Programs & Examples On #Mmix

MMIX is the next generation version of Don Knuth's famous MIX assembly language. MMIX has a syntax modelled around modern RISC machines, but with none of the idiosyncrasies that are part of all real assembly languages. Thus MMIX is ideal for theoretical investigations around computer science algorithms, data structures, and their complexity. MMIX comes with an assembler and simulator. There are even FPGA implementations of the underlying hardware!

PHP-FPM and Nginx: 502 Bad Gateway

I made all this similar tweaks, but from time to time I was getting 501/502 errors (daily).

This are my settings on /etc/php5/fpm/pool.d/www.conf to avoid 501 and 502 nginx errors… The server has 16Gb RAM. This configuration is for a 8Gb RAM server so…

sudo nano /etc/php5/fpm/pool.d/www.conf

then set the following values for

pm.max_children = 70
pm.start_servers = 20
pm.min_spare_servers = 20
pm.max_spare_servers = 35
pm.max_requests = 500

After this changes restart php-fpm

sudo service php-fpm restart

Cannot use object of type stdClass as array?

Have same problem today, solved like this:

If you call json_decode($somestring) you will get an Object and you need to access like $object->key , but if u call json_decode($somestring, true) you will get an dictionary and can access like $array['key']

How to "grep" out specific line ranges of a file

Put this in a file and make it executable:

start=`grep -n $1 < $3 | head -n1 | cut -d: -f1; exit ${PIPESTATUS[0]}`
if [ ${PIPESTATUS[0]} -ne 0 ]; then
    echo "couldn't find start pattern!" 1>&2
    exit 1
stop=`tail -n +$start < $3 | grep -n $2 | head -n1 | cut -d: -f1; exit ${PIPESTATUS[1]}`
if [ ${PIPESTATUS[0]} -ne 0 ]; then
    echo "couldn't find end pattern!" 1>&2
    exit 1

stop=$(( $stop + $start - 1))

sed "$start,$stop!d" < $3

Execute the file with arguments (NOTE that the script does not handle spaces in arguments!):

  1. Starting grep pattern
  2. Stopping grep pattern
  3. File path

To use with your example, use arguments: 1234 5555 myfile.txt

Includes lines with starting and stopping pattern.

How do I extract text that lies between parentheses (round brackets)?

A regex maybe? I think this would work...


How do I find numeric columns in Pandas?

Simple one-liner:


What is the difference between T(n) and O(n)?

Theta is a shorthand way of referring to a special situtation where the big O and Omega are the same.

Thus, if one claims The Theta is expression q, then they are also necessarily claiming that Big O is expression q and Omega is expression q.

Rough analogy:

If: Theta claims, "That animal has 5 legs." then it follows that: Big O is true ("That animal has less than or equal to 5 legs.") and Omega is true("That animal has more than or equal to 5 legs.")

It's only a rough analogy because the expressions aren't necessarily specific numbers, but instead functions of varying orders of magnitude such as log(n), n, n^2, (etc.).

Adding elements to object

push is an method of arrays , so for object you can get the index of last element ,and you can probably do the same job as push for object as below

var lastIndex = Object.keys(element)[Object.keys(element).length-1];

then add object to the new index of element

element[parseInt(lastIndex) +1] = { id: id, quantity: quantity };

How to bind RadioButtons to an enum?

You can create the radio buttons dynamically, ListBox can help you do that, without converters, quite simple.

The concrete steps are below:

  • create a ListBox and set the ItemsSource for the listbox as the enum MyLovelyEnum and binding the SelectedItem of the ListBox to the VeryLovelyEnum property.
  • then the Radio Buttons for each ListBoxItem will be created.
  • Step 1: add the enum to static resources for your Window, UserControl or Grid etc.
        <ObjectDataProvider MethodName="GetValues"
                            ObjectType="{x:Type system:Enum}"
                <x:Type TypeName="local:MyLovelyEnum" />
  • Step 2: Use the List Box and Control Template to populate each item inside as Radio button
    <ListBox ItemsSource="{Binding Source={StaticResource MyLovelyEnum}}" SelectedItem="{Binding VeryLovelyEnum, Mode=TwoWay}" >
            <Style TargetType="{x:Type ListBoxItem}">
                <Setter Property="Template">
                                Content="{TemplateBinding ContentPresenter.Content}"
                                IsChecked="{Binding Path=IsSelected,
                                RelativeSource={RelativeSource TemplatedParent},
                                Mode=TwoWay}" />

The advantage is: if someday your enum class changes, you do not need to update the GUI (XAML file).


How to call a function from a string stored in a variable?

In case someone else is brought here by google because they were trying to use a variable for a method within a class, the below is a code sample which will actually work. None of the above worked for my situation. The key difference is the & in the declaration of $c = & new... and &$c being passed in call_user_func.

My specific case is when implementing someone's code having to do with colors and two member methods lighten() and darken() from the csscolor.php class. For whatever reason, I wanted to have the same code be able to call lighten or darken rather than select it out with logic. This may be the result of my stubbornness to not just use if-else or to change the code calling this method.

$lightdark="lighten"; // or optionally can be darken
$color="fcc";   // a hex color
$c = & new CSS_Color($color);
$rtn=call_user_func( array(&$c,$lightdark),$color,$percent);

Note that trying anything with $c->{...} didn't work. Upon perusing the reader-contributed content at the bottom of's page on call_user_func, I was able to piece together the above. Also, note that $params as an array didn't work for me:

// This doesn't work:
$rtn=call_user_func( array(&$c,$lightdark),$params);

This above attempt would give a warning about the method expecting a 2nd argument (percent).

jquery $('.class').each() how many items?

If you're using chained syntax:

$(".class").each(function() {
    // ...

...I don't think there's any (reasonable) way for the code within the each function to know how many items there are. (Unreasonable ways would involve repeating the selector and using index.)

But it's easy enough to make the collection available to the function that you're calling in each. Here's one way to do that:

var collection = $(".class");
collection.each(function() {
    // You can access `collection.length` here.

As a somewhat convoluted option, you could convert your jQuery object to an array and then use the array's forEach. The arguments that get passed to forEach's callback are the entry being visited (what jQuery gives you as this and as the second argument), the index of that entry, and the array you called it on:

$(".class").get().forEach(function(entry, index, array) {
    // Here, array.length is the total number of items

That assumes an at least vaguely modern JavaScript engine and/or a shim for Array#forEach.

Or for that matter, give yourself a new tool:

// Loop through the jQuery set calling the callback:
//    loop(callback, thisArg);
// Callback gets called with `this` set to `thisArg` unless `thisArg`
// is falsey, in which case `this` will be the element being visited.
// Arguments to callback are `element`, `index`, and `set`, where
// `element` is the element being visited, `index` is its index in the
// set, and `set` is the jQuery set `loop` was called on.
// Callback's return value is ignored unless it's `=== false`, in which case
// it stops the loop.
$.fn.loop = function(callback, thisArg) {
    var me = this;
    return this.each(function(index, element) {
        return || element, element, index, me);


$(".class").loop(function(element, index, set) {
    // Here, set.length is the length of the set

C# Copy a file to another location with a different name

Use the File.Copy method instead


File.Copy(@"C:\oldFile.txt", @"C:\newFile.txt");

You can call it whatever you want in the newFile, and it will rename it accordingly.

jQuery DataTables Getting selected row values

More a comment than an answer - but I cannot add comments yet: Thanks for your help, the count was the easy part. Just for others that might come here. I hope that it will save you some time.

It took me a while to get the attributes from the rows and to understand how to access them from the data() Object (that the data() is an Array and the Attributes can be read by adding them with a dot and not with brackets:

$('#button').click( function () {
    for (var i = 0; i < table.rows('.selected').data().length; i++) { 
       console.log( table.rows('.selected').data()[i].attributeNameFromYourself);
} );

(by the way: I get the data for my table using AJAX and JSON)

json_encode function: special characters

The manual for json_encode specifies this:

All string data must be UTF-8 encoded.

Thus, try array_mapping utf8_encode() to your array before you encode it:

$arr = array_map('utf8_encode', $arr);
$json = json_encode($arr);

// {"funds":"ComStage STOXX\u00c2\u00aeEurope 600 Techn NR ETF"}

For reference, take a look at the differences between the three examples on this fiddle. The first doesn't use character encoding, the second uses htmlentities and the third uses utf8_encode - they all return different results.

For consistency, you should use utf8_encode().


open a url on click of ok button in android

    Button imageLogo = (Button)findViewById(;
    imageLogo.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            // TODO Auto-generated method stub
            String url = "";

            Intent i = new Intent(Intent.ACTION_VIEW);

How to define Singleton in TypeScript

This is a typescript decorator checking if multiple instances were accidentaly created against a service class that is designed to be singleton:

GCD to perform task in main thread

No you don't need to check if you're in the main thread. Here is how you can do this in Swift:

runThisInMainThread { () -> Void in
    runThisInMainThread { () -> Void in
        // No problem

func runThisInMainThread(block: dispatch_block_t) {
    dispatch_async(dispatch_get_main_queue(), block)

Its included as a standard function in my repo, check it out:

Can I simultaneously declare and assign a variable in VBA?

There is no shorthand in VBA unfortunately, The closest you will get is a purely visual thing using the : continuation character if you want it on one line for readability;

Dim clientToTest As String:  clientToTest = clientsToTest(i)
Dim clientString As Variant: clientString = Split(clientToTest)

Hint (summary of other answers/comments): Works with objects too (Excel 2010):

Dim ws  As Worksheet: Set ws = ActiveWorkbook.Worksheets("Sheet1")
Dim ws2 As New Worksheet: ws2.Name = "test"

Timestamp to human readable format

use Date.prototype.toLocaleTimeString() as documented here

please note the locale example en-US in the url.

Cache busting via params

Two questions: Will this effectively break the cache?

Yes. Even Stack Overflow use this method, although I remember that they (with their millions of visitors per day and zillions of different client and proxy versions and configurations) have had some freak edge cases where even this was not enough to break the cache. But the general assumption is that this will work, and is a suitable method to break caching on clients.

Will the param cause the browser to then never cache the response from that url since the param indicates that this is dynamic content?

No. The parameter will not change the caching policy; the caching headers sent by the server still apply, and if it doesn't send any, the browser's defaults.

Access props inside quotes in React JSX

If you want to use the es6 template literals, you need braces around the tick marks as well:

<img className="image" src={`images/${this.props.image}`} />

How to download Javadoc to read offline?

For the download of latest java documentation(jdk-8u77) API

Navigate to

Under Addition Resources and Under Java SE 8 Documentation
Click Download button

Under Java SE Development Kit 8 Documentation > Java SE Development Kit 8u77 Documentation

Accept the License Agreement and click on the download zip file

Unzip the downloaded file Start the API docs from jdk-8u77-docs-all\docs\api\index.html

For the other java versions api download, follow the following steps.

Navigate to

From Release dropdown select either of Java SE 7/6/5

In corresponding JAVA SE page and under Downloads left side menu Click JDK 7/6/5 Documentation or Java SE Documentation

Now in next page select the appropriate Java SE Development Kit 7uXX Documentation.

Accept License Agreement and click on Download zip file

Unzip the file and Start the API docs from

YYYY-MM-DD format date in shell script

Whenever I have a task like this I end up falling back to

$ man strftime

to remind myself of all the possibilities for time formatting options.

How to make Java Set?

Like this:

import java.util.*;
Set<Integer> a = new HashSet<Integer>();
a.add( 1);
a.add( 2);
a.add( 3);

Or adding from an Array/ or multiple literals; wrap to a list, first.

Integer[] array = new Integer[]{ 1, 4, 5};
Set<Integer> b = new HashSet<Integer>();
b.addAll( Arrays.asList( b));         // from an array variable
b.addAll( Arrays.asList( 8, 9, 10));  // from literals

To get the intersection:

// copies all from A;  then removes those not in B.
Set<Integer> r = new HashSet( a);
r.retainAll( b);
// and print;   r.toString() implied.
System.out.println("A intersect B="+r);

Hope this answer helps. Vote for it!

How to display errors on laravel 4?

Maybe not on Laravel 4 this time, but on L5.2* I had similar issue:

I simply changed the ownership of the storage/logs directory to www-data with:

# chown -R www-data:www-data logs

PS: This is on Ubuntu 15 and with apache.

My logs directory now looks like:

drwxrwxr-x  2 www-data   www-data 4096 jaan  23 09:39 logs/

Push items into mongo array via mongoose

Use $push to update document and insert new value inside an array.



result for find:

    "_id" : ObjectId("5bc061f05a4c0511a9252e88"),
    "count" : 1.0,
    "color" : "green",
    "icon" : "circle",
    "graph" : [ 
            "date" : ISODate("2018-10-24T08:55:13.331Z"),
            "count" : 2.0
    "name" : "online visitor",
    "read" : false,
    "date" : ISODate("2018-10-12T08:57:20.853Z"),
    "__v" : 0.0


   { _id: ObjectId("5bc061f05a4c0511a9252e88") }, 
   { $push: { 
             graph: {
               "date" : ISODate("2018-10-24T08:55:13.331Z"),
               "count" : 3.0

result for update:

    "_id" : ObjectId("5bc061f05a4c0511a9252e88"),
    "count" : 1.0,
    "color" : "green",
    "icon" : "circle",
    "graph" : [ 
            "date" : ISODate("2018-10-24T08:55:13.331Z"),
            "count" : 2.0
            "date" : ISODate("2018-10-24T08:55:13.331Z"),
            "count" : 3.0
    "name" : "online visitor",
    "read" : false,
    "date" : ISODate("2018-10-12T08:57:20.853Z"),
    "__v" : 0.0

How to forward declare a template class in namespace std?

The problem is not that you can't forward-declare a template class. Yes, you do need to know all of the template parameters and their defaults to be able to forward-declare it correctly:

namespace std {
  template<class T, class Allocator = std::allocator<T>>
  class list;

But to make even such a forward declaration in namespace std is explicitly prohibited by the standard: the only thing you're allowed to put in std is a template specialisation, commonly std::less on a user-defined type. Someone else can cite the relevant text if necessary.

Just #include <list> and don't worry about it.

Oh, incidentally, any name containing double-underscores is reserved for use by the implementation, so you should use something like TEST_H instead of __TEST__. It's not going to generate a warning or an error, but if your program has a clash with an implementation-defined identifier, then it's not guaranteed to compile or run correctly: it's ill-formed. Also prohibited are names beginning with an underscore followed by a capital letter, among others. In general, don't start things with underscores unless you know what magic you're dealing with.

What is the difference between C# and .NET?

C# is a programming language.

.Net is a framework used for building applications on Windows.

.Net framework is not limited to C#. Different languages can target .Net framework and build applications using that framework. Examples are F# or VB.Net

Generic Property in C#

You would need to create a generic class named MyProp. Then, you will need to add implicit or explicit cast operators so you can get and set the value as if it were the type specified in the generic type parameter. These cast operators can do the extra work that you need.

How to read an http input stream

try this code

String data = "";
InputStream iStream = httpEntity.getContent();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream, "utf8"));
StringBuffer sb = new StringBuffer();
String line = "";

while ((line = br.readLine()) != null) {

data = sb.toString();

Mail not sending with PHPMailer over SSL using SMTP

$mail->Host = "";
$mail->SMTPAuth = true;
$mail->SMTPSecure = "ssl";
$mail->Username = "[email protected]";
$mail->Password = "**********";
$mail->Port = "465";

That is a working configuration.

try to replace what you have

docker: "build" requires 1 argument. See 'docker build --help'

You need to add a dot, which means to use the Dockerfile in the local directory.

For example:

docker build -t mytag .

It means you use the Dockerfile in the local directory, and if you use docker 1.5 you can specify a Dockerfile elsewhere. Extract from the help output from docker build:

-f, --file="" Name of the Dockerfile(Default is 'Dockerfile' at context root)

Copy multiple files with Ansible

- hosts: lnx
    - find: paths="/appl/scripts/inq" recurse=yes patterns="inq.Linux*"
      register: file_to_copy
    - copy: src={{ item.path }} dest=/usr/local/sbin/
      owner: root
      mode: 0775
      with_items: "{{ files_to_copy.files }}"

How can I pad an integer with zeros on the left?

Here is another way to pad an integer with zeros on the left. You can increase the number of zeros as per your convenience. Have added a check to return the same value as is in case of negative number or a value greater than or equals to zeros configured. You can further modify as per your requirement.

 * @author Dinesh.Lomte
public class AddLeadingZerosToNum {
     * @param args
    public static void main(String[] args) {
     * @param num
     * @return
    private static String getLeadingZerosToNum(int num) {
        // Initializing the string of zeros with required size
        String zeros = new String("0000");
        // Validating if num value is less then zero or if the length of number 
        // is greater then zeros configured to return the num value as is
        if (num < 0 || String.valueOf(num).length() >= zeros.length()) {
            return String.valueOf(num);
        // Returning zeros in case if value is zero.
        if (num == 0) {
            return zeros;
        return new StringBuilder(zeros.substring(0, zeros.length() - 














UnsupportedClassVersionError unsupported major.minor version 51.0 unable to load class

java_home environment variable should point to the location of the proper version of java installation directory, so that tomcat starts with the right version. for example it you built the project with java 1.7 , then make sure that JAVA_HOME environment variable points to the jdk 1.7 installation directory in your machine.

I had same problem , when i deploy the war in tomcat and run, the link throws the error. But pointing the variable - JAVA_HOME to jdk 1.7 resolved the issue, as my war file was built in java 1.7 environment.

How do I separate an integer into separate digits in an array in JavaScript?

const number = 1435;

How do I convert from a string to an integer in Visual Basic?

You can use the following to convert string to int:

  • CInt(String) for ints
  • CDec(String) for decimals

For details refer to Type Conversion Functions (Visual Basic).

CSS force new line

Use the display property

    display: block;

This will make the link to display in new line

If you want to remove list styling, use

    list-style: none;

TypeError: unsupported operand type(s) for /: 'str' and 'str'

There is another error with the forwars=d slash.

if we get this : def get_x(r): return path/'train'/r['fname']
is the same as def get_x(r): return path + 'train' + r['fname']

Select multiple elements from a list

mylist[c(5,7,9)] should do it.

You want the sublists returned as sublists of the result list; you don't use [[]] (or rather, the function is [[) for that -- as Dason mentions in comments, [[ grabs the element.

Updating and committing only a file's permissions using git version control

Not working for me.

The mode is true, the file perms have been changed, but git says there's no work to do.

git init
git add dir/file
chmod 440 dir/file
git commit -a

The problem seems to be that git recognizes only certain permission changes.

Vue.js redirection to another page

To stay in line with your original request:

window.location.href = 'some_url'

You can do something like this:

<div @click="this.window.location='some_url'">

Note that this does not take advantage of using Vue's router, but if you want to "make a redirection in Vue.js similar to the vanilla javascript", this would work.

Generating random numbers in Objective-C

According to the manual page for rand(3), the rand family of functions have been obsoleted by random(3). This is due to the fact that the lower 12 bits of rand() go through a cyclic pattern. To get a random number, just seed the generator by calling srandom() with an unsigned seed, and then call random(). So, the equivalent of the code above would be

#import <stdlib.h>
#import <time.h>

random() % 74;

You'll only need to call srandom() once in your program unless you want to change your seed. Although you said you didn't want a discussion of truly random values, rand() is a pretty bad random number generator, and random() still suffers from modulo bias, as it will generate a number between 0 and RAND_MAX. So, e.g. if RAND_MAX is 3, and you want a random number between 0 and 2, you're twice as likely to get a 0 than a 1 or a 2.

Visual Studio 2010 - recommended extensions

AnkhSVN (free)

Even if you use other SVN shells outside VS (like TortoiseSVN), I recommend to install this Source Control Provider to automatically keep track of file renames, deletions and the like.

scp via java

JSch is a nice library to work with. It has quite an easy answer for your question.

JSch jsch=new JSch();
  Session session=jsch.getSession(user, host, 22);

  Properties config = new Properties();

  boolean ptimestamp = true;

  // exec 'scp -t rfile' remotely
  String command="scp " + (ptimestamp ? "-p" :"") +" -t "+rfile;
  Channel channel=session.openChannel("exec");

  // get I/O streams for remote scp
  OutputStream out=channel.getOutputStream();
  InputStream in=channel.getInputStream();



  File _lfile = new File(lfile);

    command="T "+(_lfile.lastModified()/1000)+" 0";
    // The access time should be sent here,
    // but it is not accessible with JavaAPI ;-<
    command+=(" "+(_lfile.lastModified()/1000)+" 0\n");
    out.write(command.getBytes()); out.flush();

You can find complete code at

React "after render" code?


This method is called once after your component is rendered. So your code would look like so.

var AppBase = React.createClass({
  componentDidMount: function() {
    var $this = $(ReactDOM.findDOMNode(this));
    // set el height and width etc.

  render: function () {
    return (
      <div className="wrapper">
        <Sidebar />
          <div className="inner-wrapper">
            <ActionBar title="Title Here" />
            <BalanceBar balance={balance} />
            <div className="app-content">
              <List items={items} />

Android: Use a SWITCH statement with setOnClickListener/onClick for more than 1 button?

public class MainActivity extends Activity
        implements View.OnClickListener {
    private Button btnForward, btnBackword, btnPause, btnPlay;

    protected void onCreate(Bundle savedInstanceState) {

    private void initControl() {
        btnForward = (Button) findViewById(;
        btnBackword = (Button) findViewById(;
        btnPause = (Button) findViewById(;
        btnPlay = (Button) findViewById(;

    public void onClick(View v) {
        switch (v.getId()) {

How to save an image locally using Python whose URL address I already know?

This is very short answer.

import urllib
urllib.urlretrieve("", "Abc.jpg")

How do I fix a .NET windows application crashing at startup with Exception code: 0xE0434352?


.Net application code aborts before it starts its execution [Console application or Windows application]

Error received: Aborted with Error code "E0434352"

Exception: Unknown exception

Scenario 1:

When an application is already executed, which have used some of the dependent resources and those resources are still in use with the application executed, when another application or the same exe is triggered from some other source then one of the app throws the error

Scenario 2:

When an application is triggered by scheduler or automatic jobs, it may be in execution state at background, meanwhile when you try to trigger the same application again, the error may be triggered.


Create an application, when & where the application release all its resources as soon as completed Kill all the background process once the application is closed Check and avoid executing the application from multiple sources like Batch Process, Task Scheduler and external tools at same time. Check for the Application and resource dependencies and clean up the code if needed.

How to change title of Activity in Android?

This worked for me.

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment, container, false);
    getActivity().setTitle("My Title");

Database cluster and load balancing

Clustering uses shared storage of some kind (a drive cage or a SAN, for example), and puts two database front-ends on it. The front end servers share an IP address and cluster network name that clients use to connect, and they decide between themselves who is currently in charge of serving client requests.

If you're asking about a particular database server, add that to your question and we can add details on their implementation, but at its core, that's what clustering is.

How to work with progress indicator in flutter?

Create a bool isLoading and set it to false. With the help of ternary operator, When user clicks on login button set state of isLoading to true. You will get circular loading indicator in place of login button

 isLoading ? new PrimaryButton(
                      key: new Key('login'),
                      text: 'Login',
                      height: 44.0,
                      onPressed: setState((){isLoading = true;}))
                  : Center(
                      child: CircularProgressIndicator(),

You can see Screenshots how it looks while before login is clicked enter image description here

After login is clicked enter image description here

In mean time you can run login process and login user. If user credentials are wrong then again you will setState of isLoading to false, such that loading indicator will become invisible and login button visible to user. By the way, primaryButton used in code is my custom button. You can do same with OnPressed in button.

How to make a new List in Java

First read this, then read this and this. 9 times out of 10 you'll use one of those two implementations.

In fact, just read Sun's Guide to the Collections framework.

string to string array conversion in java

String strName = "name";
String[] strArray = new String[] {strName};
System.out.println(strArray[0]); //prints "name"

The second line allocates a String array with the length of 1. Note that you don't need to specify a length yourself, such as:

String[] strArray = new String[1];

instead, the length is determined by the number of elements in the initalizer. Using

String[] strArray = new String[] {strName, "name1", "name2"};

creates an array with a length of 3.

Invoking a jQuery function after .each() has completed

I meet the same problem and I solved with a solution like the following code:

var drfs = new Array();
var external = $.Deferred();

$('itemSelector').each( function() {
    //initialize the context for each cycle
    var t = this; // optional
    var internal = $.Deferred();

    // after the previous deferred operation has been resolved
    drfs.pop().then( function() {

        // do stuff of the cycle, optionally using t as this
        var result; //boolean set by the stuff

        if ( result ) {
        } else {


$.when(drfs).then( function() {
    // after all each are resolved


The solution solves the following problem: to synchronize the asynchronous operations started in the .each() iteration, using Deferred object.

Why is SQL server throwing this error: Cannot insert the value NULL into column 'id'?

I'm assuming that id is supposed to be an incrementing value.

You need to set this, or else if you have a non-nullable column, with no default value, if you provide no value it will error.

To set up auto-increment in SQL Server Management Studio:

  • Open your table in Design
  • Select your column and go to Column Properties
  • Under Indentity Specification, set (Is Identity)=Yes and Indentity Increment=1

How to get exit code when using Python subprocess communicate method?

You should first make sure that the process has completed running and the return code has been read out using the .wait method. This will return the code. If you want access to it later, it's stored as .returncode in the Popen object.

How does the "this" keyword work?

Probably the most detailed and comprehensive article on this is the following:

Gentle explanation of 'this' keyword in JavaScript

The idea behind this is to understand that the function invocation types have the significant importance on setting this value.

When having troubles identifying this, do not ask yourself:

Where is this taken from?

but do ask yourself:

How is the function invoked?

For an arrow function (special case of context transparency) ask yourself:

What value has this where the arrow function is defined?

This mindset is correct when dealing with this and will save you from headache.

Writing a dictionary to a csv file with one line for every 'key: value'

Easiest way is to ignore the csv module and format it yourself.

with open('my_file.csv', 'w') as f:
    [f.write('{0},{1}\n'.format(key, value)) for key, value in my_dict.items()]

Deploying my application at the root in Tomcat

I know that my answer is kind of overlapping with some of the other answer, but this is a complete solution that has some advantages. This works on Tomcat 8:

  1. The main application is served from the root
  2. The deployment of war files through the web interface is maintained.
  3. The main application will run on port 80 while only the admins have access to the managment folders (I realize that *nix systems require superuser for binding to 80, but on windows this is not an issue).

This means that you only have to restart the tomcat once, and after updated war files can be deployed without a problem.

Step 1: In the server.xml file, find the connector entry and replace it with:

    redirectPort="8443" />

    redirectPort="8443" />

Step 2: Define contexts within the <Host ...> tag:

<Context path="/" docBase="CAS">
<Context path="/ROOT" docBase="ROOT">
<Context path="/manager" docBase="manager" privileged="true">
<Context path="/host-manager" docBase="host-manager" privileged="true">

Note that I addressed all apps in the webapp folder. The first effectively switch the root and the main app from position. ROOT is now on and the the main application is on The webapps that are password protected require the privileged="true" attribute.

When you deploy a CAS.war file that matches with the root (<Context path="/" docBase="CAS"> you have to reload that one in the admin panel as it does not refresh with the deployment.

Do not include the <Context path="/CAS" docBase="CAS"> in your contexts as it disables the manager option to deploy war files. This means that you can access the app in two ways: and

Step 3: In order to prevent unwanted access to the root and manager folder, add a valve to those context tags like this:

<Context path="/manager" docBase="manager" privileged="true">
    <Valve className="org.apache.catalina.valves.RemoteAddrValve"

This essentially limits access to the admin web app folder to people from my own domain (fake IP address) and localhost when they use the default port 8080 and maintains the ability to dynamically deploy the war files through the web interface.

If you want to use this for multiple apps that are using different IP addresses, you can add the IP address to the connector (address="").

If you want to run multiple web apps from the root, you can duplicate the Service tag (use a different name for the second) and change the docbase of the <Context path="/" docBase="CAS"> to for example <Context path="/" docBase="ICR">.

Could not extract response: no suitable HttpMessageConverter found for response type

public class Application {

    private static List<HttpMessageConverter<?>> getMessageConverters() {
        List<HttpMessageConverter<?>> converters = new ArrayList<HttpMessageConverter<?>>();
        converters.add(new MappingJacksonHttpMessageConverter());
        return converters;

    public static void main(String[] args) {
        RestTemplate restTemplate = new RestTemplate();

        HttpHeaders headers = new HttpHeaders();
        HttpEntity<String> entity = new HttpEntity<String>(headers);
        //Page page = restTemplate.getForObject("", Page.class);

        ResponseEntity<Page> response = 
        "", HttpMethod.GET, entity, Page.class, "1");
        Page page = response.getBody();
        System.out.println("Name:    " + page.getId());
        System.out.println("About:   " + page.getFirst_name());
        System.out.println("Phone:   " + page.getLast_name());
        System.out.println("Website: " + page.getMiddle_name());
        System.out.println("Website: " + page.getName());

Selecting last element in JavaScript array

var last = function( obj, key ) { 
    var a = obj[key];
    return a[a.length - 1];

last(loc, 'f096012e-2497-485d-8adb-7ec0b9352c52');

System.Data.SqlClient.SqlException: Invalid object name 'dbo.Projects'

The cause of this problem could be a property setting of the database (Sql2008R2 with .NET4).

  • Problem is reproducible at will when changing the COLLATION value of a database.

To display COLLLATION, use the Sql Server Mgmt Studio.

  • Right-click the database and select Properties -> General, Then look under Maintenance for the COLLATION value

To change COLLATION, (still) use the Sql Server Mgmt Studio.

  • Right-click the database and select Properties -> Options, From there, you can change the COLLATION value

Fixed positioned div within a relative parent div

you can fix the wrapper using absolute positioning. and the give inside div a fixed position.

 left:10%;// or some valve in px
 top:10%; // or some valve in px

and div inside that

.wrapper .fixed-element{ 
margin-left:auto; // to center this div inside at center give auto margin

try this It might work for you

Make Https call using HttpClient

Add the below declarations to your class:

public const SslProtocols _Tls12 = (SslProtocols)0x00000C00;
public const SecurityProtocolType Tls12 = (SecurityProtocolType)_Tls12;


var client = new HttpClient();


ServicePointManager.SecurityProtocol = Tls12;
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 /*| SecurityProtocolType.Tls */| Tls12;

Happy? :)


One more thing to make sure you have is the following set in your web.config:

    <modules runAllManagedModulesForAllRequests="true"/> 

How do I include a newline character in a string in Delphi?

The plattform agnostic way would be 'sLineBreak':

Write('Hello' + sLineBreak + 'World!');

Simple way to transpose columns and rows in SQL?

This way Convert all Data From Filelds(Columns) In Table To Record (Row).

Declare @TableName  [nvarchar](128)
Declare @ExecStr    nvarchar(max)
Declare @Where      nvarchar(max)
Set @TableName = 'myTableName'
--Enter Filtering If Exists
Set @Where = ''

--Set @ExecStr = N'Select * From '+quotename(@TableName)+@Where

Drop Table If Exists #tmp_Col2Row

Create Table #tmp_Col2Row
(Field_Name nvarchar(128) Not Null
,Field_Value nvarchar(max) Null

Set @ExecStr = N' Insert Into #tmp_Col2Row (Field_Name , Field_Value) '
Select @ExecStr += (Select N'Select '''''' ,Convert(nvarchar(max),'+quotename( + ') From ' + quotename(@TableName)+@Where+Char(10)+' Union All '
         from sys.columns as C
         where (C.object_id = object_id(@TableName)) 
         for xml path(''))
Select @ExecStr = Left(@ExecStr,Len(@ExecStr)-Len(' Union All '))
--Print @ExecStr
Exec (@ExecStr)

Select * From #tmp_Col2Row

What does 'const static' mean in C and C++?

In C++,

static const int foo = 42;

is the preferred way to define & use constants. I.e. use this rather than

#define foo 42

because it doesn't subvert the type-safety system.

Determining if an Object is of primitive type

This is the simplest way I could think of. The wrapper classes are present only in java.lang package. And apart from the wrapper classes, no other class in java.lang has field named TYPE. You could use that to check whether a class is Wrapper class or not.

public static boolean isBoxingClass(Class<?> clazz)
    String pack = clazz.getPackage().getName();
        return false;
    catch (NoSuchFieldException e) 
        return false;
    return true;        

Pausing a batch file for amount of time

ping -n 11 -w 1000 > nul


Beginner's mistake. Ping doesn't wait 1000 ms before or after an request, but inbetween requests. So to wait 10 seconds, you'll have to do 11 pings to have 10 'gaps' of a second inbetween.

how to get the value of a textarea in jquery?

You don't need to use textarea#message

var message = $('textarea#message').val();

You can directly use

var message = $('#message').val();

Does file_get_contents() have a timeout setting?

Yes! By passing a stream context in the third parameter:

Here with a timeout of 1s:

file_get_contents("", 0, stream_context_create(["http"=>["timeout"=>1]]));

Source in comment section of

HTTP context options:


Other contexts:

How to set TextView textStyle such as bold, italic

Try this:

textView.setTypeface(textView.getTypeface(), Typeface.BOLD);
textView.setTypeface(textView.getTypeface(), Typeface.ITALIC);
textView.setTypeface(textView.getTypeface(), Typeface.BOLD_ITALIC);

Adding blank spaces to layout

View if you need change background color , Space if not .

that dosent mean you have to change view background .


or Space


pg_config executable not found

UPDATE /etc/yum.repos.d/CentOS-Base.repo, [base] and [updates] sections
ADD exclude=postgresql*

curl -O  
rpm -ivh pgdg-centos91-9.1-4.noarch.rpm

yum install postgresql  
yum install postgresql-devel


pip install psycopg2

How do I correctly use "Not Equal" in MS Access?

I have struggled to get a query to return fields from Table 1 that do not exist in Table 2 and tried most of the answers above until I found a very simple way to obtain the results that I wanted.

I set the join properties between table 1 and table 2 to the third setting (3) (All fields from Table 1 and only those records from Table 2 where the joined fields are equal) and placed a Is Null in the criteria field of the query in Table 2 in the field that I was testing for. It works perfectly.

Thanks to all above though.

Is there a decent wait function in C++?

The appearance and disappearance of a window for displaying text is a feature of how you are running the program, not of C++.

Run in a persistent command line environment, or include windowing support in your program, or use sleep or wait on input as shown in other answers.

JS jQuery - check if value is in array

Alternate solution of the values check

//Duplicate Title Entry 
    $.each(ar , function (i, val) {
        if ( jQuery("input:first").val()== val) alert('VALUE FOUND'+Valuecheck);

How to get an object's methods?

var methods = [];
for (var key in foo.prototype) {
    if (typeof foo.prototype[key] === "function") {

You can simply loop over the prototype of a constructor and extract all methods.

What is the equivalent of ngShow and ngHide in Angular 2+?

There are two examples on Angular documents

A directive could hide the unwanted paragraph instead by setting its display style to none.

<p [style.display]="'block'">
  Expression sets display to "block".
  This paragraph is visible.

<p [style.display]="'none'">
  Expression sets display to "none".
  This paragraph is hidden but still in the DOM.

You can use [style.display]="'block'" to replace ngShow and [style.display]="'none'" to replace ngHide.

How to write UTF-8 in a CSV file

It's very simple for Python 3.x (docs).

import csv

with open('output_file_name', 'w', newline='', encoding='utf-8') as csv_file:
    writer = csv.writer(csv_file, delimiter=';')

For Python 2.x, look here.

Remove directory from remote repository after adding them to .gitignore

I do this:

git rm --cached `git ls-files -i --exclude-from=.gitignore` 
git commit -m 'Removed all files that are in the .gitignore' 
git push origin master

Which will remove all the files/folders that are in your git ignore, saving you have to pick each one manually

This seems to have stopped working for me, I now do:

 git rm -r --cached . 
 git add .
 git commit -m 'Removed all files that are in the .gitignore' 
 git push origin master

Why do I get "Exception; must be caught or declared to be thrown" when I try to compile my Java code?

In actionPerformed(ActionEvent e) you call encrypt(), which is declared to throw Exception. However, actionPerformed neither catches this Exception (with try/catch around the call to encrypt()) nor declares that it throws Exception itself.

Your encrypt method, however, does not truly throw Exception. It swallows all Exceptions without even as much as logging a complaint. (Bad practice and bad style!)

Also, your encrypt method does the following:

public static byte[] encrypt(String toEncrypt) throws Exception {
    return encrypted; // HERE YOU CORRECTLY RETURN A VALUE
  } catch(Exception e) {

That is, if you do catch any Exception, you discard it silently and then fall off the bottom of your encrypt method without actually returning anything. This won't compile (as you see), because a method that is declared to return a value must either return a value or throw an Exception for every single possible code path.

Artificially create a connection timeout error


All these are non-routable.

Check array position for null/empty

There is no bound checking in array in C programming. If you declare array as

int arr[50];

Then you can even write as

arr[51] = 10;

The compiler would not throw an error. Hope this answers your question.

How to read data From *.CSV file using javascript?

Don't split on commas -- it won't work for most CSV files, and this question has wayyyy too many views for the asker's kind of input data to apply to everyone. Parsing CSV is kind of scary since there's no truly official standard, and lots of delimited text writers don't consider edge cases.

This question is old, but I believe there's a better solution now that Papa Parse is available. It's a library I wrote, with help from contributors, that parses CSV text or files. It's the only JS library I know of that supports files gigabytes in size. It also handles malformed input gracefully.

1 GB file parsed in 1 minute: Parsed 1 GB file in 1 minute

(Update: With Papa Parse 4, the same file took only about 30 seconds in Firefox. Papa Parse 4 is now the fastest known CSV parser for the browser.)

Parsing text is very easy:

var data = Papa.parse(csvString);

Parsing files is also easy:

Papa.parse(file, {
    complete: function(results) {

Streaming files is similar (here's an example that streams a remote file):

Papa.parse("", {
    download: true,
    step: function(row) {
    complete: function() {
        console.log("All done!");

If your web page locks up during parsing, Papa can use web workers to keep your web site reactive.

Papa can auto-detect delimiters and match values up with header columns, if a header row is present. It can also turn numeric values into actual number types. It appropriately parses line breaks and quotes and other weird situations, and even handles malformed input as robustly as possible. I've drawn on inspiration from existing libraries to make Papa, so props to other JS implementations.

How to join multiple lines of file names into one with custom delimiter?

It looks like the answers already exist.

If you want a, b, c format, use ls -m ( Tulains Córdova’s answer)

Or if you want a b c format, use ls | xargs (simpified version of Chris J’s answer)

Or if you want any other delimiter like |, use ls | paste -sd'|' (application of Artem’s answer)

Python JSON encoding

Python lists translate to JSON arrays. What it is giving you is a perfectly valid JSON string that could be used in a Javascript application. To get what you expected, you would need to use a dict:

>>> json.dumps({'apple': 'cat', 'banana':'dog', 'pear':'fish'})
'{"pear": "fish", "apple": "cat", "banana": "dog"}'

How to format a java.sql Timestamp for displaying?

java.sql.Timestamp extends java.util.Date. You can do:

String s = new SimpleDateFormat("MM/dd/yyyy").format(myTimestamp);

Or to also include time:

String s = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss").format(myTimestamp);

Can I animate absolute positioned element with CSS transition?

try this:

.test {
    transition:left 1s linear;
    left: 0;

Creating a JSON Array in node js

This one helped me,

                            var responseData    = {};
                            responseData['status'] = 200;
                            responseData['outputPath']  = outputDirectoryPath;
                            responseData['sourcePath']  = url;
                            responseData['message'] = 'Scraping of requested resource initiated.';
                            responseData['logfile'] = logFileName;

How to pass url arguments (query string) to a HTTP request on Angular?

import { Http, Response } from '@angular/http';
constructor(private _http: Http, private router: Router) {

return this._http.get('http://url/login/' + email + '/' + password)
       .map((res: Response) => {
           return res.json();

How do I get a range's address including the worksheet name, but not the workbook name, in Excel VBA?

For confused old me a range

.Address(False, False, , True)

seems to give in format TheSheet!B4:K9

If it does not why the criteria .. avoid Str functons

will probably only take less a millisecond and use 153 already used electrons

about 0.3 Microsec

RaAdd=mid(RaAdd,instr(raadd,"]") +1)


'about 1.7 microsec

RaAdd= split(radd,"]")(1)

Angularjs: Get element in controller

I dont know what do you exactly mean but hope it help you.
by this directive you can access the DOM element inside controller
this is sample that help you to focus element inside controller

.directive('scopeElement', function () {
    return {
        restrict:"A", // E-Element A-Attribute C-Class M-Comments
        replace: false,
        link: function($scope, elem, attrs) {
            $scope[attrs.scopeElement] = elem[0];

now, inside HTML

<input scope-element="txtMessage" >

then, inside controller :

.controller('messageController', ['$scope', function ($scope) {

Defining a percentage width for a LinearLayout?

i know another solution, that work with weight:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android=""


Editing hosts file to redirect url?

Make sure to double the entry with an additional "www"-prefix. If you don't addresses like "" will not work!

JQuery string contains check

I use,

var text = "some/String"; text.includes("/") <-- returns bool; true if "/" exists in string, false otherwise.

How to store the hostname in a variable in a .bat file?

hmm - something like this?

echo %host%

EDIT: expanding on jitter's answer and using a technique in an answer to this question to set an environment variable with the result of running a command line app:

@echo off
hostname.exe > __t.tmp
set /p host=<__t.tmp
del __t.tmp
echo %host%

In either case, 'host' is created as an environment variable.

Include of non-modular header inside framework module

Make sure the header files are publicly available as part of the framework's public headers.

Goto Framework -> Target -> Build Phases and drag to move the relevant header files from Project to Public. Hope that helps!


How does Java import work?

In dynamic languages, when the interpreter imports, it simply reads a file and evaluates it.

In C, external libraries are located by the linker at compile time to build the final object if the library is statically compiled, while for dynamic libraries a smaller version of the linker is called at runtime which remaps addresses and so makes code in the library available to the executable.

In Java, import is simply used by the compiler to let you name your classes by their unqualified name, let's say String instead of java.lang.String. You don't really need to import java.lang.* because the compiler does it by default. However this mechanism is just to save you some typing. Types in Java are fully qualified class names, so a String is really a java.lang.String object when the code is run. Packages are intended to prevent name clashes and allow two classes to have the same simple name, instead of relying on the old C convention of prefixing types like this. java_lang_String. This is called namespacing.

BTW, in Java there's the static import construct, which allows to further save typing if you use lots of constants from a certain class. In a compilation unit (a .java file) which declares

import static java.lang.Math.*;

you can use the constant PI in your code, instead of referencing it through Math.PI, and the method cos() instead of Math.cos(). So for example you can write

double r = cos(PI * theta);

Once you understand that classes are always referenced by their fully qualified name in the final bytecode, you must understand how the class code is actually loaded. This happens the first time an object of that class is created, or the first time a static member of the class is accessed. At this time, the ClassLoader tries to locate the class and instantiate it. If it can't find the class a NoClassDefFoundError is thrown (or a a ClassNotFoundException if the class is searched programmatically). To locate the class, the ClassLoader usually checks the paths listed in the $CLASSPATH environment variable.

To solve your problem, it seems you need an applet element like this

  codebase = ""
  archive="test.jar, core.jar"
  width="550" height="550" >

BTW, you don't need to import the archives in the standard JRE.

Change CSS class properties with jQuery

You may want to take a different approach: Instead of changing the css dynamically, predefine your styles in CSS the way you want them. Then use JQuery to add and remove styles from within Javascript. (see code from Ajmal)

Is it possible to use raw SQL within a Spring Repository

It is also possible to use Spring Data JDBC repository, which is a community project built on top of Spring Data Commons to access to databases with raw SQL, without using JPA.

It is less powerful than Spring Data JPA, but if you want lightweight solution for simple projects without using a an ORM like Hibernate, that a solution worth to try.

Hide password with "•••••••" in a textField

in Swift 3.0 or Later

passwordTextField.isSecureTextEntry = true

TypeScript static classes

Defining static properties and methods of a class is described in 8.2.1 of the Typescript Language Specification:

class Point { 
  constructor(public x: number, public y: number) { 
    throw new Error('cannot instantiate using a static class');
  public distance(p: Point) { 
    var dx = this.x - p.x; 
    var dy = this.y - p.y; 
    return Math.sqrt(dx * dx + dy * dy); 
  static origin = new Point(0, 0); 
  static distance(p1: Point, p2: Point) { 
    return p1.distance(p2); 

where Point.distance() is a static (or "class") method.

Remove all files in a directory

os.remove doesn't resolve unix-style patterns. If you are on a unix-like system you can:

os.system('rm '+test)

Else you can:

import glob, os
test = '/path/*'
r = glob.glob(test)
for i in r:

how to compare the Java Byte[] array?

why a[] doesn't equals b[]? Because equals function really called on Byte[] or byte[] is Object.equals(Object obj). This functions only compares object identify , don't compare the contents of the array.

Origin null is not allowed by Access-Control-Allow-Origin

Origin null is the local file system, so that suggests that you're loading the HTML page that does the load call via a file:/// URL (e.g., just double-clicking it in a local file browser or similar). Different browsers take different approaches to applying the Same Origin Policy to local files.

My guess is that you're seeing this using Chrome. Chrome's rules for applying the SOP to local files are very tight, it disallows even loading files from the same directory as the document. So does Opera. Some other browsers, such as Firefox, allow limited access to local files. But basically, using ajax with local resources isn't going to work cross-browser.

If you're just testing something locally that you'll really be deploying to the web, rather than use local files, install a simple web server and test via http:// URLs instead. That gives you a much more accurate security picture.

UITableView set to static cells. Is it possible to hide some of the cells programmatically?

Solution from k06a ( is better because it hides whole section including cells headers and footers, where this solution ( hides everything except footer.


I just found solution if you want to hide footer in StaticDataTableViewController. This is what you need to copy in StaticTableViewController.m file:

- (NSString *)tableView:(UITableView *)tableView titleForFooterInSection:(NSInteger)section {
    if ([tableView.dataSource tableView:tableView numberOfRowsInSection:section] == 0) {
        return nil;
    } else {
        return [super tableView:tableView titleForFooterInSection:section];

- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section {

    CGFloat height = [super tableView:tableView heightForFooterInSection:section];

    if (self.originalTable == nil) {
        return height;

    if (!self.hideSectionsWithHiddenRows) {
        return height;

    OriginalSection * os = self.originalTable.sections[section];
    if ([os numberOfVissibleRows] == 0) {
       //return 0;
        return CGFLOAT_MIN;
    } else {
        return height;

    //return 0;
    return CGFLOAT_MIN;

Any good boolean expression simplifiers out there?

I found that The Boolean Expression Reducer is much easier to use than Logic Friday. Plus it doesn't require installation and is multi-platform (Java).

Also in Logic Friday the expression A | B just returns 3 entries in truth table; I expected 4.

JQuery Ajax - How to Detect Network Connection error when making Ajax call

here's what I did to alert user in case their network went down or upon page update failure:

  1. I have a div-tag on the page where I put current time and update this tag every 10 seconds. It looks something like this: <div id="reloadthis">22:09:10</div>

  2. At the end of the javascript function that updates the time in the div-tag, I put this (after time is updated with AJAX):

    var new_value = document.getElementById('reloadthis').innerHTML;
    var new_length = new_value.length;
        alert("NETWORK ERROR!");

That's it! You can replace the alert-part with anything you want, of course. Hope this helps.

ImportError: DLL load failed: The specified module could not be found

To make it short, it means that you lacked some "dependencies" for the libraries you wanted to use. Before trying to use any kind of library, first it is suggested to look up whether it needs another library in python "family". What do I mean?

Downloading "dlls" is something that I avoid. I had the same problem with another library "kivy". The problem occurred when I wanted to use Python 3.4v instead of 3.5 Everything was working correctly in 3.5 but I just wanted to use the stable version for kivy which is 3.4 as they officially "advise". So, I switched to 3.4 but then I had the very same "dll" error saying lots of things are missing. So I checked the website and learned that I needed to install extra "dependencies" from the official website of kivy, then the problem got solved.

How to make unicode string with python3

the easiest way in python 3.x

text = "hi , I'm text"

Maven artifact and groupId naming

However, I disagree the official definition of Guide to naming conventions on groupId, artifactId, and version which proposes the groupId must start with a reversed domain name you control.

com means this project belongs to a company, and org means this project belongs to a social organization. These are alright, but for those strange domain like,,, it does not make sense to name the groupId started with "tv.","cn.", the groupId should deliver the basic information of the project rather than the domain.

How to convert string to integer in PowerShell


$filelist = @("11", "1", "2")
$filelist | sort @{expression={[int]$_}} | % {$newName = [string]([int]$_ + 1)}
New-Item $newName -ItemType Directory

@HostBinding and @HostListener: what do they do and what are they for?

DECORATORS: to dynamically change the behaviour of DOM elements

@HostBinding: Dynamic binding custom logic to Host element

 activeClass = false;

@HostListen: To Listen to events on Host element

    this.activeClass = !this.activeClass;

Host Element:

  <button type='button' class="btn btn-primary btn-sm" appHost>Host</button>

How to merge 2 JSON objects from 2 files using jq?

Here's a version that works recursively (using *) on an arbitrary number of objects:

echo '{"A": {"a": 1}}' '{"A": {"b": 2}}' '{"B": 3}' |\
  jq --slurp 'reduce .[] as $item ({}; . * $item)'

  "A": {
    "a": 1,
    "b": 2
  "B": 3

Why is my JavaScript function sometimes "not defined"?

This has probably been corrected, but... apparently firefox has a caching problem which is the cause of javascript functions not being recognized.. I really don't know the specifics, but if you clear your cache that will fix the problem (until your cache is full again... not a good solution).. I've been looking around to see if firefox has a real solution to this, but so far nothing... oh not all versions, I think it may be only in some 3.6.x versions, not sure...

How can I set multiple CSS styles in JavaScript?

Using plain Javascript, you can't set all the styles at once; you need to use single lines for each of them.

However, you don't have to repeat the document.getElementById(...).style. code over and over; create an object variable to reference it, and you'll make your code much more readable:

var obj=document.getElementById("myElement").style;;

...etc. Much easier to read than your example (and frankly, just as easy to read as the jQuery alternative).

(if Javascript had been designed properly, you could also have used the with keyword, but that's best left alone, as it can cause some nasty namespace issues)

How do I remove background-image in css?

background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0, #fff), color-stop(0.5, #fff));
background-image: -webkit-linear-gradient(center top, #fff 0%, #fff 50%);
background-image: -moz-linear-gradient(center top, #fff 0%, #fff 50%);
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#ffffff', GradientType=0);
background-image: linear-gradient(to bottom, #fff 0%, #fff 50%);

for older browsers.. if you have defined css in some framewokrk.css like select2.css in IE9 background-image: -webkit-gradient etc. and you want it via another .css rewrite with "background-image: none !important" not works. I used same color to color gradient like page background color.

jQuery UI DatePicker - Change Date Format


The format for parsed and displayed dates. This attribute is one of the regionalisation attributes. For a full list of the possible formats see the formatDate function.

Code examples Initialize a datepicker with the dateFormat option specified.

$( ".selector" ).datepicker({ dateFormat: 'yy-mm-dd' });

Get or set the dateFormat option, after init.

var dateFormat = $( ".selector" ).datepicker( "option", "dateFormat" );
$( ".selector" ).datepicker( "option", "dateFormat", 'yy-mm-dd' );

How do I undo 'git add' before commit?

In Sourcetree you can do this easily via the GUI. You can check which command Sourcetree uses to unstage a file.

I created a new file and added it to Git. Then I unstaged it using the Sourcetree GUI. This is the result:

Unstaging files [08/12/15 10:43] git -c diff.mnemonicprefix=false -c core.quotepath=false -c credential.helper=sourcetree reset -q -- path/to/file/

Sourcetree uses reset to unstage new files.

Lowercase and Uppercase with jQuery

Try this:

var jIsHasKids = $('#chkIsHasKids').attr('checked');
jIsHasKids = jIsHasKids.toString().toLowerCase();
jIsHasKids = jIsHasKids.val().toLowerCase();

Possible duplicate with: How do I use jQuery to ignore case when selecting

http post - how to send Authorization header?

I had the same issue. This is my solution using angular documentation and firebase Token:

getService()  {

const accessToken=this.afAuth.auth.currentUser.getToken().then(res=>{
  const httpOptions = {
    headers: new HttpHeaders({
      'Content-Type':  'application/json',
      'Authorization': res
  return this.http.get('Url',httpOptions)
    .subscribe(res => console.log(res));
}); }}

how to loop through rows columns in excel VBA Macro

I'd recommend the Range object's AutoFill method for this:

rngSource.AutoFill Destination:=rngDest

Specify the Source range that contains the values or formulas you want to fill down, and the Destination range as the whole range that you want the cells filled to. The Destination range must include the Source range. You can fill across as well as down.

It works exactly the same way as it would if you manually "dragged" the cells at the corner with the mouse; absolute and relative formulas work as expected.

Here's an example:

'Set some example values'
Range("A1").Value = "1"
Range("B1").Formula = "=NOW()"
Range("C1").Formula = "=B1+A1"

'AutoFill the values / formulas to row 20'
Range("A1:C1").AutoFill Destination:=Range("A1:C20")

Hope this helps.

How to use font-family lato?

Download it from here and extract LatoOFL.rar then go to TTF and open this font-face-generator click at Choose File choose font which you want to use and click at generate then download it and then go html file open it and you see the code like this

@font-face {
        font-family: "Lato Black";
        src: url('698242188-Lato-Bla.eot');
        src: url('698242188-Lato-Bla.eot?#iefix') format('embedded-opentype'),
        url('698242188-Lato-Bla.svg#Lato Black') format('svg'),
        url('698242188-Lato-Bla.woff') format('woff'),
        url('698242188-Lato-Bla.ttf') format('truetype');
        font-weight: normal;
        font-style: normal;
    font-family: "Lato Black";
    direction: ltr;

change the src code and give the url where your this font directory placed, now you can use it at your website...

If you don't want to download it use this

<link type='text/css' href=',700' />

WCF Error - Could not find default endpoint element that references contract 'UserService.UserService'

In case if you are using WPF application using PRISM framework then configuration should exist in your start up project (i.e. in the project where your bootstrapper resides.)

In short just remove it from the class library and put into a start up project.

Where could I buy a valid SSL certificate?

Let's Encrypt is a free, automated, and open certificate authority made by the Internet Security Research Group (ISRG). It is sponsored by well-known organisations such as Mozilla, Cisco or Google Chrome. All modern browsers are compatible and trust Let's Encrypt.

All certificates are free (even wildcard certificates)! For security reasons, the certificates expire pretty fast (after 90 days). For this reason, it is recommended to install an ACME client, which will handle automatic certificate renewal.

There are many clients you can use to install a Let's Encrypt certificate:

Let’s Encrypt uses the ACME protocol to verify that you control a given domain name and to issue you a certificate. To get a Let’s Encrypt certificate, you’ll need to choose a piece of ACME client software to use. -

SyntaxError: missing ) after argument list

How to reproduce this error:

SyntaxError: missing ) after argument list

This code produces the error:

<script type="text/javascript" src="jquery-2.1.0.min.js"></script>
<script type="text/javascript">


If you run this and look at the error output in firebug, you get this error. The empty function passed into 'ready' is not closed. Fix it like this:

<script type="text/javascript" src="jquery-2.1.0.min.js"></script>
<script type="text/javascript">

  });      //<-- notice the right parenthesis and semicolon

And then the Javascript is interpreted correctly.

How to avoid scientific notation for large numbers in JavaScript?

If you are just doing it for display, you can build an array from the digits before they're rounded.

var num = Math.pow(2, 100);
var reconstruct = [];
while(num > 0) {
    reconstruct.unshift(num % 10);
    num = Math.floor(num / 10);

Android Paint: .measureText() vs .getTextBounds()

DISCLAIMER: This solution is not 100% accurate in terms of determining the minimal width.

I was also figuring out how to measure text on a canvas. After reading the great post from mice i had some problems on how to measure multiline text. There is no obvious way from these contributions but after some research i cam across the StaticLayout class. It allows you to measure multiline text (text with "\n") and configure much more properties of your text via the associated Paint.

Here is a snippet showing how to measure multiline text:

private StaticLayout measure( TextPaint textPaint, String text, Integer wrapWidth ) {
    int boundedWidth = Integer.MAX_VALUE;
    if (wrapWidth != null && wrapWidth > 0 ) {
       boundedWidth = wrapWidth;
    StaticLayout layout = new StaticLayout( text, textPaint, boundedWidth, Alignment.ALIGN_NORMAL, 1.0f, 0.0f, false );
    return layout;

The wrapwitdh is able to determin if you want to limit your multiline text to a certain width.

Since the StaticLayout.getWidth() only returns this boundedWidth you have to take another step to get the maximum width required by your multiline text. You are able to determine each lines width and the max width is the highest line width of course:

private float getMaxLineWidth( StaticLayout layout ) {
    float maxLine = 0.0f;
    int lineCount = layout.getLineCount();
    for( int i = 0; i < lineCount; i++ ) {
        if( layout.getLineWidth( i ) > maxLine ) {
            maxLine = layout.getLineWidth( i );
    return maxLine;

SQL Server: Importing database from .mdf?

Open SQL Management Studio Express and log in to the server to which you want to attach the database. In the 'Object Explorer' window, right-click on the 'Databases' folder and select 'Attach...' The 'Attach Databases' window will open; inside that window click 'Add...' and then navigate to your .MDF file and click 'OK'. Click 'OK' once more to finish attaching the database and you are done. The database should be available for use. best regards :)

SQL grouping by all the columns

You can use Group by All but be careful as Group by All will be removed from future versions of SQL server.

How do I find an element position in std::vector?

If a vector has N elements, there are N+1 possible answers for find. std::find and std::find_if return an iterator to the found element OR end() if no element is found. To change the code as little as possible, your find function should return the equivalent position:

size_t find( const vector<type>& where, int searchParameter )
   for( size_t i = 0; i < where.size(); i++ ) {
       if( conditionMet( where[i], searchParameter ) ) {
           return i;
    return where.size();
// caller:
const int position = find( firstVector, parameter );
if( position != secondVector.size() ) {
    doAction( secondVector[position] );

I would still use std::find_if, though.

Calculate median in c#

Thanks Rafe, this takes into account the issues your replyers posted.

public static double GetMedian(double[] sourceNumbers) {
        //Framework 2.0 version of this method. there is an easier way in F4        
        if (sourceNumbers == null || sourceNumbers.Length == 0)
            throw new System.Exception("Median of empty array not defined.");

        //make sure the list is sorted, but use a new array
        double[] sortedPNumbers = (double[])sourceNumbers.Clone();

        //get the median
        int size = sortedPNumbers.Length;
        int mid = size / 2;
        double median = (size % 2 != 0) ? (double)sortedPNumbers[mid] : ((double)sortedPNumbers[mid] + (double)sortedPNumbers[mid - 1]) / 2;
        return median;

How to get last key in an array?

Just use : echo $array[count($array) - 1];

CORS with spring-boot and angularjs not working

If you want to enable CORS without using filters or without config file just add


to the top of your controller and it work.

What is an API key?

What "exactly" an API key is used for depends very much on who issues it, and what services it's being used for. By and large, however, an API key is the name given to some form of secret token which is submitted alongside web service (or similar) requests in order to identify the origin of the request. The key may be included in some digest of the request content to further verify the origin and to prevent tampering with the values.

Typically, if you can identify the source of a request positively, it acts as a form of authentication, which can lead to access control. For example, you can restrict access to certain API actions based on who's performing the request. For companies which make money from selling such services, it's also a way of tracking who's using the thing for billing purposes. Further still, by blocking a key, you can partially prevent abuse in the case of too-high request volumes.

In general, if you have both a public and a private API key, then it suggests that the keys are themselves a traditional public/private key pair used in some form of asymmetric cryptography, or related, digital signing. These are more secure techniques for positively identifying the source of a request, and additionally, for protecting the request's content from snooping (in addition to tampering).

Can't choose class as main class in IntelliJ

Here is the complete procedure for IDEA IntelliJ 2019.3:

  1. File > Project Structure

  2. Under Project Settings > Modules

  3. Under 'Sources' tab, right-click on 'src' folder and select 'Sources'.

  4. Apply changes.

C# Sort and OrderBy comparison

Why not measure it:

class Program
    class NameComparer : IComparer<string>
        public int Compare(string x, string y)
            return string.Compare(x, y, true);

    class Person
        public Person(string id, string name)
            Id = id;
            Name = name;
        public string Id { get; set; }
        public string Name { get; set; }

    static void Main()
        List<Person> persons = new List<Person>();
        persons.Add(new Person("P005", "Janson"));
        persons.Add(new Person("P002", "Aravind"));
        persons.Add(new Person("P007", "Kazhal"));


        const int COUNT = 1000000;
        Stopwatch watch = Stopwatch.StartNew();
        for (int i = 0; i < COUNT; i++)
        Console.WriteLine("Sort: {0}ms", watch.ElapsedMilliseconds);

        watch = Stopwatch.StartNew();
        for (int i = 0; i < COUNT; i++)
        Console.WriteLine("OrderBy: {0}ms", watch.ElapsedMilliseconds);

    static void Sort(List<Person> list)
        list.Sort((p1, p2) => string.Compare(p1.Name, p2.Name, true));

    static void OrderBy(List<Person> list)
        var result = list.OrderBy(n => n.Name, new NameComparer()).ToArray();

On my computer when compiled in Release mode this program prints:

Sort: 1162ms
OrderBy: 1269ms


As suggested by @Stefan here are the results of sorting a big list fewer times:

List<Person> persons = new List<Person>();
for (int i = 0; i < 100000; i++)
    persons.Add(new Person("P" + i.ToString(), "Janson" + i.ToString()));


const int COUNT = 30;
Stopwatch watch = Stopwatch.StartNew();
for (int i = 0; i < COUNT; i++)
Console.WriteLine("Sort: {0}ms", watch.ElapsedMilliseconds);

watch = Stopwatch.StartNew();
for (int i = 0; i < COUNT; i++)
Console.WriteLine("OrderBy: {0}ms", watch.ElapsedMilliseconds);


Sort: 8965ms
OrderBy: 8460ms

In this scenario it looks like OrderBy performs better.


And using random names:

List<Person> persons = new List<Person>();
for (int i = 0; i < 100000; i++)
    persons.Add(new Person("P" + i.ToString(), RandomString(5, true)));


private static Random randomSeed = new Random();
public static string RandomString(int size, bool lowerCase)
    var sb = new StringBuilder(size);
    int start = (lowerCase) ? 97 : 65;
    for (int i = 0; i < size; i++)
        sb.Append((char)(26 * randomSeed.NextDouble() + start));
    return sb.ToString();


Sort: 8968ms
OrderBy: 8728ms

Still OrderBy is faster

How do you determine the ideal buffer size when using FileInputStream?

You could use the BufferedStreams/readers and then use their buffer sizes.

I believe the BufferedXStreams are using 8192 as the buffer size, but like Ovidiu said, you should probably run a test on a whole bunch of options. Its really going to depend on the filesystem and disk configurations as to what the best sizes are.

javascript regex - look behind alternative?

This is an equivalent solution to Tim Pietzcker's answer (see also comments of same answer):


It means, match *.js except *filename.js.

To get to this solution, you can check which patterns the negative lookbehind excludes, and then exclude exactly these patterns with a negative lookahead.

Sqlite in chrome

I'm not quite sure if you mean 'can i use sqlite (websql) in chrome' or 'can i use sqlite (websql) in firefox', so I'll answer both:

Note that WebSQL is not a full-access pipe into an .sqlite database. It's WebSQL. You will not be able to run some specific queries like VACUUM

It's awesome for Create / Read / Update / Delete though. I made a little library that helps with all the annoying nitty gritty like creating tables and querying and a provides a little ORM/ActiveRecord pattern with relations and all and a huge stack of examples that should get you started in no-time, you can check that here

Also, be aware that if you want to build a FireFox extension: Their extension format is about to change. Make sure you want to invest the time twice.

While the WebSQL spec has been deprecated for years, even now in 2017 still does not look like it will be be removed from Chrome for the foreseeable time. They are tracking usage statistics and there are still a large number of chrome extensions and websites out there in the real world implementing the spec.

Blue and Purple Default links, how to remove?

REMOVE DEFAULT LINK SOLVED that :visited thing is css.... you just go to your HTML and add a simple

< a href="" style="text-decoration: none" > < /a>

... thats the way html pages used to be

Add data to JSONObject

In order to have this result:


that holds the same data as:

    "aoColumnDefs": [
     { "aDataSort": [ 0, 1 ], "aTargets": [ 0 ] },
     { "aDataSort": [ 1, 0 ], "aTargets": [ 1 ] },
     { "aDataSort": [ 2, 3, 4 ], "aTargets": [ 2 ] }

you could use this code:

    JSONObject jo = new JSONObject();
    Collection<JSONObject> items = new ArrayList<JSONObject>();

    JSONObject item1 = new JSONObject();
    item1.put("aDataSort", new JSONArray(0, 1));
    item1.put("aTargets", new JSONArray(0));
    JSONObject item2 = new JSONObject();
    item2.put("aDataSort", new JSONArray(1, 0));
    item2.put("aTargets", new JSONArray(1));
    JSONObject item3 = new JSONObject();
    item3.put("aDataSort", new JSONArray(2, 3, 4));
    item3.put("aTargets", new JSONArray(2));

    jo.put("aoColumnDefs", new JSONArray(items));


How to compare arrays in C#?

There is no static Equals method in the Array class, so what you are using is actually Object.Equals, which determines if the two object references point to the same object.

If you want to check if the arrays contains the same items in the same order, you can use the SequenceEquals extension method:



To use SequenceEquals with multidimensional arrays, you can use an extension to enumerate them. Here is an extension to enumerate a two dimensional array:

public static IEnumerable<T> Flatten<T>(this T[,] items) {
  for (int i = 0; i < items.GetLength(0); i++)
    for (int j = 0; j < items.GetLength(1); j++)
      yield return items[i, j];



If your array has more dimensions than two, you would need an extension that supports that number of dimensions. If the number of dimensions varies, you would need a bit more complex code to loop a variable number of dimensions.

You would of course first make sure that the number of dimensions and the size of the dimensions of the arrays match, before comparing the contents of the arrays.

Edit 2:

Turns out that you can use the OfType<T> method to flatten an array, as RobertS pointed out. Naturally that only works if all the items can actually be cast to the same type, but that is usually the case if you can compare them anyway. Example:


Restore a postgres backup file using the command line?

Follow these 3 steps :

  1. start postgres server - sudo systemctl start postgresql
  2. enable same - sudo systemctl enable postgresql
  3. restore command - pg_restore -h localhost -p 5432 -U postgres -d old_db

assuming that the dump is there in the same directory

Links :

What are the differences between using the terminal on a mac vs linux?

If you did a new or clean install of OS X version 10.3 or more recent, the default user terminal shell is bash.

Bash is essentially an enhanced and GNU freeware version of the original Bourne shell, sh. If you have previous experience with bash (often the default on GNU/Linux installations), this makes the OS X command-line experience familiar, otherwise consider switching your shell either to tcsh or to zsh, as some find these more user-friendly.

If you upgraded from or use OS X version 10.2.x, 10.1.x or 10.0.x, the default user shell is tcsh, an enhanced version of csh('c-shell'). Early implementations were a bit buggy and the programming syntax a bit weird so it developed a bad rap.

There are still some fundamental differences between mac and linux as Gordon Davisson so aptly lists, for example no useradd on Mac and ifconfig works differently.

The following table is useful for knowing the various unix shells.

sh      The original Bourne shell   Present on every unix system 
ksh     Original Korn shell         Richer shell programming environment than sh 
csh     Original C-shell            C-like syntax; early versions buggy 
tcsh    Enhanced C-shell            User-friendly and less buggy csh implementation 
bash    GNU Bourne-again shell      Enhanced and free sh implementation 
zsh     Z shell                     Enhanced, user-friendly ksh-like shell

You may also find these guides helpful:

On a final note, I am on Linux (Ubuntu 11) and Mac osX so I use bash and the thing I like the most is customizing the .bashrc (source'd from .bash_profile on OSX) file with aliases, some examples below. I now placed all my aliases in a separate .bash_aliases file and include it with:

if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases

in the .bashrc or .bash_profile file.

Note that this is an example of a mac-linux difference because on a Mac you can't have the --color=auto. The first time I did this (without knowing) I redefined ls to be invalid which was a bit alarming until I removed --auto-color !

You may also find useful

# ~/.bash_aliases
# ls variants
#alias l='ls -CF' 
alias la='ls -A' 
alias l='ls -alFtr' 
alias lsd='ls -d .*' 
# Various
alias h='history | tail'
alias hg='history | grep'
alias mv='mv -i' 
alias zap='rm -i'
# One letter quickies:
alias p='pwd'
alias x='exit'
alias {ack,ak}='ack-grep'
# Directories
alias s='cd ..'
alias play='cd ~/play/'
# Rails
alias src='script/rails console'
alias srs='script/rails server'
alias raked='rake db:drop db:create db:migrate db:seed' 
alias rvm-restart='source '\''/home/durrantm/.rvm/scripts/rvm'\'''
alias rrg='rake routes | grep '
alias rspecd='rspec --drb '
# DropBox - syncd
alias work="cd $WORKBASE"
alias code="cd $WORKBASE/ror/code"
# DropNot - NOT syncd !
alias {dropnot,not}="cd $WORKBASE_GIT"
alias {webs,ww}="cd $WORKBASE_GIT/webs"
alias {setups,docs}="cd $WORKBASE_GIT/setups_and_docs"
alias {linker,lnk}="cd $WORKBASE_GIT/webs/rails_v3/linker"
# git
alias {gsta,gst}='git status' 
# Warning: gst conflicts with gnu-smalltalk (when used).
alias {gbra,gb}='git branch'
alias {gco,go}='git checkout'
alias {gcob,gob}='git checkout -b '
alias {gadd,ga}='git add '
alias {gcom,gc}='git commit'
alias {gpul,gl}='git pull '
alias {gpus,gh}='git push '
alias glom='git pull origin master'
alias ghom='git push origin master'
alias gg='git grep '
# vim
alias v='vim'
# tmux
alias {ton,tn}='tmux set -g mode-mouse on'
alias {tof,tf}='tmux set -g mode-mouse off'
# dmc
alias {dmc,dm}='cd ~/Dropnot/webs/rails_v3/dmc/'
alias wf='cd ~/Dropnot/webs/rails_v3/dmc/dmWorkflow'
alias ws='cd ~/Dropnot/webs/rails_v3/dmc/dmStaffing'

When and where to use GetType() or typeof()?

typeof is applied to a name of a type or generic type parameter known at compile time (given as identifier, not as string). GetType is called on an object at runtime. In both cases the result is an object of the type System.Type containing meta-information on a type.

Example where compile-time and run-time types are equal

string s = "hello";

Type t1 = typeof(string);
Type t2 = s.GetType();

t1 == t2 ==> true

Example where compile-time and run-time types are different

object obj = "hello";

Type t1 = typeof(object); // ==> object
Type t2 = obj.GetType();  // ==> string!

t1 == t2 ==> false

i.e., the compile time type (static type) of the variable obj is not the same as the runtime type of the object referenced by obj.

Testing types

If, however, you only want to know whether mycontrol is a TextBox then you can simply test

if (mycontrol is TextBox)

Note that this is not completely equivalent to

if (mycontrol.GetType() == typeof(TextBox))    

because mycontrol could have a type that is derived from TextBox. In that case the first comparison yields true and the second false! The first and easier variant is OK in most cases, since a control derived from TextBox inherits everything that TextBox has, probably adds more to it and is therefore assignment compatible to TextBox.

public class MySpecializedTextBox : TextBox

MySpecializedTextBox specialized = new MySpecializedTextBox();
if (specialized is TextBox)       ==> true

if (specialized.GetType() == typeof(TextBox))        ==> false


If you have the following test followed by a cast and T is nullable ...

if (obj is T) {
    T x = (T)obj; // The casting tests, whether obj is T again!

... you can change it to ...

T x = obj as T;
if (x != null) {

Testing whether a value is of a given type and casting (which involves this same test again) can both be time consuming for long inheritance chains. Using the as operator followed by a test for null is more performing.

Starting with C# 7.0 you can simplify the code by using pattern matching:

if (obj is T t) {
    // t is a variable of type T having a non-null value.

Btw.: this works for value types as well. Very handy for testing and unboxing. Note that you cannot test for nullable value types:

if (o is int? ni) ===> does NOT compile!

This is because either the value is null or it is an int. This works for int? o as well as for object o = new Nullable<int>(x);:

if (o is int i) ===> OK!

I like it, because it eliminates the need to access the Nullable<T>.Value property.

How should I throw a divide by zero exception in Java without actually dividing by zero?

Do this:

if (denominator == 0) throw new ArithmeticException("denominator == 0");

ArithmeticException is the exception which is normally thrown when you divide by 0.

How to convert SQL Server's timestamp column to datetime format

I had the same problem with timestamp eg:'29-JUL-20 PM'. I wanted to turn it into 'yyyy-MM-dd' format. The solution that finally works for me is

SELECT TO_CHAR(mytimestamp, 'YYYY-MM-DD') FROM mytable;

psql: FATAL: Ident authentication failed for user "postgres"

In case none of the above works for you:

I've done quite a few Postgres installations, but was flummoxed today on a RedHat 6.5 system (installing Postgres 9.3). My typical hba.conf configuration that Aron shows above didn't work. It turned out that my system was using IPV6, and ignoring the IPV4 configuration. Adding the line:

host    all             all             ::1/128                 password

allowed me to login successfully.

Android - R cannot be resolved to a variable

check your R directory ...sometimes if a file name is not all lower case and has special characters you can get this error. Im using eclipse and it only accepts file names a-z0-9_.

SQL: Two select statements in one query

If you like to keep records separate and not do the union.
Try query below

        FROM   tblMadrid
        WHERE  name = 'ronaldo') AS table_a,
       (SELECT name,
        FROM   tblBarcelona
        WHERE  name = 'messi')   AS table_b

Get selected value of a dropdown's item using jQuery

For single select dom elements, to get the currently selected value:


To get the currently selected text:

$('#dropDownId :selected').text();

Spring - download response as a file

I've wrestled with this myself, trying to make it work from the server. Couldn't. Instead...

  1. To clarify on @dnc253's answer, $ is a method for having an Angular application open a given URL in another window. (It's really just a testable angular proxy for the universal This is a great solution, preserves your history, and gets the file downloaded and possibly renders it in that fresh browser window if that's supported. But it often runs into popup blockers, which is a huge problem for reliability. Users often simply don't understand what's going on with them. So, if you don't mind immediately downloading the file with the current window, you can simply use the equally effective universal javascript method: location.href = "uriString", which works like a charm for me. Angular doesn't even realize anything has happened. I call it in a promise handler for once my POST/PUT operation has completed. If need be, have the POST/PUT return the URL to call, if you can't already infer it. You'll get the same behavior for the user as if it had downloaded in response to the PUT/POST. For example:

    $, payload).then(function(returnData){
        var uriString = parseReturn(returnData);
  2. You can, in fact, download something directly from an XHR request, but it requires full support for the HTML5 file API and is usually more trouble than it's worth unless you need to perform local transformations upon the file before you make it available to the user. (Sadly, I lack the time to provide details on that but there are other SO posts about using it.)

Error when deploying an artifact in Nexus

This can also happen if you have a naming policy around version, prohibiting the version# you are trying to deploy. In my case I was trying to upload a version (to release repo) 2.0.1 but later found out that our nexus configuration doesn't allow anything other than whole number for releases.

I tried later with version 2 and deployed it successfully.

The error message definitely dosen't help:

Return code is: 400, ReasonPhrase: Repository does not allow updating assets: maven-releases-xxx. -> [Help 1]

A better message could have been version 2.0.1 violates naming policy

C++: Converting Hexadecimal to Decimal

#include <iostream>
#include <iomanip>
#include <sstream>

int main()
    int x, y;
    std::stringstream stream;

    std::cin >> x;
    stream << x;
    stream >> std::hex >> y;
    std::cout << y;

    return 0;

Convert UIImage to NSData and convert back to UIImage in Swift?

UIImage(data:imageData,scale:1.0) presuming the image's scale is 1.

In swift 4.2, use below code for get Data().


Creating an R dataframe row-by-row

I've found this way to create dataframe by raw without matrix.

With automatic column name

        ,row.names = NULL,stringsAsFactors = FALSE

With column name

            ,row.names = NULL,stringsAsFactors = FALSE

Inject service in app.config

A solution very easy to do it

Note : it's only for an asynchrone call, because service isn't initialized on config execution.

You can use run() method. Example :

  1. Your service is called "MyService"
  2. You want to use it for an asynchrone execution on a provider "MyProvider"

Your code :

(function () { //To isolate code TO NEVER HAVE A GLOBAL VARIABLE!

    //Store your service into an internal variable
    //It's an internal variable because you have wrapped this code with a (function () { --- })();
    var theServiceToInject = null;

    //Declare your application
    var myApp = angular.module("MyApplication", []);

    //Set configuration
    myApp.config(['MyProvider', function (MyProvider) {
        MyProvider.callMyMethod(function () {

    //When application is initialized inject your service['MyService', function (MyService) {
        theServiceToInject = MyService;

How can I Remove .DS_Store files from a Git repository?

Best way to get rid of this file forever and never have to worry about it again is

make a global .gitignore file:

echo .DS_Store >> ~/.gitignore_global

And let git know that you want to use this file for all of your repositories:

git config --global core.excludesfile ~/.gitignore_global And that’s it! .DS_Store is out of your way.

jQuery dialog popup

It's quite simple, first HTML must be added:

<div id="dialog"></div>

Then, it must be initialized:

<script type="text/javascript">
  jQuery( document ).ready( function() {
    jQuery( '#dialog' ).dialog( { 'autoOpen': false } );

After this you can show it by code:

jQuery( '#dialog' ).dialog( 'open' );

equals vs Arrays.equals in Java

Look inside the implementation of the two methods to understand them deeply:

 * Indicates whether some other object is "equal to" this one.
 * <p>
 * The {@code equals} method implements an equivalence relation
 * on non-null object references:
 * <ul>
 * <li>It is <i>reflexive</i>: for any non-null reference value
 *     {@code x}, {@code x.equals(x)} should return
 *     {@code true}.
 * <li>It is <i>symmetric</i>: for any non-null reference values
 *     {@code x} and {@code y}, {@code x.equals(y)}
 *     should return {@code true} if and only if
 *     {@code y.equals(x)} returns {@code true}.
 * <li>It is <i>transitive</i>: for any non-null reference values
 *     {@code x}, {@code y}, and {@code z}, if
 *     {@code x.equals(y)} returns {@code true} and
 *     {@code y.equals(z)} returns {@code true}, then
 *     {@code x.equals(z)} should return {@code true}.
 * <li>It is <i>consistent</i>: for any non-null reference values
 *     {@code x} and {@code y}, multiple invocations of
 *     {@code x.equals(y)} consistently return {@code true}
 *     or consistently return {@code false}, provided no
 *     information used in {@code equals} comparisons on the
 *     objects is modified.
 * <li>For any non-null reference value {@code x},
 *     {@code x.equals(null)} should return {@code false}.
 * </ul>
 * <p>
 * The {@code equals} method for class {@code Object} implements
 * the most discriminating possible equivalence relation on objects;
 * that is, for any non-null reference values {@code x} and
 * {@code y}, this method returns {@code true} if and only
 * if {@code x} and {@code y} refer to the same object
 * ({@code x == y} has the value {@code true}).
 * <p>
 * Note that it is generally necessary to override the {@code hashCode}
 * method whenever this method is overridden, so as to maintain the
 * general contract for the {@code hashCode} method, which states
 * that equal objects must have equal hash codes.
 * @param   obj   the reference object with which to compare.
 * @return  {@code true} if this object is the same as the obj
 *          argument; {@code false} otherwise.
 * @see     #hashCode()
 * @see     java.util.HashMap
public boolean equals(Object obj) {
    return (this == obj);


Arrays.equals(array1, array2);
 * Returns <tt>true</tt> if the two specified arrays of Objects are
 * <i>equal</i> to one another.  The two arrays are considered equal if
 * both arrays contain the same number of elements, and all corresponding
 * pairs of elements in the two arrays are equal.  Two objects <tt>e1</tt>
 * and <tt>e2</tt> are considered <i>equal</i> if <tt>(e1==null ? e2==null
 * : e1.equals(e2))</tt>.  In other words, the two arrays are equal if
 * they contain the same elements in the same order.  Also, two array
 * references are considered equal if both are <tt>null</tt>.<p>
 * @param a one array to be tested for equality
 * @param a2 the other array to be tested for equality
 * @return <tt>true</tt> if the two arrays are equal
public static boolean equals(Object[] a, Object[] a2) {
    if (a==a2)
        return true;
    if (a==null || a2==null)
        return false;

    int length = a.length;
    if (a2.length != length)
        return false;

    for (int i=0; i<length; i++) {
        Object o1 = a[i];
        Object o2 = a2[i];
        if (!(o1==null ? o2==null : o1.equals(o2)))
            return false;

    return true;

Check if element exists in jQuery

You can use native JS to test for the existence of an object:

if (document.getElementById('elemId') instanceof Object){
    // do something here

Don't forget, jQuery is nothing more than a sophisticated (and very useful) wrapper around native Javascript commands and properties

How to set UICollectionViewCell Width and Height programmatically

Swift 5

Add these protocols

 - `UICollectionViewDelegate`
 - `UICollectionViewDataSource`
 - `UICollectionViewDelegateFlowLayout`

Your code will then look like this

extension YourViewController: UICollectionViewDelegate {
    //Write Delegate Code Here

extension YourViewController: UICollectionViewDataSource {
    //Write DataSource Code Here

extension YourViewController: UICollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: screenWidth, height: screenWidth)

Now the final and crucial step to see this take effect is to go to your viedDidLoad function inside your Viewcontroller.

    override func viewDidLoad() {
        collection.dataSource = self // Add this
        collection.delegate = self // Add this
        // Do any additional setup after loading the view.

Without telling your view which class the delegate is it won't work.

DateTimeFormat in TypeScript

This should work...

var displayDate = new Date().toLocaleDateString();


But I suspect you are trying it on something else, for example:

var displayDate =; // No!


How to detect my browser version and operating system using JavaScript?

To detect operating system using JavaScript it is better to use navigator.userAgent instead of navigator.appVersion

  var OSName = "Unknown OS";_x000D_
  if (navigator.userAgent.indexOf("Win") != -1) OSName = "Windows";_x000D_
  if (navigator.userAgent.indexOf("Mac") != -1) OSName = "Macintosh";_x000D_
  if (navigator.userAgent.indexOf("Linux") != -1) OSName = "Linux";_x000D_
  if (navigator.userAgent.indexOf("Android") != -1) OSName = "Android";_x000D_
  if (navigator.userAgent.indexOf("like Mac") != -1) OSName = "iOS";_x000D_
  console.log('Your OS: ' + OSName);_x000D_

How does System.out.print() work?

Even though it look as if System.put.print...() take a variable number of arguments it doesn't. If you look closely, the string is simply concatenated and you can do the same with any string. The only thing that happens is, that the objects you are passing in, are implicitily converted to a string by java calling the toString() method.

If you try to do this it will fail:

int i = 0;
String s = i;

Reason is, because here the implicit conversion is not done.

However if you change it to

int i = 0;
String s = "" + i;

It works and this is what happens when using System.put.print...() as well.

If you want to implement a variable number of arguments in java to mimimc something like C printf you can declare it like this:

public void t(String s, String ... args)
    String val = args[1];

What happens here is that an array of Strings is passed in, with the length of the provided arguments. Here Java can do the type checking for you.

If you want truly a printf then you have to do it like this:

public void t(String s, Object ... args)
    String val = args[1].toString();

Then would you have to cast or interpret the arguments accordingly.

How to force C# .net app to run only one instance in Windows?

I prefer a mutex solution similar to the following. As this way it re-focuses on the app if it is already loaded

using System.Threading;

[return: MarshalAs(UnmanagedType.Bool)]
static extern bool SetForegroundWindow(IntPtr hWnd);

/// <summary>
/// The main entry point for the application.
/// </summary>
static void Main()
   bool createdNew = true;
   using (Mutex mutex = new Mutex(true, "MyApplicationName", out createdNew))
      if (createdNew)
         Application.Run(new MainForm());
         Process current = Process.GetCurrentProcess();
         foreach (Process process in Process.GetProcessesByName(current.ProcessName))
            if (process.Id != current.Id)

sum two columns in R

The sum function will add all numbers together to produce a single number, not a vector (well, at least not a vector of length greater than 1).

It looks as though at least one of your columns is a factor. You could convert them into numeric vectors by checking this

head(as.numeric(data$col1))  # make sure this gives you the right output

And if that looks right, do

data$col1 <- as.numeric(data$col1)
data$col2 <- as.numeric(data$col2)

You might have to convert them into characters first. In which case do

data$col1 <- as.numeric(as.character(data$col1))
data$col2 <- as.numeric(as.character(data$col2))

It's hard to tell which you should do without being able to see your data.

Once the columns are numeric, you just have to do

data$col3 <- data$col1 + data$col2

Nesting CSS classes

Try this...

Give the element an ID, and also a class Name. Then you can nest the #IDName.className in your CSS.

Here's a better explanation

Read response headers from API response - Angular 5 + TypeScript

Try this simple code.

1. Components side code: to get both body and header property. Here there's a token in body and Authorization in the header.

loginUser() {
    subscribe(res => {
        let output1 = res;

2. Service side code: sending login data in the body and observe the response in Observable any which be subscribed in the component side.

loginTest(loginCred: LoginParams): Observable<any> {
    const header1= {'Content-Type':'application/json',};
    const body =  JSON.stringify(loginCred);
        headers: header1,
        observe: 'response',
        responseType: 'json'

MySQL timestamp select date range

Whenever possible, avoid applying functions to a column in the where clause:

  FROM table_name
 WHERE timestamp >= UNIX_TIMESTAMP('2010-10-01 00:00:00') 
   AND timestamp <  UNIX_TIMESTAMP('2010-11-01 00:00:00');

Applying a function to the timestamp column (e.g., FROM_UNIXTIME(timestamp) = ...) makes indexing much harder.

How can I view a git log of just one user's commits?

If using GitHub:

  • go to branch
  • click on commits

it will show list in below format

branch_x: < comment> 
author_name committed 2 days ago
  • to see individual author's commit ; click on author_name and there you can see all the commit's of that author on that branch

Differences between Ant and Maven

I'd say it depends upon the size of your project... Personnally, I would use Maven for simple projects that need straightforward compiling, packaging and deployment. As soon as you need to do some more complicated things (many dependencies, creating mapping files...), I would switch to Ant...

How to execute a shell script in PHP?

If you are having a small script that you need to run (I simply needed to copy a file), I found it much easier to call the commands on the PHP script by calling

exec("sudo cp /tmp/testfile1 /var/www/html/testfile2");

and enabling such transaction by editing (or rather adding) a permitting line to the sudoers by first calling sudo visudo and adding the following line to the very end of it

www-data ALL=(ALL) NOPASSWD:/bin/cp /tmp/testfile1 /var/www/html/testfile2

All I wanted to do was to copy a file and I have been having problems with doing so because of the root password problem, and as you mentioned I did NOT want to expose the system to have no password for all root transactions.

Get Last Part of URL PHP

The absolute simplest way to accomplish this, is with basename()

echo basename('');

Which will print


Of course, if there is a query string at the end it will be included in the returned value, in which case the accepted answer is a better solution.

How can I select rows by range?

Have you tried your own code?
This should work:


Make div stay at bottom of page's content all the time even when there are scrollbars

if you have a fixed height footer (for example 712px) you can do this with js like so:

var bgTop = 0;
function theResize(){
    bgTop = winHeight - 712;
    document.getElementById("bg").style.marginTop = bgTop+"px";

Change div height on button click

Look at to vwphillips' post from 03-06-2010, 03:35 PM in

      <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">

      <script type="text/javascript">

        function Div(id,ud) {
           var div=document.getElementById(id);
           var h=parseInt(;
           if (h>=1){
     = h + "em"; // I'm using "em" instead of "px", but you can use px like measure...

         <input type="button" value="+" onclick="Div('my_div', 1);">&nbsp;&nbsp; 
         <input type="button" value="-" onclick="Div('my_div', -1);"></div>

      <div id="my_div" style="height: 1em; width: 1em; overflow: auto;"></div>


This worked for me :)

Best regards!

openpyxl - adjust column width size

This is a dirty fix. But openpyxl actually supports auto_fit. But there is no method to access the property.

import openpyxl
from openpyxl.utils import get_column_letter

wb = openpyxl.load_workbook("Example.xslx")
ws = wb["Sheet1"]
for i in range(1, ws.max_column+1):
    ws.column_dimensions[get_column_letter(i)].bestFit = True
    ws.column_dimensions[get_column_letter(i)].auto_size = True

C string append

You could use asprintf to concatenate both into a new string:

char *new_str;

Retrieve WordPress root directory path?

For retrieving the path you can use a function <?php $path = get_home_path(); ?>. I do not want to just repeat what had been already said here, but I want to add one more thing:

If you are using windows server, which is rare case for WordPress installation, but still happens sometimes, you might face a problem with the path output. It might miss a "\" somewhere and you will get an error if you will be using such a path. So when outputting make sure to sanitize the path:


$path = get_home_path(); 
$path = wp_normalize_path ($path);

// now $path is ready to be used :)


Update style of a component onScroll in React.js

If what you're interested in is a child component that's scrolling, then this example might be of help:

class ScrollAwareDiv extends React.Component {
  constructor(props) {
    this.myRef = React.createRef()
    this.state = {scrollTop: 0}

  onScroll = () => {
     const scrollTop = this.myRef.current.scrollTop
     console.log(`myRef.scrollTop: ${scrollTop}`)
        scrollTop: scrollTop

  render() {
    const {
    } = this.state
    return (
           border: '1px solid black',
           width: '600px',
           height: '100px',
           overflow: 'scroll',
         }} >
        <p>This demonstrates how to get the scrollTop position within a scrollable 
           react component.</p>
        <p>ScrollTop is {scrollTop}</p>

Updating a dataframe column in spark

While you cannot modify a column as such, you may operate on a column and return a new DataFrame reflecting that change. For that you'd first create a UserDefinedFunction implementing the operation to apply and then selectively apply that function to the targeted column only. In Python:

from pyspark.sql.functions import UserDefinedFunction
from pyspark.sql.types import StringType

name = 'target_column'
udf = UserDefinedFunction(lambda x: 'new_value', StringType())
new_df =*[udf(column).alias(name) if column == name else column for column in old_df.columns])

new_df now has the same schema as old_df (assuming that old_df.target_column was of type StringType as well) but all values in column target_column will be new_value.

Swift Set to Array


Swift has no DEFINED ORDER for Set and Dictionary.For that reason you should use sorted() method to prevent from getting unexpected results such as your array can be like ["a","b"] or ["b","a"] and you do not want this.



var example:Set = ["a","b","c"]
let makeExampleArray = [example.sorted()]

Result: ["a","b","c"]

Without sorted()

It can be:

["a","b","c"] or ["b","c","a",] or ["c","a","b"] or ["a","c","b"] or ["b","a","c"] or ["c","b","a"] 

simple math : 3! = 6

Git push rejected after feature branch rebase

As the OP does understand the problem, just looks for a nicer solution...

How about this as a practice ?

  • Have on actual feature-develop branch (where you never rebase and force-push, so your fellow feature developers don't hate you). Here, regularly grab those changes from main with a merge. Messier history, yes, but life is easy and no one get's interupted in his work.

  • Have a second feature-develop branch, where one feature team member regulary pushes all feature commits to, indeed rebased, indeed forced. So almost cleanly based on a fairly recent master commit. Upon feature complete, push that branch on top of master.

There might be a pattern name for this method already.

Easy way to make a confirmation dialog in Angular?

Here's a slghtly different take using javascript's native confirm functionality and a custom Angular directive. It's super flexible and pretty lightweight:


<button (hrsAreYouSure) (then)="confirm(arg1)" (else)="cancel(arg2)">
  This will execute confirm if user presses Ok on the confirmation dialog, or cancel if they
  hit Cancel


import {Directive, ElementRef, EventEmitter, Inject, OnInit, Output} from '@angular/core';

  selector: '[hrsAreYouSure]'

export class AreYouSureDirective implements OnInit {

  @Output() then = new EventEmitter<boolean>();
  @Output() else = new EventEmitter<boolean>();

  constructor(@Inject(ElementRef) private element: ElementRef) { }

  ngOnInit(): void {
    const directive = this;
    this.element.nativeElement.onclick = function() {
      const result = confirm('Are you sure?');
      if (result) {
      } else {

How to replace four spaces with a tab in Sublime Text 2?

create a keybinding for quickest way

{ "keys": ["super+alt+t"], "command": "unexpand_tabs", "args": { "set_translate_tabs": true } }

add this to Preferences > Key Bindings (user) when you press super+alt+t it will convert spaces to tabs

How do I set the focus to the first input element in an HTML form independent from the id?

You also need to skip any hidden inputs.

for (var i = 0; document.forms[0].elements[i].type == 'hidden'; i++);

'numpy.ndarray' object is not callable error

The error TypeError: 'numpy.ndarray' object is not callable means that you tried to call a numpy array as a function. We can reproduce the error like so in the repl:

In [16]: import numpy as np

In [17]: np.array([1,2,3])()
TypeError                                 Traceback (most recent call last)
/home/user/<ipython-input-17-1abf8f3c8162> in <module>()
----> 1 np.array([1,2,3])()

TypeError: 'numpy.ndarray' object is not callable

If we are to assume that the error is indeed coming from the snippet of code that you posted (something that you should check,) then you must have reassigned either pd.rolling_mean or pd.rolling_std to a numpy array earlier in your code.

What I mean is something like this:

In [1]: import numpy as np

In [2]: import pandas as pd

In [3]: pd.rolling_mean(np.array([1,2,3]), 20, min_periods=5) # Works
Out[3]: array([ nan,  nan,  nan])

In [4]: pd.rolling_mean = np.array([1,2,3])

In [5]: pd.rolling_mean(np.array([1,2,3]), 20, min_periods=5) # Doesn't work anymore...
TypeError                                 Traceback (most recent call last)
/home/user/<ipython-input-5-f528129299b9> in <module>()
----> 1 pd.rolling_mean(np.array([1,2,3]), 20, min_periods=5) # Doesn't work anymore...

TypeError: 'numpy.ndarray' object is not callable

So, basically you need to search the rest of your codebase for pd.rolling_mean = ... and/or pd.rolling_std = ... to see where you may have overwritten them.

Also, if you'd like, you can put in reload(pd) just before your snippet, which should make it run by restoring the value of pd to what you originally imported it as, but I still highly recommend that you try to find where you may have reassigned the given functions.

Is it possible to use JS to open an HTML select to show its option list?

Unfortunately there's a simple answer to this question, and it's "No"

Merge two (or more) lists into one, in C# .NET

You can use the LINQ Concat and ToList methods:

var allProducts = productCollection1.Concat(productCollection2)

Note that there are more efficient ways to do this - the above will basically loop through all the entries, creating a dynamically sized buffer. As you can predict the size to start with, you don't need this dynamic sizing... so you could use:

var allProducts = new List<Product>(productCollection1.Count +
                                    productCollection2.Count +

(AddRange is special-cased for ICollection<T> for efficiency.)

I wouldn't take this approach unless you really have to though.

Image UriSource and Data Binding

you may use

ImageSourceConverter class

to get what you want

    img1.Source = (ImageSource)new ImageSourceConverter().ConvertFromString("/Assets/check.png");

Why does an SSH remote command get fewer environment variables then when run manually?

I found an easy resolution for this issue was to add source /etc/profile to the top of the file I was trying to run on the target system. On the systems here, this caused the environmental variables which were needed by to be configured as if running from a login shell.

In one of the prior responses it was suggested that ~/.bashr_profile etc... be used. I didn't spend much time on this but, the problem with this is if you ssh to a different user on the target system than the shell on the source system from which you log in it appeared to me that this causes the source system user name to be used for the ~.

Ignore Duplicates and Create New List of Unique Values in Excel

Honestly I followed these examples to a tee and they simply didn't work. What I ended up doing after struggling pointlessly trying to get Excel to work was to just copy the entire contents of my column to NotePad++ where I was able to find an easy solution within minutes. Take a look at this: Removing duplicate rows in Notepad++

Edit: Here is a brief overview of how to do it in TextFX:

Plugins -> Plugin Manager -> Show Plugin Manager -> Available tab -> TextFX -> Install

After TextFX is installed in NotePad++, then you select all your text you want to remove duplicates from, then make sure to check: TextFX -> TextFX Tools -> Sort outputs only UNIQUE lines

Then click "sort lines case sensitive" or "sort lines case insensitive" and it will perform the unique sort.

Fastest way to extract frames using ffmpeg?

I tried it. 3600 frame in 32 seconds. your method is really slow. You should try this.

ffmpeg -i file.mpg -s 240x135 -vf fps=1 %d.jpg