHTML = "&nbsp;&nbsp;";_x000D_
            }_x000D_
        }_x000D_
_x000D_
        function deleteRow() {_x000D_
            document.getElementById("myTable").deleteRow(0);_x000D_
        }_x000D_
_x000D_
        function deleteColumn() {_x000D_
            // var row = document.getElementById("myRow");_x000D_
            var table = document.getElementById('myTable');_x000D_
            for (var r = 0, n = table.rows.length; r < n; r++) {_x000D_
                table.rows[r].deleteCell(0); // var table handle_x000D_
            }_x000D_
        }_x000D_
    </script>_x000D_
_x000D_
    <body>_x000D_
        <input type="button" value="row +" onClick="addRow()" border=0 style='cursor:hand'>_x000D_
        <input type="button" value="row -" onClick='deleteRow()' border=0 style='cursor:hand'>_x000D_
        <input type="button" value="column +" onClick="addColumn()" border=0 style='cursor:hand'>_x000D_
        <input type="button" value="column -" onClick='deleteColumn()' border=0 style='cursor:hand'>_x000D_
_x000D_
        <table  id='myTable' border=1 cellpadding=0 cellspacing=0>_x000D_
            <tr id='myRow'>_x000D_
                <td>&nbsp;</td>_x000D_
                <td>&nbsp;</td>_x000D_
                <td>&nbsp;</td>_x000D_
            </tr>_x000D_
            <tr>_x000D_
                <td>&nbsp;</td>_x000D_
                <td>&nbsp;</td>_x000D_
                <td>&nbsp;</td>_x000D_
            </tr>_x000D_
        </table>_x000D_
    </body>_x000D_
</html>
_x000D_
_x000D_
_x000D_

And cells.

Setting table column width

Use the CSS below, the first declaration will ensure your table sticks to the widths you provide (you'll need to add the classes in your HTML):

table{
  table-layout:fixed;
}
th.from, th.date {
  width: 15%;
}
th.subject{
  width: 70%;
}

Http Post request with content type application/x-www-form-urlencoded not working in Spring

The problem is that when we use application/x-www-form-urlencoded, Spring doesn't understand it as a RequestBody. So, if we want to use this we must remove the @RequestBody annotation.

Then try the following:

@RequestMapping(value = "/patientdetails", method = RequestMethod.POST,consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
public @ResponseBody List<PatientProfileDto> getPatientDetails(
        PatientProfileDto name) {


    List<PatientProfileDto> list = new ArrayList<PatientProfileDto>();
    list = service.getPatient(name);
    return list;
}

Note that removed the annotation @RequestBody

Get file content from URL?

1) local simplest methods

<?php
echo readfile("http://example.com/");   //needs "Allow_url_include" enabled
//OR
echo include("http://example.com/");    //needs "Allow_url_include" enabled
//OR
echo file_get_contents("http://example.com/");
//OR
echo stream_get_contents(fopen('http://example.com/', "rb")); //you may use "r" instead of "rb"  //needs "Allow_url_fopen" enabled
?> 

2) Better Way is CURL:

echo get_remote_data('http://example.com'); // GET request 
echo get_remote_data('http://example.com', "var2=something&var3=blabla" ); // POST request

It automatically handles FOLLOWLOCATION problem + Remote urls:
src="./imageblabla.png" turned into:
src="http://example.com/path/imageblabla.png"

Code : https://github.com/tazotodua/useful-php-scripts/blob/master/get-remote-url-content-data.php

Querying Datatable with where condition

Something like this...

var res = from row in myDTable.AsEnumerable()
where row.Field<int>("EmpID") == 5 &&
(row.Field<string>("EmpName") != "abc" ||
row.Field<string>("EmpName") != "xyz")
select row;

See also LINQ query on a DataTable

How to convert SecureString to System.String?

I derived from This answer by sclarke81. I like his answer and I'm using the derivative but sclarke81's has a bug. I don't have reputation so I can't comment. The problem seems small enough that it didn't warrant another answer and I could edit it. So I did. It got rejected. So now we have another answer.

sclarke81 I hope you see this (in finally):

Marshal.Copy(new byte[length], 0, insecureStringPointer, length);

should be:

Marshal.Copy(new byte[length * 2], 0, insecureStringPointer, length * 2);

And the full answer with the bug fix:


    /// 
    /// Allows a decrypted secure string to be used whilst minimising the exposure of the
    /// unencrypted string.
    /// 
    /// Generic type returned by Func delegate.
    /// The string to decrypt.
    /// 
    /// Func delegate which will receive the decrypted password as a string object
    /// 
    /// Result of Func delegate
    /// 
    /// This method creates an empty managed string and pins it so that the garbage collector
    /// cannot move it around and create copies. An unmanaged copy of the the secure string is
    /// then created and copied into the managed string. The action is then called using the
    /// managed string. Both the managed and unmanaged strings are then zeroed to erase their
    /// contents. The managed string is unpinned so that the garbage collector can resume normal
    /// behaviour and the unmanaged string is freed.
    /// 
    public static T UseDecryptedSecureString(this SecureString secureString, Func action)
    {
        int length = secureString.Length;
        IntPtr sourceStringPointer = IntPtr.Zero;

        // Create an empty string of the correct size and pin it so that the GC can't move it around.
        string insecureString = new string('\0', length);
        var insecureStringHandler = GCHandle.Alloc(insecureString, GCHandleType.Pinned);

        IntPtr insecureStringPointer = insecureStringHandler.AddrOfPinnedObject();

        try
        {
            // Create an unmanaged copy of the secure string.
            sourceStringPointer = Marshal.SecureStringToBSTR(secureString);

            // Use the pointers to copy from the unmanaged to managed string.
            for (int i = 0; i < secureString.Length; i++)
            {
                short unicodeChar = Marshal.ReadInt16(sourceStringPointer, i * 2);
                Marshal.WriteInt16(insecureStringPointer, i * 2, unicodeChar);
            }

            return action(insecureString);
        }
        finally
        {
            // Zero the managed string so that the string is erased. Then unpin it to allow the
            // GC to take over.
            Marshal.Copy(new byte[length * 2], 0, insecureStringPointer, length * 2);
            insecureStringHandler.Free();

            // Zero and free the unmanaged string.
            Marshal.ZeroFreeBSTR(sourceStringPointer);
        }
    }

    /// 
    /// Allows a decrypted secure string to be used whilst minimising the exposure of the
    /// unencrypted string.
    /// 
    /// The string to decrypt.
    /// 
    /// Func delegate which will receive the decrypted password as a string object
    /// 
    /// Result of Func delegate
    /// 
    /// This method creates an empty managed string and pins it so that the garbage collector
    /// cannot move it around and create copies. An unmanaged copy of the the secure string is
    /// then created and copied into the managed string. The action is then called using the
    /// managed string. Both the managed and unmanaged strings are then zeroed to erase their
    /// contents. The managed string is unpinned so that the garbage collector can resume normal
    /// behaviour and the unmanaged string is freed.
    /// 
    public static void UseDecryptedSecureString(this SecureString secureString, Action action)
    {
        UseDecryptedSecureString(secureString, (s) =>
        {
            action(s);
            return 0;
        });
    }
}

PHP Create and Save a txt file to root directory

It's creating the file in the same directory as your script. Try this instead.

$content = "some text here";
$fp = fopen($_SERVER['DOCUMENT_ROOT'] . "/myText.txt","wb");
fwrite($fp,$content);
fclose($fp);

How to move the layout up when the soft keyboard is shown android

This will definitely work for you.

android:windowSoftInputMode="adjustPan"

The service cannot be started, either because it is disabled or because it has no enabled devices associated with it

This error can occur on anything that requires elevated privileges in Windows.

It happens when the "Application Information" service is disabled in Windows services. There are a few viruses that use this as an attack vector to prevent people from removing the virus. It also prevents people from installing software to remove viruses.

The normal way to fix this would be to run services.msc, or to go into Administrative Tools and run "Services". However, you will not be able to do that if the "Application Information" service is disabled.

Instead, reboot your computer into Safe Mode (reboot and press F8 until the Windows boot menu appears, select Safe Mode with Networking). Then run services.msc and look for services that are designated as "Disabled" in the Startup Type column. Change these "Disabled" services to "Automatic".

Make sure the "Application Information" service is set to a Startup Type of "Automatic".

When you are done enabling your services, click Ok at the bottom of the tool and reboot your computer back into normal mode. The problem should be resolved when Windows reboots.

CSS: how do I create a gap between rows in a table?

If you don't have borders, or have borders and want the spacing inside the cells, you can use padding, or line-height. As far as I know, margin has no effect on cells and rows.
A CSS property for spacing of cells is border-spacing, but it doesn't work on IE6/7 (so you can use it depending on your crowd).

If all else fails you can use the old cellspacing attribute in your markup - but this will also give you spacing between the columns. Some CSS reset suggest you should set it anyway to get cross-browser support:

/* tables still need cellspacing="0" in the markup */

Tuple unpacking in for loops

Enumerate basically gives you an index to work with in the for loop. So:

for i,a in enumerate([4, 5, 6, 7]):
    print i, ": ", a

Would print:

0: 4
1: 5
2: 6
3: 7

How to center align the cells of a UICollectionView?

I think you can achieve the single line look by implementing something like this:

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
    return UIEdgeInsetsMake(0, 100, 0, 0);
}

You will have to play around with that number to figure out how to force the content into a single line. The first 0, is the top edge argument, you could adjust that one too, if you want to center the content vertically in the screen.

Notification Icon with the new Firebase Cloud Messaging system

I'm triggering my notifications from FCM console and through HTTP/JSON ... with the same result.

I can handle the title, full message, but the icon is always a default white circle:

Notification screenshot

Instead of my custom icon in the code (setSmallIcon or setSmallIcon) or default icon from the app:

 Intent intent = new Intent(this, MainActivity.class);
    // use System.currentTimeMillis() to have a unique ID for the pending intent
    PendingIntent pIntent = PendingIntent.getActivity(this, (int) System.currentTimeMillis(), intent, 0);

    if (Build.VERSION.SDK_INT < 16) {
        Notification n  = new Notification.Builder(this)
                .setContentTitle(messageTitle)
                .setContentText(messageBody)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentIntent(pIntent)
                .setAutoCancel(true).getNotification();
        NotificationManager notificationManager =
                (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        //notificationManager.notify(0, n);
        notificationManager.notify(id, n);
    } else {
        Bitmap bm = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);

        Notification n  = new Notification.Builder(this)
                .setContentTitle(messageTitle)
                .setContentText(messageBody)
                .setSmallIcon(R.drawable.ic_stat_ic_notification)
                .setLargeIcon(bm)
                .setContentIntent(pIntent)
                .setAutoCancel(true).build();

        NotificationManager notificationManager =
                (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        //notificationManager.notify(0, n);
        notificationManager.notify(id, n);
    }