Programs & Examples On #Gstreamer

Questions related to GStreamer (also known as Gst), an open source multimedia framework, powering everything from linux servers and linux desktop systems to a host of embedded devices.

How do you access the matched groups in a JavaScript regular expression?

You can access capturing groups like this:

_x000D_
_x000D_
var myString = "something format_abc";_x000D_
var myRegexp = /(?:^|\s)format_(.*?)(?:\s|$)/g;_x000D_
var match = myRegexp.exec(myString);_x000D_
console.log(match[1]); // abc
_x000D_
_x000D_
_x000D_

And if there are multiple matches you can iterate over them:

_x000D_
_x000D_
var myString = "something format_abc";_x000D_
var myRegexp = /(?:^|\s)format_(.*?)(?:\s|$)/g;_x000D_
match = myRegexp.exec(myString);_x000D_
while (match != null) {_x000D_
  // matched text: match[0]_x000D_
  // match start: match.index_x000D_
  // capturing group n: match[n]_x000D_
  console.log(match[0])_x000D_
  match = myRegexp.exec(myString);_x000D_
}
_x000D_
_x000D_
_x000D_

Edit: 2019-09-10

As you can see the way to iterate over multiple matches was not very intuitive. This lead to the proposal of the String.prototype.matchAll method. This new method is expected to ship in the ECMAScript 2020 specification. It gives us a clean API and solves multiple problems. It has been started to land on major browsers and JS engines as Chrome 73+ / Node 12+ and Firefox 67+.

The method returns an iterator and is used as follows:

_x000D_
_x000D_
const string = "something format_abc";_x000D_
const regexp = /(?:^|\s)format_(.*?)(?:\s|$)/g;_x000D_
const matches = string.matchAll(regexp);_x000D_
    _x000D_
for (const match of matches) {_x000D_
  console.log(match);_x000D_
  console.log(match.index)_x000D_
}
_x000D_
_x000D_
_x000D_

As it returns an iterator, we can say it's lazy, this is useful when handling particularly large numbers of capturing groups, or very large strings. But if you need, the result can be easily transformed into an Array by using the spread syntax or the Array.from method:

function getFirstGroup(regexp, str) {
  const array = [...str.matchAll(regexp)];
  return array.map(m => m[1]);
}

// or:
function getFirstGroup(regexp, str) {
  return Array.from(str.matchAll(regexp), m => m[1]);
}

In the meantime, while this proposal gets more wide support, you can use the official shim package.

Also, the internal workings of the method are simple. An equivalent implementation using a generator function would be as follows:

function* matchAll(str, regexp) {
  const flags = regexp.global ? regexp.flags : regexp.flags + "g";
  const re = new RegExp(regexp, flags);
  let match;
  while (match = re.exec(str)) {
    yield match;
  }
}

A copy of the original regexp is created; this is to avoid side-effects due to the mutation of the lastIndex property when going through the multple matches.

Also, we need to ensure the regexp has the global flag to avoid an infinite loop.

I'm also happy to see that even this StackOverflow question was referenced in the discussions of the proposal.

How to deal with "java.lang.OutOfMemoryError: Java heap space" error?

Ultimately you always have a finite max of heap to use no matter what platform you are running on. In Windows 32 bit this is around 2GB (not specifically heap but total amount of memory per process). It just happens that Java chooses to make the default smaller (presumably so that the programmer can't create programs that have runaway memory allocation without running into this problem and having to examine exactly what they are doing).

So this given there are several approaches you could take to either determine what amount of memory you need or to reduce the amount of memory you are using. One common mistake with garbage collected languages such as Java or C# is to keep around references to objects that you no longer are using, or allocating many objects when you could reuse them instead. As long as objects have a reference to them they will continue to use heap space as the garbage collector will not delete them.

In this case you can use a Java memory profiler to determine what methods in your program are allocating large number of objects and then determine if there is a way to make sure they are no longer referenced, or to not allocate them in the first place. One option which I have used in the past is "JMP" http://www.khelekore.org/jmp/.

If you determine that you are allocating these objects for a reason and you need to keep around references (depending on what you are doing this might be the case), you will just need to increase the max heap size when you start the program. However, once you do the memory profiling and understand how your objects are getting allocated you should have a better idea about how much memory you need.

In general if you can't guarantee that your program will run in some finite amount of memory (perhaps depending on input size) you will always run into this problem. Only after exhausting all of this will you need to look into caching objects out to disk etc. At this point you should have a very good reason to say "I need Xgb of memory" for something and you can't work around it by improving your algorithms or memory allocation patterns. Generally this will only usually be the case for algorithms operating on large datasets (like a database or some scientific analysis program) and then techniques like caching and memory mapped IO become useful.

"for" vs "each" in Ruby

Your first example,

@collection.each do |item|
  # do whatever
end

is more idiomatic. While Ruby supports looping constructs like for and while, the block syntax is generally preferred.

Another subtle difference is that any variable you declare within a for loop will be available outside the loop, whereas those within an iterator block are effectively private.

Delete many rows from a table using id in Mysql

DELETE FROM table_name WHERE id BETWEEN 1 AND 256;

Try This.

How can I initialize an array without knowing it size?

You can't... an array's size is always fixed in Java. Typically instead of using an array, you'd use an implementation of List<T> here - usually ArrayList<T>, but with plenty of other alternatives available.

You can create an array from the list as a final step, of course - or just change the signature of the method to return a List<T> to start with.

Python locale error: unsupported locale setting

If you're on a Debian (or Debian fork), you can add locales using :

dpkg-reconfigure locales

How do I combine two lists into a dictionary in Python?

I found myself needing to create a dictionary of three lists (latitude, longitude, and a value), with the following doing the trick:

> lat = [45.3,56.2,23.4,60.4]
> lon = [134.6,128.7,111.9,75.8]
> val = [3,6,2,5]
> dict(zip(zip(lat,lon),val))
{(56.2, 128.7): 6, (60.4, 75.8): 5, (23.4, 111.9): 2, (45.3, 134.6): 3}

or similar to the above examples:

> list1 = [1,2,3,4]
> list2 = [1,2,3,4]
> list3 = ['a','b','c','d']
> dict(zip(zip(list1,list2),list3))
{(3, 3): 'c', (4, 4): 'd', (1, 1): 'a', (2, 2): 'b'}

Note: Dictionaries are "orderless", but if you would like to view it as "sorted", refer to THIS question if you'd like to sort by key, or THIS question if you'd like to sort by value.

How do you get centered content using Twitter Bootstrap?

Update 2019 - Bootstrap 4

"Centered content" can mean many different things, and Bootstrap centering has changed a lot since the original post.

Horizontal Center

Bootstrap 3

  • text-center is used for display:inline elements
  • center-block to center display:block elements
  • col-*offset-* to center grid columns
  • see this answer to center the navbar

Demo Bootstrap 3 Horizontal Centering

Bootstrap 4

  • text-center is still used for display:inline elements
  • mx-auto replaces center-block to center display:block elements
  • offset-* or mx-auto can be used to center grid columns
  • justify-content-center in row can also be used to center col-*

mx-auto (auto x-axis margins) will center display:block or display:flex elements that have a defined width, (%, vw, px, etc..). Flexbox is used by default on grid columns, so there are also various flexbox centering methods.

Demo Bootstrap 4 Horizontal Centering


Vertical Center

Now that Bootstrap 4 is flexbox by default there are many different approaches to vertical alignment using: auto-margins, flexbox utils, or the display utils along with vertical align utils. At first "vertical align utils" seems obvious but these only work with inline and table display elements. Here are some Bootstrap 4 vertical centering options..


1 - Vertical Center Using Auto Margins:

Another way to vertically center is to use my-auto. This will center the element within it's container. For example, h-100 makes the row full height, and my-auto will vertically center the col-sm-12 column.

<div class="row h-100">
    <div class="col-sm-12 my-auto">
        <div class="card card-block w-25">Card</div>
    </div>
</div>

Vertical Center Using Auto Margins Demo

my-auto represents margins on the vertical y-axis and is equivalent to:

margin-top: auto;
margin-bottom: auto;

2 - Vertical Center with Flexbox:

vertical center grid columns

Since Bootstrap 4 .row is now display:flex you can simply use align-self-center on any column to vertically center it...

       <div class="row">
           <div class="col-6 align-self-center">
                <div class="card card-block">
                 Center
                </div>
           </div>
           <div class="col-6">
                <div class="card card-inverse card-danger">
                    Taller
                </div>
          </div>
    </div>

or, use align-items-center on the entire .row to vertically center align all col-* in the row...

       <div class="row align-items-center">
           <div class="col-6">
                <div class="card card-block">
                 Center
                </div>
           </div>
           <div class="col-6">
                <div class="card card-inverse card-danger">
                    Taller
                </div>
          </div>
    </div>

Vertical Center Different Height Columns Demo


3 - Vertical Center Using Display Utils:

Bootstrap 4 has display utils that can be used for display:table, display:table-cell, display:inline, etc.. These can be used with the vertical alignment utils to align inline, inline-block or table cell elements.

<div class="row h-50">
    <div class="col-sm-12 h-100 d-table">
        <div class="card card-block d-table-cell align-middle">
            I am centered vertically
        </div>
    </div>
</div>

Vertical Center Using Display Utils Demo

multiple where condition codeigniter

you can try this function for multi-purpose

function ManageData($table_name='',$condition=array(),$udata=array(),$is_insert=false){
$resultArr = array();
$ci = & get_instance();
if($condition && count($condition))
    $ci->db->where($condition);
if($is_insert)
{
    $ci->db->insert($table_name,$udata);
    return 0;
}
else
{
    $ci->db->update($table_name,$udata);
    return 1;
}

}

Using find command in bash script

You can use this:

list=$(find /home/user/Desktop -name '*.pdf' -o -name '*.txt' -o -name '*.bmp')

Besides, you might want to use -iname instead of -name to catch files with ".PDF" (upper-case) extension as well.

When does SQLiteOpenHelper onCreate() / onUpgrade() run?

Points to remember when extending SQLiteOpenHelper

  1. super(context, DBName, null, DBversion); - This should be invoked first line of constructor
  2. override onCreate and onUpgrade (if needed)
  3. onCreate will be invoked only when getWritableDatabase() or getReadableDatabase() is executed. And this will only invoked once when a DBName specified in the first step is not available. You can add create table query on onCreate method
  4. Whenever you want to add new table just change DBversion and do the queries in onUpgrade table or simply uninstall then install the app.

You don't have write permissions for the /var/lib/gems/2.3.0 directory

Rather than changing owners, which might lock out other local users, or –some day– your own ruby server/deployment-things... running under a different user...

I would rather simply extend rights of that particular folder to... well, everybody:

cd /var/lib
sudo chmod -R a+w gems/

(I did encounter your error as well. So this is fairly verified.)

Back button and refreshing previous activity

One option would be to use the onResume of your first activity.

@Override
public void onResume()
    {  // After a pause OR at startup
    super.onResume();
    //Refresh your stuff here
     }

Or you can start Activity for Result:

Intent i = new Intent(this, SecondActivity.class);
startActivityForResult(i, 1);

In secondActivity if you want to send back data:

 Intent returnIntent = new Intent();
 returnIntent.putExtra("result",result);
 setResult(RESULT_OK,returnIntent);     
 finish();

if you don't want to return data:

Intent returnIntent = new Intent();
setResult(RESULT_CANCELED, returnIntent);        
finish();

Now in your FirstActivity class write following code for onActivityResult() method

protected void onActivityResult(int requestCode, int resultCode, Intent data) {

  if (requestCode == 1) {

     if(resultCode == RESULT_OK){      
         //Update List         
     }
     if (resultCode == RESULT_CANCELED) {    
         //Do nothing?
     }
  }
}//onActivityResult

How to make g++ search for header files in a specific directory?

gcc -I/path -L/path
  • -I /path path to include, gcc will find .h files in this path

  • -L /path contains library files, .a, .so

How to split a delimited string in Ruby and convert it to an array?

"1,2,3,4".split(",") as strings

"1,2,3,4".split(",").map { |s| s.to_i } as integers

How to make Apache serve index.php instead of index.html?

As of today (2015, Aug., 1st), Apache2 in Debian Jessie, you need to edit:

root@host:/etc/apache2/mods-enabled$ vi dir.conf 

And change the order of that line, bringing index.php to the first position:

DirectoryIndex index.php index.html index.cgi index.pl index.xhtml index.htm

Performing SQL queries on an Excel Table within a Workbook with VBA Macro

I am a beginner tinkering on somebody else's code so please be lenient and further correct my errors. I tried your code and played with the VBA help The following worked with me:

Function currAddressTest(dataRangeTest As Range) As String

    currAddressTest = ActiveSheet.Name & "$" & dataRangeTest.Address(False, False)

End Function

When I select data source argument for my function, it is turned into Sheet1$A1:G3 format. If excel changes it to Table1[#All] reference in my formula, the function still works properly

I then used it in your function (tried to play and add another argument to be injected to WHERE...

Function SQL(dataRange As Range, CritA As String)

Dim cn As ADODB.Connection
Dim rs As ADODB.Recordset
Dim currAddress As String



currAddress = ActiveSheet.Name & "$" & dataRange.Address(False, False)

strFile = ThisWorkbook.FullName
strCon = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & strFile _
& ";Extended Properties=""Excel 12.0;HDR=Yes;IMEX=1"";"

Set cn = CreateObject("ADODB.Connection")
Set rs = CreateObject("ADODB.Recordset")

cn.Open strCon


strSQL = "SELECT * FROM [" & currAddress & "]" & _
         "WHERE [A] =  '" & CritA & "'  " & _
         "ORDER BY 1 ASC"

rs.Open strSQL, cn

SQL = rs.GetString

End Function

Hope your function develops further, I find it very useful. Have a nice day!

What is the difference between angular-route and angular-ui-router?

ngRoute is a basic routing library, where you can specify just one view and controller for any route.

With ui-router, you can specify multiple views, both parallel and nested. So if your application requires (or may require in future) any kind of complex routing/views, then go ahead with ui-router.

This is best getting started guide for AngularUI Router.

HTTP 404 when accessing .svc file in IIS

Verifies that you directory has been converted into an Application is your IIS.

ASP.NET Setting width of DataBound column in GridView

add HeaderStyle in your bound field:

    <asp:BoundField HeaderText="UserId"
                DataField="UserId" 
                SortExpression="UserId">

                <HeaderStyle Width="200px" />

</asp:BoundField>

wait() or sleep() function in jquery?

I found a function called sleep function on the internet and don't know who made it. Here it is.

function sleep(milliseconds) {
  var start = new Date().getTime();
  for (var i = 0; i < 1e7; i++) {
    if ((new Date().getTime() - start) > milliseconds){
      break;
    }
  }
}

sleep(2000);

Stop setInterval

USE this i hope help you

var interval;

function updateDiv(){
    $.ajax({
        url: 'getContent.php',
        success: function(data){
            $('.square').html(data);
        },
        error: function(){
            /* clearInterval(interval); */
            stopinterval(); // stop the interval
            $.playSound('oneday.wav');
            $('.square').html('<span style="color:red">Connection problems</span>');
        }
    });
}

function playinterval(){
  updateDiv(); 
  interval = setInterval(function(){updateDiv();},3000); 
  return false;
}

function stopinterval(){
  clearInterval(interval); 
  return false;
}

$(document)
.on('ready',playinterval)
.on({click:playinterval},"#playinterval")
.on({click:stopinterval},"#stopinterval");

IIS: Where can I find the IIS logs?

I think the Default place for IIS logging is: c:\inetpub\wwwroot\log\w3svc

Set min-width either by content or 200px (whichever is greater) together with max-width

The problem is that flex: 1 sets flex-basis: 0. Instead, you need

.container .box {
  min-width: 200px;
  max-width: 400px;
  flex-basis: auto; /* default value */
  flex-grow: 1;
}

_x000D_
_x000D_
.container {_x000D_
  display: -webkit-flex;_x000D_
  display: flex;_x000D_
  -webkit-flex-wrap: wrap;_x000D_
  flex-wrap: wrap;_x000D_
}_x000D_
_x000D_
.container .box {_x000D_
  -webkit-flex-grow: 1;_x000D_
  flex-grow: 1;_x000D_
  min-width: 100px;_x000D_
  max-width: 400px;_x000D_
  height: 200px;_x000D_
  background-color: #fafa00;_x000D_
  overflow: hidden;_x000D_
}
_x000D_
<div class="container">_x000D_
  <div class="box">_x000D_
    <table>_x000D_
      <tr>_x000D_
        <td>Content</td>_x000D_
        <td>Content</td>_x000D_
        <td>Content</td>_x000D_
      </tr>_x000D_
    </table>    _x000D_
  </div>_x000D_
  <div class="box">_x000D_
    <table>_x000D_
      <tr>_x000D_
        <td>Content</td>_x000D_
      </tr>_x000D_
    </table>    _x000D_
  </div>_x000D_
  <div class="box">_x000D_
    <table>_x000D_
      <tr>_x000D_
        <td>Content</td>_x000D_
        <td>Content</td>_x000D_
      </tr>_x000D_
    </table>    _x000D_
  </div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

Simple proof that GUID is not unique

Any two GUIDs are very likely unique (not equal).

See this SO entry, and from Wikipedia

While each generated GUID is not guaranteed to be unique, the total number of unique keys (2^128 or 3.4×10^38) is so large that the probability of the same number being generated twice is very small. For example, consider the observable universe, which contains about 5×10^22 stars; every star could then have 6.8×10^15 universally unique GUIDs.

So probably you have to wait for many more billion of years, and hope that you hit one before the universe as we know it comes to an end.

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException

ArrayIndexOutOfBoundsException in simple words is -> you have 10 students in your class (int array size 10) and you want to view the value of the 11th student (a student who does not exist)

if you make this int i[3] then i takes values i[0] i[1] i[2]

for your problem try this code structure

double[] array = new double[50];

    for (int i = 0; i < 24; i++) {

    }

    for (int j = 25; j < 50; j++) {

    }

Sorting by date & time in descending order?

Following Query works for me. Database Tabel t_sonde_results has domain d_date (datatype DATE) and d_time (datatype TIME) The intention is to query for last entry in t_sonde_results sorted by Date and Time

select * from (select * from (SELECT * FROM t_sonde_results WHERE d_user_name = 'kenis' and d_smartbox_id = 6 order by d_time asc) AS tmp order by d_date and d_time limit 1) as tmp1

How to use org.apache.commons package?

Download commons-net binary from here. Extract the files and reference the commons-net-x.x.jar file.

How to connect to LocalDb

 <add name="Default" connectionString="Data Source=(LocalDb)\MSSqlLocalDB; Initial Catalog=CRM_Default_v1; Integrated Security=True"
      providerName="System.Data.SqlClient"/>

your web.config files in visual studio under connectiionString or Go to View > SQL Server Object Viewer > Add Sql Server> add your server there

How to getElementByClass instead of GetElementById with JavaScript?

adding to CMS's answer, this is a more generic approach of toggle_visibility I've just used myself:

function toggle_visibility(className,display) {
   var elements = getElementsByClassName(document, className),
       n = elements.length;
   for (var i = 0; i < n; i++) {
     var e = elements[i];

     if(display.length > 0) {
       e.style.display = display;
     } else {
       if(e.style.display == 'block') {
         e.style.display = 'none';
       } else {
         e.style.display = 'block';
       }
     }
  }
}

When should I use h:outputLink instead of h:commandLink?

I also see that the page loading (performance) takes a long time on using h:commandLink than h:link. h:link is faster compared to h:commandLink

How to redirect verbose garbage collection output to a file?

Java 9 & Unified JVM Logging

JEP 158 introduces a common logging system for all components of the JVM which will change (and IMO simplify) how logging works with GC. JEP 158 added a new command-line option to control logging from all components of the JVM:

-Xlog

For example, the following option:

-Xlog:gc

will log messages tagged with gc tag using info level to stdout. Or this one:

-Xlog:gc=debug:file=gc.txt:none

would log messages tagged with gc tag using debug level to a file called gc.txt with no decorations. For more detailed discussion, you can checkout the examples in the JEP page.

What character represents a new line in a text area

&#10;- Line Feed and &#13; Carriage Return

These HTML entities will insert a new line or carriage return inside a text area.

java: How can I do dynamic casting of a variable from one type to another?

Regarding your update, the only way to solve this in Java is to write code that covers all cases with lots of if and else and instanceof expressions. What you attempt to do looks as if are used to program with dynamic languages. In static languages, what you attempt to do is almost impossible and one would probably choose a totally different approach for what you attempt to do. Static languages are just not as flexible as dynamic ones :)

Good examples of Java best practice are the answer by BalusC (ie ObjectConverter) and the answer by Andreas_D (ie Adapter) below.


That does not make sense, in

String a = (theType) 5;

the type of a is statically bound to be String so it does not make any sense to have a dynamic cast to this static type.

PS: The first line of your example could be written as Class<String> stringClass = String.class; but still, you cannot use stringClass to cast variables.

Which language uses .pde extension?

This code is from Processing.org an open source Java based IDE. You can find it Processing.org. The Arduino IDE also uses this extension, although they run on a hardware board.

EDIT - And yes it is C syntax, used mostly for art or live media presentations.

How to read pdf file and write it to outputStream

import java.io.*;


public class FileRead {


    public static void main(String[] args) throws IOException {


        File f=new File("C:\\Documents and Settings\\abc\\Desktop\\abc.pdf");

        OutputStream oos = new FileOutputStream("test.pdf");

        byte[] buf = new byte[8192];

        InputStream is = new FileInputStream(f);

        int c = 0;

        while ((c = is.read(buf, 0, buf.length)) > 0) {
            oos.write(buf, 0, c);
            oos.flush();
        }

        oos.close();
        System.out.println("stop");
        is.close();

    }

}

The easiest way so far. Hope this helps.

Shared folder between MacOSX and Windows on Virtual Box

Using a Windows 10 guest, after I performed steps 1 through 3 from @xinampc's answer, I had to open a new File Explorer and navigated to This PC > CD Drive (D:) VirtualBox Guest Additions to run VBoxWindowsAdditions. After I ran that and went through the command prompts, Windows rebooted and I was able to see VBOXSVR under Network.

Difference between DataFrame, Dataset, and RDD in Spark

Most of answers are correct only want to add one point here

In Spark 2.0 the two APIs (DataFrame +DataSet) will be unified together into a single API.

"Unifying DataFrame and Dataset: In Scala and Java, DataFrame and Dataset have been unified, i.e. DataFrame is just a type alias for Dataset of Row. In Python and R, given the lack of type safety, DataFrame is the main programming interface."

Datasets are similar to RDDs, however, instead of using Java serialization or Kryo they use a specialized Encoder to serialize the objects for processing or transmitting over the network.

Spark SQL supports two different methods for converting existing RDDs into Datasets. The first method uses reflection to infer the schema of an RDD that contains specific types of objects. This reflection based approach leads to more concise code and works well when you already know the schema while writing your Spark application.

The second method for creating Datasets is through a programmatic interface that allows you to construct a schema and then apply it to an existing RDD. While this method is more verbose, it allows you to construct Datasets when the columns and their types are not known until runtime.

Here you can find RDD tof Data frame conversation answer

How to convert rdd object to dataframe in spark

How to get element by classname or id

getElementsByClassName is a function on the DOM Document. It is neither a jQuery nor a jqLite function.

Don't add the period before the class name when using it:

var result = document.getElementsByClassName("multi-files");

Wrap it in jqLite (or jQuery if jQuery is loaded before Angular):

var wrappedResult = angular.element(result);

If you want to select from the element in a directive's link function you need to access the DOM reference instead of the the jqLite reference - element[0] instead of element:

link: function (scope, element, attrs) {

  var elementResult = element[0].getElementsByClassName('multi-files');
}

Alternatively you can use the document.querySelector function (need the period here if selecting by class):

var queryResult = element[0].querySelector('.multi-files');
var wrappedQueryResult = angular.element(queryResult);

Demo: http://plnkr.co/edit/AOvO47ebEvrtpXeIzYOH?p=preview

Setting device orientation in Swift iOS

Swift 3

Orientation rotation is more complicated if a view controller is embedded in UINavigationController or UITabBarController the navigation or tab bar controller takes precedence and makes the decisions on autorotation and supported orientations.

Use the following extensions on UINavigationController and UITabBarController so that view controllers that are embedded in one of these controllers get to make the decisions:

UINavigationController extension

extension UINavigationController {

override open var shouldAutorotate: Bool {
    get {
        if let visibleVC = visibleViewController {
            return visibleVC.shouldAutorotate
        }
        return super.shouldAutorotate
    }
}

override open var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation{
    get {
        if let visibleVC = visibleViewController {
            return visibleVC.preferredInterfaceOrientationForPresentation
        }
        return super.preferredInterfaceOrientationForPresentation
    }
}

override open var supportedInterfaceOrientations: UIInterfaceOrientationMask{
    get {
        if let visibleVC = visibleViewController {
            return visibleVC.supportedInterfaceOrientations
        }
        return super.supportedInterfaceOrientations
    }
 }}

UITabBarController extension

extension UITabBarController {

override open var shouldAutorotate: Bool {
    get {
        if let selectedVC = selectedViewController{
            return selectedVC.shouldAutorotate
        }
        return super.shouldAutorotate
    }
}

override open var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation{
    get {
        if let selectedVC = selectedViewController{
            return selectedVC.preferredInterfaceOrientationForPresentation
        }
        return super.preferredInterfaceOrientationForPresentation
    }
}

override open var supportedInterfaceOrientations: UIInterfaceOrientationMask{
    get {
        if let selectedVC = selectedViewController{
            return selectedVC.supportedInterfaceOrientations
        }
        return super.supportedInterfaceOrientations
    }
}}

Now you can override the supportedInterfaceOrientations, shouldAutoRotate and preferredInterfaceOrientationForPresentation in the view controller you want to lock down otherwise you can leave out the overrides in other view controllers that you want to inherit the default orientation behavior specified in your app's plist.

Lock to Specific Orientation

class YourViewController: UIViewController {
open override var supportedInterfaceOrientations: UIInterfaceOrientationMask{
    get {
        return .portrait
    }
}}

Disable Rotation

    class YourViewController: UIViewController {
open override var shouldAutorotate: Bool {
    get {
        return false
    }
}}

Change Preferred Interface Orientation For Presentation

class YourViewController: UIViewController {
open override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation{
    get {
        return .portrait
    }
}}

Where does mysql store data?

I just installed MySQL Server 5.7 on Windows 10 and my.ini file is located here c:\ProgramData\MySQL\MySQL Server 5.7\my.ini.

The Data folder (where your dbs are created) is here C:/ProgramData/MySQL/MySQL Server 5.7\Data.

Warn user before leaving web page with unsaved changes

Tested Eli Grey's universal solution, only worked after I simplified the code to

  'use strict';
  (() => {
    const modified_inputs = new Set();
    const defaultValue = 'defaultValue';
    // store default values
    addEventListener('beforeinput', evt => {
      const target = evt.target;
      if (!(defaultValue in target.dataset)) {
        target.dataset[defaultValue] = ('' + (target.value || target.textContent)).trim();
      }
    });

    // detect input modifications
    addEventListener('input', evt => {
      const target = evt.target;
      let original = target.dataset[defaultValue];

      let current = ('' + (target.value || target.textContent)).trim();

      if (original !== current) {
        if (!modified_inputs.has(target)) {
          modified_inputs.add(target);
        }
      } else if (modified_inputs.has(target)) {
        modified_inputs.delete(target);
      }
    });

    addEventListener(
      'saved',
      function(e) {
        modified_inputs.clear()
      },
      false
    );

    addEventListener('beforeunload', evt => {
      if (modified_inputs.size) {
        const unsaved_changes_warning = 'Changes you made may not be saved.';
        evt.returnValue = unsaved_changes_warning;
        return unsaved_changes_warning;
      }
    });

  })();

The modifications to his is deleted the usage of target[defaultValue] and only use target.dataset[defaultValue] to store the real default value.

And I added a 'saved' event listener where the 'saved' event will be triggered by yourself on your saving action succeeded.

But this 'universal' solution only works in browsers, not works in app's webview, for example, wechat browsers.

To make it work in wechat browsers(partially) also, another improvements again:

  'use strict';
  (() => {
    const modified_inputs = new Set();
    const defaultValue = 'defaultValue';
    // store default values
    addEventListener('beforeinput', evt => {
      const target = evt.target;
      if (!(defaultValue in target.dataset)) {
        target.dataset[defaultValue] = ('' + (target.value || target.textContent)).trim();
      }
    });

    // detect input modifications
    addEventListener('input', evt => {
      const target = evt.target;
      let original = target.dataset[defaultValue];

      let current = ('' + (target.value || target.textContent)).trim();

      if (original !== current) {
        if (!modified_inputs.has(target)) {
          modified_inputs.add(target);
        }
      } else if (modified_inputs.has(target)) {
        modified_inputs.delete(target);
      }

      if(modified_inputs.size){
        const event = new Event('needSave')
        window.dispatchEvent(event);
      }
    });

    addEventListener(
      'saved',
      function(e) {
        modified_inputs.clear()
      },
      false
    );

    addEventListener('beforeunload', evt => {
      if (modified_inputs.size) {
        const unsaved_changes_warning = 'Changes you made may not be saved.';
        evt.returnValue = unsaved_changes_warning;
        return unsaved_changes_warning;
      }
    });

    const ua = navigator.userAgent.toLowerCase();

    if(/MicroMessenger/i.test(ua)) {
      let pushed = false

      addEventListener('needSave', evt => {
        if(!pushed) {
          pushHistory();

          window.addEventListener("popstate", function(e) {
            if(modified_inputs.size) {
              var cfi = confirm('???????????' + JSON.stringify(e));
              if (cfi) {
                modified_inputs.clear()
                history.go(-1)
              }else{
                e.preventDefault();
                e.stopPropagation();
              }
            }
          }, false);
        }

        pushed = true
      });
    }

    function pushHistory() {
      var state = {
        title: document.title,
        url: "#flag"
      };
      window.history.pushState(state, document.title, "#flag");
    }
  })();

Instance member cannot be used on type

For anyone else who stumbles on this make sure you're not attempting to modify the class rather than the instance! (unless you've declared the variable as static)

eg.

MyClass.variable = 'Foo' // WRONG! - Instance member 'variable' cannot be used on type 'MyClass'

instanceOfMyClass.variable = 'Foo' // Right!

how to hide a vertical scroll bar when not needed

overflow: auto; or overflow: hidden; should do it I think.

Why use the 'ref' keyword when passing an object?

Ref denotes whether the function can get its hands on the object itself, or only on its value.

Passing by reference is not bound to a language; it's a parameter binding strategy next to pass-by-value, pass by name, pass by need etc...

A sidenote: the class name TestRef is a hideously bad choice in this context ;).

Is there a <meta> tag to turn off caching in all browsers?

For modern web browsers (After IE9)

See the Duplicate listed at the top of the page for correct information!

See answer here: How to control web page caching, across all browsers?


For IE9 and before

Do not blindly copy paste this!

The list is just examples of different techniques, it's not for direct insertion. If copied, the second would overwrite the first and the fourth would overwrite the third because of the http-equiv declarations AND fail with the W3C validator. At most, one could have one of each http-equiv declarations; pragma, cache-control and expires. These are completely outdated when using modern up to date browsers. After IE9 anyway. Chrome and Firefox specifically does not work with these as you would expect, if at all.

<meta http-equiv="cache-control" content="max-age=0" />
<meta http-equiv="cache-control" content="no-cache" />
<meta http-equiv="expires" content="0" />
<meta http-equiv="expires" content="Tue, 01 Jan 1980 1:00:00 GMT" />
<meta http-equiv="pragma" content="no-cache" />

Actually do not use these at all!

Caching headers are unreliable in meta elements; for one, any web proxies between the site and the user will completely ignore them. You should always use a real HTTP header for headers such as Cache-Control and Pragma.

Stopping an Android app from console

If you have access to the application package, then you can install with the -r option and it will kill the process if it is currently running as a side effect. Like this:

adb -d install -r MyApp.apk ; adb -d shell am start -a android.intent.action.MAIN -n com.MyCompany.MyApp/.MyActivity

The -r option preserves the data currently associated with the app. However, if you want a clean slate like you mention you might not want to use that option.

FtpWebRequest Download File

I know this is an old Post but I am adding here for future reference. Here is a solution that I found:

    private void DownloadFileFTP()
    {
        string inputfilepath = @"C:\Temp\FileName.exe";
        string ftphost = "xxx.xx.x.xxx";
        string ftpfilepath = "/Updater/Dir1/FileName.exe";

        string ftpfullpath = "ftp://" + ftphost + ftpfilepath;

        using (WebClient request = new WebClient())
        {
            request.Credentials = new NetworkCredential("UserName", "P@55w0rd");
            byte[] fileData = request.DownloadData(ftpfullpath);

            using (FileStream file = File.Create(inputfilepath))
            {
                file.Write(fileData, 0, fileData.Length);
                file.Close();
            }
            MessageBox.Show("Download Complete");
        }
    }

Updated based upon excellent suggestion by Ilya Kogan

'any' vs 'Object'

Object appears to be a more specific declaration than any. From the TypeScript spec (section 3):

All types in TypeScript are subtypes of a single top type called the Any type. The any keyword references this type. The Any type is the one type that can represent any JavaScript value with no constraints. All other types are categorized as primitive types, object types, or type parameters. These types introduce various static constraints on their values.

Also:

The Any type is used to represent any JavaScript value. A value of the Any type supports the same operations as a value in JavaScript and minimal static type checking is performed for operations on Any values. Specifically, properties of any name can be accessed through an Any value and Any values can be called as functions or constructors with any argument list.

Objects do not allow the same flexibility.

For example:

var myAny : any;

myAny.Something(); // no problemo

var myObject : Object;

myObject.Something(); // Error: The property 'Something' does not exist on value of type 'Object'.

What does the following Oracle error mean: invalid column index

I also got this type error, problem is wrong usage of parameters to statement like, Let's say you have a query like this

SELECT * FROM EMPLOYE E WHERE E.ID = ?

and for the preparedStatement object (JDBC) if you set the parameters like

preparedStatement.setXXX(1,value);
preparedStatement.setXXX(2,value)

then it results in SQLException: Invalid column index

So, I removed that second parameter setting to prepared statement then problem solved

Vue is not defined

I found two main problems with that implementation. First, when you import the vue.js script you use type="JavaScript" as content-type which is wrong. You should remove this type parameter because by default script tags have text/javascript as default content-type. Or, just replace the type parameter with the correct content-type which is type="text/javascript".

The second problem is that your script is embedded in the same HTML file means that it may be triggered first and probably the vue.js file was not loaded yet. You can fix this using a jQuery snippet $(function(){ /* ... */ }); or adding a javascript function as shown in this example:

_x000D_
_x000D_
// Verifies if the document is ready_x000D_
function ready(f) {_x000D_
  /in/.test(document.readyState) ? setTimeout('ready(' + f + ')', 9) : f();_x000D_
}_x000D_
_x000D_
ready(function() {_x000D_
  var demo = new Vue({_x000D_
    el: '#demo',_x000D_
    data: {_x000D_
      message: 'Hello Vue.js!'_x000D_
    }_x000D_
  })_x000D_
});
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>_x000D_
<div id="demo">_x000D_
  <p>{{message}}</p>_x000D_
  <input v-model="message">_x000D_
</div>
_x000D_
_x000D_
_x000D_

What is the difference between Nexus and Maven?

Sonatype Nexus and Apache Maven are two pieces of software that often work together but they do very different parts of the job. Nexus provides a repository while Maven uses a repository to build software.

Here's a quote from "What is Nexus?":

Nexus manages software "artifacts" required for development. If you develop software, your builds can download dependencies from Nexus and can publish artifacts to Nexus creating a new way to share artifacts within an organization. While Central repository has always served as a great convenience for developers you shouldn't be hitting it directly. You should be proxying Central with Nexus and maintaining your own repositories to ensure stability within your organization. With Nexus you can completely control access to, and deployment of, every artifact in your organization from a single location.

And here is a quote from "Maven and Nexus Pro, Made for Each Other" explaining how Maven uses repositories:

Maven leverages the concept of a repository by retrieving the artifacts necessary to build an application and deploying the result of the build process into a repository. Maven uses the concept of structured repositories so components can be retrieved to support the build. These components or dependencies include libraries, frameworks, containers, etc. Maven can identify components in repositories, understand their dependencies, retrieve all that are needed for a successful build, and deploy its output back to repositories when the build is complete.

So, when you want to use both you will have a repository managed by Nexus and Maven will access this repository.

How to delete a folder in C++?

If you are using windows, then take a look at this link. Otherwise, you may look for your OS specific version api. I don't think C++ comes with a cross-platform way to do it. At the end, it's NOT C++'s work, it's the OS's work.

Sass .scss: Nesting and multiple classes?

You can use the parent selector reference &, it will be replaced by the parent selector after compilation:

For your example:

.container {
    background:red;
    &.desc{
       background:blue;
    }
}

/* compiles to: */
.container {
    background: red;
}
.container.desc {
    background: blue;
}

The & will completely resolve, so if your parent selector is nested itself, the nesting will be resolved before replacing the &.

This notation is most often used to write pseudo-elements and -classes:

.element{
    &:hover{ ... }
    &:nth-child(1){ ... }
}

However, you can place the & at virtually any position you like*, so the following is possible too:

.container {
    background:red;
    #id &{
       background:blue;
    }
}

/* compiles to: */
.container {
    background: red;
}
#id .container {
    background: blue;
}

However be aware, that this somehow breaks your nesting structure and thus may increase the effort of finding a specific rule in your stylesheet.

*: No other characters than whitespaces are allowed in front of the &. So you cannot do a direct concatenation of selector+& - #id& would throw an error.

Laravel Query Builder where max id

For objects you can nest the queries:

DB::table('orders')->find(DB::table('orders')->max('id'));

So the inside query looks up the max id in the table and then passes that to the find, which gets you back the object.

Can I escape a double quote in a verbatim string literal?

Use double quotation marks.

string foo = @"this ""word"" is escaped";

Is "delete this" allowed in C++?

The C++ FAQ Lite has a entry specifically for this

I think this quote sums it up nicely

As long as you're careful, it's OK for an object to commit suicide (delete this).

Handling warning for possible multiple enumeration of IEnumerable

If your data is always going to be repeatable, perhaps don't worry about it. However, you can unroll it too - this is especially useful if the incoming data could be large (for example, reading from disk/network):

if(objects == null) throw new ArgumentException();
using(var iter = objects.GetEnumerator()) {
    if(!iter.MoveNext()) throw new ArgumentException();

    var firstObject = iter.Current;
    var list = DoSomeThing(firstObject);  

    while(iter.MoveNext()) {
        list.Add(DoSomeThingElse(iter.Current));
    }
    return list;
}

Note I changed the semantic of DoSomethingElse a bit, but this is mainly to show unrolled usage. You could re-wrap the iterator, for example. You could make it an iterator block too, which could be nice; then there is no list - and you would yield return the items as you get them, rather than add to a list to be returned.

How to keep console window open

Put a Console.Read() as the last line in your program. That will prevent it from closing until you press a key

static void Main(string[] args)
{
    StringAddString s = new StringAddString();
    Console.Read();            
}

Importing Excel spreadsheet data into another Excel spreadsheet containing VBA

This should get you started: Using VBA in your own Excel workbook, have it prompt the user for the filename of their data file, then just copy that fixed range into your target workbook (that could be either the same workbook as your macro enabled one, or a third workbook). Here's a quick vba example of how that works:

' Get customer workbook...
Dim customerBook As Workbook
Dim filter As String
Dim caption As String
Dim customerFilename As String
Dim customerWorkbook As Workbook
Dim targetWorkbook As Workbook

' make weak assumption that active workbook is the target
Set targetWorkbook = Application.ActiveWorkbook

' get the customer workbook
filter = "Text files (*.xlsx),*.xlsx"
caption = "Please Select an input file "
customerFilename = Application.GetOpenFilename(filter, , caption)

Set customerWorkbook = Application.Workbooks.Open(customerFilename)

' assume range is A1 - C10 in sheet1
' copy data from customer to target workbook
Dim targetSheet As Worksheet
Set targetSheet = targetWorkbook.Worksheets(1)
Dim sourceSheet As Worksheet
Set sourceSheet = customerWorkbook.Worksheets(1)

targetSheet.Range("A1", "C10").Value = sourceSheet.Range("A1", "C10").Value

' Close customer workbook
customerWorkbook.Close

Elegant Python function to convert CamelCase to snake_case?

Wow I just stole this from django snippets. ref http://djangosnippets.org/snippets/585/

Pretty elegant

camelcase_to_underscore = lambda str: re.sub(r'(?<=[a-z])[A-Z]|[A-Z](?=[^A-Z])', r'_\g<0>', str).lower().strip('_')

Example:

camelcase_to_underscore('ThisUser')

Returns:

'this_user'

REGEX DEMO

How to download a file from my server using SSH (using PuTTY on Windows)

If your server have a http service you can compress your directory and download the compressed file.

Compress:

tar -zcvf archive-name.tar.gz -C directory-name .

Download throught your browser:

http://the-server-ip/archive-name.tar.gz

If you don't have direct access to the server ip, do a ssh tunnel throught putty, and forward the 80 port in some local port, and you can download the file.

Best practices when running Node.js with port 80 (Ubuntu / Linode)

Port 80

What I do on my cloud instances is I redirect port 80 to port 3000 with this command:

sudo iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 3000

Then I launch my Node.js on port 3000. Requests to port 80 will get mapped to port 3000.

You should also edit your /etc/rc.local file and add that line minus the sudo. That will add the redirect when the machine boots up. You don't need sudo in /etc/rc.local because the commands there are run as root when the system boots.

Logs

Use the forever module to launch your Node.js with. It will make sure that it restarts if it ever crashes and it will redirect console logs to a file.

Launch on Boot

Add your Node.js start script to the file you edited for port redirection, /etc/rc.local. That will run your Node.js launch script when the system starts.

Digital Ocean & other VPS

This not only applies to Linode, but Digital Ocean, AWS EC2 and other VPS providers as well. However, on RedHat based systems /etc/rc.local is /ect/rc.d/local.

Set IDENTITY_INSERT ON is not working

In VB code, when trying to submit an INSERT query, you must submit a double query in the same 'executenonquery' like this:

sqlQuery = "SET IDENTITY_INSERT dbo.TheTable ON; INSERT INTO dbo.TheTable (Col1, COl2) VALUES (Val1, Val2); SET IDENTITY_INSERT dbo.TheTable OFF;"

I used a ; separator instead of a GO.

Works for me. Late but efficient!

How to print the data in byte array as characters?

Try this one : new String(byte[])

Can promises have multiple arguments to onFulfilled?

Great question, and great answer by Benjamin, Kris, et al - many thanks!

I'm using this in a project and have created a module based on Benjamin Gruenwald's code. It's available on npmjs:

npm i -S promise-spread

Then in your code, do

require('promise-spread');

If you're using a library such as any-promise

var Promise = require('any-promise');
require('promise-spread')(Promise);

Maybe others find this useful, too!

Angular 2 - Setting selected value on dropdown list

Angular 2 simple dropdown selected value

It may help someone as I need to only show selected value, don't need to declare something in component and etc.

If your status is coming from the database then you can show selected value this way.

<div class="form-group">
    <label for="status">Status</label>
    <select class="form-control" name="status" [(ngModel)]="category.status">
       <option [value]="1" [selected]="category.status ==1">Active</option>
       <option [value]="0" [selected]="category.status ==0">In Active</option>
    </select>
</div>

The easiest way to replace white spaces with (underscores) _ in bash

This is borderline programming, but look into using tr:

$ echo "this is just a test" | tr -s ' ' | tr ' ' '_'

Should do it. The first invocation squeezes the spaces down, the second replaces with underscore. You probably need to add TABs and other whitespace characters, this is for spaces only.

Selecting a Record With MAX Value

Here's an option if you have multiple records for each Customer and are looking for the latest balance for each (say they are dated records):

SELECT ID, BALANCE FROM (
    SELECT ROW_NUMBER() OVER (PARTITION BY ID ORDER BY DateModified DESC) as RowNum, ID, BALANCE
    FROM CUSTOMERS
) C
WHERE RowNum = 1

Modifying a file inside a jar

Check out TrueZip.

It does exactly what you want (to edit files inline inside a jar file), through a virtual file system API. It also supports nested archives (jar inside a jar) as well.

How can I set my Cygwin PATH to find javac?

Although all other answers are technically correct, I would recommend you adding the custom path to the beginning of your PATH, not at the end. That way it would be the first place to look for instead of the last:

Add to bottom of ~/.bash_profile:

export PATH="/cygdrive/C/Program Files/Java/jdk1.6.0_23/bin/":$PATH

That way if you have more than one java or javac it will use the one you provided first.

PHP fwrite new line

You append a newline to both the username and the password, i.e. the output would be something like

Sebastian
password
John
hfsjaijn

use fwrite($fh,$user." ".$password."\n"); instead to have them both on one line.
Or use fputcsv() to write the data and fgetcsv() to fetch it. This way you would at least avoid encoding problems like e.g. with $username='Charles, III';

...i.e. setting aside all the things that are wrong about storing plain passwords in plain files and using _GET for this type of operation (use _POST instead) ;-)

Complex CSS selector for parent of active child

Future answer with CSS4 selectors

New CSS Specs contain an experimental :has pseudo selector that might be able to do this thing.

li:has(a:active) {
  /* ... */
}

The browser support on this is basically non-existent at this time, but it is in consideration on the official specs.


Answer in 2012 that was wrong in 2012 and is even more wrong in 2018

While it is true that CSS cannot ASCEND, it is incorrect that you cannot grab the parent element of another element. Let me reiterate:

Using your HTML example code, you are able to grab the li without specifying li

ul * a {
    property:value;
}

In this example, the ul is the parent of some element and that element is the parent of anchor. The downside of using this method is that if there is a ul with any child element that contains an anchor, it inherits the styles specified.

You may also use the child selector as well since you'll have to specify the parent element anyway.

ul>li a {
    property:value;
}

In this example, the anchor must be a descendant of an li that MUST be a child of ul, meaning it must be within the tree following the ul declaration. This is going to be a bit more specific and will only grab a list item that contains an anchor AND is a child of ul.

SO, to answer your question by code.

ul.menu > li a.active {
    property:value;
}

This should grab the ul with the class of menu, and the child list item that contains only an anchor with the class of active.

MySQL ON DUPLICATE KEY UPDATE for multiple rows insert in single query

I was looking for the same behavior using jdbi's BindBeanList and found the syntax is exactly the same as Peter Lang's answer above. In case anybody is running into this question, here's my code:

  @SqlUpdate("INSERT INTO table_one (col_one, col_two) VALUES <beans> ON DUPLICATE KEY UPDATE col_one=VALUES(col_one), col_two=VALUES(col_two)")
void insertBeans(@BindBeanList(value = "beans", propertyNames = {"colOne", "colTwo"}) List<Beans> beans);

One key detail to note is that the propertyName you specify within @BindBeanList annotation is not same as the column name you pass into the VALUES() call on update.

Order a List (C#) by many fields?

Use ThenBy:

var orderedCustomers = Customer.OrderBy(c => c.LastName).ThenBy(c => c.FirstName)

See MSDN: http://msdn.microsoft.com/en-us/library/bb549422.aspx

How correctly produce JSON by RESTful web service?

@POST
@Path ("Employee")
@Consumes("application/json")
@Produces("application/json")
public JSONObject postEmployee(JSONObject jsonObject)throws Exception{
    return jsonObject;
}       

Auto detect mobile browser (via user-agent?)

There are open source scripts on Detect Mobile Browser that do this in Apache, ASP, ColdFusion, JavaScript and PHP.

How to convert object to Dictionary<TKey, TValue> in C#?

this should work:

for numbers, strings, date, etc.:

    public static void MyMethod(object obj)
    {
        if (typeof(IDictionary).IsAssignableFrom(obj.GetType()))
        {
            IDictionary idict = (IDictionary)obj;

            Dictionary<string, string> newDict = new Dictionary<string, string>();
            foreach (object key in idict.Keys)
            {
                newDict.Add(key.ToString(), idict[key].ToString());
            }
        }
        else
        {
            // My object is not a dictionary
        }
    }

if your dictionary also contains some other objects:

    public static void MyMethod(object obj)
    {
        if (typeof(IDictionary).IsAssignableFrom(obj.GetType()))
        {
            IDictionary idict = (IDictionary)obj;
            Dictionary<string, string> newDict = new Dictionary<string, string>();

            foreach (object key in idict.Keys)
            {
                newDict.Add(objToString(key), objToString(idict[key]));
            }
        }
        else
        {
            // My object is not a dictionary
        }
    }

    private static string objToString(object obj)
    {
        string str = "";
        if (obj.GetType().FullName == "System.String")
        {
            str = (string)obj;
        }
        else if (obj.GetType().FullName == "test.Testclass")
        {
            TestClass c = (TestClass)obj;
            str = c.Info;
        }
        return str;
    }

Cannot start MongoDB as a service

If you look in the service details, you can see that the command to start the service is something like:

"C:\Program Files\MongoDB\bin\mongod" --config  C:\Program Files\MongoDB\mongod.cfg  --service 

The MongoDB team forgot to add the " around the --config option. So just edit the registry to correct it and it will work.

$.ajax - dataType

(ps: the answer given by Nick Craver is incorrect)

contentType specifies the format of data being sent to the server as part of request(it can be sent as part of response too, more on that later).

dataType specifies the expected format of data to be received by the client(browser).

Both are not interchangable.

  • contentType is the header sent to the server, specifying the format of data(i.e the content of message body) being being to the server. This is used with POST and PUT requests. Usually when u send POST request, the message body comprises of passed in parameters like:

==============================

Sample request:

POST /search HTTP/1.1 
Content-Type: application/x-www-form-urlencoded 
<<other header>>

name=sam&age=35

==============================

The last line above "name=sam&age=35" is the message body and contentType specifies it as application/x-www-form-urlencoded since we are passing the form parameters in the message body. However we aren't limited to just sending the parameters, we can send json, xml,... like this(sending different types of data is especially useful with RESTful web services):

==============================

Sample request:

POST /orders HTTP/1.1
Content-Type: application/xml
<<other header>>

<order>
   <total>$199.02</total>
   <date>December 22, 2008 06:56</date>
...
</order>

==============================

So the ContentType this time is: application/xml, cause that's what we are sending. The above examples showed sample request, similarly the response send from the server can also have the Content-Type header specifying what the server is sending like this:

==============================

sample response:

HTTP/1.1 201 Created
Content-Type: application/xml
<<other headers>>

<order id="233">
   <link rel="self" href="http://example.com/orders/133"/>
   <total>$199.02</total>
   <date>December 22, 2008 06:56</date>
...
</order>

==============================

  • dataType specifies the format of response to expect. Its related to Accept header. JQuery will try to infer it based on the Content-Type of the response.

==============================

Sample request:

GET /someFolder/index.html HTTP/1.1
Host: mysite.org
Accept: application/xml
<<other headers>>

==============================

Above request is expecting XML from the server.

Regarding your question,

contentType: "application/json; charset=utf-8",
dataType: "json",

Here you are sending json data using UTF8 character set, and you expect back json data from the server. As per the JQuery docs for dataType,

The json type parses the fetched data file as a JavaScript object and returns the constructed object as the result data.

So what you get in success handler is proper javascript object(JQuery converts the json object for you)

whereas

contentType: "application/json",
dataType: "text",

Here you are sending json data, since you haven't mentioned the encoding, as per the JQuery docs,

If no charset is specified, data will be transmitted to the server using the server's default charset; you must decode this appropriately on the server side.

and since dataType is specified as text, what you get in success handler is plain text, as per the docs for dataType,

The text and xml types return the data with no processing. The data is simply passed on to the success handler

Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_u64 on Intel CPUs

This is not an answer, but it's hard to read if I put results in comment.

I get these results with a Mac Pro (Westmere 6-Cores Xeon 3.33 GHz). I compiled it with clang -O3 -msse4 -lstdc++ a.cpp -o a (-O2 get same result).

clang with uint64_t size=atol(argv[1])<<20;

unsigned    41950110000 0.811198 sec    12.9263 GB/s
uint64_t    41950110000 0.622884 sec    16.8342 GB/s

clang with uint64_t size=1<<20;

unsigned    41950110000 0.623406 sec    16.8201 GB/s
uint64_t    41950110000 0.623685 sec    16.8126 GB/s

I also tried to:

  1. Reverse the test order, the result is the same so it rules out the cache factor.
  2. Have the for statement in reverse: for (uint64_t i=size/8;i>0;i-=4). This gives the same result and proves the compile is smart enough to not divide size by 8 every iteration (as expected).

Here is my wild guess:

The speed factor comes in three parts:

  • code cache: uint64_t version has larger code size, but this does not have an effect on my Xeon CPU. This makes the 64-bit version slower.

  • Instructions used. Note not only the loop count, but the buffer is accessed with a 32-bit and 64-bit index on the two versions. Accessing a pointer with a 64-bit offset requests a dedicated 64-bit register and addressing, while you can use immediate for a 32-bit offset. This may make the 32-bit version faster.

  • Instructions are only emitted on the 64-bit compile (that is, prefetch). This makes 64-bit faster.

The three factors together match with the observed seemingly conflicting results.

How to convert DATE to UNIX TIMESTAMP in shell script on MacOS

date -j -f "%Y-%m-%d %H:%M:%S" "2020-04-07 00:00:00" "+%s"

It will print the dynamic seconds when without %H:%M:%S and 00:00:00.

export html table to csv

I found there is a library for this. See example here:

https://editor.datatables.net/examples/extensions/exportButtons.html

In addition to the above code, the following Javascript library files are loaded for use in this example:

In HTML, include following scripts:

jquery.dataTables.min.js   
dataTables.editor.min.js   
dataTables.select.min.js
dataTables.buttons.min.js  
jszip.min.js    
pdfmake.min.js
vfs_fonts.js  
buttons.html5.min.js    
buttons.print.min.js

Enable buttons by adding scripts like:

<script>
$(document).ready( function () {
    $('#table-arrays').DataTable({
        dom: '<"top"Blf>rt<"bottom"ip>',
        buttons: ['copy', 'excel', 'csv', 'pdf', 'print'],
        select: true,
    });
} );
</script>

For some reason, the excel export results in corrupted file, but can be repaired. Alternatively, disable excel and use csv export.

String to list in Python

You can use the split() function, which returns a list, to separate them.

letters = 'QH QD JC KD JS'

letters_list = letters.split()

Printing letters_list would now format it like this:

['QH', 'QD', 'JC', 'KD', 'JS']

Now you have a list that you can work with, just like you would with any other list. For example accessing elements based on indexes:

print(letters_list[2])

This would print the third element of your list, which is 'JC'

How to Check byte array empty or not?

In Android Studio version 3.4.1

if(Attachment != null)
{
   code here ...
}

How to enable PHP short tags?

; Default Value: On
; Development Value: Off
; Production Value: Off
; http://php.net/short-open-tag
;short_open_tag=Off   <--Comment this out
; XAMPP for Linux is currently old fashioned
short_open_tag = On   <--Uncomment this

CSS Outside Border

Way late, but I just ran into a similar issue.
My solution was pseudo elements - no additional markup, and you get to draw the border without affecting the width.
Position the pseudo element absolutely (with the main positioned relatively) and whammo.

See below, JSFiddle here.

.hello {
    position: relative;
    /* Styling not important */
    background: black;
    color: white;
    padding: 20px;
    width: 200px;
    height: 200px;
}

.hello::before {
    content: "";
    position: absolute;
    display: block;
    top: 0;
    left: -5px;
    right: -5px;
    bottom: 0;
    border-left: 5px solid red;
    border-right: 5px solid red;
    z-index: -1;
}

What is callback in Android?

CallBack Interface are used for Fragment to Fragment communication in android.

Refer here for your understanding.

How to make child process die after parent exits?

Some posters have already mentioned pipes and kqueue. In fact you can also create a pair of connected Unix domain sockets by the socketpair() call. The socket type should be SOCK_STREAM.

Let us suppose you have the two socket file descriptors fd1, fd2. Now fork() to create the child process, which will inherit the fds. In the parent you close fd2 and in the child you close fd1. Now each process can poll() the remaining open fd on its own end for the POLLIN event. As long as each side doesn't explicitly close() its fd during normal lifetime, you can be fairly sure that a POLLHUP flag should indicate the other's termination (no matter clean or not). Upon notified of this event, the child can decide what to do (e.g. to die).

#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <poll.h>
#include <stdio.h>

int main(int argc, char ** argv)
{
    int sv[2];        /* sv[0] for parent, sv[1] for child */
    socketpair(AF_UNIX, SOCK_STREAM, 0, sv);

    pid_t pid = fork();

    if ( pid > 0 ) {  /* parent */
        close(sv[1]);
        fprintf(stderr, "parent: pid = %d\n", getpid());
        sleep(100);
        exit(0);

    } else {          /* child */
        close(sv[0]);
        fprintf(stderr, "child: pid = %d\n", getpid());

        struct pollfd mon;
        mon.fd = sv[1];
        mon.events = POLLIN;

        poll(&mon, 1, -1);
        if ( mon.revents & POLLHUP )
            fprintf(stderr, "child: parent hung up\n");
        exit(0);
    }
}

You can try compiling the above proof-of-concept code, and run it in a terminal like ./a.out &. You have roughly 100 seconds to experiment with killing the parent PID by various signals, or it will simply exit. In either case, you should see the message "child: parent hung up".

Compared with the method using SIGPIPE handler, this method doesn't require trying the write() call.

This method is also symmetric, i.e. the processes can use the same channel to monitor each other's existence.

This solution calls only the POSIX functions. I tried this in Linux and FreeBSD. I think it should work on other Unixes but I haven't really tested.

See also:

  • unix(7) of Linux man pages, unix(4) for FreeBSD, poll(2), socketpair(2), socket(7) on Linux.

Compile throws a "User-defined type not defined" error but does not go to the offending line of code

I've seen this error too when the code stopped at the line:

Dim myNode As MSXML2.IXMLDOMNode

I found out that I had to add "Microsoft XML, v6.0" via Tools > Preferences.

Then it worked for me.

Why does the C preprocessor interpret the word "linux" as the constant "1"?

Use this command

gcc -dM -E - < /dev/null

to get this

    #define _LP64 1
#define _STDC_PREDEF_H 1
#define __ATOMIC_ACQUIRE 2
#define __ATOMIC_ACQ_REL 4
#define __ATOMIC_CONSUME 1
#define __ATOMIC_HLE_ACQUIRE 65536
#define __ATOMIC_HLE_RELEASE 131072
#define __ATOMIC_RELAXED 0
#define __ATOMIC_RELEASE 3
#define __ATOMIC_SEQ_CST 5
#define __BIGGEST_ALIGNMENT__ 16
#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __CHAR16_TYPE__ short unsigned int
#define __CHAR32_TYPE__ unsigned int
#define __CHAR_BIT__ 8
#define __DBL_DECIMAL_DIG__ 17
#define __DBL_DENORM_MIN__ ((double)4.94065645841246544177e-324L)
#define __DBL_DIG__ 15
#define __DBL_EPSILON__ ((double)2.22044604925031308085e-16L)
#define __DBL_HAS_DENORM__ 1
#define __DBL_HAS_INFINITY__ 1
#define __DBL_HAS_QUIET_NAN__ 1
#define __DBL_MANT_DIG__ 53
#define __DBL_MAX_10_EXP__ 308
#define __DBL_MAX_EXP__ 1024
#define __DBL_MAX__ ((double)1.79769313486231570815e+308L)
#define __DBL_MIN_10_EXP__ (-307)
#define __DBL_MIN_EXP__ (-1021)
#define __DBL_MIN__ ((double)2.22507385850720138309e-308L)
#define __DEC128_EPSILON__ 1E-33DL
#define __DEC128_MANT_DIG__ 34
#define __DEC128_MAX_EXP__ 6145
#define __DEC128_MAX__ 9.999999999999999999999999999999999E6144DL
#define __DEC128_MIN_EXP__ (-6142)
#define __DEC128_MIN__ 1E-6143DL
#define __DEC128_SUBNORMAL_MIN__ 0.000000000000000000000000000000001E-6143DL
#define __DEC32_EPSILON__ 1E-6DF
#define __DEC32_MANT_DIG__ 7
#define __DEC32_MAX_EXP__ 97
#define __DEC32_MAX__ 9.999999E96DF
#define __DEC32_MIN_EXP__ (-94)
#define __DEC32_MIN__ 1E-95DF
#define __DEC32_SUBNORMAL_MIN__ 0.000001E-95DF
#define __DEC64_EPSILON__ 1E-15DD
#define __DEC64_MANT_DIG__ 16
#define __DEC64_MAX_EXP__ 385
#define __DEC64_MAX__ 9.999999999999999E384DD
#define __DEC64_MIN_EXP__ (-382)
#define __DEC64_MIN__ 1E-383DD
#define __DEC64_SUBNORMAL_MIN__ 0.000000000000001E-383DD
#define __DECIMAL_BID_FORMAT__ 1
#define __DECIMAL_DIG__ 21
#define __DEC_EVAL_METHOD__ 2
#define __ELF__ 1
#define __FINITE_MATH_ONLY__ 0
#define __FLOAT_WORD_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __FLT_DECIMAL_DIG__ 9
#define __FLT_DENORM_MIN__ 1.40129846432481707092e-45F
#define __FLT_DIG__ 6
#define __FLT_EPSILON__ 1.19209289550781250000e-7F
#define __FLT_EVAL_METHOD__ 0
#define __FLT_HAS_DENORM__ 1
#define __FLT_HAS_INFINITY__ 1
#define __FLT_HAS_QUIET_NAN__ 1
#define __FLT_MANT_DIG__ 24
#define __FLT_MAX_10_EXP__ 38
#define __FLT_MAX_EXP__ 128
#define __FLT_MAX__ 3.40282346638528859812e+38F
#define __FLT_MIN_10_EXP__ (-37)
#define __FLT_MIN_EXP__ (-125)
#define __FLT_MIN__ 1.17549435082228750797e-38F
#define __FLT_RADIX__ 2
#define __FXSR__ 1
#define __GCC_ASM_FLAG_OUTPUTS__ 1
#define __GCC_ATOMIC_BOOL_LOCK_FREE 2
#define __GCC_ATOMIC_CHAR16_T_LOCK_FREE 2
#define __GCC_ATOMIC_CHAR32_T_LOCK_FREE 2
#define __GCC_ATOMIC_CHAR_LOCK_FREE 2
#define __GCC_ATOMIC_INT_LOCK_FREE 2
#define __GCC_ATOMIC_LLONG_LOCK_FREE 2
#define __GCC_ATOMIC_LONG_LOCK_FREE 2
#define __GCC_ATOMIC_POINTER_LOCK_FREE 2
#define __GCC_ATOMIC_SHORT_LOCK_FREE 2
#define __GCC_ATOMIC_TEST_AND_SET_TRUEVAL 1
#define __GCC_ATOMIC_WCHAR_T_LOCK_FREE 2
#define __GCC_HAVE_DWARF2_CFI_ASM 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1
#define __GCC_IEC_559 2
#define __GCC_IEC_559_COMPLEX 2
#define __GNUC_MINOR__ 3
#define __GNUC_PATCHLEVEL__ 0
#define __GNUC_STDC_INLINE__ 1
#define __GNUC__ 6
#define __GXX_ABI_VERSION 1010
#define __INT16_C(c) c
#define __INT16_MAX__ 0x7fff
#define __INT16_TYPE__ short int
#define __INT32_C(c) c
#define __INT32_MAX__ 0x7fffffff
#define __INT32_TYPE__ int
#define __INT64_C(c) c ## L
#define __INT64_MAX__ 0x7fffffffffffffffL
#define __INT64_TYPE__ long int
#define __INT8_C(c) c
#define __INT8_MAX__ 0x7f
#define __INT8_TYPE__ signed char
#define __INTMAX_C(c) c ## L
#define __INTMAX_MAX__ 0x7fffffffffffffffL
#define __INTMAX_TYPE__ long int
#define __INTPTR_MAX__ 0x7fffffffffffffffL
#define __INTPTR_TYPE__ long int
#define __INT_FAST16_MAX__ 0x7fffffffffffffffL
#define __INT_FAST16_TYPE__ long int
#define __INT_FAST32_MAX__ 0x7fffffffffffffffL
#define __INT_FAST32_TYPE__ long int
#define __INT_FAST64_MAX__ 0x7fffffffffffffffL
#define __INT_FAST64_TYPE__ long int
#define __INT_FAST8_MAX__ 0x7f
#define __INT_FAST8_TYPE__ signed char
#define __INT_LEAST16_MAX__ 0x7fff
#define __INT_LEAST16_TYPE__ short int
#define __INT_LEAST32_MAX__ 0x7fffffff
#define __INT_LEAST32_TYPE__ int
#define __INT_LEAST64_MAX__ 0x7fffffffffffffffL
#define __INT_LEAST64_TYPE__ long int
#define __INT_LEAST8_MAX__ 0x7f
#define __INT_LEAST8_TYPE__ signed char
#define __INT_MAX__ 0x7fffffff
#define __LDBL_DENORM_MIN__ 3.64519953188247460253e-4951L
#define __LDBL_DIG__ 18
#define __LDBL_EPSILON__ 1.08420217248550443401e-19L
#define __LDBL_HAS_DENORM__ 1
#define __LDBL_HAS_INFINITY__ 1
#define __LDBL_HAS_QUIET_NAN__ 1
#define __LDBL_MANT_DIG__ 64
#define __LDBL_MAX_10_EXP__ 4932
#define __LDBL_MAX_EXP__ 16384
#define __LDBL_MAX__ 1.18973149535723176502e+4932L
#define __LDBL_MIN_10_EXP__ (-4931)
#define __LDBL_MIN_EXP__ (-16381)
#define __LDBL_MIN__ 3.36210314311209350626e-4932L
#define __LONG_LONG_MAX__ 0x7fffffffffffffffLL
#define __LONG_MAX__ 0x7fffffffffffffffL
#define __LP64__ 1
#define __MMX__ 1
#define __NO_INLINE__ 1
#define __ORDER_BIG_ENDIAN__ 4321
#define __ORDER_LITTLE_ENDIAN__ 1234
#define __ORDER_PDP_ENDIAN__ 3412
#define __PIC__ 2
#define __PIE__ 2
#define __PRAGMA_REDEFINE_EXTNAME 1
#define __PTRDIFF_MAX__ 0x7fffffffffffffffL
#define __PTRDIFF_TYPE__ long int
#define __REGISTER_PREFIX__ 
#define __SCHAR_MAX__ 0x7f
#define __SEG_FS 1
#define __SEG_GS 1
#define __SHRT_MAX__ 0x7fff
#define __SIG_ATOMIC_MAX__ 0x7fffffff
#define __SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)
#define __SIG_ATOMIC_TYPE__ int
#define __SIZEOF_DOUBLE__ 8
#define __SIZEOF_FLOAT128__ 16
#define __SIZEOF_FLOAT80__ 16
#define __SIZEOF_FLOAT__ 4
#define __SIZEOF_INT128__ 16
#define __SIZEOF_INT__ 4
#define __SIZEOF_LONG_DOUBLE__ 16
#define __SIZEOF_LONG_LONG__ 8
#define __SIZEOF_LONG__ 8
#define __SIZEOF_POINTER__ 8
#define __SIZEOF_PTRDIFF_T__ 8
#define __SIZEOF_SHORT__ 2
#define __SIZEOF_SIZE_T__ 8
#define __SIZEOF_WCHAR_T__ 4
#define __SIZEOF_WINT_T__ 4
#define __SIZE_MAX__ 0xffffffffffffffffUL
#define __SIZE_TYPE__ long unsigned int
#define __SSE2_MATH__ 1
#define __SSE2__ 1
#define __SSE_MATH__ 1
#define __SSE__ 1
#define __SSP_STRONG__ 3
#define __STDC_HOSTED__ 1
#define __STDC_IEC_559_COMPLEX__ 1
#define __STDC_IEC_559__ 1
#define __STDC_ISO_10646__ 201605L
#define __STDC_NO_THREADS__ 1
#define __STDC_UTF_16__ 1
#define __STDC_UTF_32__ 1
#define __STDC_VERSION__ 201112L
#define __STDC__ 1
#define __UINT16_C(c) c
#define __UINT16_MAX__ 0xffff
#define __UINT16_TYPE__ short unsigned int
#define __UINT32_C(c) c ## U
#define __UINT32_MAX__ 0xffffffffU
#define __UINT32_TYPE__ unsigned int
#define __UINT64_C(c) c ## UL
#define __UINT64_MAX__ 0xffffffffffffffffUL
#define __UINT64_TYPE__ long unsigned int
#define __UINT8_C(c) c
#define __UINT8_MAX__ 0xff
#define __UINT8_TYPE__ unsigned char
#define __UINTMAX_C(c) c ## UL
#define __UINTMAX_MAX__ 0xffffffffffffffffUL
#define __UINTMAX_TYPE__ long unsigned int
#define __UINTPTR_MAX__ 0xffffffffffffffffUL
#define __UINTPTR_TYPE__ long unsigned int
#define __UINT_FAST16_MAX__ 0xffffffffffffffffUL
#define __UINT_FAST16_TYPE__ long unsigned int
#define __UINT_FAST32_MAX__ 0xffffffffffffffffUL
#define __UINT_FAST32_TYPE__ long unsigned int
#define __UINT_FAST64_MAX__ 0xffffffffffffffffUL
#define __UINT_FAST64_TYPE__ long unsigned int
#define __UINT_FAST8_MAX__ 0xff
#define __UINT_FAST8_TYPE__ unsigned char
#define __UINT_LEAST16_MAX__ 0xffff
#define __UINT_LEAST16_TYPE__ short unsigned int
#define __UINT_LEAST32_MAX__ 0xffffffffU
#define __UINT_LEAST32_TYPE__ unsigned int
#define __UINT_LEAST64_MAX__ 0xffffffffffffffffUL
#define __UINT_LEAST64_TYPE__ long unsigned int
#define __UINT_LEAST8_MAX__ 0xff
#define __UINT_LEAST8_TYPE__ unsigned char
#define __USER_LABEL_PREFIX__ 
#define __VERSION__ "6.3.0 20170406"
#define __WCHAR_MAX__ 0x7fffffff
#define __WCHAR_MIN__ (-__WCHAR_MAX__ - 1)
#define __WCHAR_TYPE__ int
#define __WINT_MAX__ 0xffffffffU
#define __WINT_MIN__ 0U
#define __WINT_TYPE__ unsigned int
#define __amd64 1
#define __amd64__ 1
#define __code_model_small__ 1
#define __gnu_linux__ 1
#define __has_include(STR) __has_include__(STR)
#define __has_include_next(STR) __has_include_next__(STR)
#define __k8 1
#define __k8__ 1
#define __linux 1
#define __linux__ 1
#define __pic__ 2
#define __pie__ 2
#define __unix 1
#define __unix__ 1
#define __x86_64 1
#define __x86_64__ 1
#define linux 1
#define unix 1

string.split - by multiple character delimiter

Regex.Split("abc][rfd][5][,][.", @"\]\]");

How to check string length with JavaScript

That's the function I wrote to get string in Unicode characters:

function nbUnicodeLength(string){
    var stringIndex = 0;
    var unicodeIndex = 0;
    var length = string.length;
    var second;
    var first;
    while (stringIndex < length) {

        first = string.charCodeAt(stringIndex);  // returns an integer between 0 and 65535 representing the UTF-16 code unit at the given index.
        if (first >= 0xD800 && first <= 0xDBFF && string.length > stringIndex + 1) {
            second = string.charCodeAt(stringIndex + 1);
            if (second >= 0xDC00 && second <= 0xDFFF) {
                stringIndex += 2;
            } else {
                stringIndex += 1;
            }
        } else {
            stringIndex += 1;
        }

        unicodeIndex += 1;
    }
    return unicodeIndex;
}

How to convert an integer (time) to HH:MM:SS::00 in SQL Server 2008?

Convert the integer into a string and then you can use the STUFF function to insert in your colons into time string. Once you've done that you can convert the string into a time datatype.

SELECT CAST(STUFF(STUFF(STUFF(cast(23421155 as varchar),3,0,':'),6,0,':'),9,0,'.') AS TIME)

That should be the simplest way to convert it to a time without doing anything to crazy.

In your example you also had an int where the leading zeros are not there. In that case you can simple do something like this:

SELECT CAST(STUFF(STUFF(STUFF(RIGHT('00000000' + CAST(421151 AS VARCHAR),8),3,0,':'),6,0,':'),9,0,'.') AS TIME)

How to solve this java.lang.NoClassDefFoundError: org/apache/commons/io/output/DeferredFileOutputStream?

just put all apache comons jar and file upload jar in lib folder of tomcat

Are there benefits of passing by pointer over passing by reference in C++?

Clarifications to the preceding posts:


References are NOT a guarantee of getting a non-null pointer. (Though we often treat them as such.)

While horrifically bad code, as in take you out behind the woodshed bad code, the following will compile & run: (At least under my compiler.)

bool test( int & a)
{
  return (&a) == (int *) NULL;
}

int
main()
{
  int * i = (int *)NULL;
  cout << ( test(*i) ) << endl;
};

The real issue I have with references lies with other programmers, henceforth termed IDIOTS, who allocate in the constructor, deallocate in the destructor, and fail to supply a copy constructor or operator=().

Suddenly there's a world of difference between foo(BAR bar) and foo(BAR & bar). (Automatic bitwise copy operation gets invoked. Deallocation in destructor gets invoked twice.)

Thankfully modern compilers will pick up this double-deallocation of the same pointer. 15 years ago, they didn't. (Under gcc/g++, use setenv MALLOC_CHECK_ 0 to revisit the old ways.) Resulting, under DEC UNIX, in the same memory being allocated to two different objects. Lots of debugging fun there...


More practically:

  • References hide that you are changing data stored someplace else.
  • It's easy to confuse a Reference with a Copied object.
  • Pointers make it obvious!

How can I fix "Design editor is unavailable until a successful build" error?

I have the latest Android Studio 3.6.1 and yet couldn't build a simple 'Hello World' app as documented here "https://codelabs.developers.google.com/codelabs/android-training-hello-world/index.html?index=..%2F..%2Fandroid-training#3". I applied various steps discussed above including the 2 most viable options which should have really solved this issue,

  1. 'File->Sync Project with Gradle Files' and
  2. 'File->Invalidate Caches/Restart' but to no avail.

Even though, I suspect standard answer should be one of these 2 options only for most, but for me the resolution came only after I went inside the 'File->Project Structure' and checked my SDK versions configured! Android Studio and Gradle were using different JDK versions and locations.

  • Android Studio: C:\Program Files\Java\jdk1.8.0_241
  • Gradle: C:\Program Files\Java\jdk-13.0.2

I had previously defined my JAVA_HOME environment variable by downloading latest JAVA SDK on my own from ORACLE website. Where Gradle was using the %JAVA_HOME% JAVA SDK version and Android Studio the built in SDK which came along with Android Studio.

Once I switched both to versions JDK 1.8.* (Any version as long as it is JDK 1.8. for that matter*) then simple 'File->Synch...' option worked perfectly fine for me!

Good luck the solution is in between one of these 2 options only if you are stuck, just ensure you validate JDK versions being referred to!

How to stop EditText from gaining focus at Activity startup in Android

I had an issue like this and it was due to my selector. The first state was focus even thogh my view was disabled it took the focus state since it was the first one that matched and used it. you can set the first state to disabled like this:

<selector xmlns:android="http://schemas.android.com/apk/res/android">


<item android:drawable="@drawable/text_field_disabled" android:state_enabled="false"/>
<item android:drawable="@drawable/text_field_focused" android:state_focused="true"/>
<item android:drawable="@drawable/text_field_normal"/>

Display Images Inline via CSS

You have a line break <br> in-between the second and third images in your markup. Get rid of that, and it'll show inline.

Check if application is installed - Android

Robin Kanters' answer is right, but it does check for installed apps regardless of their enabled or disabled state.

We all know an app can be installed but disabled by the user, therefore unusable.

This checks for installed AND enabled apps:

public static boolean isPackageInstalled(String packageName, PackageManager packageManager) {
    try {
        return packageManager.getApplicationInfo(packageName, 0).enabled;
    }
    catch (PackageManager.NameNotFoundException e) {
        return false;
    }
}

You can put this method in a class like Utils and call it everywhere using:

boolean isInstalled = Utils.isPackageInstalled("com.package.name", context.getPackageManager())

With android studio no jvm found, JAVA_HOME has been set

Just delete the folder highlighted below. Depending on your Android Studio version, mine is 3.5 and reopen Android studio.

enter image description here

Missing visible-** and hidden-** in Bootstrap v4

i like the bootstrap3 style as the device width of bootstrap4
so i modify the css as below
<pre>
.visible-xs, .visible-sm, .visible-md, .visible-lg { display:none !important; }
.visible-xs-block, .visible-xs-inline, .visible-xs-inline-block,
.visible-sm-block, .visible-sm-inline, .visible-sm-inline-block,
.visible-md-block, .visible-md-inline, .visible-md-inline-block,
.visible-lg-block, .visible-lg-inline, .visible-lg-inline-block { display:none !important; }
@media (max-width:575px) {
table.visible-xs                { display:table !important; }
tr.visible-xs                   { display:table-row !important; }
th.visible-xs, td.visible-xs    { display:table-cell !important; }

.visible-xs                 { display:block !important; }
.visible-xs-block { display:block !important; }
.visible-xs-inline { display:inline !important; }
.visible-xs-inline-block { display:inline-block !important; }
}

@media (min-width:576px) and (max-width:767px) {
table.visible-sm { display:table !important; }
tr.visible-sm { display:table-row !important; }
th.visible-sm,
td.visible-sm { display:table-cell !important; }

.visible-sm { display:block !important; }
.visible-sm-block { display:block !important; }
.visible-sm-inline { display:inline !important; }
.visible-sm-inline-block { display:inline-block !important; }
}

@media (min-width:768px) and (max-width:991px) {
table.visible-md { display:table !important; }
tr.visible-md { display:table-row !important; }
th.visible-md,
td.visible-md { display:table-cell !important; }

.visible-md { display:block !important; }
.visible-md-block { display:block !important; }
.visible-md-inline { display:inline !important; }
.visible-md-inline-block { display:inline-block !important; }
}

@media (min-width:992px) and (max-width:1199px) {
table.visible-lg { display:table !important; }
tr.visible-lg { display:table-row !important; }
th.visible-lg,
td.visible-lg { display:table-cell !important; }

.visible-lg { display:block !important; }
.visible-lg-block { display:block !important; }
.visible-lg-inline { display:inline !important; }
.visible-lg-inline-block { display:inline-block !important; }
}

@media (min-width:1200px) {
table.visible-xl { display:table !important; }
tr.visible-xl { display:table-row !important; }
th.visible-xl,
td.visible-xl { display:table-cell !important; }

.visible-xl { display:block !important; }
.visible-xl-block { display:block !important; }
.visible-xl-inline { display:inline !important; }
.visible-xl-inline-block { display:inline-block !important; }
}

@media (max-width:575px)                        { .hidden-xs{display:none !important;} }
@media (min-width:576px) and (max-width:767px)  { .hidden-sm{display:none !important;} }
@media (min-width:768px) and (max-width:991px)  { .hidden-md{display:none !important;} }
@media (min-width:992px) and (max-width:1199px) { .hidden-lg{display:none !important;} }
@media (min-width:1200px)                       { .hidden-xl{display:none !important;} }
</pre>

Getting "method not valid without suitable object" error when trying to make a HTTP request in VBA?

Check out this one:

https://github.com/VBA-tools/VBA-Web

It's a high level library for dealing with REST. It's OOP, works with JSON, but also works with any other format.

"sed" command in bash

It reads Hello World (cat), replaces all (g) occurrences of % by $ and (over)writes it to /etc/init.d/dropbox as root.

How to get the PID of a process by giving the process name in Mac OS X ?

You can try this

pid=$(ps -o pid=,comm= | grep -m1 $procname | cut -d' ' -f1)

How to return an array from an AJAX call?

well, I know that I'm a bit too late, but I tried all of your solutions and with no success! So here is how I managed to do it. First of all, I'm working on an Asp.Net MVC project. The Only thing I changed was in my c# method getInvitation:

public ActionResult getInvitation (Guid s_ID)
{
    using (var db = new cRM_Verband_BWEntities())
    {
        var listSidsMit = (from data in db.TERMINEINLADUNGEN where data.RECID_KOMMUNIKATIONEN == s_ID select data.RECID_MITARBEITER.ToString()).ToArray();
        return Json(listSidsMit);
    }
}

SuccessFunction in JS :

function successFunction(result) {
    console.log(result);
}

I changed the Method Type from string[] to ActionResult and of course at the end I wrapped my array listSidsMit with the Json method.

GetType used in PowerShell, difference between variables

Select-Object returns a custom PSObject with just the properties specified. Even with a single property, you don't get the ACTUAL variable; it is wrapped inside the PSObject.

Instead, do:

Get-Date | Select-Object -ExpandProperty DayOfWeek

That will get you the same result as:

(Get-Date).DayOfWeek

The difference is that if Get-Date returns multiple objects, the pipeline way works better than the parenthetical way as (Get-ChildItem), for example, is an array of items. This has changed in PowerShell v3 and (Get-ChildItem).FullPath works as expected and returns an array of just the full paths.

iOS: Compare two dates

Check the following Function for date comparison first of all create two NSDate objects and pass to the function: Add the bellow lines of code in viewDidload or according to your scenario.

-(void)testDateComaparFunc{

NSString *getTokon_Time1 = @"2016-05-31 03:19:05 +0000";
NSString *getTokon_Time2 = @"2016-05-31 03:18:05 +0000";
NSDateFormatter *dateFormatter=[NSDateFormatter new];
[dateFormatter setDateFormat:@"yyyy-MM-dd hh:mm:ss Z"];
NSDate *tokonExpireDate1=[dateFormatter dateFromString:getTokon_Time1];
NSDate *tokonExpireDate2=[dateFormatter dateFromString:getTokon_Time2];
BOOL isTokonValid = [self dateComparision:tokonExpireDate1 andDate2:tokonExpireDate2];}

here is the function

-(BOOL)dateComparision:(NSDate*)date1 andDate2:(NSDate*)date2{

BOOL isTokonValid;

if ([date1 compare:date2] == NSOrderedDescending) {
    //"date1 is later than date2
    isTokonValid = YES;
} else if ([date1 compare:date2] == NSOrderedAscending) {
    //date1 is earlier than date2
    isTokonValid = NO;
} else {
   //dates are the same
    isTokonValid = NO;

}

return isTokonValid;}

Simply change the date and test above function :)

Python os.path.join on Windows

You have a few possible approaches to treat path on Windows, from the most hardcoded ones (as using raw string literals or escaping backslashes) to the least ones. Here follows a few examples that will work as expected. Use what better fits your needs.

In[1]: from os.path import join, isdir

In[2]: from os import sep

In[3]: isdir(join("c:", "\\", "Users"))
Out[3]: True

In[4]: isdir(join("c:", "/", "Users"))
Out[4]: True

In[5]: isdir(join("c:", sep, "Users"))
Out[5]: True

Matplotlib discrete colorbar

You could follow this example:

#!/usr/bin/env python
"""
Use a pcolor or imshow with a custom colormap to make a contour plot.

Since this example was initially written, a proper contour routine was
added to matplotlib - see contour_demo.py and
http://matplotlib.sf.net/matplotlib.pylab.html#-contour.
"""

from pylab import *


delta = 0.01
x = arange(-3.0, 3.0, delta)
y = arange(-3.0, 3.0, delta)
X,Y = meshgrid(x, y)
Z1 = bivariate_normal(X, Y, 1.0, 1.0, 0.0, 0.0)
Z2 = bivariate_normal(X, Y, 1.5, 0.5, 1, 1)
Z = Z2 - Z1 # difference of Gaussians

cmap = cm.get_cmap('PiYG', 11)    # 11 discrete colors

im = imshow(Z, cmap=cmap, interpolation='bilinear',
            vmax=abs(Z).max(), vmin=-abs(Z).max())
axis('off')
colorbar()

show()

which produces the following image:

poormans_contour

How does autowiring work in Spring?

The whole concept of inversion of control means you are free from a chore to instantiate objects manually and provide all necessary dependencies. When you annotate class with appropriate annotation (e.g. @Service) Spring will automatically instantiate object for you. If you are not familiar with annotations you can also use XML file instead. However, it's not a bad idea to instantiate classes manually (with the new keyword) in unit tests when you don't want to load the whole spring context.

What exactly is OAuth (Open Authorization)?

What exactly is OAuth (Open Authorization)?

OAuth allows notifying a resource provider (e.g. Facebook) that the resource owner (e.g. you) grants permission to a third-party (e.g. a Facebook Application) access to their information (e.g. the list of your friends).

If you read it stated as plainly, I would understand your confusion. So let's go with a concrete example: joining yet another social network!

Say you have an existing GMail account. You decide to join LinkedIn. Adding all of your many, many friends manually is tiresome and error-prone. You might get fed up half-way or insert typos in their e-mail address for invitation. So you might be tempted not to create an account after all.

Facing this situation, LinkedIn has the Good Idea(TM) to write a program that adds your list of friends automatically because computers are far more efficient and effective at tiresome and error prone tasks. Since joining the network is now so easy, there is no way you would refuse such an offer, now would you?

Without an API for exchanging this list of contacts, you would have to give LinkedIn the username and password to your GMail account, thereby giving them too much power.

This is where OAuth comes in. If your GMail supports the OAuth protocol, then LinkedIn can ask you to authorize them to access your GMail list of contacts.

OAuth allows for:

  1. Different access levels: read-only VS read-write. This allows you to grant access to your user list or a bi-directional access to automatically synchronize your new LinkedIn friends to your GMail contacts.
  2. Access granularity: you can decide to grant access to only your contact information (username, e-mail, date of birth, etc.) or to your entire list of friends, calendar and what not.
  3. It allows you to manage access from the resource provider's application. If the third-party application does not provide mechanism for cancelling access, you would be stuck with them having access to your information. With OAuth, there is provision for revoking access at any time.

Will it become a de facto (standard?) in near future?

Well, although OAuth is a significant step forward, it doesn't solve problems if people don't use it correctly. For instance, if a resource provider gives only a single read-write access level to all your resources at once and doesn't provide mechanism for managing access, then there is no point to it. In other words, OAuth is a framework to provide authorization functionality and not just authentication.

In practice, it fits the social network model very well. It is especially popular for those social networks that want to allow third-party "plugins". This is an area where access to the resources is inherently necessary and is also inherently unreliable (i.e. you have little or no quality control over those applications).

I haven't seen so many other uses out in the wild. I mean, I don't know of an online financial advice firm that will access your bank records automatically, although it could technically be used that way.

How to get folder path from file path with CMD

The accepted answer is helpful, but it isn't immediately obvious how to retrieve a filename from a path if you are NOT using passed in values. I was able to work this out from this thread, but in case others aren't so lucky, here is how it is done:

@echo off
setlocal enabledelayedexpansion enableextensions

set myPath=C:\Somewhere\Somewhere\SomeFile.txt
call :file_name_from_path result !myPath!
echo %result%
goto :eof

:file_name_from_path <resultVar> <pathVar>
(
    set "%~1=%~nx2"
    exit /b
)

:eof
endlocal

Now the :file_name_from_path function can be used anywhere to retrieve the value, not just for passed in arguments. This can be extremely helpful if the arguments can be passed into the file in an indeterminate order or the path isn't passed into the file at all.

Bug? #1146 - Table 'xxx.xxxxx' doesn't exist

I had the same issue. It happened after windows start up error, it seems some files got corrupted due to this. I did import the DB again from the saved script and it works fine.

Simple way to understand Encapsulation and Abstraction

Abstraction- Abstraction in simple words can be said as a way out in which the user is kept away from the complex details or detailed working of some system. You can also assume it as a simple way to solve any problem at the design and interface level.

You can say the only purpose of abstraction is to hide the details that can confuse a user. So for simplification purposes, we can use abstraction. Abstraction is also a concept of object-oriented programming. It hides the actual data and only shows the necessary information. For example, in an ATM machine, you are not aware that how it works internally. Only you are concerned to use the ATM interface. So that can be considered as a type of abstraction process.

Encapsulation- Encapsulation is also part of object-oriented programming. In this, all you have to do is to wrap up the data and code together so that they can work as a single unit. it works at the implementation level. it also improves the application Maintainance.

Encapsulation focuses on the process which will save information. Here you have to protect your data from external use.

How to save a new sheet in an existing excel file, using Pandas?

Thank you. I believe that a complete example could be good for anyone else who have the same issue:

import pandas as pd
import numpy as np

path = r"C:\Users\fedel\Desktop\excelData\PhD_data.xlsx"

x1 = np.random.randn(100, 2)
df1 = pd.DataFrame(x1)

x2 = np.random.randn(100, 2)
df2 = pd.DataFrame(x2)

writer = pd.ExcelWriter(path, engine = 'xlsxwriter')
df1.to_excel(writer, sheet_name = 'x1')
df2.to_excel(writer, sheet_name = 'x2')
writer.save()
writer.close()

Here I generate an excel file, from my understanding it does not really matter whether it is generated via the "xslxwriter" or the "openpyxl" engine.

When I want to write without loosing the original data then

import pandas as pd
import numpy as np
from openpyxl import load_workbook

path = r"C:\Users\fedel\Desktop\excelData\PhD_data.xlsx"

book = load_workbook(path)
writer = pd.ExcelWriter(path, engine = 'openpyxl')
writer.book = book

x3 = np.random.randn(100, 2)
df3 = pd.DataFrame(x3)

x4 = np.random.randn(100, 2)
df4 = pd.DataFrame(x4)

df3.to_excel(writer, sheet_name = 'x3')
df4.to_excel(writer, sheet_name = 'x4')
writer.save()
writer.close()

this code do the job!

How to mock a final class with mockito

Mockito 2 now supports final classes and methods!

But for now that's an "incubating" feature. It requires some steps to activate it which are described in What's New in Mockito 2:

Mocking of final classes and methods is an incubating, opt-in feature. It uses a combination of Java agent instrumentation and subclassing in order to enable mockability of these types. As this works differently to our current mechanism and this one has different limitations and as we want to gather experience and user feedback, this feature had to be explicitly activated to be available ; it can be done via the mockito extension mechanism by creating the file src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker containing a single line:

mock-maker-inline

After you created this file, Mockito will automatically use this new engine and one can do :

 final class FinalClass {
   final String finalMethod() { return "something"; }
 }

 FinalClass concrete = new FinalClass(); 

 FinalClass mock = mock(FinalClass.class);
 given(mock.finalMethod()).willReturn("not anymore");

 assertThat(mock.finalMethod()).isNotEqualTo(concrete.finalMethod());

In subsequent milestones, the team will bring a programmatic way of using this feature. We will identify and provide support for all unmockable scenarios. Stay tuned and please let us know what you think of this feature!

How to check if "Radiobutton" is checked?

If you need for espresso test the solutions is like this :

onView(withId(id)).check(matches(isChecked()));

Bye,

Setting custom UITableViewCells height

Your UITableViewDelegate should implement tableView:heightForRowAtIndexPath:

Objective-C

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return [indexPath row] * 20;
}

Swift 5

func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    return indexPath.row * 20
}

You will probably want to use NSString's sizeWithFont:constrainedToSize:lineBreakMode: method to calculate your row height rather than just performing some silly math on the indexPath :)

max(length(field)) in mysql

select * 
from my_table 
where length( Name ) = ( 
      select max( length( Name ) ) 
      from my_table
      limit 1 
);

It this involves two table scans, and so might not be very fast !

T-SQL: Deleting all duplicate rows but keeping one

You didn't say what version you were using, but in SQL 2005 and above, you can use a common table expression with the OVER Clause. It goes a little something like this:

WITH cte AS (
  SELECT[foo], [bar], 
     row_number() OVER(PARTITION BY foo, bar ORDER BY baz) AS [rn]
  FROM TABLE
)
DELETE cte WHERE [rn] > 1

Play around with it and see what you get.

(Edit: In an attempt to be helpful, someone edited the ORDER BY clause within the CTE. To be clear, you can order by anything you want here, it needn't be one of the columns returned by the cte. In fact, a common use-case here is that "foo, bar" are the group identifier and "baz" is some sort of time stamp. In order to keep the latest, you'd do ORDER BY baz desc)

Access-Control-Allow-Origin Multiple Origin Domains?

Here's a solution for Java web app, based the answer from yesthatguy.

I am using Jersey REST 1.x

Configure the web.xml to be aware of Jersey REST and the CORSResponseFilter

 <!-- Jersey REST config -->
  <servlet>    
    <servlet-name>JAX-RS Servlet</servlet-name>
    <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
    <init-param> 
        <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
        <param-value>true</param-value>
    </init-param>
    <init-param>
      <param-name>com.sun.jersey.spi.container.ContainerResponseFilters</param-name>
      <param-value>com.your.package.CORSResponseFilter</param-value>
    </init-param>   
    <init-param>
        <param-name>com.sun.jersey.config.property.packages</param-name>
        <param-value>com.your.package</param-value>
    </init-param>        
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>JAX-RS Servlet</servlet-name>
    <url-pattern>/ws/*</url-pattern>
  </servlet-mapping>

Here's the code for CORSResponseFilter

import com.sun.jersey.spi.container.ContainerRequest;
import com.sun.jersey.spi.container.ContainerResponse;
import com.sun.jersey.spi.container.ContainerResponseFilter;


public class CORSResponseFilter implements ContainerResponseFilter{

@Override
public ContainerResponse filter(ContainerRequest request,
        ContainerResponse response) {

    String[] allowDomain = {"http://localhost:9000","https://my.domain.example"};
    Set<String> allowedOrigins = new HashSet<String>(Arrays.asList (allowDomain));                  

    String originHeader = request.getHeaderValue("Origin");

    if(allowedOrigins.contains(originHeader)) {
        response.getHttpHeaders().add("Access-Control-Allow-Origin", originHeader);

        response.getHttpHeaders().add("Access-Control-Allow-Headers",
                "origin, content-type, accept, authorization");
        response.getHttpHeaders().add("Access-Control-Allow-Credentials", "true");
        response.getHttpHeaders().add("Access-Control-Allow-Methods",
                "GET, POST, PUT, DELETE, OPTIONS, HEAD");
    }

    return response;
}

}

How to auto-generate a C# class file from a JSON string

If you install Web Essentials into Visual studio you can go to Edit => Past special => paste JSON as class.

That is probably the easiest there is.

Web Essentials: http://vswebessentials.com/

Maximum call stack size exceeded error

I got this error in express/nodejs app, when the schema of MongoDB database and the models which we have created don't match.

Why do Sublime Text 3 Themes not affect the sidebar?

Just install package Synced?Sidebar?Bg:it will change the sidebar theme based on current color scheme.But it seems that every time you change the color scheme,sidebar will be changed after you open file Preferences.sublime-settings

How to change bower's default components folder?

Something worth mentioning...

As noted above by other contributors, using a .bowerrc file with the JSON

{ "directory": "some/path" }

is necessary -- HOWEVER, you may run into an issue on Windows while creating that file. If Windows gives you a message imploring you to add a "file name", simply use a text editor / IDE such as Notepad++.

Add the JSON to an unnamed file, save it as .bowerrc -- you're good to go!

Probably an easy assumption, but I hope this save others the unnecessary headache :)

SQL: set existing column as Primary Key in MySQL

alter table table_name
add constraint myprimarykey primary key(column);

reference : http://www.w3schools.com/sql/sql_primarykey.asp

Unable to install pyodbc on Linux

Execute the following commands (tested on centos 6.5):

yum install install unixodbc-dev
yum install gcc-c++
yum install python-devel
pip install --allow-external pyodbc --allow-unverified pyodbc pyodbc

Where should I put <script> tags in HTML markup?

Depending on the script and its usage the best possible (in terms of page load and rendering time) may be to not use a conventional <script>-tag per se, but to dynamically trigger the loading of the script asynchronously.

There are some different techniques, but the most straight forward is to use document.createElement("script") when the window.onload event is triggered. Then the script is loaded first when the page itself has rendered, thus not impacting the time the user has to wait for the page to appear.

This naturally requires that the script itself is not needed for the rendering of the page.

For more information, see the post Coupling async scripts by Steve Souders (creator of YSlow but now at Google).

Where does Anaconda Python install on Windows?

Update May 2020, installed Anaconda 3 Individual Edition from https://www.anaconda.com/products/individual, chose 32-bit installer for Python 3.7, and installed with Default options.

enter image description here

Here is the directory where Anaconda was installed (C:\ProgramData\Anaconda3). Note ProgramData is a hidden folder not visible via Windows File Explorer. enter image description here

And launching Anaconda command prompt from Start Menu>>Anaconda3 gives below command shell

enter image description here

"where anaconda" command gives below output C:\ProgramData\Anaconda3\Scripts\anaconda.exe and versions for anaconda, conda, python enter image description here

Updated original question which was asked 3 years ago, and is relevant today as well in May 2020 as I had similar question/doubt when installing Anaconda recently.

How to convert BigInteger to String in java

You want to use BigInteger.toByteArray()

String msg = "Hello there!";
BigInteger bi = new BigInteger(msg.getBytes());
System.out.println(new String(bi.toByteArray())); // prints "Hello there!"

The way I understand it is that you're doing the following transformations:

  String  -----------------> byte[] ------------------> BigInteger
          String.getBytes()         BigInteger(byte[])

And you want the reverse:

  BigInteger ------------------------> byte[] ------------------> String
             BigInteger.toByteArray()          String(byte[])

Note that you probably want to use overloads of String.getBytes() and String(byte[]) that specifies an explicit encoding, otherwise you may run into encoding issues.

How to restore PostgreSQL dump file into Postgres databases?

1.open the terminal.

2.backup your database with following command

your postgres bin - /opt/PostgreSQL/9.1/bin/

your source database server - 192.168.1.111

your backup file location and name - /home/dinesh/db/mydb.backup

your source db name - mydatabase

/opt/PostgreSQL/9.1/bin/pg_dump --host '192.168.1.111' --port 5432 --username "postgres" --no-password --format custom --blobs --file "/home/dinesh/db/mydb.backup" "mydatabase"

3.restore mydb.backup file into destination.

your destination server - localhost

your destination database name - mydatabase

create database for restore the backup.

/opt/PostgreSQL/9.1/bin/psql -h 'localhost' -p 5432 -U postgres -c "CREATE DATABASE mydatabase"

restore the backup.

/opt/PostgreSQL/9.1/bin/pg_restore --host 'localhost' --port 5432 --username "postgres" --dbname "mydatabase" --no-password --clean "/home/dinesh/db/mydb.backup"

jQuery scroll() detect when user stops scrolling

Here is how you can handle this:

_x000D_
_x000D_
    var scrollStop = function (callback) {_x000D_
        if (!callback || typeof callback !== 'function') return;_x000D_
        var isScrolling;_x000D_
        window.addEventListener('scroll', function (event) {_x000D_
            window.clearTimeout(isScrolling);_x000D_
            isScrolling = setTimeout(function() {_x000D_
                callback();_x000D_
            }, 66);_x000D_
        }, false);_x000D_
    };_x000D_
    scrollStop(function () {_x000D_
        console.log('Scrolling has stopped.');_x000D_
    });
_x000D_
<!DOCTYPE html>_x000D_
<html lang="en">_x000D_
<head>_x000D_
    <meta charset="UTF-8">_x000D_
    <title>Title</title>_x000D_
</head>_x000D_
<body>_x000D_
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</body>_x000D_
</html>
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What's the difference between SoftReference and WeakReference in Java?

Weak references are collected eagerly. If GC finds that an object is weakly reachable (reachable only through weak references), it'll clear the weak references to that object immediately. As such, they're good for keeping a reference to an object for which your program also keeps (strongly referenced) "associated information" somewere, like cached reflection information about a class, or a wrapper for an object, etc. Anything that makes no sense to keep after the object it is associated with is GC-ed. When the weak reference gets cleared, it gets enqueued in a reference queue that your code polls somewhere, and it discards the associated objects as well. That is, you keep extra information about an object, but that information is not needed once the object it refers to goes away. Actually, in certain situations you can even subclass WeakReference and keep the associated extra information about the object in the fields of the WeakReference subclass. Another typical use of WeakReference is in conjunction with Maps for keeping canonical instances.

SoftReferences on the other hand are good for caching external, recreatable resources as the GC typically delays clearing them. It is guaranteed though that all SoftReferences will get cleared before OutOfMemoryError is thrown, so they theoretically can't cause an OOME[*].

Typical use case example is keeping a parsed form of a contents from a file. You'd implement a system where you'd load a file, parse it, and keep a SoftReference to the root object of the parsed representation. Next time you need the file, you'll try to retrieve it through the SoftReference. If you can retrieve it, you spared yourself another load/parse, and if the GC cleared it in the meantime, you reload it. That way, you utilize free memory for performance optimization, but don't risk an OOME.

Now for the [*]. Keeping a SoftReference can't cause an OOME in itself. If on the other hand you mistakenly use SoftReference for a task a WeakReference is meant to be used (namely, you keep information associated with an Object somehow strongly referenced, and discard it when the Reference object gets cleared), you can run into OOME as your code that polls the ReferenceQueue and discards the associated objects might happen to not run in a timely fashion.

So, the decision depends on usage - if you're caching information that is expensive to construct, but nonetheless reconstructible from other data, use soft references - if you're keeping a reference to a canonical instance of some data, or you want to have a reference to an object without "owning" it (thus preventing it from being GC'd), use a weak reference.

Call Activity method from adapter

You can do it this way:

Declare interface:

public interface MyInterface{
    public void foo();
}

Let your Activity imlement it:

    public class MyActivity extends Activity implements MyInterface{
        public void foo(){
            //do stuff
        }
        
        public onCreate(){
            //your code
            MyAdapter adapter = new MyAdapter(this); //this will work as your 
                                                     //MyInterface listener
        }
    }

Then pass your activity to ListAdater:

public MyAdapter extends BaseAdater{
    private MyInterface listener;

    public MyAdapter(MyInterface listener){
        this.listener = listener;
    }
}

And somewhere in adapter, when you need to call that Activity method:

listener.foo();

Convert String to SecureString

unsafe 
{
    fixed(char* psz = password)
        return new SecureString(psz, password.Length);
}

How can I get all element values from Request.Form without specifying exactly which one with .GetValues("ElementIdName")

Waqas Raja's answer with some LINQ lambda fun:

List<int> listValues = new List<int>();
Request.Form.AllKeys
    .Where(n => n.StartsWith("List"))
    .ToList()
    .ForEach(x => listValues.Add(int.Parse(Request.Form[x])));

inline if statement java, why is not working

The ternary operator ? : is to return a value, don't use it when you want to use if for flow control.

if (compareChar(curChar, toChar("0"))) getButtons().get(i).setText("§");

would work good enough.

https://docs.oracle.com/javase/tutorial/java/nutsandbolts/operators.html

PDOException “could not find driver”

For Linux Mint

I had the same issue whilst using PhpBrew ( 5.5.9 / 7.0.14 ) and trying to create a PDO connection.

After I had tried most of the solutions on this post I did the following:

  1. Powered off PhpBrew

  2. Executed sudo apt-get install php7.0 (Linux Mint 17.2 / PHP7.0.16) - installed fresh php version

How to remove last n characters from every element in the R vector

Although this is mostly the same with the answer by @nfmcclure, I prefer using stringr package as it provdies a set of functions whose names are most consistent and descriptive than those in base R (in fact I always google for "how to get the number of characters in R" as I can't remember the name nchar()).

library(stringr)
str_sub(iris$Species, end=-4)
#or 
str_sub(iris$Species, 1, str_length(iris$Species)-3)

This removes the last 3 characters from each value at Species column.

.NET: Simplest way to send POST with data and read response

private void PostForm()
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://dork.com/service");
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";
    string postData ="home=Cosby&favorite+flavor=flies";
    byte[] bytes = Encoding.UTF8.GetBytes(postData);
    request.ContentLength = bytes.Length;

    Stream requestStream = request.GetRequestStream();
    requestStream.Write(bytes, 0, bytes.Length);

    WebResponse response = request.GetResponse();
    Stream stream = response.GetResponseStream();
    StreamReader reader = new StreamReader(stream);

    var result = reader.ReadToEnd();
    stream.Dispose();
    reader.Dispose();
}

How can an html element fill out 100% of the remaining screen height, using css only?

The accepted answer does not work. And the highest voted answer does not answer the actual question. With a fixed pixel height header, and a filler in the remaining display of the browser, and scroll for owerflow. Here is a solution that actually works, using absolute positioning. I also assume that the height of the header is known, by the sound of "fixed header" in the question. I use 150px as an example here:

HTML:

<html>
    <body>
        <div id="Header">
        </div>
        <div id="Content">      
        </div>
    </body>
</html>

CSS:(adding background-color for visual effect only)

#Header
{
    height: 150px;
    width: 100%;
    background-color: #ddd;
}
#Content
{
   position: absolute;
   width: 100%;
   top: 150px;
   bottom: 0;
   background-color: #aaa;
   overflow-y: scroll;
}

For a more detailed look how this works, with actual content inside the #Content, have a look at this jsfiddle, using bootstrap rows and columns.

How to retrieve value from elements in array using jQuery?

jQuery collections have a built in iterator with .each:

$("input[name^='card']").each(function () {
   console.log($(this).val());
}

Javascript counting number of objects in object

Try Demo Here

var list ={}; var count= Object.keys(list).length;

Safely override C++ virtual functions

As far as I know, can't you just make it abstract?

class parent {
public:
  virtual void handle_event(int something) const = 0 {
    // boring default code
  }
};

I thought I read on www.parashift.com that you can actually implement an abstract method. Which makes sense to me personally, the only thing it does is force subclasses to implement it, no one said anything about it not being allowed to have an implementation itself.

How to Display blob (.pdf) in an AngularJS app

First of all you need to set the responseType to arraybuffer. This is required if you want to create a blob of your data. See Sending_and_Receiving_Binary_Data. So your code will look like this:

$http.post('/postUrlHere',{myParams}, {responseType:'arraybuffer'})
  .success(function (response) {
       var file = new Blob([response], {type: 'application/pdf'});
       var fileURL = URL.createObjectURL(file);
});

The next part is, you need to use the $sce service to make angular trust your url. This can be done in this way:

$scope.content = $sce.trustAsResourceUrl(fileURL);

Do not forget to inject the $sce service.

If this is all done you can now embed your pdf:

<embed ng-src="{{content}}" style="width:200px;height:200px;"></embed>

How to remove Firefox's dotted outline on BUTTONS as well as links?

There's no way to remove these dotted focus in Firefox using CSS.

If you have access to the computers where your webapplication works, go to about:config in Firefox and set browser.display.focus_ring_width to 0. Then Firefox won't show any dotted borders at all.

The following bug explains the topic: https://bugzilla.mozilla.org/show_bug.cgi?id=74225

onActivityResult is not being called in Fragment

Just simply call:

startActivityForResult(intent, "1");

DB2 SQL error: SQLCODE: -206, SQLSTATE: 42703

That only means that an undefined column or parameter name was detected. The errror that DB2 gives should point what that may be:

DB2 SQL Error: SQLCODE=-206, SQLSTATE=42703, SQLERRMC=[THE_UNDEFINED_COLUMN_OR_PARAMETER_NAME], DRIVER=4.8.87

Double check your table definition. Maybe you just missed adding something.

I also tried google-ing this problem and saw this:

http://www.coderanch.com/t/515475/JDBC/databases/sql-insert-statement-giving-sqlcode

What is the difference between require and require-dev sections in composer.json?

From the composer site (it's clear enough)

require#

Lists packages required by this package. The package will not be installed unless those requirements can be met.

require-dev (root-only)#

Lists packages required for developing this package, or running tests, etc. The dev requirements of the root package are installed by default. Both install or update support the --no-dev option that prevents dev dependencies from being installed.

Using require-dev in Composer you can declare the dependencies you need for development/testing the project but don't need in production. When you upload the project to your production server (using git) require-dev part would be ignored.

Also check this answer posted by the author and this post as well.

How to convert int to float in C?

I routinely multiply by 1.0 if I want floating point, it's easier than remembering the rules.

Bootstrap 4 File Input

Without JQuery

HTML:

<INPUT type="file" class="custom-file-input"  onchange="return onChangeFileInput(this);">

JS:

function onChangeFileInput(elem){
  var sibling = elem.nextSibling.nextSibling;
  sibling.innerHTML=elem.value;
  return true;
}

KliG

Adding minutes to date time in PHP

If you want to give a variable that contains the minutes.

Then I think this is a great way to achieve this.

$minutes = 10;
$maxAge = new DateTime('2011-11-17 05:05');
$maxAge->modify("+{$minutes} minutes");

Random state (Pseudo-random number) in Scikit learn

random_state number splits the test and training datasets with a random manner. In addition to what is explained here, it is important to remember that random_state value can have significant effect on the quality of your model (by quality I essentially mean accuracy to predict). For instance, If you take a certain dataset and train a regression model with it, without specifying the random_state value, there is the potential that everytime, you will get a different accuracy result for your trained model on the test data. So it is important to find the best random_state value to provide you with the most accurate model. And then, that number will be used to reproduce your model in another occasion such as another research experiment. To do so, it is possible to split and train the model in a for-loop by assigning random numbers to random_state parameter:

for j in range(1000):

            X_train, X_test, y_train, y_test = train_test_split(X, y , random_state =j,     test_size=0.35)
            lr = LarsCV().fit(X_train, y_train)

            tr_score.append(lr.score(X_train, y_train))
            ts_score.append(lr.score(X_test, y_test))

        J = ts_score.index(np.max(ts_score))

        X_train, X_test, y_train, y_test = train_test_split(X, y , random_state =J, test_size=0.35)
        M = LarsCV().fit(X_train, y_train)
        y_pred = M.predict(X_test)`

Ruby replace string with captured regex pattern

$ variables are only set to matches into the block:

"Z_sdsd: sdsd".gsub(/^(Z_.*): .*/) { "#{ $1.strip }" }

This is also the only way to call a method on the match. This will not change the match, only strip "\1" (leaving it unchanged):

"Z_sdsd: sdsd".gsub(/^(Z_.*): .*/, "\\1".strip)

Animate an element's width from 0 to 100%, with it and it's wrapper being only as wide as they need to be, without a pre-set width, in CSS3 or jQuery

Got it to work by transitioning the padding as well as the width.

JSFiddle: http://jsfiddle.net/tuybk748/1/

<div class='label gray'>+
</div><!-- must be connected to prevent gap --><div class='contents-wrapper'>
    <div class="gray contents">These are the contents of this div</div>
</div>
.gray {
    background: #ddd;
}
.contents-wrapper, .label, .contents {
    display: inline-block;
}
.label, .contents {
    overflow: hidden; /* must be on both divs to prevent dropdown behavior */
    height: 20px;
}
.label {
    padding: 10px 10px 15px;
}
.contents {
    padding: 10px 0px 15px; /* no left-right padding at beginning */
    white-space: nowrap; /* keeps text all on same line */
    width: 0%;
    -webkit-transition: width 1s ease-in-out, padding-left 1s ease-in-out, 
        padding-right 1s ease-in-out;
    -moz-transition: width 1s ease-in-out, padding-left 1s ease-in-out, 
        padding-right 1s ease-in-out;
    -o-transition: width 1s ease-in-out, padding-left 1s ease-in-out, 
        padding-right 1s ease-in-out;
    transition: width 1s ease-in-out, padding-left 1s ease-in-out, 
        padding-right 1s ease-in-out;
}
.label:hover + .contents-wrapper .contents {
    width: 100%;
    padding-left: 10px;
    padding-right: 10px;
}

Security of REST authentication schemes

A previous answer only mentioned SSL in the context of data transfer and didn't actually cover authentication.

You're really asking about securely authenticating REST API clients. Unless you're using TLS client authentication, SSL alone is NOT a viable authentication mechanism for a REST API. SSL without client authc only authenticates the server, which is irrelevant for most REST APIs because you really want to authenticate the client.

If you don't use TLS client authentication, you'll need to use something like a digest-based authentication scheme (like Amazon Web Service's custom scheme) or OAuth 1.0a or even HTTP Basic authentication (but over SSL only).

These schemes authenticate that the request was sent by someone expected. TLS (SSL) (without client authentication) ensures that the data sent over the wire remains untampered. They are separate - but complementary - concerns.

For those interested, I've expanded on an SO question about HTTP Authentication Schemes and how they work.

Making view resize to its parent when added with addSubview

If you aren’t using Auto Layout, have you tried setting the child view’s autoresize mask? Try this:

myChildeView.autoresizingMask = (UIViewAutoresizingFlexibleWidth |
                                 UIViewAutoresizingFlexibleHeight);

Also, you may need to call

myParentView.autoresizesSubviews = YES;

to get the parent view to resize its subviews automatically when its frame changes.

If you’re still seeing the child view drawing outside of the parent view’s frame, there’s a good chance that the parent view is not clipping its contents. To fix that, call

myParentView.clipsToBounds = YES;

Exception in thread "main" java.lang.Error: Unresolved compilation problems

Your problem is in this line: Message messageObject = new Message ();
This error says that the Message class is not known at compile time.

So you need to import the Message class.

Something like this:

import package1.package2.Message;

Check this out.

http://docs.oracle.com/javase/tutorial/java/package/usepkgs.html

How to create a GUID/UUID using iOS

In iOS 6 you can easily use:

NSUUID  *UUID = [NSUUID UUID];
NSString* stringUUID = [UUID UUIDString];

More details in Apple's Documentations

WPF What is the correct way of using SVG files as icons in WPF

Another alternative is dotnetprojects SVGImage

This allows native use of .svg files directly in xaml.

The nice part is, it is only one assembly which is about 100k. In comparision to sharpvectors which is much bigger any many files.

Usage:

...
xmlns:svg1="clr-namespace:SVGImage.SVG;assembly=DotNetProjects.SVGImage"
...
<svg1:SVGImage Name="mySVGImage" Source="/MyDemoApp;component/Resources/MyImage.svg"/>
...

That's all.

See:

How do I convert a TimeSpan to a formatted string?

Would TimeSpan.ToString() do the trick for you? If not, it looks like the code sample on that page describes how to do custom formatting of a TimeSpan object.

What is the parameter "next" used for in Express?

Next is used to pass control to the next middleware function. If not the request will be left hanging or open.

Set initial focus in an Android application

@Someone Somewhere, I tried all of the above to no avail. The fix I found is from http://www.helloandroid.com/tutorials/remove-autofocus-edittext-android . Basically, you need to create an invisible layout just above the problematic Button:

<LinearLayout android:focusable="true"
              android:focusableInTouchMode="true" 
              android:layout_width="0px"
              android:layout_height="0px" >
    <requestFocus />
</LinearLayout>

Where to put Gradle configuration (i.e. credentials) that should not be committed?

You could put the credentials in a properties file and read it using something like this:

Properties props = new Properties() 
props.load(new FileInputStream("yourPath/credentials.properties")) 
project.setProperty('props', props)

Another approach is to define environment variables at the OS level and read them using:

System.getenv()['YOUR_ENV_VARIABLE']

Python urllib2 Basic Auth Problem

The second parameter must be a URI, not a domain name. i.e.

passman = urllib2.HTTPPasswordMgrWithDefaultRealm()
passman.add_password(None, "http://api.foursquare.com/", username, password)

Splitting a continuous variable into equal sized groups

You can also use the bin function with method = "content" from the OneR package for that:

library(OneR)
das$wt_2 <- as.numeric(bin(das$wt, nbins = 3, method = "content"))
das
##    anim    wt wt_2
## 1     1 181.0    1
## 2     2 179.0    1
## 3     3 180.5    1
## 4     4 201.0    2
## 5     5 201.5    2
## 6     6 245.0    2
## 7     7 246.4    3
## 8     8 189.3    1
## 9     9 301.0    3
## 10   10 354.0    3
## 11   11 369.0    3
## 12   12 205.0    2
## 13   13 199.0    1
## 14   14 394.0    3
## 15   15 231.3    2

Generate a random point within a circle (uniformly)

The area element in a circle is dA=rdr*dphi. That extra factor r destroyed your idea to randomly choose a r and phi. While phi is distributed flat, r is not, but flat in 1/r (i.e. you are more likely to hit the boundary than "the bull's eye").

So to generate points evenly distributed over the circle pick phi from a flat distribution and r from a 1/r distribution.

Alternatively use the Monte Carlo method proposed by Mehrdad.

EDIT

To pick a random r flat in 1/r you could pick a random x from the interval [1/R, infinity] and calculate r=1/x. r is then distributed flat in 1/r.

To calculate a random phi pick a random x from the interval [0, 1] and calculate phi=2*pi*x.

ImportError: cannot import name main when running pip --version command in windows7 32 bit

On Windows 10, I had the same problem. PIP 19 was already installed in my system but wasn't showing up. The error was No Module Found.

python -m pip uninstall pip
python -m pip install pip==9.0.3

Downgrading pip to 9.0.3 worked fine for me.

jQuery: Slide left and slide right

You can do this with the additional effects in jQuery UI: See here for details

Quick example:

$(this).hide("slide", { direction: "left" }, 1000);
$(this).show("slide", { direction: "left" }, 1000);

Scale image to fit a bounding box

This helped me:

.img-class {
  width: <img width>;
  height: <img height>;
  content: url('/path/to/img.png');
}

Then on the element (you can use javascript or media queries to add responsiveness):

<div class='img-class' style='transform: scale(X);'></div>

Hope this helps!

How to serve an image using nodejs

I like using Restify for REST services. In my case, I had created a REST service to serve up images and then if an image source returned 404/403, I wanted to return an alternative image. Here's what I came up with combining some of the stuff here:

function processRequest(req, res, next, url) {
    var httpOptions = {
        hostname: host,
        path: url,
        port: port,
        method: 'GET'
    };

    var reqGet = http.request(httpOptions, function (response) {
        var statusCode = response.statusCode;

        // Many images come back as 404/403 so check explicitly
        if (statusCode === 404 || statusCode === 403) {
            // Send default image if error
            var file = 'img/user.png';
            fs.stat(file, function (err, stat) {
                var img = fs.readFileSync(file);
                res.contentType = 'image/png';
                res.contentLength = stat.size;
                res.end(img, 'binary');
            });

        } else {
            var idx = 0;
            var len = parseInt(response.header("Content-Length"));
            var body = new Buffer(len);

            response.setEncoding('binary');

            response.on('data', function (chunk) {
                body.write(chunk, idx, "binary");
                idx += chunk.length;
            });

            response.on('end', function () {
                res.contentType = 'image/jpg';
                res.send(body);
            });

        }
    });

    reqGet.on('error', function (e) {
        // Send default image if error
        var file = 'img/user.png';
        fs.stat(file, function (err, stat) {
            var img = fs.readFileSync(file);
            res.contentType = 'image/png';
            res.contentLength = stat.size;
            res.end(img, 'binary');
        });
    });

    reqGet.end();

    return next();
}

How to insert &nbsp; in XSLT

When you use the following (without disable-output-escaping!) you'll get a single non-breaking space:

<xsl:text>&#160;</xsl:text>

Cannot inline bytecode built with JVM target 1.8 into bytecode that is being built with JVM target 1.6

For me the reason was this configuration in my build gradle was in some modules and in some it wasnt

android {  
...      
kotlinOptions {
        val options = this as KotlinJvmOptions
        options.jvmTarget = "1.8"
    }
...
android {

How do I keep CSS floats in one line?

The way I got around this was to use some jQuery. The reason I did it this way was because A and B were percent widths.

HTML:

<div class="floatNoWrap">
    <div id="A" style="float: left;">
        Content A
    </div>
    <div id="B" style="float: left;">
        Content B
    </div>
    <div style="clear: both;"></div>
</div>

CSS:

.floatNoWrap
{
    width: 100%;
    height: 100%;
}

jQuery:

$("[class~='floatNoWrap']").each(function () {
    $(this).css("width", $(this).outerWidth());
});

configuring project ':app' failed to find Build Tools revision

also try to increase gradle version in your project's build.gradle. It helped me

WPF TemplateBinding vs RelativeSource TemplatedParent

TemplateBinding is not quite the same thing. MSDN docs are often written by people that have to quiz monosyllabic SDEs about software features, so the nuances are not quite right.

TemplateBindings are evaluated at compile time against the type specified in the control template. This allows for much faster instantiation of compiled templates. Just fumble the name in a templatebinding and you'll see that the compiler will flag it.

The binding markup is resolved at runtime. While slower to execute, the binding will resolve property names that are not visible on the type declared by the template. By slower, I'll point out that its kind of relative since the binding operation takes very little of the application's cpu. If you were blasting control templates around at high speed you might notice it.

As a matter of practice use the TemplateBinding when you can but don't fear the Binding.

How to copy directory recursively in python and overwrite all?

My simple answer.

def get_files_tree(src="src_path"):
    req_files = []
    for r, d, files in os.walk(src):
        for file in files:
            src_file = os.path.join(r, file)
            src_file = src_file.replace('\\', '/')
            if src_file.endswith('.db'):
                continue
            req_files.append(src_file)

    return req_files
def copy_tree_force(src_path="",dest_path=""):
    """
    make sure that all the paths has correct slash characters.
    """
    for cf in get_files_tree(src=src_path):
        df= cf.replace(src_path, dest_path)
        if not os.path.exists(os.path.dirname(df)):
            os.makedirs(os.path.dirname(df))
        shutil.copy2(cf, df)

The ternary (conditional) operator in C

It's crucial for code obfuscation, like this:

Look->       See?!

No
:(
Oh, well
);

Sending XML data using HTTP POST with PHP

you can use cURL library for posting data: http://www.php.net/curl

$ch = curl_init();
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_URL, "http://websiteURL");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, "XML=".$xmlcontent."&password=".$password."&etc=etc");
$content=curl_exec($ch);

where postfield contains XML you need to send - you will need to name the postfield the API service (Clickatell I guess) expects

How to debug "ImagePullBackOff"?

I was facing the similar problem, but instead of one all of my pods were not ready and displaying Ready status 0/1 Something like enter image description here

I tried a lot of things but at last i found that the context was not correctly set. Please use following command and ensure you are in correct context

kubectl config get-contexts

Is it safe to shallow clone with --depth 1, create commits, and pull updates again?

See some of the answers to my similar question why-cant-i-push-from-a-shallow-clone and the link to the recent thread on the git list.

Ultimately, the 'depth' measurement isn't consistent between repos, because they measure from their individual HEADs, rather than (a) your Head, or (b) the commit(s) you cloned/fetched, or (c) something else you had in mind.

The hard bit is getting one's Use Case right (i.e. self-consistent), so that distributed, and therefore probably divergent repos will still work happily together.

It does look like the checkout --orphan is the right 'set-up' stage, but still lacks clean (i.e. a simple understandable one line command) guidance on the "clone" step. Rather it looks like you have to init a repo, set up a remote tracking branch (you do want the one branch only?), and then fetch that single branch, which feels long winded with more opportunity for mistakes.

Edit: For the 'clone' step see this answer

HttpGet with HTTPS : SSLPeerUnverifiedException

Note: Do not do this in production code, use http instead, or the actual self signed public key as suggested above.

On HttpClient 4.xx:

import static org.junit.Assert.assertEquals;

import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.X509Certificate;

import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.conn.scheme.Scheme;
import org.apache.http.conn.ssl.SSLSocketFactory;
import org.apache.http.impl.client.DefaultHttpClient;
import org.junit.Test;

public class HttpClientTrustingAllCertsTest {

    @Test
    public void shouldAcceptUnsafeCerts() throws Exception {
        DefaultHttpClient httpclient = httpClientTrustingAllSSLCerts();
        HttpGet httpGet = new HttpGet("https://host_with_self_signed_cert");
        HttpResponse response = httpclient.execute( httpGet );
        assertEquals("HTTP/1.1 200 OK", response.getStatusLine().toString());
    }

    private DefaultHttpClient httpClientTrustingAllSSLCerts() throws NoSuchAlgorithmException, KeyManagementException {
        DefaultHttpClient httpclient = new DefaultHttpClient();

        SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, getTrustingManager(), new java.security.SecureRandom());

        SSLSocketFactory socketFactory = new SSLSocketFactory(sc);
        Scheme sch = new Scheme("https", 443, socketFactory);
        httpclient.getConnectionManager().getSchemeRegistry().register(sch);
        return httpclient;
    }

    private TrustManager[] getTrustingManager() {
        TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() {
            @Override
            public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                return null;
            }

            @Override
            public void checkClientTrusted(X509Certificate[] certs, String authType) {
                // Do nothing
            }

            @Override
            public void checkServerTrusted(X509Certificate[] certs, String authType) {
                // Do nothing
            }

        } };
        return trustAllCerts;
    }
}

how to configuring a xampp web server for different root directory

For XAMMP versions >=7.5.9-0 also change the DocumentRoot in file "/opt/lampp/etc/extra/httpd-ssl.conf" accordingly.

What do the different readystates in XMLHttpRequest mean, and how can I use them?

onreadystatechange Stores a function (or the name of a function) to be called automatically each time the readyState property changes readyState Holds the status of the XMLHttpRequest. Changes from 0 to 4:

0: request not initialized

1: server connection established

2: request received

3: processing request

4: request finished and response is ready

status 200: "OK"

404: Page not found

Angular - res.json() is not a function

HttpClient.get() applies res.json() automatically and returns Observable<HttpResponse<string>>. You no longer need to call this function yourself.

See Difference between HTTP and HTTPClient in angular 4?

ASP.NET Core return JSON with status code

The most basic version responding with a JsonResult is:

// GET: api/authors
[HttpGet]
public JsonResult Get()
{
    return Json(_authorRepository.List());
}

However, this isn't going to help with your issue because you can't explicitly deal with your own response code.

The way to get control over the status results, is you need to return a ActionResult which is where you can then take advantage of the StatusCodeResult type.

for example:

// GET: api/authors/search?namelike=foo
[HttpGet("Search")]
public IActionResult Search(string namelike)
{
    var result = _authorRepository.GetByNameSubstring(namelike);
    if (!result.Any())
    {
        return NotFound(namelike);
    }
    return Ok(result);
}

Note both of these above examples came from a great guide available from Microsoft Documentation: Formatting Response Data


Extra Stuff

The issue I come across quite often is that I wanted more granular control over my WebAPI rather than just go with the defaults configuration from the "New Project" template in VS.

Let's make sure you have some of the basics down...

Step 1: Configure your Service

In order to get your ASP.NET Core WebAPI to respond with a JSON Serialized Object along full control of the status code, you should start off by making sure that you have included the AddMvc() service in your ConfigureServices method usually found in Startup.cs.

It's important to note thatAddMvc() will automatically include the Input/Output Formatter for JSON along with responding to other request types.

If your project requires full control and you want to strictly define your services, such as how your WebAPI will behave to various request types including application/json and not respond to other request types (such as a standard browser request), you can define it manually with the following code:

public void ConfigureServices(IServiceCollection services)
{
    // Build a customized MVC implementation, without using the default AddMvc(), instead use AddMvcCore().
    // https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc/MvcServiceCollectionExtensions.cs

    services
        .AddMvcCore(options =>
        {
            options.RequireHttpsPermanent = true; // does not affect api requests
            options.RespectBrowserAcceptHeader = true; // false by default
            //options.OutputFormatters.RemoveType<HttpNoContentOutputFormatter>();

            //remove these two below, but added so you know where to place them...
            options.OutputFormatters.Add(new YourCustomOutputFormatter()); 
            options.InputFormatters.Add(new YourCustomInputFormatter());
        })
        //.AddApiExplorer()
        //.AddAuthorization()
        .AddFormatterMappings()
        //.AddCacheTagHelper()
        //.AddDataAnnotations()
        //.AddCors()
        .AddJsonFormatters(); // JSON, or you can build your own custom one (above)
}

You will notice that I have also included a way for you to add your own custom Input/Output formatters, in the event you may want to respond to another serialization format (protobuf, thrift, etc).

The chunk of code above is mostly a duplicate of the AddMvc() method. However, we are implementing each "default" service on our own by defining each and every service instead of going with the pre-shipped one with the template. I have added the repository link in the code block, or you can check out AddMvc() from the GitHub repository..

Note that there are some guides that will try to solve this by "undoing" the defaults, rather than just not implementing it in the first place... If you factor in that we're now working with Open Source, this is redundant work, bad code and frankly an old habit that will disappear soon.


Step 2: Create a Controller

I'm going to show you a really straight-forward one just to get your question sorted.

public class FooController
{
    [HttpPost]
    public async Task<IActionResult> Create([FromBody] Object item)
    {
        if (item == null) return BadRequest();

        var newItem = new Object(); // create the object to return
        if (newItem != null) return Ok(newItem);

        else return NotFound();
    }
}

Step 3: Check your Content-Type and Accept

You need to make sure that your Content-Type and Accept headers in your request are set properly. In your case (JSON), you will want to set it up to be application/json.

If you want your WebAPI to respond as JSON as default, regardless of what the request header is specifying you can do that in a couple ways.

Way 1 As shown in the article I recommended earlier (Formatting Response Data) you could force a particular format at the Controller/Action level. I personally don't like this approach... but here it is for completeness:

Forcing a Particular Format If you would like to restrict the response formats for a specific action you can, you can apply the [Produces] filter. The [Produces] filter specifies the response formats for a specific action (or controller). Like most Filters, this can be applied at the action, controller, or global scope.

[Produces("application/json")]
public class AuthorsController

The [Produces] filter will force all actions within the AuthorsController to return JSON-formatted responses, even if other formatters were configured for the application and the client provided an Accept header requesting a different, available format.

Way 2 My preferred method is for the WebAPI to respond to all requests with the format requested. However, in the event that it doesn't accept the requested format, then fall-back to a default (ie. JSON)

First, you'll need to register that in your options (we need to rework the default behavior, as noted earlier)

options.RespectBrowserAcceptHeader = true; // false by default

Finally, by simply re-ordering the list of the formatters that were defined in the services builder, the web host will default to the formatter you position at the top of the list (ie position 0).

More information can be found in this .NET Web Development and Tools Blog entry

Invalid syntax when using "print"?

The syntax is changed in new 3.x releases rather than old 2.x releases: for example in python 2.x you can write: print "Hi new world" but in the new 3.x release you need to use the new syntax and write it like this: print("Hi new world")

check the documentation: http://docs.python.org/3.3/library/functions.html?highlight=print#print

Multiple INNER JOIN SQL ACCESS

Thanks HansUp for your answer, it is very helpful and it works!

I found three patterns working in Access, yours is the best, because it works in all cases.

  • INNER JOIN, your variant. I will call it "closed set pattern". It is possible to join more than two tables to the same table with good performance only with this pattern.

    SELECT C_Name, cr.P_FirstName+" "+cr.P_SurName AS ClassRepresentativ, cr2.P_FirstName+" "+cr2.P_SurName AS ClassRepresentativ2nd
    FROM
         ((class
           INNER JOIN person AS cr 
           ON class.C_P_ClassRep=cr.P_Nr
         )
         INNER JOIN person AS cr2
         ON class.C_P_ClassRep2nd=cr2.P_Nr
      )
    

    ;

  • INNER JOIN "chained-set pattern"

    SELECT C_Name, cr.P_FirstName+" "+cr.P_SurName AS ClassRepresentativ, cr2.P_FirstName+" "+cr2.P_SurName AS ClassRepresentativ2nd
    FROM person AS cr
    INNER JOIN ( class 
       INNER JOIN ( person AS cr2
       ) ON class.C_P_ClassRep2nd=cr2.P_Nr
    ) ON class.C_P_ClassRep=cr.P_Nr
    ;
    
  • CROSS JOIN with WHERE

    SELECT C_Name, cr.P_FirstName+" "+cr.P_SurName AS ClassRepresentativ, cr2.P_FirstName+" "+cr2.P_SurName AS ClassRepresentativ2nd
    FROM class, person AS cr, person AS cr2
    WHERE class.C_P_ClassRep=cr.P_Nr AND class.C_P_ClassRep2nd=cr2.P_Nr
    ;
    

.NET 4.0 has a new GAC, why?

I also wanted to know why 2 GAC and found the following explanation by Mark Miller in the comments section of .NET 4.0 has 2 Global Assembly Cache (GAC):

Mark Miller said... June 28, 2010 12:13 PM

Thanks for the post. "Interference issues" was intentionally vague. At the time of writing, the issues were still being investigated, but it was clear there were several broken scenarios.

For instance, some applications use Assemby.LoadWithPartialName to load the highest version of an assembly. If the highest version was compiled with v4, then a v2 (3.0 or 3.5) app could not load it, and the app would crash, even if there were a version that would have worked. Originally, we partitioned the GAC under it's original location, but that caused some problems with windows upgrade scenarios. Both of these involved code that had already shipped, so we moved our (version-partitioned GAC to another place.

This shouldn't have any impact to most applications, and doesn't add any maintenance burden. Both locations should only be accessed or modified using the native GAC APIs, which deal with the partitioning as expected. The places where this does surface are through APIs that expose the paths of the GAC such as GetCachePath, or examining the path of mscorlib loaded into managed code.

It's worth noting that we modified GAC locations when we released v2 as well when we introduced architecture as part of the assembly identity. Those added GAC_MSIL, GAC_32, and GAC_64, although all still under %windir%\assembly. Unfortunately, that wasn't an option for this release.

Hope it helps future readers.

Round a floating-point number down to the nearest integer?

Just make round(x-0.5) this will always return the next rounded down Integer value of your Float. You can also easily round up by do round(x+0.5)

Create Django model or update if exists

Thought I'd add an answer since your question title looks like it is asking how to create or update, rather than get or create as described in the question body.

If you did want to create or update an object, the .save() method already has this behaviour by default, from the docs:

Django abstracts the need to use INSERT or UPDATE SQL statements. Specifically, when you call save(), Django follows this algorithm:

If the object’s primary key attribute is set to a value that evaluates to True (i.e., a value other than None or the empty string), Django executes an UPDATE. If the object’s primary key attribute is not set or if the UPDATE didn’t update anything, Django executes an INSERT.

It's worth noting that when they say 'if the UPDATE didn't update anything' they are essentially referring to the case where the id you gave the object doesn't already exist in the database.

Retrieve filename from file descriptor in C

In Windows, with GetFileInformationByHandleEx, passing FileNameInfo, you can retrieve the file name.

Length of string in bash

Using your example provided

#KISS (Keep it simple stupid)
size=${#myvar}
echo $size

Default behavior of "git push" without a branch specified

I just committed my code to a branch and pushed it to github, like this:

git branch SimonLowMemoryExperiments
git checkout SimonLowMemoryExperiments
git add .
git commit -a -m "Lots of experimentation with identifying the memory problems"
git push origin SimonLowMemoryExperiments

PHP to write Tab Characters inside a file?

The tab character is \t. Notice the use of " instead of '.

$chunk = "abc\tdef\tghi";

PHP Strings - Double quoted

If the string is enclosed in double-quotes ("), PHP will interpret more escape sequences for special characters:

...

\t horizontal tab (HT or 0x09 (9) in ASCII)


Also, let me recommend the fputcsv() function which is for the purpose of writing CSV files.

The builds tools for v120 (Platform Toolset = 'v120') cannot be found

if you are using visual 2012 right-click on project name -> properties -> configuration properties -> general -> platform toolset -> Visual Studio 2012 (v110)

Angularjs - Pass argument to directive

Here is how I solved my problem:

Directive

app.directive("directive_name", function(){
    return {
        restrict: 'E',
        transclude: true,
        template: function(elem, attr){
           return '<div><h2>{{'+attr.scope+'}}</h2></div>';
        },
        replace: true
    };
})

Controller

$scope.building = function(data){
    var chart = angular.element(document.createElement('directive_name'));
    chart.attr('scope', data);
    $compile(chart)($scope);
    angular.element(document.getElementById('wrapper')).append(chart);
  }

I now can use different scopes through the same directive and append them dynamically.

httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName

Your hosts file does not include a valid FQDN, nor is localhost an FQDN. An FQDN must include a hostname part, as well as a domain name part. For example, the following is a valid FQDN:

host.server4-245.com

Choose an FQDN and include it both in your /etc/hosts file on both the IPv4 and IPv6 addresses you are using (in your case, localhost or 127.0.0.1), and change your ServerName in your httpd configuration to match.

/etc/hosts:

127.0.0.1    localhost.localdomain localhost host.server4-245.com
::1          localhost.localdomain localhost host.server4-245.com

httpd.conf:

ServerName host.server4-245.com