Programs & Examples On #Hidden

Hidden could refer to a style value in CSS for the visibility property, a selector in jQuery, a possible value for the type attribute of an input or to an `HTML5` attribute.

What's the best way to identify hidden characters in the result of a query in SQL Server (Query Analyzer)?

Create a function that addresses all the whitespace possibilites and enable only those that seem appropriate:

SELECT dbo.ShowWhiteSpace(myfield) from mytable

Uncomment only those whitespace cases you want to test for:

CREATE FUNCTION dbo.ShowWhiteSpace (@str varchar(8000))
RETURNS varchar(8000)
     DECLARE @ShowWhiteSpace varchar(8000);
     SET @ShowWhiteSpace = @str
     SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(32), '[?]')
     SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(13), '[CR]')
     SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(10), '[LF]')
     SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(9),  '[TAB]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(1),  '[SOH]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(2),  '[STX]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(3),  '[ETX]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(4),  '[EOT]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(5),  '[ENQ]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(6),  '[ACK]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(7),  '[BEL]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(8),  '[BS]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(11), '[VT]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(12), '[FF]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(14), '[SO]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(15), '[SI]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(16), '[DLE]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(17), '[DC1]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(18), '[DC2]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(19), '[DC3]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(20), '[DC4]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(21), '[NAK]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(22), '[SYN]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(23), '[ETB]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(24), '[CAN]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(25), '[EM]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(26), '[SUB]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(27), '[ESC]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(28), '[FS]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(29), '[GS]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(30), '[RS]')
--   SET @ShowWhiteSpace = REPLACE( @ShowWhiteSpace, CHAR(31), '[US]')

Making a button invisible by clicking another button in HTML

To get an element by its ID, use this:


Instead of:


So the final product would be:

document.getElementsById("p2").style.visibility = "hidden";

Check div is hidden using jquery

You can check the CSS display property:

if ($('#car').css('display') == 'none') {
    alert('Car 2 is hidden');

Here is a demo:

How to get current formatted date dd/mm/yyyy in Javascript and append it to an input

Use the DOM's getElementByid method:

document.getElementById("DATE").value = "your date";

A date can be made with the Date class:

d = new Date();

(Protip: install a javascript console such as in Chrome or Firefox' Firebug extension. It enables you to play with the DOM and Javascript)

How do you create a hidden div that doesn't create a line break or horizontal space?

To hide the element visually, but keep it in the html, you can use:

<div style='visibility:hidden; overflow:hidden; height:0; width:0;'>


<div style='visibility:hidden; overflow:hidden; position:absolute;'>

What may go wrong with display:none? It removes the element completely from the html, so some functionalities may be broken if they need to access something in the hidden element.

Windows batch script to unhide files hidden by virus

Try this one. Hope this is working fine.. :)

@ECHO off



set drvltr=

set /p drvltr=Enter Drive letter: 

attrib -s -h -a /s /d  %drvltr%:\*.*

ECHO Unhide Completed


posting hidden value

You have to use $_POST['date'] instead of $date if it's coming from a POST request ($_GET if it's a GET request).

Make one div visible and another invisible

You can use the display property of style. Intialy set the result section style as

style = "display:none"

Then the div will not be visible and there won't be any white space.

Once the search results are being populated change the display property using the java script like

document.getElementById("someObj").style.display = "block"

Using java script you can make the div invisible

document.getElementById("someObj").style.display = "none"

How can I get Eclipse to show .* files?

Cory is correct

@ If you're using Eclipse PDT, this is done by opening up the PHP explorer view

I just spent about half an hour looking for the little arrow, until I actually looked up what the 'PHP Explorer' view is. Here is a screenshot:

PHP perspective edit image

bootstrap 4 responsive utilities visible / hidden xs sm lg not working

With Bootstrap 4 .hidden-* classes were completely removed (yes, they were replaced by hidden-*-* but those classes are also gone from v4 alphas).

Starting with v4-beta, you can combine .d-*-none and .d-*-block classes to achieve the same result.

visible-* was removed as well; instead of using explicit .visible-* classes, make the element visible by not hiding it (again, use combinations of .d-none .d-md-block). Here is the working example:

<div class="col d-none d-sm-block">
    <span class="vcard">
<div class="col d-none d-xl-block">
    <div class="d-none d-md-block">
    <div class="d-none d-sm-block">

class="hidden-xs" becomes class="d-none d-sm-block" (or d-none d-sm-inline-block) ...

<span class="d-none d-sm-inline">hidden-xs</span>

<span class="d-none d-sm-inline-block">hidden-xs</span>

An example of Bootstrap 4 responsive utilities:

<div class="d-none d-sm-block"> hidden-xs           
  <div class="d-none d-md-block"> visible-md and up (hidden-sm and down)
    <div class="d-none d-lg-block"> visible-lg and up  (hidden-md and down)
      <div class="d-none d-xl-block"> visible-xl </div>

<div class="d-sm-none"> eXtra Small <576px </div>
<div class="d-none d-sm-block d-md-none d-lg-none d-xl-none"> SMall =576px </div>
<div class="d-none d-md-block d-lg-none d-xl-none"> MeDium =768px </div>
<div class="d-none d-lg-block d-xl-none"> LarGe =992px </div>
<div class="d-none d-xl-block"> eXtra Large =1200px </div>

<div class="d-xl-none"> hidden-xl (visible-lg and down)         
  <div class="d-lg-none d-xl-none"> visible-md and down (hidden-lg and up)
    <div class="d-md-none d-lg-none d-xl-none"> visible-sm and down  (or hidden-md and up)
      <div class="d-sm-none"> visible-xs </div>


Hidden property of a button in HTML

<script src=""></script>

function showButtons () { $('#b1, #b2, #b3').show(); }

<style type="text/css">
#b1, #b2, #b3 {
display: none;


<a href="#" onclick="showButtons();">Show me the money!</a>

<input type="submit" id="b1" value="B1" />
<input type="submit" id="b2" value="B2"/>
<input type="submit" id="b3" value="B3" />


Make child visible outside an overflow:hidden parent

For others, if clearfix does not solve this for you, add margins to the non-floated sibling that is/are the same as the width(s) of the floated sibling(s).

jQuery - Detect value change on hidden input field

It is possible to use Object.defineProperty() in order to redefine the 'value' property of the input element and do anything during its changing.

Object.defineProperty() allows us to define a getter and setter for a property, thus controlling it.

replaceWithWrapper($("#hid1")[0], "value", function(obj, property, value) { 
  console.log("new value:", value)

function replaceWithWrapper(obj, property, callback) {
  Object.defineProperty(obj, property, new function() {
    var _value = obj[property];
    return {
      set: function(value) {
        _value = value;
        callback(obj, property, value)
      get: function() {
        return _value;


Why must wait() always be in synchronized block

What is the potential damage if it was possible to invoke wait() outside a synchronized block, retaining it's semantics - suspending the caller thread?

Let's illustrate what issues we would run into if wait() could be called outside of a synchronized block with a concrete example.

Suppose we were to implement a blocking queue (I know, there is already one in the API :)

A first attempt (without synchronization) could look something along the lines below

class BlockingQueue {
    Queue<String> buffer = new LinkedList<String>();

    public void give(String data) {
        notify();                   // Since someone may be waiting in take!

    public String take() throws InterruptedException {
        while (buffer.isEmpty())    // don't use "if" due to spurious wakeups.
        return buffer.remove();

This is what could potentially happen:

  1. A consumer thread calls take() and sees that the buffer.isEmpty().

  2. Before the consumer thread goes on to call wait(), a producer thread comes along and invokes a full give(), that is, buffer.add(data); notify();

  3. The consumer thread will now call wait() (and miss the notify() that was just called).

  4. If unlucky, the producer thread won't produce more give() as a result of the fact that the consumer thread never wakes up, and we have a dead-lock.

Once you understand the issue, the solution is obvious: Use synchronized to make sure notify is never called between isEmpty and wait.

Without going into details: This synchronization issue is universal. As Michael Borgwardt points out, wait/notify is all about communication between threads, so you'll always end up with a race condition similar to the one described above. This is why the "only wait inside synchronized" rule is enforced.

A paragraph from the link posted by @Willie summarizes it quite well:

You need an absolute guarantee that the waiter and the notifier agree about the state of the predicate. The waiter checks the state of the predicate at some point slightly BEFORE it goes to sleep, but it depends for correctness on the predicate being true WHEN it goes to sleep. There's a period of vulnerability between those two events, which can break the program.

The predicate that the producer and consumer need to agree upon is in the above example buffer.isEmpty(). And the agreement is resolved by ensuring that the wait and notify are performed in synchronized blocks.

This post has been rewritten as an article here: Java: Why wait must be called in a synchronized block

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

The user Klaro suggested to restore the old visibility classes, which is a good idea. Unfortunately, their solution did not work in my project.

I think that it is a better idea to restore the old mixin of bootstrap, because it is covering all breakpoints which can be individually defined by the user.

Here is the code:

// Restore Bootstrap 3 "hidden" utility classes.
@each $bp in map-keys($grid-breakpoints) {
  .hidden-#{$bp}-up {
    @include media-breakpoint-up($bp) {
      display: none !important;
  .hidden-#{$bp}-down {
    @include media-breakpoint-down($bp) {
      display: none !important;
    @include media-breakpoint-only($bp){
      display:none !important;

In my case, I have inserted this part in a _custom.scss file which is included at this point in the bootstrap.scss:

 * Bootstrap v4.0.0-beta (
 * Copyright 2011-2017 The Bootstrap Authors
 * Copyright 2011-2017 Twitter, Inc.
 * Licensed under MIT (

@import "functions";
@import "variables";
@import "mixins";
@import "custom"; // <-- my custom file for overwriting default vars and adding the snippet from above
@import "print";
@import "reboot";

Why is there an unexplainable gap between these inline-block div elements?

Found a solution not involving Flex, because Flex doesn't work in older Browsers. Example:

.container {
    margin:0 auto;

.cols {
    margin:0 auto;

.cols:last-child {

jQuery select change event get selected option

You can use this jquery select change event for get selected option value

For Demo

$(document).ready(function () {   _x000D_
    $('body').on('change','#select', function() {_x000D_
<!DOCTYPE html>  _x000D_
<html>  _x000D_
<title>Learn Jquery value Method</title>_x000D_
<head> _x000D_
<script src=""></script> _x000D_
</head>  _x000D_
<body>  _x000D_
<select id="select">_x000D_
 <option value="">Select One</option>_x000D_
    <option value="PHP">PHP</option>_x000D_
    <option value="jAVA">JAVA</option>_x000D_
    <option value="Jquery">jQuery</option>_x000D_
    <option value="Python">Python</option>_x000D_
    <option value="Mysql">Mysql</option>_x000D_
<br><br>  _x000D_
<input type="text" id="show_selected">_x000D_
</body>  _x000D_

Exit from app when click button in android phonegap?

There are different ways to close the app, depending on:

if ( {;
} else if (navigator.device) {
} else {

What does the PHP error message "Notice: Use of undefined constant" mean?

Looks like the predefined fetch constants went away with the MySQL extension, so we need to add them before the first function...

//predifined fetch constants


I tested and succeeded.

Exponentiation in Python - should I prefer ** operator instead of math.pow and math.sqrt?

Even in base Python you can do the computation in generic form

result = sum(x**2 for x in some_vector) ** 0.5

x ** 2 is surely not an hack and the computation performed is the same (I checked with cpython source code). I actually find it more readable (and readability counts).

Using instead x ** 0.5 to take the square root doesn't do the exact same computations as math.sqrt as the former (probably) is computed using logarithms and the latter (probably) using the specific numeric instruction of the math processor.

I often use x ** 0.5 simply because I don't want to add math just for that. I'd expect however a specific instruction for the square root to work better (more accurately) than a multi-step operation with logarithms.

Bootstrap get div to align in the center

In bootstrap you can use .text-centerto align center. also add .row and .col-md-* to your code.

align= is deprecated,

Added .col-xs-* for demo

<link href="" rel="stylesheet" />
<link href="" rel="stylesheet" />
<div class="footer">
  <div class="container">
    <div class="row">
      <div class="col-xs-4">
        <p>Hello there</p>
      <div class="col-xs-4 text-center">
        <a href="#" class="btn btn-warning" onclick="changeLook()">Re</a>
        <a href="#" class="btn btn-warning" onclick="changeBack()">Rs</a>
      <div class="col-xs-4 text-right">
        <a href="#"><i class="fa fa-facebook-square fa-2x"></i></a>
        <a href="#"><i class="fa fa-twitter fa-2x"></i></a>
        <a href="#"><i class="fa fa-google-plus fa-2x"></i></a>


For those who are reading this and want to use the new version of bootstrap (beta version), you can do the above in a simpler way, using Boostrap Flexbox utilities classes

<link href="" rel="stylesheet" />
<link href="" rel="stylesheet" />
<div class="container footer">
  <div class="d-flex justify-content-between">
    <div class="p-1">
      <p>Hello there</p>
    <div class="p-1">
      <a href="#" class="btn btn-warning" onclick="changeLook()">Re</a>
      <a href="#" class="btn btn-warning" onclick="changeBack()">Rs</a>
    <div class="p-1">
      <a href="#"><i class="fa fa-facebook-square fa-2x"></i></a>
      <a href="#"><i class="fa fa-twitter fa-2x"></i></a>
      <a href="#"><i class="fa fa-google-plus fa-2x"></i></a>

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder"

Most likely your problem was because of <scope>test</scope> (in some cases also <scope>provided</scope>), as mentioned @thangaraj.

Documentation says:

This scope indicates that the dependency is not required for normal use of the application, and is only available for the test compilation and execution phases. Test dependencies aren’t transitive and are only present for test and execution classpaths.

So, if you don't need dependecies for test purposes then you can use instead of (what you will see in mvnrepository):

<!-- -->

Without any scopes (by default would be compile scope when no other scope is provided):

<!-- -->

This is the same as:

 <!-- -->

How to restrict the selectable date ranges in Bootstrap Datepicker?

i am using v3.1.3 and i had to use data('DateTimePicker') like this

var fromE = $( "#" + fromInput );
var toE = $( "#" + toInput );

$('.form-datepicker').on('change', function(e){
   var isTo = $(this).attr('name') === 'to';

   $( "#" + ( isTo ? fromInput : toInput  ) )
      .data('DateTimePicker')[ isTo ? 'setMaxDate' : 'setMinDate' ](moment($(this).val(), 'DD/MM/YYYY'))

JPanel vs JFrame in Java

JFrame is the window; it can have one or more JPanel instances inside it. JPanel is not the window.

You need a Swing tutorial:

Comparing Arrays of Objects in JavaScript

Here is my attempt, using Node's assert module + npm package object-hash.

I suppose that you would like to check if two arrays contain the same objects, even if those objects are ordered differently between the two arrays.

var assert = require('assert');
var hash = require('object-hash');

var obj1 = {a: 1, b: 2, c: 333},
    obj2 = {b: 2, a: 1, c: 444},
    obj3 = {b: "AAA", c: 555},
    obj4 = {c: 555, b: "AAA"};

var array1 = [obj1, obj2, obj3, obj4];
var array2 = [obj3, obj2, obj4, obj1]; // [obj3, obj3, obj2, obj1] should work as well

// calling assert.deepEquals(array1, array2) at this point FAILS (throws an AssertionError)
// even if array1 and array2 contain the same objects in different order,
// because array1[0].c !== array2[0].c

// sort objects in arrays by their hashes, so that if the arrays are identical,
// their objects can be compared in the same order, one by one
var array1 = sortArrayOnHash(array1);
var array2 = sortArrayOnHash(array2);

// then, this should output "PASS"
try {
    assert.deepEqual(array1, array2);
} catch (e) {

// You could define as well something like Array.prototype.sortOnHash()...
function sortArrayOnHash(array) {
    return array.sort(function(a, b) {
        return hash(a) > hash(b);

How to append rows in a pandas dataframe in a for loop?

I have created a data frame in a for loop with the help of a temporary empty data frame. Because for every iteration of for loop, a new data frame will be created thereby overwriting the contents of previous iteration.

Hence I need to move the contents of the data frame to the empty data frame that was created already. It's as simple as that. We just need to use .append function as shown below :

temp_df = pd.DataFrame() #Temporary empty dataframe
for sent in Sentences:
    New_df = pd.DataFrame({'words': sent.words}) #Creates a new dataframe and contains tokenized words of input sentences
    temp_df = temp_df.append(New_df, ignore_index=True) #Moving the contents of newly created dataframe to the temporary dataframe

Outside the for loop, you can copy the contents of the temporary data frame into the master data frame and then delete the temporary data frame if you don't need it

groovy.lang.MissingPropertyException: No such property: jenkins for class: groovy.lang.Binding

For me this problem occurred because I had a some invalid character in my Groovy script. In our case this was an extra blank line after the closing bracket of the script.

how does multiplication differ for NumPy Matrix vs Array classes?

the key things to know for operations on NumPy arrays versus operations on NumPy matrices are:

  • NumPy matrix is a subclass of NumPy array

  • NumPy array operations are element-wise (once broadcasting is accounted for)

  • NumPy matrix operations follow the ordinary rules of linear algebra

some code snippets to illustrate:

>>> from numpy import linalg as LA
>>> import numpy as NP

>>> a1 = NP.matrix("4 3 5; 6 7 8; 1 3 13; 7 21 9")
>>> a1
matrix([[ 4,  3,  5],
        [ 6,  7,  8],
        [ 1,  3, 13],
        [ 7, 21,  9]])

>>> a2 = NP.matrix("7 8 15; 5 3 11; 7 4 9; 6 15 4")
>>> a2
matrix([[ 7,  8, 15],
        [ 5,  3, 11],
        [ 7,  4,  9],
        [ 6, 15,  4]])

>>> a1.shape
(4, 3)

>>> a2.shape
(4, 3)

>>> a2t = a2.T
>>> a2t.shape
(3, 4)

>>> a1 * a2t         # same as, a2t) 
matrix([[127,  84,  85,  89],
        [218, 139, 142, 173],
        [226, 157, 136, 103],
        [352, 197, 214, 393]])

but this operations fails if these two NumPy matrices are converted to arrays:

>>> a1 = NP.array(a1)
>>> a2t = NP.array(a2t)

>>> a1 * a2t
Traceback (most recent call last):
   File "<pyshell#277>", line 1, in <module>
   a1 * a2t
   ValueError: operands could not be broadcast together with shapes (4,3) (3,4) 

though using the syntax works with arrays; this operations works like matrix multiplication:

>>, a2t)
array([[127,  84,  85,  89],
       [218, 139, 142, 173],
       [226, 157, 136, 103],
       [352, 197, 214, 393]])

so do you ever need a NumPy matrix? ie, will a NumPy array suffice for linear algebra computation (provided you know the correct syntax, ie,

the rule seems to be that if the arguments (arrays) have shapes (m x n) compatible with the a given linear algebra operation, then you are ok, otherwise, NumPy throws.

the only exception i have come across (there are likely others) is calculating matrix inverse.

below are snippets in which i have called a pure linear algebra operation (in fact, from Numpy's Linear Algebra module) and passed in a NumPy array

determinant of an array:

>>> m = NP.random.randint(0, 10, 16).reshape(4, 4)
>>> m
array([[6, 2, 5, 2],
       [8, 5, 1, 6],
       [5, 9, 7, 5],
       [0, 5, 6, 7]])

>>> type(m)
<type 'numpy.ndarray'>

>>> md = LA.det(m)
>>> md

eigenvectors/eigenvalue pairs:

>>> LA.eig(m)
(array([ 19.703+0.j   ,   0.097+4.198j,   0.097-4.198j,   5.103+0.j   ]), 
array([[-0.374+0.j   , -0.091+0.278j, -0.091-0.278j, -0.574+0.j   ],
       [-0.446+0.j   ,  0.671+0.j   ,  0.671+0.j   , -0.084+0.j   ],
       [-0.654+0.j   , -0.239-0.476j, -0.239+0.476j, -0.181+0.j   ],
       [-0.484+0.j   , -0.387+0.178j, -0.387-0.178j,  0.794+0.j   ]]))

matrix norm:

>>>> LA.norm(m)

qr factorization:

>>> LA.qr(a1)
(array([[ 0.5,  0.5,  0.5],
        [ 0.5,  0.5, -0.5],
        [ 0.5, -0.5,  0.5],
        [ 0.5, -0.5, -0.5]]), 
 array([[ 6.,  6.,  6.],
        [ 0.,  0.,  0.],
        [ 0.,  0.,  0.]]))

matrix rank:

>>> m = NP.random.rand(40).reshape(8, 5)
>>> m
array([[ 0.545,  0.459,  0.601,  0.34 ,  0.778],
       [ 0.799,  0.047,  0.699,  0.907,  0.381],
       [ 0.004,  0.136,  0.819,  0.647,  0.892],
       [ 0.062,  0.389,  0.183,  0.289,  0.809],
       [ 0.539,  0.213,  0.805,  0.61 ,  0.677],
       [ 0.269,  0.071,  0.377,  0.25 ,  0.692],
       [ 0.274,  0.206,  0.655,  0.062,  0.229],
       [ 0.397,  0.115,  0.083,  0.19 ,  0.701]])
>>> LA.matrix_rank(m)

matrix condition:

>>> a1 = NP.random.randint(1, 10, 12).reshape(4, 3)
>>> LA.cond(a1)

inversion requires a NumPy matrix though:

>>> a1 = NP.matrix(a1)
>>> type(a1)
<class 'numpy.matrixlib.defmatrix.matrix'>

>>> a1.I
matrix([[ 0.028,  0.028,  0.028,  0.028],
        [ 0.028,  0.028,  0.028,  0.028],
        [ 0.028,  0.028,  0.028,  0.028]])
>>> a1 = NP.array(a1)
>>> a1.I

Traceback (most recent call last):
   File "<pyshell#230>", line 1, in <module>
   AttributeError: 'numpy.ndarray' object has no attribute 'I'

but the Moore-Penrose pseudoinverse seems to works just fine

>>> LA.pinv(m)
matrix([[ 0.314,  0.407, -1.008, -0.553,  0.131,  0.373,  0.217,  0.785],
        [ 1.393,  0.084, -0.605,  1.777, -0.054, -1.658,  0.069, -1.203],
        [-0.042, -0.355,  0.494, -0.729,  0.292,  0.252,  1.079, -0.432],
        [-0.18 ,  1.068,  0.396,  0.895, -0.003, -0.896, -1.115, -0.666],
        [-0.224, -0.479,  0.303, -0.079, -0.066,  0.872, -0.175,  0.901]])

>>> m = NP.array(m)

>>> LA.pinv(m)
array([[ 0.314,  0.407, -1.008, -0.553,  0.131,  0.373,  0.217,  0.785],
       [ 1.393,  0.084, -0.605,  1.777, -0.054, -1.658,  0.069, -1.203],
       [-0.042, -0.355,  0.494, -0.729,  0.292,  0.252,  1.079, -0.432],
       [-0.18 ,  1.068,  0.396,  0.895, -0.003, -0.896, -1.115, -0.666],
       [-0.224, -0.479,  0.303, -0.079, -0.066,  0.872, -0.175,  0.901]])

Add a row number to result set of a SQL query

So before MySQL 8.0 there is no ROW_NUMBER() function. Accpted answer rewritten to support older versions of MySQL:

SET @row_number = 0;
SELECT t.A, t.B, t.C, (@row_number:=@row_number + 1) AS number
FROM dbo.tableZ AS t ORDER BY t.A;

Carriage return in C?








Carriage return, does not cause a newline. Under some circumstances a single CR or LF may be translated to a CR-LF pair. This is console and/or stream dependent.

Replace and overwrite instead of appending

You need seek to the beginning of the file before writing and then use file.truncate() if you want to do inplace replace:

import re

myfile = "path/test.xml"

with open(myfile, "r+") as f:
    data =
    f.write(re.sub(r"<string>ABC</string>(\s+)<string>(.*)</string>", r"<xyz>ABC</xyz>\1<xyz>\2</xyz>", data))

The other way is to read the file then open it again with open(myfile, 'w'):

with open(myfile, "r") as f:
    data =

with open(myfile, "w") as f:
    f.write(re.sub(r"<string>ABC</string>(\s+)<string>(.*)</string>", r"<xyz>ABC</xyz>\1<xyz>\2</xyz>", data))

Neither truncate nor open(..., 'w') will change the inode number of the file (I tested twice, once with Ubuntu 12.04 NFS and once with ext4).

By the way, this is not really related to Python. The interpreter calls the corresponding low level API. The method truncate() works the same in the C programming language: See

Passing data between view controllers

There are many answers to this questions offering many different ways to perform view controller communication that would indeed work, but I don't see anywhere mentioned which one are actually best to use and which ones to avoid.

In practice, in my opinion only a few solutions are recommended:

  • To pass data forward:
    • override the prepare(for:sender:) method of UIViewController when using a storyboard and segues
    • pass data through an initializer or through properties when performing view controller transitions thtough code
  • To pass data backwards
    • update the app shared state (which you can pass forward between view controllers with either one of the methods above)
    • use delegation
    • use an unwind segue

Solutions I recommend NOT to use:

  • Referencing the previous controller directly instead of using delegation
  • Sharing data through a singleton
  • Passing data through the app delegate
  • Sharing data through the user defaults
  • Passing data through notifications

These solutions, although working in the short term, introduce too many dependencies that will garble the architecture of the app and create more problems later.

For those interested, I wrote some articles that address these points more in depth and highlight the various drawbacks:

Keyboard shortcut for Jump to Previous View Location (Navigate back/forward) in IntelliJ IDEA

Press Ctrl + Alt + S then choose Keymap and finally find the keyboard shortcut by type back word in search bar at the top right corner.

Bootstrap 3 Horizontal Divider (not in a dropdown)

Yes there is, you can simply put <hr> in your code where you want it, I already use it in one of my admin panel side bar.

Algorithm for solving Sudoku

I wrote a simple program that solved the easy ones. It took its input from a file which was just a matrix with spaces and numbers. The datastructure to solve it was just a 9 by 9 matrix of a bit mask. The bit mask would specify which numbers were still possible on a certain position. Filling in the numbers from the file would reduce the numbers in all rows/columns next to each known location. When that is done you keep iterating over the matrix and reducing possible numbers. If each location has only one option left you're done. But there are some sudokus that need more work. For these ones you can just use brute force: try all remaining possible combinations until you find one that works.

jQuery onclick toggle class name

It can even be made dependent to another attribute changes. like this:

$('.classA').toggleClass('classB', $('input').prop('disabled'));

In this case, classB are added each time the input is disabled

What is attr_accessor in Ruby?

Attributes and accessor methods

Attributes are class components that can be accessed from outside the object. They are known as properties in many other programming languages. Their values are accessible by using the "dot notation", as in object_name.attribute_name. Unlike Python and a few other languages, Ruby does not allow instance variables to be accessed directly from outside the object.

class Car
  def initialize
    @wheels = 4  # This is an instance variable

c =
c.wheels     # Output: NoMethodError: undefined method `wheels' for #<Car:0x00000000d43500>

In the above example, c is an instance (object) of the Car class. We tried unsuccessfully to read the value of the wheels instance variable from outside the object. What happened is that Ruby attempted to call a method named wheels within the c object, but no such method was defined. In short, object_name.attribute_name tries to call a method named attribute_name within the object. To access the value of the wheels variable from the outside, we need to implement an instance method by that name, which will return the value of that variable when called. That's called an accessor method. In the general programming context, the usual way to access an instance variable from outside the object is to implement accessor methods, also known as getter and setter methods. A getter allows the value of a variable defined within a class to be read from the outside and a setter allows it to be written from the outside.

In the following example, we have added getter and setter methods to the Car class to access the wheels variable from outside the object. This is not the "Ruby way" of defining getters and setters; it serves only to illustrate what getter and setter methods do.

class Car
  def wheels  # getter method

  def wheels=(val)  # setter method
    @wheels = val

f =
f.wheels = 4  # The setter method was invoked
f.wheels  # The getter method was invoked
# Output: => 4

The above example works and similar code is commonly used to create getter and setter methods in other languages. However, Ruby provides a simpler way to do this: three built-in methods called attr_reader, attr_writer and attr_acessor. The attr_reader method makes an instance variable readable from the outside, attr_writer makes it writeable, and attr_acessor makes it readable and writeable.

The above example can be rewritten like this.

class Car
  attr_accessor :wheels

f =
f.wheels = 4
f.wheels  # Output: => 4

In the above example, the wheels attribute will be readable and writable from outside the object. If instead of attr_accessor, we used attr_reader, it would be read-only. If we used attr_writer, it would be write-only. Those three methods are not getters and setters in themselves but, when called, they create getter and setter methods for us. They are methods that dynamically (programmatically) generate other methods; that's called metaprogramming.

The first (longer) example, which does not employ Ruby's built-in methods, should only be used when additional code is required in the getter and setter methods. For instance, a setter method may need to validate data or do some calculation before assigning a value to an instance variable.

It is possible to access (read and write) instance variables from outside the object, by using the instance_variable_get and instance_variable_set built-in methods. However, this is rarely justifiable and usually a bad idea, as bypassing encapsulation tends to wreak all sorts of havoc.

CSS text-align not working

I try to avoid floating elements unless the design really needs it. Because you have floated the <li> they are out of normal flow.

If you add .navigation { text-align:center; } and change .navigation li { float: left; } to .navigation li { display: inline-block; } then entire navigation will be centred.

One caveat to this approach is that display: inline-block; is not supported in IE6 and needs a workaround to make it work in IE7.

How can I extract audio from video with ffmpeg?

To encode mp3 audio shows the following example:

ffmpeg -i input.wav -codec:a libmp3lame -qscale:a 2 output.mp3

I extracted the audio from a video just by replacing input.wav with the video filename. The 2 means 190 kb/sec. You can see the other quality levels at my link above.

What are the various "Build action" settings in Visual Studio project properties and what do they do?

How about this page from Microsoft Connect (explaining the DesignData and DesignDataWithDesignTimeCreatableTypes) types. Quoting:

The following describes the two Build Actions for Sample Data files.

Sample data .xaml files must be assigned one of the below Build Actions:

DesignData: Sample data types will be created as faux types. Use this Build Action when the sample data types are not creatable or have read-only properties that you want to defined sample data values for.

DesignDataWithDesignTimeCreatableTypes: Sample data types will be created using the types defined in the sample data file. Use this Build Action when the sample data types are creatable using their default empty constructor.

Not so incredibly exhaustive, but it at least gives a hint. This MSDN walkthrough also gives some ideas. I don't know whether these Build Actions are applicable for non-Silverlight projects also.

Node.js connect only works on localhost

in my case I had to use both symbolic IP address "" and call back while listen to server "cors": "^2.8.5", "express": "^4.17.1",

const cors = require("cors");

const port = process.env.PORT || 8000;
app.listen(port,"" ,() => {
  console.log(`Server is running on port ${port}`);

you can also use, your local IP address instead of "", In OS Ubuntu you can find your Ip address by using command

ifconfig | grep "inet " | grep -v

enter image description here Then use the Ip Address:

app.listen(port,"" ,() => {
  console.log(`Server is running on port ${port}`);

If you use fixed Ip address such as "", then you must use it while calling to the server, such as, My api calling configuration for react client is bellow:


how to create a cookie and add to http response from inside my service layer?

A cookie is a object with key value pair to store information related to the customer. Main objective is to personalize the customer's experience.

An utility method can be created like

private Cookie createCookie(String cookieName, String cookieValue) {
    Cookie cookie = new Cookie(cookieName, cookieValue);
    return cookie;

If storing important information then we should alsways put setHttpOnly so that the cookie cannot be accessed/modified via javascript. setSecure is applicable if you are want cookies to be accessed only over https protocol.

using above utility method you can add cookies to response as

Cookie cookie = createCookie("name","value");

Open a URL without using a browser from a batch file

You can try put in a shortcut to the site and tell the .bat file to open that.

start Google.HTML

Wireshark localhost traffic capture

If you're using Windows it's not possible - read below. You can use the local address of your machine instead and then you'll be able to capture stuff. See CaptureSetup/Loopback.

Summary: you can capture on the loopback interface on Linux, on various BSDs including Mac OS X, and on Digital/Tru64 UNIX, and you might be able to do it on Irix and AIX, but you definitely cannot do so on Solaris, HP-UX....

Although the page mentions that this is not possible on Windows using Wireshark alone, you can actually record it using a workaround as mentioned in a different answer.

EDIT: Some 3 years later, this answer is no longer completely correct. The linked page contains instructions for capturing on the loopback interface.

Convert hex color value ( #ffffff ) to integer value

The real answer is to use:

Color.parseColor(myPassedColor) in Android, myPassedColor being the hex value like #000 or #000000 or #00000000.

However, this function does not support shorthand hex values such as #000.

How to copy a file to another path?

TO Copy The Folder I Use Two Text Box To Know The Place Of Folder And Anther Text Box To Know What The Folder To Copy It And This Is The Code

MessageBox.Show("The File is Create in The Place Of The Programe If you Don't Write The Place Of copy And You write Only Name Of Folder");// It Is To Help The User TO Know
          if (Fromtb.Text=="")
            MessageBox.Show("Ples You Should Write All Text Box");
        else if (Nametb.Text == "")
            MessageBox.Show("Ples You Should Write The Third Text Box");
        else if (Totb.Text == "")
            MessageBox.Show("Ples You Should Write The Second Text Box");

        string fileName = Nametb.Text;
        string sourcePath = @"" + Fromtb.Text;
        string targetPath = @"" + Totb.Text;

        string sourceFile = System.IO.Path.Combine(sourcePath, fileName);
        string destFile = System.IO.Path.Combine(targetPath, fileName);

        if (!System.IO.Directory.Exists(targetPath))
            //when The User Write The New Folder It Will Create 
            MessageBox.Show("The File is Create in "+" "+Totb.Text);

        System.IO.File.Copy(sourceFile, destFile, true);

        if (System.IO.Directory.Exists(sourcePath))
            string[] files = System.IO.Directory.GetFiles(sourcePath);

            foreach (string s in files)
                fileName = System.IO.Path.GetFileName(s);
                destFile = System.IO.Path.Combine(targetPath, fileName);
                System.IO.File.Copy(s, destFile, true);

            MessageBox.Show("The File is copy To " + Totb.Text);


How to read a file line-by-line into a list?

Here is a Python(3) helper library class that I use to simplify file I/O:

import os

# handle files using a callback method, prevents repetition
def _FileIO__file_handler(file_path, mode, callback = lambda f: None):
  f = open(file_path, mode)
    return callback(f)
  except Exception as e:
    raise IOError("Failed to %s file" % ["write to", "read from"][mode.lower() in "r rb r+".split(" ")])

class FileIO:
  # return the contents of a file
  def read(file_path, mode = "r"):
    return __file_handler(file_path, mode, lambda rf:

  # get the lines of a file
  def lines(file_path, mode = "r", filter_fn = lambda line: len(line) > 0):
    return [line for line in, mode).strip().split("\n") if filter_fn(line)]

  # create or update a file (NOTE: can also be used to replace a file's original content)
  def write(file_path, new_content, mode = "w"):
    return __file_handler(file_path, mode, lambda wf: wf.write(new_content))

  # delete a file (if it exists)
  def delete(file_path):
    return os.remove() if os.path.isfile(file_path) else None

You would then use the FileIO.lines function, like this:

file_ext_lines = FileIO.lines("./path/to/file.ext"):
for i, line in enumerate(file_ext_lines):
  print("Line {}: {}".format(i + 1, line))

Remember that the mode ("r" by default) and filter_fn (checks for empty lines by default) parameters are optional.

You could even remove the read, write and delete methods and just leave the FileIO.lines, or even turn it into a separate method called read_lines.

CSV with comma or semicolon?

Well to just to have some saying about semicolon. In lot of country, comma is what use for decimal not period. Mostly EU colonies, which consist of half of the world, another half follow UK standard (how the hell UK so big O_O) so in turn make using comma for database that include number create much of the headache because Excel refuse to recognize it as delimiter.

Like wise in my country, Viet Nam, follow France's standard, our partner HongKong use UK standard so comma make CSV unusable, and we use \t or ; instead for international use, but it still not "standard" per the document of CSV.

How to make an Android device vibrate? with different frequency?

Vibrate without using permission

If you want to simply vibrate the device once to provide a feedback on a user action. You can use performHapticFeedback() function of a View. This doesn't need the VIBRATE permission to be declared in the manifest.

Use the following function as a top level function in some common class like Utils.kt of your project:

 * Vibrates the device. Used for providing feedback when the user performs an action.
fun vibrate(view: View) {

And then use it anywhere in your Fragment or Activity as following:


Simple as that!

Revert to Eclipse default settings

Not even a single answer of the above let me able to get the original theme as I expected. I tried myself & got my default theme by changing the workspace. This led me to the original theme (same-to-same) that I used to saw when installing eclipse !

How to extract numbers from string in c?

A possible solution using sscanf() and scan sets:

const char* s = "ab234cid*(s349*(20kd";
int i1, i2, i3;
if (3 == sscanf(s,
    printf("%d %d %d\n", i1, i2, i3);

where %*[^0123456789] means ignore input until a digit is found. See demo at .

Or, if the number of numbers is unknown you can use %n specifier to record the last position read in the buffer:

const char* s = "ab234cid*(s349*(20kd";
int total_n = 0;
int n;
int i;
while (1 == sscanf(s + total_n, "%*[^0123456789]%d%n", &i, &n))
    total_n += n;
    printf("%d\n", i);

PHP calculate age

If you don't need great precision, just the number of years, you could consider using the code below ...

 print floor((time() - strtotime("1971-11-20")) / (60*60*24*365));

You only need to put this into a function and replace the date "1971-11-20" with a variable.

Please note that precision of the code above is not high because of the leap years, i.e. about every 4 years the days are 366 instead of 365. The expression 60*60*24*365 calculates the number of seconds in one year - you can replace it with 31536000.

Another important thing is that because of the use of UNIX Timestamp it has both the Year 1901 and Year 2038 problem which means the the expression above will not work correctly for dates before year 1901 and after year 2038.

If you can live with the limitations mentioned above that code should work for you.

How can I represent an 'Enum' in Python?

Use the following.

TYPE = {'EAN13':   u'EAN-13',
        'CODE39':  u'Code 39',
        'CODE128': u'Code 128',
        'i25':     u'Interleaved 2 of 5',}

>>> TYPE.items()
[('EAN13', u'EAN-13'), ('i25', u'Interleaved 2 of 5'), ('CODE39', u'Code 39'), ('CODE128', u'Code 128')]
>>> TYPE.keys()
['EAN13', 'i25', 'CODE39', 'CODE128']
>>> TYPE.values()
[u'EAN-13', u'Interleaved 2 of 5', u'Code 39', u'Code 128']

I used that for Django model choices, and it looks very pythonic. It is not really an Enum, but it does the job.

Difference between JOIN and INNER JOIN

They are functionally equivalent, but INNER JOIN can be a bit clearer to read, especially if the query has other join types (i.e. LEFT or RIGHT or CROSS) included in it.

Tesseract OCR simple example

I had same problem, now its resolved. I have tesseract2, under this folders for 32 bit and 64 bit, I copied files 64 bit folder(as my system is 64 bit) to main folder ("Tesseract2") and under bin/Debug folder. Now my solution is working fine.

How to add directory to classpath in an application run profile in IntelliJ IDEA?

Simply check that the directory/package of the class is marked as "Sources Root". I believe the package should be application or execution in your case.

To do so, right click on the package, and select Mark Directory As->Sources Root.


Convert Mercurial project to Git

This would be better as a comment, sorry I do not have commenting permissions.

@mar10 comment was the missing piece I needed to do this.

Note that '/path/to/old/mercurial_repo' must be a path on the file system (not a URL), so you have to clone the original repository before. – mar10 Dec 27 '13 at 16:30

This comment was in regards to the answer that solved this for me, which is the same answer as the one marked correct here,

This moved our hg project to git with the commit history intact.

How can I convert a comma-separated string to an array?



var str = "January,February,March,April,May,June,July,August,September,October,November,December";_x000D_
let arr = str.split`,`;_x000D_

What do 'lazy' and 'greedy' mean in the context of regular expressions?

'Greedy' means match longest possible string.

'Lazy' means match shortest possible string.

For example, the greedy h.+l matches 'hell' in 'hello' but the lazy h.+?l matches 'hel'.

How to printf uint64_t? Fails with: "spurious trailing ‘%’ in format"

Since you've included the C++ tag, you could use the {fmt} library and avoid the PRIu64 macro and other printf issues altogether:

#include <fmt/core.h>

int main() {
  uint64_t ui64 = 90;
  fmt::print("test uint64_t : {}\n", ui64);

The formatting facility based on this library is proposed for standardization in C++20: P0645.

Disclaimer: I'm the author of {fmt}.

How to fix "Only one expression can be specified in the select list when the subquery is not introduced with EXISTS" error?

Try this:

    (Select Count(*) 
        From LoginFails 
        Where username = '" + LoginModel.Username + "' And IP = '" + Request.ServerVariables["REMOTE_ADDR"] + "')
 From Users 
 Where username = '" + LoginModel.Username + "'

And I recommend you strongly to use parameters in your query to avoid security risks with sql injection attacks!

Hope that helps!

Http Post request with content type application/x-www-form-urlencoded not working in Spring

The easiest thing to do is to set the content type of your ajax request to "application/json; charset=utf-8" and then let your API method consume JSON. Like this:

var basicInfo = JSON.stringify({
    firstName: playerProfile.firstName(),
    lastName: playerProfile.lastName(),
    gender: playerProfile.gender(),
    address: playerProfile.address(),

    url: "http://localhost:8080/social/profile/update",
    type: 'POST',
    dataType: 'json',
    contentType: "application/json; charset=utf-8",
    data: basicInfo,
    success: function(data) {
        // ...

    value = "/profile/update",
    method = RequestMethod.POST,
    produces = MediaType.APPLICATION_JSON_VALUE,
    consumes = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<ResponseModel> UpdateUserProfile(
    @RequestBody User usersNewDetails,
    HttpServletRequest request,
    HttpServletResponse response
) {
    // ...

I guess the problem is that Spring Boot has issues submitting form data which is not JSON via ajax request.

Note: the default content type for ajax is "application/x-www-form-urlencoded".

Getting the last revision number in SVN?

$ svn log | head -10 on whatever directory that has a .svn folder

SQL UPDATE with sub-query that references the same table in MySQL

UPDATE user_account 
SET (student_education_facility_id) = ( 
    SELECT teacher.education_facility_id
    FROM user_account teacher
    WHERE teacher.user_account_id = teacher_id
    AND teacher.user_type = 'ROLE_TEACHER'
WHERE user_type = 'ROLE_STUDENT'

Above are the sample update query...

You can write sub query with update SQL statement, you don't need to give alias name for that table. give alias name to sub query table. I tried and it's working fine for me....

SVG drop shadow using css3

You can easily add a drop-shadow effect to an svg-element using the drop-shadow() CSS function and rgba color values. By using rgba color values you can change the opacity of your shadow.

  filter: drop-shadow(0px 3px 3px rgba(0, 0, 0, 0.4));_x000D_
  filter: drop-shadow(0px 3px 3px rgba(0, 0, 0, 1));_x000D_
<img class="light-shadow" src="" />_x000D_
<img class="dark-shadow" src="" />

Iterate over object attributes in python

For all the pythonian zealots out there I'm sure Johan Cleeze would approve of your dogmatism ;). I'm leaving this answer keep demeriting it It actually makes me more confidant. Leave a comment you chickens!

For python 3.6

class SomeClass:

    def attr_list1(self, should_print=False):

        for k in self.__dict__.keys():
            v = self.__dict__.__getitem__(k)
            if should_print:
                print(f"attr: {k}    value: {v}")

    def attr_list(self, should_print=False):

        b = [(k, v) for k, v in self.__dict__.items()]
        if should_print:
            [print(f"attr: {a[0]}    value: {a[1]}") for a in b]
        return b

In jQuery how can I set "top,left" properties of an element with position values relative to the parent and not the document?

Refreshing my memory on setting position, I'm coming to this so late I don't know if anyone else will see it, but --

I don't like setting position using css(), though often it's fine. I think the best bet is to use jQuery UI's position() setter as noted by xdazz. However if jQuery UI is, for some reason, not an option (yet jQuery is), I prefer this:

const leftOffset = 200;
const topOffset = 200;
let $div = $("#mydiv");
let baseOffset = $div.offsetParent().offset();
  left: baseOffset.left + leftOffset,
  top: + topOffset

This has the advantage of not arbitrarily setting $div's parent to relative positioning (what if $div's parent was, itself, absolute positioned inside something else?). I think the only major edge case is if $div doesn't have any offsetParent, not sure if it would return document, null, or something else entirely.

offsetParent has been available since jQuery 1.2.6, sometime in 2008, so this technique works now and when the original question was asked.

Pandas - Get first row value of a given column

To access a single value you can use the method iat that is much faster than iloc:




Using regular expression in css?

there is another simple way to select particular elements in css too...

#s1, #s2, #s3 {
    // set css attributes here

if you only have a few elements to choose from, and dont want to bother with classes, this will work easily too.

Creating Duplicate Table From Existing Table

Use this query to create the new table with the values from existing table

CREATE TABLE New_Table_name AS SELECT * FROM Existing_table_Name; 

Now you can get all the values from existing table into newly created table.

how to get the base url in javascript

This is done simply by doing this variable.

var base_url = '<?php echo base_url();?>'

This will have base url now. And now make a javascript function that will use this variable

function base_url(string){
    return base_url + string;

And now this will always use the correct path.

var path    =   "assets/css/themes/" + color_ + ".css"
$('#style_color').attr("href", base_url(path) );

Can't access object property, even though it shows up in a console log

The output of console.log(anObject) is misleading; the state of the object displayed is only resolved when you expand the Object tree displayed in the console, by clicking on >. It is not the state of the object when you console.log'd the object.

Instead, try console.log(Object.keys(config)), or even console.log(JSON.stringify(config)) and you will see the keys, or the state of the object at the time you called console.log.

You will (usually) find the keys are being added after your console.log call.

Javascript equivalent of php's strtotime()?

I jealous the strtotime() in php, but I do mine in javascript using moment. Not as sweet as that from php, but does the trick neatly too.

// first day of the month
var firstDayThisMonth = moment(firstDayThisMonth).startOf('month').toDate();

Go back and forth using the subtract() and add() with the endOf() and startOf():

// last day of previous month
var yesterMonthLastDay = moment(yesterMonthLastDay).subtract(1,'months').endOf('month').toDate();

Is there a function to copy an array in C/C++?

As others have mentioned, in C you would use memcpy. Note however that this does a raw memory copy, so if your data structures have pointer to themselves or to each other, the pointers in the copy will still point to the original objects.

In C++ you can also use memcpy if your array members are POD (that is, essentially types which you could also have used unchanged in C), but in general, memcpy will not be allowed. As others mentioned, the function to use is std::copy.

Having said that, in C++ you rarely should use raw arrays. Instead you should either use one of the standard containers (std::vector is the closest to a built-in array, and also I think the closest to Java arrays — closer than plain C++ arrays, indeed —, but std::deque or std::list may be more appropriate in some cases) or, if you use C++11, std::array which is very close to built-in arrays, but with value semantics like other C++ types. All the types I mentioned here can be copied by assignment or copy construction. Moreover, you can "cross-copy" from opne to another (and even from a built-in array) using iterator syntax.

This gives an overview of the possibilities (I assume all relevant headers have been included):

int main()
  // This works in C and C++
  int a[] = { 1, 2, 3, 4 };
  int b[4];
  memcpy(b, a, 4*sizeof(int)); // int is a POD

  // This is the preferred method to copy raw arrays in C++ and works with all types that can be copied:
  std::copy(a, a+4, b);

  // In C++11, you can also use this:
  std::copy(std::begin(a), std::end(a), std::begin(b));

  // use of vectors
  std::vector<int> va(a, a+4); // copies the content of a into the vector
  std::vector<int> vb = va;    // vb is a copy of va

  // this initialization is only valid in C++11:
  std::vector<int> vc { 5, 6, 7, 8 }; // note: no equal sign!

  // assign vc to vb (valid in all standardized versions of C++)
  vb = vc;

  //alternative assignment, works also if both container types are different
  vb.assign(vc.begin(), vc.end());

  std::vector<int> vd; // an *empty* vector

  // you also can use std::copy with vectors
  // Since vd is empty, we need a `back_inserter`, to create new elements:
  std::copy(va.begin(), va.end(), std::back_inserter(vd));

  // copy from array a to vector vd:
  // now vd already contains four elements, so this new copy doesn't need to
  // create elements, we just overwrite the existing ones.
  std::copy(a, a+4, vd.begin());

  // C++11 only: Define a `std::array`:
  std::array<int, 4> sa = { 9, 10, 11, 12 };

  // create a copy:
  std::array<int, 4> sb = sa;

  // assign the array:
  sb = sa;

Uncaught TypeError: Cannot read property 'toLowerCase' of undefined

This Works For me !!!

Call a Function without Parameter

$("#CourseSelect").change(function(e1) {

Call a Function with Parameter

$("#CourseSelect").change(function(e1) {

JQuery find first parent element with specific class prefix

Use .closest() with a selector:

var $div = $('#divid').closest('div[class^="div-a"]');

How to resolve this JNI error when trying to run LWJGL "Hello World"?

I had same issue using different dependancy what helped me is to set scope to compile.


angular.js ng-repeat li items with html content

You can use NGBindHTML or NGbindHtmlUnsafe this will not escape the html content of your model.

<div ng-app ng-controller="MyCtrl">
    <li ng-repeat=" opt in opts"  ng-bind-html-unsafe="opt.text">
        {{ opt.text }}


This works, anyway you should be very careful when using unsanitized html content, you should really trust the source of the content.

Generate a dummy-variable

Hi i wrote this general function to generate a dummy variable which essentially replicates the replace function in Stata.

If x is the data frame is x and i want a dummy variable called a which will take value 1 when x$b takes value c

  for(i in 1:n){

Show values from a MySQL database table inside a HTML table on a webpage

First, connect to the database:


You can use this to display a single record:

For example, if the URL was /index.php?sequence=123, the code below would select from the table, where the sequence = 123.

$sql="SELECT * from table where sequence = '".$_GET["sequence"]."' ";
$rs=mysql_query($sql,$conn) or die(mysql_error());

echo '<table>

Or, if you want to list all values that match the criteria in a table:

echo '<table>
$sql="SELECT * from table where sequence = '".$_GET["sequence"]."' ";
$rs=mysql_query($sql,$conn) or die(mysql_error());
echo '<tr>
echo '</table>';

mysql count group by having


SELECT count(*) FROM (
    SELECT COUNT(*) FROM Movies GROUP BY ID HAVING count(Genre) = 4
) AS the_count_total

although that would not be the sum of all the movies, just how many have 4 genre's.

So maybe you want

    SELECT COUNT(*) FROM Movies GROUP BY ID having Count(Genre) = 4
) as the_sum_total

R - Concatenate two dataframes?

Here's a simple little function that will rbind two datasets together after auto-detecting what columns are missing from each and adding them with all NAs.

For whatever reason this returns MUCH faster on larger datasets than using the merge function.

fastmerge <- function(d1, d2) {
  d1.names <- names(d1)
  d2.names <- names(d2)

  # columns in d1 but not in d2
  d2.add <- setdiff(d1.names, d2.names)

  # columns in d2 but not in d1
  d1.add <- setdiff(d2.names, d1.names)

  # add blank columns to d2
  if(length(d2.add) > 0) {
    for(i in 1:length(d2.add)) {
      d2[d2.add[i]] <- NA

  # add blank columns to d1
  if(length(d1.add) > 0) {
    for(i in 1:length(d1.add)) {
      d1[d1.add[i]] <- NA

  return(rbind(d1, d2))

Android Fragment handle back button press

The most ideal way of doing this is found here: Fragment: which callback invoked when press back button & customize it

public class MyActivity extends Activity
    //Defined in Activity class, so override
    public void onBackPressed()

public class MyFragment extends Fragment
    //Your created method
    public static void onBackPressed()
        //Pop Fragments off backstack and do your other checks

How do I kill an Activity when the Back button is pressed?

add this to your activity

public boolean onKeyDown(int keyCode, KeyEvent event)
    if ((keyCode == KeyEvent.KEYCODE_BACK))
    return super.onKeyDown(keyCode, event);

Collections sort(List<T>,Comparator<? super T>) method example

To use Collections sort(List,Comparator) , you need to create a class that implements Comparator Interface, and code for the compare() in it, through Comparator Interface

You can do something like this:

class StudentComparator implements Comparator
    public int compare (Student s1 Student s2)
        // code to compare 2 students

To sort do this:

 Collections.sort(List,new StudentComparator())

Split output of command by columns using Bash?


ps |&
while read -p first second third fourth etc ; do
   if [[ $first == '11383' ]]
       echo got: $fourth

Javascript, Time and Date: Getting the current minute, hour, day, week, month, year of a given millisecond time

Here is another method to get date

new Date().getDate()          // Get the day as a number (1-31)
new Date().getDay()           // Get the weekday as a number (0-6)
new Date().getFullYear()      // Get the four digit year (yyyy)
new Date().getHours()         // Get the hour (0-23)
new Date().getMilliseconds()  // Get the milliseconds (0-999)
new Date().getMinutes()       // Get the minutes (0-59)
new Date().getMonth()         // Get the month (0-11)
new Date().getSeconds()       // Get the seconds (0-59)
new Date().getTime()          // Get the time (milliseconds since January 1, 1970)

Dynamic type languages versus static type languages

There are lots of different things about static and dynamic languages. For me, the main difference is that in dynamic languages the variables don't have fixed types; instead, the types are tied to values. Because of this, the exact code that gets executed is undetermined until runtime.

In early or naïve implementations this is a huge performance drag, but modern JITs get tantalizingly close to the best you can get with optimizing static compilers. (in some fringe cases, even better than that).

Color picker utility (color pipette) in Ubuntu

You can install the package gcolor2 for this:

sudo apt-get install gcolor2


Applications -> Graphics -> GColor2 Button OnClick event not firing

I had the same problem, my aspnet button's click was not firing. It turns out that some where on other part of the page has an input with html "required" attribute on.

This might be sound strange, but once I remove the required attribute, the button just works normally.

Import CSV file into SQL Server

I know that there are accepted answer but still, I want to share my scenario that maybe help someone to solve their problem TOOLS

  • SSMS

SCENARIO i was loading the dataset which's in CSV format which was later to be shown on the View i tried to use the bulk load but I's unable to load as BULK LOAD was using


and Excel cell was also using , however, I also couldn't use Flat file source directly because I was using Code-First Approach and doing that only made model in SSMS DB, not in the model from which I had to use the properties later.


  1. I used flat-file source and made DB table from CSV file (Right click DB in SSMS -> Import Flat FIle -> select CSV path and do all the settings as directed)
  2. Made Model Class in Visual Studio (You MUST KEEP all the datatypes and names same as that of CSV file loaded in sql)
  3. use Add-Migration in NuGet package console
  4. Update DB

Select2 open dropdown on focus

Working Code for v4.0+ *(including 4.0.7)

The following code will open the menu on the initial focus, but won't get stuck in an infinite loop when the selection re-focuses after the menu closes.

// on first focus (bubbles up to document), open the menu
$(document).on('focus', '.select2-selection.select2-selection--single', function (e) {

// steal focus during close - only capture once and stop propogation
$('select.select2').on('select2:closing', function (e) {
  $("select2").$'focus focusin', function (e) {


Prevent Infinite Focus Loop

Note: The focus event is fired twice

  1. Once when tabbing into the field
  2. Again when tabbing with an open dropdown to restore focus

focus menu states

We can prevent an infinite loop by looking for differences between the types of focus events. Since we only want to open the menu on the initial focus to the control, we have to somehow distinguish between the following raised events:

event timeline

Doing so it a cross browser friendly way is hard, because browsers send different information along with different events and also Select2 has had many minor changes to their internal firing of events, which interrupt previous flows.

One way that seems to work is to attach an event handler during the closing event for the menu and use it to capture the impending focus event and prevent it from bubbling up the DOM. Then, using a delegated listener, we'll call the actual focus -> open code only when the focus event bubbles all the way up to the document

Prevent Opening Disabled Selects

As noted in this github issue #4025 - Dropdown does not open on tab focus, we should check to make sure we only call 'open' on :enabled select elements like this:


Select2 DOM traversal

We have to traverse the DOM a little bit, so here's a map of the HTML structure generated by Select2

Select2 DOM

Source Code on GitHub

Here are some of the relevant code sections in play:

.on('mousedown' ... .trigger('toggle')
.on('toggle' ... .toggleDropdown()
.toggleDropdown ... .open()
.on('focus' ... .trigger('focus'
.on('close' ... $selection.focus()

It used to be the case that opening select2 fired twice, but it was fixed in Issue #3503 and that should prevent some jank

PR #5357 appears to be what broke the previous focus code that was working in 4.05

Working Demo in jsFiddle & Stack Snippets:

// on first focus (bubbles up to document), open the menu_x000D_
$(document).on('focus', '.select2-selection.select2-selection--single', function (e) {_x000D_
// steal focus during close - only capture once and stop propogation_x000D_
$('select.select2').on('select2:closing', function (e) {_x000D_
  $("select2").$'focus focusin', function (e) {_x000D_
<link href="" rel="stylesheet"/>_x000D_
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<select class="select2" style="width:200px" >_x000D_
  <option value="1">Apple</option>_x000D_
  <option value="2">Banana</option>_x000D_
  <option value="3">Carrot</option>_x000D_
  <option value="4">Donut</option>_x000D_

Tested on Chrome, FF, Edge, IE11

Getting next element while cycling through a list

You can use a pairwise cyclic iterator:

from itertools import izip, cycle, tee

def pairwise(seq):
    a, b = tee(seq)
    return izip(a, b)

for elem, next_elem in pairwise(cycle(li)):

javac is not recognized as an internal or external command, operable program or batch file

Check your environment variables.

In my case I had JAVA_HOME set in the System variables as well as in my User Account variables and the latter was set to a wrong version of Java. I also had the same problem with the Path variable.

After deleting JAVA_HOME from my User Account variables and removing the wrong path from the Path variable it worked correctly.

How to grep (search) committed code in the Git history

To search for commit content (i.e., actual lines of source, as opposed to commit messages and the like), you need to do:

git grep <regexp> $(git rev-list --all)

git rev-list --all | xargs git grep <expression> will work if you run into an "Argument list too long" error.

If you want to limit the search to some subtree (for instance, "lib/util"), you will need to pass that to the rev-list subcommand and grep as well:

git grep <regexp> $(git rev-list --all -- lib/util) -- lib/util

This will grep through all your commit text for regexp.

The reason for passing the path in both commands is because rev-list will return the revisions list where all the changes to lib/util happened, but also you need to pass to grep so that it will only search in lib/util.

Just imagine the following scenario: grep might find the same <regexp> on other files which are contained in the same revision returned by rev-list (even if there was no change to that file on that revision).

Here are some other useful ways of searching your source:

Search working tree for text matching regular expression regexp:

git grep <regexp>

Search working tree for lines of text matching regular expression regexp1 or regexp2:

git grep -e <regexp1> [--or] -e <regexp2>

Search working tree for lines of text matching regular expression regexp1 and regexp2, reporting file paths only:

git grep -l -e <regexp1> --and -e <regexp2>

Search working tree for files that have lines of text matching regular expression regexp1 and lines of text matching regular expression regexp2:

git grep -l --all-match -e <regexp1> -e <regexp2>

Search working tree for changed lines of text matching pattern:

git diff --unified=0 | grep <pattern>

Search all revisions for text matching regular expression regexp:

git grep <regexp> $(git rev-list --all)

Search all revisions between rev1 and rev2 for text matching regular expression regexp:

git grep <regexp> $(git rev-list <rev1>..<rev2>)

How to convert Nonetype to int or string?

This can happen if you forget to return a value from a function: it then returns None. Look at all places where you are assigning to that variable, and see if one of them is a function call where the function lacks a return statement.

Add target="_blank" in CSS

This is actually javascript but related/relevant because .querySelectorAll targets by CSS syntax:

var i_will_target_self = document.querySelectorAll(" li a#example")

this example uses css to target links in a menu with id = "example"

that creates a variable which is a collection of the elements we want to change, but we still have actually change them by setting the new target ("_blank"):

for (var i = 0; i < 5; i++) {
i_will_target_self[i].target = "_blank";

That code assumes that there are 5 or less elements. That can be changed easily by changing the phrase "i < 5."

read more here:

Android Studio drawable folders

Just to make complete all answers, 'drawable' is, literally, a drawable image, not a complete and ready set of pixels, as .png

In other word words, drawable is only for vectorial images, just try right-click on 'drawable' and go New > Vector Asset, it will accept it, while Image Asset won't be added.

The data for 'drawing', generating the image is recorded on a XML file like this:

<vector xmlns:android=""
    android:pathData="M6,18c0,0.55 0.45,1 1,1h1v3.5c0,0.83 0.67,1.5 1.5,1.5s1.5,
    -0.67 1.5,-1.5L11,19h2v3.5c0,0.83 0.67,1.5 1.5,1.5s1.5,-0.67 1.5,-1.5L16,
    19h1c0.55,0 1,-0.45 1,-1L18,8L6,8v10zM3.5,8C2.67,8 2,8.67 2,9.5v7c0,0.83 0.67,
    1.5 1.5,1.5S5,17.33 5,16.5v-7C5,8.67 4.33,8 3.5,8zM20.5,8c-0.83,0 -1.5,0.67 -1.5,
    1.5v7c0,0.83 0.67,1.5 1.5,1.5s1.5,-0.67 1.5,-1.5v-7c0,-0.83 -0.67,-1.5 -1.5,-1.5zM15.53,
    2.16l1.3,-1.3c0.2,-0.2 0.2,-0.51 0,-0.71 -0.2,-0.2 -0.51,-0.2 -0.71,0l-1.48,1.48C13.85,
    1.23 12.95,1 12,1c-0.96,0 -1.86,0.23 -2.66,0.63L7.85,0.15c-0.2,-0.2 -0.51,-0.2 -0.71,0 -0.2,
    0.2 -0.2,0.51 0,0.71l1.31,1.31C6.97,3.26 6,5.01 6,7h12c0,-1.99 -0.97,-3.75 -2.47,-4.84zM10,

That's the code for ic_android_black_24dp

How to clear cache in Yarn?

Ok I found out the answer myself. Much like npm cache clean, Yarn also has its own

yarn cache clean

How to return data from promise

One of the fundamental principles behind a promise is that it's handled asynchronously. This means that you cannot create a promise and then immediately use its result synchronously in your code (e.g. it's not possible to return the result of a promise from within the function that initiated the promise).

What you likely want to do instead is to return the entire promise itself. Then whatever function needs its result can call .then() on the promise, and the result will be there when the promise has been resolved.

Here is a resource from HTML5Rocks that goes over the lifecycle of a promise, and how its output is resolved asynchronously:

How can I use a carriage return in a HTML tooltip?

Just use this:

<a title='Tool&#x0aTip&#x0aOn&#x0aNew&#x0aLine'>link with tip</a>

You can add new line on title by using this &#x0a.

Running a script inside a docker container using shell script

Assuming that your docker container is up and running, you can run commands as:

docker exec mycontainer /bin/sh -c "cmd1;cmd2;...;cmdn"

Apache Proxy: No protocol handler was valid

This was happening for me in my Apache/2.4.18 (Ubuntu) setup. In my case, the error I was seeing was:

... AH01144: No protocol handler was valid for the URL / If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.

The configuration related to this was:

  ProxyPass / ws://
  ProxyPassReverse / ws://

"No protocol handler was valid for the URL /" meant that Apache could not handle the request being sent to "ws://"

I had proxy_http loaded, but also needed proxy_wstunnel. Once that was enabled all was good.

What does the return keyword do in a void method in Java?

The keyword simply pops a frame from the call stack returning the control to the line following the function call.

How do I use the includes method in lodash to check if an object is in the collection?

The includes (formerly called contains and include) method compares objects by reference (or more precisely, with ===). Because the two object literals of {"b": 2} in your example represent different instances, they are not equal. Notice:

({"b": 2} === {"b": 2})
> false

However, this will work because there is only one instance of {"b": 2}:

var a = {"a": 1}, b = {"b": 2};
_.includes([a, b], b);
> true

On the other hand, the where(deprecated in v4) and find methods compare objects by their properties, so they don't require reference equality. As an alternative to includes, you might want to try some (also aliased as any):

_.some([{"a": 1}, {"b": 2}], {"b": 2})
> true

Compiling/Executing a C# Source File in Command Prompt

LinqPad is a quick way to test out some C# code, and its free.

How to get a ListBox ItemTemplate to stretch horizontally the full width of the ListBox?

The fix for me was to set property HorizontalAlignment="Stretch" on ItemsPresenter inside ScrollViewer..

Hope this helps someone...

<Setter Property="Template">
                <ControlTemplate TargetType="ListBox">
                    <ScrollViewer x:Name="ScrollViewer" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Foreground="{TemplateBinding Foreground}" Padding="{TemplateBinding Padding}" HorizontalAlignment="Stretch">
                        <ItemsPresenter  Height="252" HorizontalAlignment="Stretch"/>

Converting SVG to PNG using C#

When I had to rasterize svgs on the server, I ended up using P/Invoke to call librsvg functions (you can get the dlls from a windows version of the GIMP image editing program).

[DllImport("kernel32.dll", SetLastError = true)]
static extern bool SetDllDirectory(string pathname);

[DllImport("libgobject-2.0-0.dll", SetLastError = true)]
static extern void g_type_init(); 

[DllImport("librsvg-2-2.dll", SetLastError = true)]
static extern IntPtr rsvg_pixbuf_from_file_at_size(string file_name, int width, int height, out IntPtr error);

[DllImport("libgdk_pixbuf-2.0-0.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
static extern bool gdk_pixbuf_save(IntPtr pixbuf, string filename, string type, out IntPtr error, __arglist);

public static void RasterizeSvg(string inputFileName, string outputFileName)
    bool callSuccessful = SetDllDirectory("C:\\Program Files\\GIMP-2.0\\bin");
    if (!callSuccessful)
        throw new Exception("Could not set DLL directory");
    IntPtr error;
    IntPtr result = rsvg_pixbuf_from_file_at_size(inputFileName, -1, -1, out error);
    if (error != IntPtr.Zero)
        throw new Exception(Marshal.ReadInt32(error).ToString());
    callSuccessful = gdk_pixbuf_save(result, outputFileName, "png", out error, __arglist(null));
    if (!callSuccessful)
        throw new Exception(error.ToInt32().ToString());

Solving "adb server version doesn't match this client" error

This issue for me was caused by having apowermirror running at the same time, from what I can tell any software that could use a different version of adb could cause these issues as others mention in this thread this can include Genymotion or from other threads unreal studio was the problem.

div hover background-color change?

div hover background color change

Try like this:


How to describe "object" arguments in jsdoc?

There's a new @config tag for these cases. They link to the preceding @param.

/** My function does X and Y.
    @params {object} parameters An object containing the parameters
    @config {integer} setting1 A required setting.
    @config {string} [setting2] An optional setting.
    @params {MyClass~FuncCallback} callback The callback function
function(parameters, callback) {
    // ...

 * This callback is displayed as part of the MyClass class.
 * @callback MyClass~FuncCallback
 * @param {number} responseCode
 * @param {string} responseMessage

Html.fromHtml deprecated in Android N

Compare of the flags of fromHtml().

<p style="color: blue;">This is a paragraph with a style</p>

<h4>Heading H4</h4>

   <li style="color: yellow;">
      <font color=\'#FF8000\'>li orange element</font>
   <li>li #2 element</li>

<blockquote>This is a blockquote</blockquote>

Text after blockquote
Text before div

<div>This is a div</div>

Text after div


MVC Razor Radio Button

This works for me.

@{ var dic = new Dictionary<string, string>() { { "checked", "" } }; }
@Html.RadioButtonFor(_ => _.BoolProperty, true, (@Model.BoolProperty)? dic: null) Yes
@Html.RadioButtonFor(_ => _.BoolProperty, false, ([email protected])? dic: null) No

Disable submit button when form invalid with AngularJS

We can create a simple directive and disable the button until all the mandatory fields are filled.

function() {
 return {
  restrict : 'A',
  link : function(scope, element, attrs) {
   var $el = $(element);
   var submitBtn = $el.find('button[type="submit"]');
   var _name =;
   scope.$watch(_name + '.$valid', function(val) {
    if (val) {
    } else {
     submitBtn.attr('disabled', 'disabled');

For More Info click here

Why is HttpClient BaseAddress not working?

It turns out that, out of the four possible permutations of including or excluding trailing or leading forward slashes on the BaseAddress and the relative URI passed to the GetAsync method -- or whichever other method of HttpClient -- only one permutation works. You must place a slash at the end of the BaseAddress, and you must not place a slash at the beginning of your relative URI, as in the following example.

using (var handler = new HttpClientHandler())
using (var client = new HttpClient(handler))
    client.BaseAddress = new Uri("");
    var response = await client.GetAsync("resource/7");

Even though I answered my own question, I figured I'd contribute the solution here since, again, this unfriendly behavior is undocumented. My colleague and I spent most of the day trying to fix a problem that was ultimately caused by this oddity of HttpClient.

How to change current working directory using a batch file

Specify /D to change the drive also.

CD /D %root%

No space left on device

Such difference between the output of du -sh and df -h may happen if some large file has been deleted, but is still opened by some process. Check with the command lsof | grep deleted to see which processes have opened descriptors to deleted files. You can restart the process and the space will be freed.

How do I redirect a user when a button is clicked?

Or, if none of the above works then you can use following approach as it worked for me.

Imagine this is your button

<button class="btn" onclick="NavigateToPdf(${Id});"></button>

I got the value for ${Id} filled using jquery templates. You can use whatever suits your requirement. In the following function, I am setting window.location.href equal to controller name then action name and then finally parameter. I am able to successfully navigate.

function NavigateToPdf(id) {
    window.location.href = "Link/Pdf/" + id;

I hope it helps.

What does void* mean and how to use it?

A pointer to void is a "generic" pointer type. A void * can be converted to any other pointer type without an explicit cast. You cannot dereference a void * or do pointer arithmetic with it; you must convert it to a pointer to a complete data type first.

void * is often used in places where you need to be able to work with different pointer types in the same code. One commonly cited example is the library function qsort:

void qsort(void *base, size_t nmemb, size_t size, 
           int (*compar)(const void *, const void *));

base is the address of an array, nmemb is the number of elements in the array, size is the size of each element, and compar is a pointer to a function that compares two elements of the array. It gets called like so:

int iArr[10];
double dArr[30];
long lArr[50];
qsort(iArr, sizeof iArr/sizeof iArr[0], sizeof iArr[0], compareInt);
qsort(dArr, sizeof dArr/sizeof dArr[0], sizeof dArr[0], compareDouble);
qsort(lArr, sizeof lArr/sizeof lArr[0], sizeof lArr[0], compareLong);

The array expressions iArr, dArr, and lArr are implicitly converted from array types to pointer types in the function call, and each is implicitly converted from "pointer to int/double/long" to "pointer to void".

The comparison functions would look something like:

int compareInt(const void *lhs, const void *rhs)
  const int *x = lhs;  // convert void * to int * by assignment
  const int *y = rhs;

  if (*x > *y) return 1;
  if (*x == *y) return 0;
  return -1;

By accepting void *, qsort can work with arrays of any type.

The disadvantage of using void * is that you throw type safety out the window and into oncoming traffic. There's nothing to protect you from using the wrong comparison routine:

qsort(dArr, sizeof dArr/sizeof dArr[0], sizeof dArr[0], compareInt);

compareInt is expecting its arguments to be pointing to ints, but is actually working with doubles. There's no way to catch this problem at compile time; you'll just wind up with a missorted array.

How to calculate Average Waiting Time and average Turn-around time in SJF Scheduling?

The Gantt charts given by Hifzan and Raja are for FCFS algorithms.

With an SJF algorithm, processes can be interrupted. That is, every process doesn't necessarily execute straight through their given burst time.



P3 arrives at 1ms, then is interrupted by P2 and P4 since they both have smaller burst times, and then P3 resumes. P5 starts executing next, then is interrupted by P1 since P1's burst time is smaller than P5's. You must note the arrival times and be careful. These problems can be trickier than how they appear at-first-glance.

EDIT: This applies only to Preemptive SJF algorithms. A plain SJF algorithm is non-preemptive, meaning it does not interrupt a process.

Difference between two dates in MySQL

SELECT TIMESTAMPDIFF(SECOND,'2018-01-19 14:17:15','2018-01-20 14:17:15');

Second approach

SELECT ( DATEDIFF('1993-02-20','1993-02-19')*( 24*60*60) )AS 'seccond';

CURRENT_TIME() --this will return current Date
DATEDIFF('','') --this function will return  DAYS and in 1 day there are 24hh 60mm 60sec

How to crop(cut) text files based on starting and ending line-numbers in cygwin?

If you are interested only in the last X lines, you can use the "tail" command like this.

$ tail -n XXXXX yourlogfile.log >> mycroppedfile.txt

This will save the last XXXXX lines of your log file to a new file called "mycroppedfile.txt"

SHA512 vs. Blowfish and Bcrypt

Blowfish is not a hashing algorithm. It's an encryption algorithm. What that means is that you can encrypt something using blowfish, and then later on you can decrypt it back to plain text.

SHA512 is a hashing algorithm. That means that (in theory) once you hash the input you can't get the original input back again.

They're 2 different things, designed to be used for different tasks. There is no 'correct' answer to "is blowfish better than SHA512?" You might as well ask "are apples better than kangaroos?"

If you want to read some more on the topic here's some links:

ListView with Add and Delete Buttons in each Row in android

public class UserCustomAdapter extends ArrayAdapter<User> {
 Context context;
 int layoutResourceId;
 ArrayList<User> data = new ArrayList<User>();

 public UserCustomAdapter(Context context, int layoutResourceId,
   ArrayList<User> data) {
  super(context, layoutResourceId, data);
  this.layoutResourceId = layoutResourceId;
  this.context = context; = data;

 public View getView(int position, View convertView, ViewGroup parent) {
  View row = convertView;
  UserHolder holder = null;

  if (row == null) {
   LayoutInflater inflater = ((Activity) context).getLayoutInflater();
   row = inflater.inflate(layoutResourceId, parent, false);
   holder = new UserHolder();
   holder.textName = (TextView) row.findViewById(;
   holder.textAddress = (TextView) row.findViewById(;
   holder.textLocation = (TextView) row.findViewById(;
   holder.btnEdit = (Button) row.findViewById(;
   holder.btnDelete = (Button) row.findViewById(;
  } else {
   holder = (UserHolder) row.getTag();
  User user = data.get(position);
  holder.btnEdit.setOnClickListener(new OnClickListener() {

   public void onClick(View v) {
    // TODO Auto-generated method stub
    Log.i("Edit Button Clicked", "**********");
    Toast.makeText(context, "Edit button Clicked",
  holder.btnDelete.setOnClickListener(new OnClickListener() {

   public void onClick(View v) {
    // TODO Auto-generated method stub
    Log.i("Delete Button Clicked", "**********");
    Toast.makeText(context, "Delete button Clicked",
  return row;


 static class UserHolder {
  TextView textName;
  TextView textAddress;
  TextView textLocation;
  Button btnEdit;
  Button btnDelete;

Hey Please have a look here-

I have same answer here on my blog ..

What are queues in jQuery?

The uses of jQuery .queue() and .dequeue()

Queues in jQuery are used for animations. You can use them for any purpose you like. They are an array of functions stored on a per element basis, using They are First-In-First-Out (FIFO). You can add a function to the queue by calling .queue(), and you remove (by calling) the functions using .dequeue().

To understand the internal jQuery queue functions, reading the source and looking at examples helps me out tremendously. One of the best examples of a queue function I've seen is .delay():

$.fn.delay = function( time, type ) {
  time = jQuery.fx ? jQuery.fx.speeds[time] || time : time;
  type = type || "fx";

  return this.queue( type, function() {
    var elem = this;
    setTimeout(function() {
      jQuery.dequeue( elem, type );
    }, time );

The default queue - fx

The default queue in jQuery is fx. The default queue has some special properties that are not shared with other queues.

  1. Auto Start: When calling $(elem).queue(function(){}); the fx queue will automatically dequeue the next function and run it if the queue hasn't started.
  2. 'inprogress' sentinel: Whenever you dequeue() a function from the fx queue, it will unshift() (push into the first location of the array) the string "inprogress" - which flags that the queue is currently being run.
  3. It's the default! The fx queue is used by .animate() and all functions that call it by default.

NOTE: If you are using a custom queue, you must manually .dequeue() the functions, they will not auto start!

Retrieving/Setting the queue

You can retrieve a reference to a jQuery queue by calling .queue() without a function argument. You can use the method if you want to see how many items are in the queue. You can use push, pop, unshift, shift to manipulate the queue in place. You can replace the entire queue by passing an array to the .queue() function.

Quick Examples:

// lets assume $elem is a jQuery object that points to some element we are animating.
var queue = $elem.queue();
// remove the last function from the animation queue.
var lastFunc = queue.pop(); 
// insert it at the beginning:    
// replace queue with the first three items in the queue

An animation (fx) queue example:

Run example on jsFiddle

$(function() {
    // lets do something with google maps:
    var $map = $("#map_canvas");
    var myLatlng = new google.maps.LatLng(-34.397, 150.644);
    var myOptions = {zoom: 8, center: myLatlng, mapTypeId: google.maps.MapTypeId.ROADMAP};
    var geocoder = new google.maps.Geocoder();
    var map = new google.maps.Map($map[0], myOptions);
    var resized = function() {
        // simple animation callback - let maps know we resized
        google.maps.event.trigger(map, 'resize');

    // wait 2 seconds
    // resize the div:
        width: 250,
        height: 250,
        marginLeft: 250,
    }, resized);
    // geocode something
    $map.queue(function(next) {
        // find stackoverflow's whois address:
      geocoder.geocode({'address': '55 Broadway New York NY 10006'},handleResponse);

      function handleResponse(results, status) {
          if (status == google.maps.GeocoderStatus.OK) {
              var location = results[0].geometry.location;
              new google.maps.Marker({ map: map, position: location });
          // geocoder result returned, continue with animations:
    // after we find stack overflow, wait 3 more seconds
    // and resize the map again
        width: 500,
        height: 500,
        marginTop: 0
    }, resized);

Another custom queue example

Run example on jsFiddle

var theQueue = $({}); // jQuery on an empty object - a perfect queue holder

$.each([1,2,3],function(i, num) {
  // lets add some really simple functions to a queue:
  theQueue.queue('alerts', function(next) { 
    // show something, and if they hit "yes", run the next function.
    if (confirm('index:'+i+' = '+num+'\nRun the next function?')) {

// create a button to run the queue:
$("<button>", {
  text: 'Run Queue', 
  click: function() { 

// create a button to show the length:
$("<button>", {
  text: 'Show Length', 
  click: function() { 

Queueing Ajax Calls:

I developed an $.ajaxQueue() plugin that uses the $.Deferred, .queue(), and $.ajax() to also pass back a promise that is resolved when the request completes. Another version of $.ajaxQueue that still works in 1.4 is posted on my answer to Sequencing Ajax Requests

* jQuery.ajaxQueue - A queue for ajax requests
* (c) 2011 Corey Frang
* Dual licensed under the MIT and GPL licenses.
* Requires jQuery 1.5+
(function($) {

// jQuery on an empty object, we are going to use this as our Queue
var ajaxQueue = $({});

$.ajaxQueue = function( ajaxOpts ) {
    var jqXHR,
        dfd = $.Deferred(),
        promise = dfd.promise();

    // queue our ajax request
    ajaxQueue.queue( doRequest );

    // add the abort method
    promise.abort = function( statusText ) {

        // proxy abort to the jqXHR if it is active
        if ( jqXHR ) {
            return jqXHR.abort( statusText );

        // if there wasn't already a jqXHR we need to remove from queue
        var queue = ajaxQueue.queue(),
            index = $.inArray( doRequest, queue );

        if ( index > -1 ) {
            queue.splice( index, 1 );

        // and then reject the deferred
        dfd.rejectWith( ajaxOpts.context || ajaxOpts,
            [ promise, statusText, "" ] );

        return promise;

    // run the actual query
    function doRequest( next ) {
        jqXHR = $.ajax( ajaxOpts )
            .done( dfd.resolve )
            .fail( dfd.reject )
            .then( next, next );

    return promise;


I have now added this as an article on, there are other great articles on that site about queues, go look.

Setting the character encoding in form submit for Internet Explorer

I am pretty sure it won't be possible with older versions of IE. Before the accept-charset attribute was devised, there was no way for form elements to specify which character encoding they accepted, and the best that browsers could do is assume the encoding of the page the form is in will do.

It is a bit sad that you need to know which encoding was used -- nowadays we would expect our web frameworks to take care of such details invisibly and expose the text data to the application as Unicode strings, already decoded...

Making a DateTime field in a database automatic?

You need to set the "default value" for the date field to getdate(). Any records inserted into the table will automatically have the insertion date as their value for this field.

The location of the "default value" property is dependent on the version of SQL Server Express you are running, but it should be visible if you select the date field of your table when editing the table.

Git error on commit after merge - fatal: cannot do a partial commit during a merge

git commit -am 'Conflicts resolved'

This worked for me. You can try this also.

Generate random number between two numbers in JavaScript

I was searching random number generator written in TypeScript and I have written this after reading all of the answers, hope It would work for TypeScript coders.

    Rand(min: number, max: number): number {
        return (Math.random() * (max - min + 1) | 0) + min;

How to truncate milliseconds off of a .NET DateTime

DateTime d = DateTime.Now;
d = d.AddMilliseconds(-d.Millisecond);

Update a column value, replacing part of a string

UPDATE yourtable
SET url = REPLACE(url, '', '')
WHERE url LIKE ('');

relevant docs:

How to animate a View with Translate Animation in Android

In order to move a View anywhere on the screen, I would recommend placing it in a full screen layout. By doing so, you won't have to worry about clippings or relative coordinates.

You can try this sample code:


<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android=""
    android:orientation="vertical" android:id="@+id/rootLayout">

        android:text="MOVE" android:layout_centerHorizontal="true"/>

        android:src="@drawable/ic_launcher" android:layout_marginLeft="10dip"/>
        android:src="@drawable/ic_launcher" android:layout_centerVertical="true" android:layout_alignParentRight="true"/>
        android:src="@drawable/ic_launcher" android:layout_marginLeft="60dip" android:layout_alignParentBottom="true" android:layout_marginBottom="100dip"/>

        android:orientation="vertical" android:clipChildren="false" android:clipToPadding="false">

            android:src="@drawable/ic_launcher" android:layout_marginLeft="60dip" android:layout_marginTop="150dip"/>


Your activity

public void onCreate(Bundle savedInstanceState) {

    ((Button) findViewById( )).setOnClickListener( new OnClickListener()
        public void onClick(View v)
            ImageView img = (ImageView) findViewById( );              
            moveViewToScreenCenter( img );
            img = (ImageView) findViewById( );
            moveViewToScreenCenter( img );
            img = (ImageView) findViewById( );                
            moveViewToScreenCenter( img );
            img = (ImageView) findViewById( );
            moveViewToScreenCenter( img );

private void moveViewToScreenCenter( View view )
    RelativeLayout root = (RelativeLayout) findViewById( );
    DisplayMetrics dm = new DisplayMetrics();
    this.getWindowManager().getDefaultDisplay().getMetrics( dm );
    int statusBarOffset = dm.heightPixels - root.getMeasuredHeight();

    int originalPos[] = new int[2];
    view.getLocationOnScreen( originalPos );

    int xDest = dm.widthPixels/2;
    xDest -= (view.getMeasuredWidth()/2);
    int yDest = dm.heightPixels/2 - (view.getMeasuredHeight()/2) - statusBarOffset;

    TranslateAnimation anim = new TranslateAnimation( 0, xDest - originalPos[0] , 0, yDest - originalPos[1] );
    anim.setFillAfter( true );

The method moveViewToScreenCenter gets the View's absolute coordinates and calculates how much distance has to move from its current position to reach the center of the screen. The statusBarOffset variable measures the status bar height.

I hope you can keep going with this example. Remember that after the animation your view's position is still the initial one. If you tap the MOVE button again and again the same movement will repeat. If you want to change your view's position do it after the animation is finished.

How can I use tabs for indentation in IntelliJ IDEA?

IntelliJ IDEA 15

Only for the current file

You have the following options:

  1. Ctrl + Shift + A > write "tabs" > double click on "To Tabs"

    To Tabs

    If you want to convert tabs to spaces, you can write "spaces", then choose "To Spaces".

  2. Edit > Convert Indents > To Tabs

    To convert tabs to spaces, you can chose "To Spaces" from the same place.

For all files

The paths in the other answers were changed a little:

  • File > Settings... > Editor > Code Style > Java > Tabs and Indents > Use tab character Use tab character
  • File > Other Settings > Default Settings... > Editor > Code Style > Java > Tabs and Indents > Use tab character
  • File > Settings... > Editor > Code Style > Detect and use existing file indents for editing
  • File > Other Settings > Default Settings... > Editor > Code Style > Detect and use existing file indents for editing

It seems that it doesn't matter if you check/uncheck the box from Settings... or from Other Settings > Default Settings..., because the change from one window will be available in the other window.

The changes above will be applied for the new files, but if you want to change spaces to tabs in an existing file, then you should format the file by pressing Ctrl + Alt + L.

What does <> mean?

It means not equal to. The same as != seen in C style languages, as well as actionscript.

Winforms TableLayoutPanel adding rows programmatically

This works perfectly for adding rows and controls in a TableLayoutPanel.

Define a blank Tablelayoutpanel with 3 columns in the design page

    Dim TableLayoutPanel3 As New TableLayoutPanel()

    TableLayoutPanel3.Name = "TableLayoutPanel3"

    TableLayoutPanel3.Location = New System.Drawing.Point(32, 287)

    TableLayoutPanel3.AutoSize = True

    TableLayoutPanel3.Size = New System.Drawing.Size(620, 20)

    TableLayoutPanel3.ColumnCount = 3

    TableLayoutPanel3.CellBorderStyle = TableLayoutPanelCellBorderStyle.Single

    TableLayoutPanel3.BackColor = System.Drawing.Color.Transparent

    TableLayoutPanel3.ColumnStyles.Add(New ColumnStyle(SizeType.Percent, 26.34146!))

    TableLayoutPanel3.ColumnStyles.Add(New ColumnStyle(SizeType.Percent, 73.65854!))

    TableLayoutPanel3.ColumnStyles.Add(New ColumnStyle(SizeType.Absolute, 85.0!))


Create a button btnAddRow to add rows on each click

     Private Sub btnAddRow_Click(sender As System.Object, e As System.EventArgs) Handles btnAddRow.Click

          TableLayoutPanel3.GrowStyle = TableLayoutPanelGrowStyle.AddRows

          TableLayoutPanel3.RowStyles.Add(New RowStyle(SizeType.Absolute, 20))


          TableLayoutPanel3.RowCount += 1

          Dim tb1 As New TextBox()

          Dim tb2 As New TextBox()

          Dim tb3 As New TextBox()

          TableLayoutPanel3.Controls.Add(tb1 , 0, TableLayoutPanel3.RowCount - 1)

          TableLayoutPanel3.Controls.Add(tb2, 1, TableLayoutPanel3.RowCount - 1)

          TableLayoutPanel3.Controls.Add(tb3, 2, TableLayoutPanel3.RowCount - 1)



 End Sub

How to get active user's UserDetails

Starting with Spring Security version 3.2, the custom functionality that has been implemented by some of the older answers, exists out of the box in the form of the @AuthenticationPrincipal annotation that is backed by AuthenticationPrincipalArgumentResolver.

An simple example of it's use is:

public class MyController {
   public String show(@AuthenticationPrincipal CustomUser customUser) {
        // do something with CustomUser
       return "view";

CustomUser needs to be assignable from authentication.getPrincipal()

Here are the corresponding Javadocs of AuthenticationPrincipal and AuthenticationPrincipalArgumentResolver

How to install PHP intl extension in Ubuntu 14.04

you could search with aptitude search intl after you can choose the right one, for example sudo aptitude install php-intl and finally sudo service apache2 restart

good Luck!

one line if statement in php

Something like this?

($var > 2 ? echo "greater" : echo "smaller")

How to check whether a Button is clicked by using JavaScript

Just hook up the onclick event:

<input id="button" type="submit" name="button" value="enter" onclick="myFunction();"/>

remove duplicates from sql union

Others have already answered your direct question, but perhaps you could simplify the query to eliminate the question (or have I missed something, and a query like the following will really produce substantially different results?):

select * 
    from calls c join users u
        on c.assigned_to = u.user_id 
        or c.requestor_id = u.user_id
    where u.dept = 4

What's the difference between emulation and simulation?

I do not know whether this is the general opinion, but I've always differentiated the two by what they are used for. An emulator is used if you actually want to use the emulated machine for its output. A simulator, on the other hand, is for when you want to study the simulated machine or test its behaviour.

For example, if you want to write some state machine logic in your application (which is running on a general purpose CPU), you write a small state machine emulator. If you want to study the efficiency or viability of a state machine for a particular problem, you write a simulator.

How to check if an option is selected?

You can get the selected option this way:

$('#mySelectBox option:selected')...


But if you want to iterate all the options, do it with this.selected instead of this.isChecked which doesn't exist:

$('#mySelectBox option').each(function() {
    if (this.selected)
       alert('this option is selected');
       alert('this is not');



You got plenty of answers suggesting you to use this:

$(this).is(':selected') well, it can be done a lot faster and easier with this.selected so why should you use it and not the native DOM element method?!

Read Know Your DOM Properties and Functions in the jQuery tag info

forward declaration of a struct in C?

A struct (without a typedef) often needs to (or should) be with the keyword struct when used.

struct A;                      // forward declaration
void function( struct A *a );  // using the 'incomplete' type only as pointer

If you typedef your struct you can leave out the struct keyword.

typedef struct A A;          // forward declaration *and* typedef
void function( A *a );

Note that it is legal to reuse the struct name

Try changing the forward declaration to this in your code:

typedef struct context context;

It might be more readable to do add a suffix to indicate struct name and type name:

typedef struct context_s context_t;

What is the Record type in typescript?

A Record lets you create a new type from a Union. The values in the Union are used as attributes of the new type.

For example, say I have a Union like this:

type CatNames = "miffy" | "boris" | "mordred";

Now I want to create an object that contains information about all the cats, I can create a new type using the values in the CatName Union as keys.

type CatList = Record<CatNames, {age: number}>

If I want to satisfy this CatList, I must create an object like this:

const cats:CatList = {
  miffy: { age:99 },
  boris: { age:16 },
  mordred: { age:600 }

You get very strong type safety:

  • If I forget a cat, I get an error.
  • If I add a cat that's not allowed, I get an error.
  • If I later change CatNames, I get an error. This is especially useful because CatNames is likely imported from another file, and likely used in many places.

Real-world React example.

I used this recently to create a Status component. The component would receive a status prop, and then render an icon. I've simplified the code quite a lot here for illustrative purposes

I had a union like this:

type Statuses = "failed" | "complete";

I used this to create an object like this:

const icons: Record<
  { iconType: IconTypes; iconColor: IconColors }
> = {
  failed: {
    iconType: "warning",
    iconColor: "red"
  complete: {
    iconType: "check",
    iconColor: "green"

I could then render by destructuring an element from the object into props, like so:

const Status = ({status}) => <Icon {...icons[status]} />

If the Statuses union is later extended or changed, I know my Status component will fail to compile and I'll get an error that I can fix immediately. This allows me to add additional error states to the app.

Note that the actual app had dozens of error states that were referenced in multiple places, so this type safety was extremely useful.

TypeError: 'list' object cannot be interpreted as an integer

For me i was getting this error because i needed to put the arrays in paratheses. The error is a bit tricky in this case...

ie. concatenate((a, b)) is right

not concatenate(a, b)

hope that helps.

CSS3 transition events

If you simply want to detect only a single transition end, without using any JS framework here's a little convenient utility function:

function once = function(object,event,callback){
    var handle={};

    var eventNames=event.split(" ");

    var cbWrapper=function(){
            object.removeEventListener(e,cbWrapper, false );


            object.removeEventListener(e,cbWrapper, false );

    return handle;


var handler = once(document.querySelector('#myElement'), 'transitionend', function(){
   //do something

then if you wish to cancel at some point you can still do it with


It's good for other event usages as well :)

How do I sort an observable collection?

This simple extension worked beautifully for me. I just had to make sure that MyObject was IComparable. When the sort method is called on the observable collection of MyObjects, the CompareTo method on MyObject is called, which calls my Logical Sort method. While it doesn't have all the bells and whistles of the rest of the answers posted here, it's exactly what I needed.

static class Extensions
    public static void Sort<T>(this ObservableCollection<T> collection) where T : IComparable
        List<T> sorted = collection.OrderBy(x => x).ToList();
        for (int i = 0; i < sorted.Count(); i++)
            collection.Move(collection.IndexOf(sorted[i]), i);

public class MyObject: IComparable
    public int CompareTo(object o)
        MyObject a = this;
        MyObject b = (MyObject)o;
        return Utils.LogicalStringCompare(a.Title, b.Title);

    public string Title;

myCollection = new ObservableCollection<MyObject>();
//add stuff to collection

NuGet Packages are missing

Solution that works in my case - Visual Studio 2015 Enterprice, project .NET 4.6.1

  1. Upgrade to Update 3
  2. Install Web developer tools

Visual studio installation wizzard

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

It would be cleaner and less error-prone to use a function like the one below:

func empty(s string) bool {
    return len(strings.TrimSpace(s)) == 0

Does MS Access support "CASE WHEN" clause if connect with ODBC?

You could use IIF statement like in the next example:

   IIF(test_expression, value_if_true, value_if_false) AS FIELD_NAME

Convert comma separated string to array in PL/SQL

    v_str varchar2(100) := '1,2,3,4,6,7,8,9,0,';
    v_str1 varchar2(100); 
    v_comma_pos number := 0;    
    v_start_pos number := 1;
    v_comma_pos := instr(v_str,',',v_start_pos);   
    v_str1 := substr(v_str,v_start_pos,(v_comma_pos - v_start_pos)); 
    if  v_comma_pos = 0 then     
    v_str1 := substr(v_str,v_start_pos);  
    end if;    
    v_start_pos := v_comma_pos + 1;  
    if  v_comma_pos = 0 then    
    end if;       
    end loop; 

Recursively find all files newer than a given time

Given a unix timestamp (seconds since epoch) of 1494500000, do:

find . -type f -newermt "$(date '+%Y-%m-%d %H:%M:%S' -d @1494500000)"

To grep those files for "foo":

find . -type f -newermt "$(date '+%Y-%m-%d %H:%M:%S' -d @1494500000)" -exec grep -H 'foo' '{}' \;

Do Facebook Oauth 2.0 Access Tokens Expire?

Note that Facebook is now deprecating the offline_access permission in favor of tokens for which you can request an "upgrade" to the expiry. I'm just now dealing with this, myself, so I don't have much more to say, but this doc may help:

jQuery If DIV Doesn't Have Class "x"

Use the "not" selector.

For example, instead of:




Get the height and width of the browser viewport without scrollbars using jquery?

Here is a generic JS which should work in most browsers (FF, Cr, IE6+):

var viewportHeight;
var viewportWidth;
if (document.compatMode === 'BackCompat') {
    viewportHeight = document.body.clientHeight;
    viewportWidth = document.body.clientWidth;
} else {
    viewportHeight = document.documentElement.clientHeight;
    viewportWidth = document.documentElement.clientWidth;

New lines (\r\n) are not working in email body

You need to use a <br> because your Content-Type is text/html.

It works without the Content-Type header because then your e-mail will be interpreted as plain text. If you really want to use \n you should use Content-Type: text/plain but then you'll lose any markup.

Also check out similar question here.

CKEditor, Image Upload (filebrowserUploadUrl)

May be it's too late. Your code is correct so please check again your url in filebrowserUploadUrl

CKEDITOR.replace( 'editor1', {
    filebrowserUploadUrl: "upload/upload.php" 
} );

And the Upload.php file

if (file_exists("images/" . $_FILES["upload"]["name"]))
 echo $_FILES["upload"]["name"] . " already exists. ";
 "images/" . $_FILES["upload"]["name"]);
 echo "Stored in: " . "images/" . $_FILES["upload"]["name"];

jQuery event to trigger action when a div is made visible

There is a jQuery plugin available for watching change in DOM attributes,

The plugin wraps All you need do is bind MutationObserver

You can then use it to watch the div using:

$("#selector").watch('css', function() {
    console.log("Visibility: " + == 'none'?'hidden':'shown'));
    //or any random events

How to force composer to reinstall a library?

First execute composer clearcache

Then clear your vendors folder

rm -rf vendor/*

or better yet just remove the specific module which makes problems to avoid having to download all over again.

How do I set headers using python's urllib?

For both Python 3 and Python 2, this works:

    from urllib.request import Request, urlopen  # Python 3
except ImportError:
    from urllib2 import Request, urlopen  # Python 2

req = Request('')
req.add_header('apikey', 'xxx')
content = urlopen(req).read()


Paused in debugger in chrome?

Its really a bad experience. if the above answer didn't work for you try this.

Click on the Settings icon and then click on the Restore defaults and reload button.

Press 'F8' until its became normal.

Happy coding!!

Why functional languages?

I have a hard time envisioning a purely functional language being the common language of the day, the reasons for which I won't get in to (because they're flame fodder). That being said, programming in a functional way can provide benefits no matter the language (if it allows such). For me, it's the ability to test my code much easier. I work with databases a lot... I tend to:

  1. write a function that takes data, manipulates it, and returns data
  2. write a dead simple wrapper that calls the database and then returns the result of passing that data through my function

Doing so allows me to write unit tests for my manipulation function, without the need to create mocks and the like.

I do think purely functional languages are very interesting... I just think it's what we can learn from them that matters to me, not what we can do with them.

Is there a way to detach matplotlib plots so that the computation can continue?

It is better to always check with the library you are using if it supports usage in a non-blocking way.

But if you want a more generic solution, or if there is no other way, you can run anything that blocks in a separated process by using the multprocessing module included in python. Computation will continue:

from multiprocessing import Process
from matplotlib.pyplot import plot, show

def plot_graph(*args):
    for data in args:

p = Process(target=plot_graph, args=([1, 2, 3],))

print 'yay'
print 'computation continues...'
print 'that rocks.'

print 'Now lets wait for the graph be closed to continue...:'

That has the overhead of launching a new process, and is sometimes harder to debug on complex scenarios, so I'd prefer the other solution (using matplotlib's nonblocking API calls)

Could not create the Java virtual machine

Just be careful. You will get this message if you try to enter a command that doesn't exist like this

/usr/bin/java -v

How to add constraints programmatically using Swift

Try this elegant UIView extension for constraints. You can do constraints easy as:

 - firstView.coverWholeSuperview()
 - firstView.constraints(size: CGSize(width: 44, height: 44), centerX: view.centerXAnchor, centerY: view.centerXAnchor)
 - firstView.constraints(top: view.topAnchor, 
                         leading: secondView.leadingAnchor, 
                         bottom: view.bottomAnchor, 
                         trailing: secondView.trailingAnchor, 
                         padding: UIEdgeInsets(top: 12, left: 12, bottom: 12, right: 12))

Here is extension, just copy it to your project.

extension UIView {
    /// Attaches all sides of the receiver to its parent view
    func coverWholeSuperview(margin: CGFloat = 0.0) {
        let view = superview
        layoutAttachTop(to: view, margin: margin)
        layoutAttachBottom(to: view, margin: margin)
        layoutAttachLeading(to: view, margin: margin)
        layoutAttachTrailing(to: view, margin: margin)


    /// Attaches the top of the current view to the given view's top if it's a superview of the current view
    /// or to it's bottom if it's not (assuming this is then a sibling view).
    func layoutAttachTop(to: UIView? = nil, margin: CGFloat = 0.0) -> NSLayoutConstraint {

        let view: UIView? = to ?? superview
        let isSuperview = view == superview
        let constraint = NSLayoutConstraint(item: self, attribute: .top, relatedBy: .equal,
                                            toItem: view, attribute: isSuperview ? .top : .bottom, multiplier: 1.0,
                                            constant: margin)

        return constraint

    /// Attaches the bottom of the current view to the given view
    func layoutAttachBottom(to: UIView? = nil, margin: CGFloat = 0.0, priority: UILayoutPriority? = nil) -> NSLayoutConstraint {

        let view: UIView? = to ?? superview
        let isSuperview = (view == superview) || false
        let constraint = NSLayoutConstraint(item: self, attribute: .bottom, relatedBy: .equal,
                                            toItem: view, attribute: isSuperview ? .bottom : .top, multiplier: 1.0,
                                            constant: -margin)
        if let priority = priority {
            constraint.priority = priority

        return constraint

    /// Attaches the leading edge of the current view to the given view
    func layoutAttachLeading(to: UIView? = nil, margin: CGFloat = 0.0) -> NSLayoutConstraint {

        let view: UIView? = to ?? superview
        let isSuperview = (view == superview) || false
        let constraint = NSLayoutConstraint(item: self, attribute: .leading, relatedBy: .equal,
                                            toItem: view, attribute: isSuperview ? .leading : .trailing, multiplier: 1.0,
                                            constant: margin)

        return constraint

    /// Attaches the trailing edge of the current view to the given view
    func layoutAttachTrailing(to: UIView? = nil, margin: CGFloat = 0.0, priority: UILayoutPriority? = nil) -> NSLayoutConstraint {

        let view: UIView? = to ?? superview
        let isSuperview = (view == superview) || false
        let constraint = NSLayoutConstraint(item: self, attribute: .trailing, relatedBy: .equal,
                                            toItem: view, attribute: isSuperview ? .trailing : .leading, multiplier: 1.0,
                                            constant: -margin)
        if let priority = priority {
            constraint.priority = priority

        return constraint

    // For anchoring View
    struct AnchoredConstraints {
        var top, leading, bottom, trailing, width, height, centerX, centerY: NSLayoutConstraint?

    func constraints(top: NSLayoutYAxisAnchor? = nil, leading: NSLayoutXAxisAnchor? = nil, bottom: NSLayoutYAxisAnchor? = nil,
                trailing: NSLayoutXAxisAnchor? = nil, padding: UIEdgeInsets = .zero, size: CGSize = .zero,
                centerX: NSLayoutXAxisAnchor? = nil, centerY: NSLayoutYAxisAnchor? = nil,
                centerXOffset: CGFloat = 0, centerYOffset: CGFloat = 0) -> AnchoredConstraints {

        translatesAutoresizingMaskIntoConstraints = false
        var anchoredConstraints = AnchoredConstraints()

        if let top = top {
   = topAnchor.constraint(equalTo: top, constant:

        if let leading = leading {
            anchoredConstraints.leading = leadingAnchor.constraint(equalTo: leading, constant: padding.left)

        if let bottom = bottom {
            anchoredConstraints.bottom = bottomAnchor.constraint(equalTo: bottom, constant: -padding.bottom)

        if let trailing = trailing {
            anchoredConstraints.trailing = trailingAnchor.constraint(equalTo: trailing, constant: -padding.right)

        if size.width != 0 {
            anchoredConstraints.width = widthAnchor.constraint(equalToConstant: size.width)

        if size.height != 0 {
            anchoredConstraints.height = heightAnchor.constraint(equalToConstant: size.height)

        if let centerX = centerX {
            anchoredConstraints.centerX = centerXAnchor.constraint(equalTo: centerX, constant: centerXOffset)

        if let centerY = centerY {
            anchoredConstraints.centerY = centerYAnchor.constraint(equalTo: centerY, constant: centerYOffset)

        [, anchoredConstraints.leading, anchoredConstraints.bottom,
         anchoredConstraints.trailing, anchoredConstraints.width,
         anchoredConstraints.height, anchoredConstraints.centerX,
         anchoredConstraints.centerY].forEach { $0?.isActive = true }

        return anchoredConstraints

How might I extract the property values of a JavaScript object into an array?

This one worked for me

var dataArray = Object.keys(dataObject).map(function(k){return dataObject[k]});

What could cause java.lang.reflect.InvocationTargetException?

I was facing the same problem. I used e.getCause().getCause() then I found that it was because of wrong parameters I was passing. There was nullPointerException in fetching the value of one of the parameters. Hope this will help you.

How to give a pattern for new line in grep?

Thanks to @jarno I know about the -z option and I found out that when using GNU grep with the -P option, matching against \n is possible. :)


grep -zoP 'foo\n\K.*'<<<$'foo\nbar'

Prints bar

HTML5 video (mp4 and ogv) problems in Safari and Firefox - but Chrome is all good

Incidentally, .ogv files are video, so "video/ogg", .ogg files are Vorbis audio, so "audio/ogg" and .oga files are general Ogg audio, so also "audio/ogg". Checked in Firefox and work. "application/ogg" is deprecated for all audio or video uses. See

Add my custom http header to Spring RestTemplate request / extend RestTemplate

If the goal is to have a reusable RestTemplate which is in general useful for attaching the same header to a series of similar request a org.springframework.boot.web.client.RestTemplateCustomizer parameter can be used with a RestTemplateBuilder:

 String accessToken= "<the oauth 2 token>";
 RestTemplate restTemplate = new RestTemplateBuilder(rt-> rt.getInterceptors().add((request, body, execution) -> {
        request.getHeaders().add("Authorization", "Bearer "+accessToken);
        return execution.execute(request, body);

iOS change navigation bar title font and color

I had one problem because when I tried to change my NavigationItem title programmatically i was not able to find my family font (tried many things but impossible to make it run correctly) so I found one workaround very nice and easy in storyboard.

  1. Firstly you add under Navigation Item one view in middle and don't forget to set backGroundColor to clear color to have the same color of navBar:

enter image description here

  1. Then you add one Label which you can edit (set color of text, font, size...) in this view
  2. You add constraints to label (Top = 0, Bottom = 0, Trailing = 0 and Leading = 0) to View and center text of label

Finally you should have something like that in document outline:

enter image description here

And something like that in your ViewController:

enter image description here

Hope it can help.

Clicking the back button twice to exit an activity

This also helps when you have previous stack activity stored in stack.

I have modified Sudheesh's answer

boolean doubleBackToExitPressedOnce = false;

public void onBackPressed() {
    if (doubleBackToExitPressedOnce) {

  Intent intent = new Intent(Intent.ACTION_MAIN);
                    intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);//***Change Here***

    this.doubleBackToExitPressedOnce = true;
    Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();

    new Handler().postDelayed(new Runnable() {

        public void run() {
    }, 2000);

Subtract 1 day with PHP

Answear taken from Php manual strtotime function comments :

echo date( "Y-m-d", strtotime( "2009-01-31 -1 day"));


$date = "2009-01-31";
echo date( "Y-m-d", strtotime( $date . "-1 day"));

Refused to load the script because it violates the following Content Security Policy directive

The probable reason why you get this error is likely because you've added the /build folder to your .gitignore file or generally haven't checked it into Git.

So when you Git push Heroku master, the build folder you're referencing don't get pushed to Heroku. And that's why it shows this error.

That's the reason it works properly locally, but not when you deployed to Heroku.

how to parse xml to java object?

One thing that is really important to understand considering you have an XML file as :

<customer id="100">

I am sorry to inform you but :

public void setAge(int age) {
    this.age = age;

will not help you, as it tries to look for "age" instead of "Age" element name from the XML.

I encourage you to manually specify the element name matching the one in the XML file :

public void setAge(int age) {
    this.age = age;

And if you have for example :

@XmlAccessorType (XmlAccessType.FIELD)
public class Customer {

It means it will use java beans by default, and at this time if you specify that you must not set another


annotation above a setter method for an element <NAME>..</NAME> it will fail saying that there cannot be two elements on one single variables.

I hope that it helps.

Convert integer to binary in C#

using System;

class Program 
    static void Main(string[] args) {

        try {

            int i = (int) Convert.ToInt64(args[0]);
            Console.WriteLine("\n{0} converted to Binary is {1}\n", i, ToBinary(i));

        } catch(Exception e) {
            Console.WriteLine("\n{0}\n", e.Message);

    public static string ToBinary(Int64 Decimal) {
        // Declare a few variables we're going to need
        Int64 BinaryHolder;
        char[] BinaryArray;
        string BinaryResult = "";

        while (Decimal > 0) {
            BinaryHolder = Decimal % 2;
            BinaryResult += BinaryHolder;
            Decimal = Decimal / 2;

        BinaryArray = BinaryResult.ToCharArray();
        BinaryResult = new string(BinaryArray);

        return BinaryResult;

Drop all data in a pandas dataframe

You need to pass the labels to be dropped.

df.drop(df.index, inplace=True)

By default, it operates on axis=0.

You can achieve the same with


which is much more efficient.

How to disable Google Chrome auto update?

For latest versions, use following steps:

  1. Go to "msconfig" from Win+R
  2. Go to Service tab
  3. Uncheck both "Google Update Service" boxes.
  4. Click OK and Restart computer to save changes.

git: updates were rejected because the remote contains work that you do not have locally

I had the same problem. It happened that I have created .Readme file on the repository without pulling it first.

You may want to delete .Readme file or pull it before pushing.

No tests found with test runner 'JUnit 4'

This happened to me as well. I tried restarting Eclipse and also prefixed my test-methods with tests. Neither worked.

The following step worked: Change all your test methods present in @BeforeClass and @AfterClass to static methods.

i.e. if you have your test method in the below format:

public void testBeforeClass(){

then change it to:

public static void testBeforeClass(){

This worked for me.

Angular HTML binding

You can apply multiple pipe for style, link and HTML as following in .html

<div [innerHTML]="announcementContent | safeUrl| safeHtml">

and in .ts pipe for 'URL' sanitizer

import { Component, Pipe, PipeTransform } from '@angular/core';
import { DomSanitizer } from '@angular/platform-browser';

@Pipe({ name: 'safeUrl' })
export class SafeUrlPipe implements PipeTransform {
    constructor(private sanitizer: DomSanitizer) {}
    transform(url) {
        return this.sanitizer.bypassSecurityTrustResourceUrl(url);

pipe for 'HTML' sanitizer

import { Component, Pipe, PipeTransform } from '@angular/core';
import { DomSanitizer } from '@angular/platform-browser';

    name: 'safeHtml'
export class SafeHtmlPipe implements PipeTransform {
    constructor(private sanitized: DomSanitizer) {}
    transform(value) {
        return this.sanitized.bypassSecurityTrustHtml(value);

this will apply both without disturbing any style and link click event

Run local java applet in browser (chrome/firefox) "Your security settings have blocked a local application from running"

This problem happens when older versions of java still on your system disrupt any new versions installed. To stop this problem you need to first remove all java software using - Control Panel + Remove Programs + then uninstall java. (At this stage, I recommend cleaning out your registry using CCleaner using their Registry option or similar program to ensure a clean sweep then reboot) After rebooting reinstall the most recent version of java and all will be well. -LINK TO CCLEANER

Creating multiple objects with different names in a loop to store in an array list

ArrayList<Customer> custArr = new ArrayList<Customer>();
while(youWantToContinue) {
    //get a customerName
    //get an amount
    custArr.add(new Customer(customerName, amount);

For this to work... you'll have to fix your constructor...

Assuming your Customer class has variables called name and sale, your constructor should look like this:

public Customer(String customerName, double amount) {
    name = customerName;
    sale = amount;

Change your Store class to something more like this:

public class Store {

    private ArrayList<Customer> custArr;

    public new Store() {
        custArr = new ArrayList<Customer>();

    public void addSale(String customerName, double amount) {
        custArr.add(new Customer(customerName, amount));

    public Customer getSaleAtIndex(int index) {
        return custArr.get(index);

    //or if you want the entire ArrayList:
    public ArrayList getCustArr() {
        return custArr;

How to read data when some numbers contain commas as thousand separator?

"Preprocess" in R:

lines <- "www, rrr, 1,234, ttt \n rrr,zzz, 1,234,567,987, rrr"

Can use readLines on a textConnection. Then remove only the commas that are between digits:

gsub("([0-9]+)\\,([0-9])", "\\1\\2", lines)

## [1] "www, rrr, 1234, ttt \n rrr,zzz, 1234567987, rrr"

It's als useful to know but not directly relevant to this question that commas as decimal separators can be handled by read.csv2 (automagically) or read.table(with setting of the 'dec'-parameter).

Edit: Later I discovered how to use colClasses by designing a new class. See:

How to load df with 1000 separator in R as numeric class?

Why am I getting a " Traceback (most recent call last):" error?

At the beginning of your file you set raw_input to 0. Do not do this, at it modifies the built-in raw_input() function. Therefore, whenever you call raw_input(), it is essentially calling 0(), which raises the error. To remove the error, remove the first line of your code:

M = 1.6
# Miles to Kilometers 
# Celsius Celsius = (var1 - 32) * 5/9
# Gallons to liters Gallons = 3.6
# Pounds to kilograms Pounds = 0.45
# Inches to centimete Inches = 2.54

def intro():
    print("Welcome! This program will convert measures for you.")

def main():
    print("Select operation.")
    print("1.Miles to Kilometers")
    print("2.Fahrenheit to Celsius")
    print("3.Gallons to liters")
    print("4.Pounds to kilograms")
    print("5.Inches to centimeters")

    choice = input("Enter your choice by number: ")

    if choice == '1':

    elif choice == '2':

    elif choice == '3':

    elif choice == '4':

    elif choice == '5':


def convertMK():
    input_M = float(raw_input(("Miles: ")))
    M_conv = (M) * input_M
    print("Kilometers: %f\n" % M_conv)
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print("I didn't quite understand that answer. Terminating.")

def converCF():
    input_F = float(raw_input(("Fahrenheit: ")))
    F_conv = (input_F - 32) * 5/9
    print("Celcius: %f\n") % F_conv
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print("I didn't quite understand that answer. Terminating.")

def convertGL():
    input_G = float(raw_input(("Gallons: ")))
    G_conv = input_G * 3.6
    print("Centimeters: %f\n" % G_conv)
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print ("I didn't quite understand that answer. Terminating.")

def convertPK():
    input_P = float(raw_input(("Pounds: ")))
    P_conv = input_P * 0.45
    print("Centimeters: %f\n" % P_conv)
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print ("I didn't quite understand that answer. Terminating.")

def convertIC():
    input_cm = float(raw_input(("Inches: ")))
    inches_conv = input_cm * 2.54
    print("Centimeters: %f\n" % inches_conv)
    restart = str(input("Do you wish to make another conversion? [y]Yes or [n]no: "))
    if restart == 'y':
    elif restart == 'n':
        print ("I didn't quite understand that answer. Terminating.")

def end():
    print("This program will close.")


Add a new item to a dictionary in Python

It can be as simple as:

default_data['item3'] = 3

As Chris' answer says, you can use update to add more than one item. An example:

default_data.update({'item4': 4, 'item5': 5})

Please see the documentation about dictionaries as data structures and dictionaries as built-in types.

Perform debounce in React.js

Extend useState hook

import { useState } from "react";
import _ from "underscore"
export const useDebouncedState = (initialState, durationInMs = 500) => {
    const [internalState, setInternalState] = useState(initialState);
    const debouncedFunction = _.debounce(setInternalState, durationInMs);
    return [internalState, debouncedFunction];
export default useDebouncedState;

Use hook

import useDebouncedState from "../hooks/useDebouncedState"
const [usernameFilter, setUsernameFilter] = useDebouncedState("")
<input id="username" type="text" onChange={e => setUsernameFilter(}></input>

MySQL Error 1093 - Can't specify target table for update in FROM clause

If you can't do

UPDATE table SET a=value WHERE x IN
    (SELECT x FROM table WHERE condition);

because it is the same table, you can trick and do :

UPDATE table SET a=value WHERE x IN
    (SELECT * FROM (SELECT x FROM table WHERE condition) as t)

[update or delete or whatever]

How to increment a datetime by one day?

All of the current answers are wrong in some cases as they do not consider that timezones change their offset relative to UTC. So in some cases adding 24h is different from adding a calendar day.

Proposed solution

The following solution works for Samoa and keeps the local time constant.

def add_day(today):
    Add a day to the current day.

    This takes care of historic offset changes and DST.

    today : timezone-aware datetime object

    tomorrow : timezone-aware datetime object
    today_utc = today.astimezone(datetime.timezone.utc)
    tz = today.tzinfo
    tomorrow_utc = today_utc + datetime.timedelta(days=1)
    tomorrow_utc_tz = tomorrow_utc.astimezone(tz)
    tomorrow_utc_tz = tomorrow_utc_tz.replace(hour=today.hour,
    return tomorrow_utc_tz

Tested Code

# core modules
import datetime

# 3rd party modules
import pytz

# add_day methods
def add_day(today):
    Add a day to the current day.

    This takes care of historic offset changes and DST.

    today : timezone-aware datetime object

    tomorrow : timezone-aware datetime object
    today_utc = today.astimezone(datetime.timezone.utc)
    tz = today.tzinfo
    tomorrow_utc = today_utc + datetime.timedelta(days=1)
    tomorrow_utc_tz = tomorrow_utc.astimezone(tz)
    tomorrow_utc_tz = tomorrow_utc_tz.replace(hour=today.hour,
    return tomorrow_utc_tz

def add_day_datetime_timedelta_conversion(today):
    # Correct for Samoa, but dst shift
    today_utc = today.astimezone(datetime.timezone.utc)
    tz = today.tzinfo
    tomorrow_utc = today_utc + datetime.timedelta(days=1)
    tomorrow_utc_tz = tomorrow_utc.astimezone(tz)
    return tomorrow_utc_tz

def add_day_dateutil_relativedelta(today):
    # WRONG!
    from dateutil.relativedelta import relativedelta
    return today + relativedelta(days=1)

def add_day_datetime_timedelta(today):
    # WRONG!
    return today + datetime.timedelta(days=1)

# Test cases
def test_samoa(add_day):
    Test if add_day properly increases the calendar day for Samoa.

    Due to economic considerations, Samoa went from 2011-12-30 10:00-11:00
    to 2011-12-30 10:00+13:00. Hence the country skipped 2011-12-30 in its
    local time.


    A common wrong result here is 2011-12-30T23:59:00-10:00. This date never
    happened in Samoa.
    tz = pytz.timezone('Pacific/Apia')
    today_utc = datetime.datetime(2011, 12, 30, 9, 59,
    today_tz = today_utc.astimezone(tz)  # 2011-12-29T23:59:00-10:00
    tomorrow = add_day(today_tz)
    return tomorrow.isoformat() == '2011-12-31T23:59:00+14:00'

def test_dst(add_day):
    """Test if add_day properly increases the calendar day if DST happens."""
    tz = pytz.timezone('Europe/Berlin')
    today_utc = datetime.datetime(2018, 3, 25, 0, 59,
    today_tz = today_utc.astimezone(tz)  # 2018-03-25T01:59:00+01:00
    tomorrow = add_day(today_tz)
    return tomorrow.isoformat() == '2018-03-26T01:59:00+02:00'

to_test = [(add_day_dateutil_relativedelta, 'relativedelta'),
           (add_day_datetime_timedelta, 'timedelta'),
           (add_day_datetime_timedelta_conversion, 'timedelta+conversion'),
           (add_day, 'timedelta+conversion+dst')]
print('{:<25}: {:>5} {:>5}'.format('Method', 'Samoa', 'DST'))
for method, name in to_test:
    print('{:<25}: {:>5} {:>5}'

Test results

Method                   : Samoa   DST
relativedelta            :     0     0
timedelta                :     0     0
timedelta+conversion     :     1     0
timedelta+conversion+dst :     1     1

How to check if input file is empty in jQuery

To check whether the input file is empty or not by using the file length property, index should be specified like the following:

var vidFileLength = $("#videoUploadFile")[0].files.length;
if(vidFileLength === 0){
    alert("No file selected.");

Android splash screen image sizes to fit all devices

Using PNG is not such a good idea. Actually it's costly as far as performance is concerned. You can use drawable XML files, for example, Facebook's background.

This will help you to smooth and speed up your performance, and for the logo use .9 patch images.

VSCode Change Default Terminal

Go to File > Preferences > Settings (or press Ctrl+,) then click the leftmost icon in the top right corner, "Open Settings (JSON)"

screenshot showing location of icon

In the JSON settings window, add this (within the curly braces {}):

"": "C:\\WINDOWS\\System32\\bash.exe"`

(Here you can put any other custom settings you want as well)

Checkout that path to make sure your bash.exe file is there otherwise find out where it is and point to that path instead.

Now if you open a new terminal window in VS Code, it should open with bash instead of PowerShell.

How to ignore deprecation warnings in Python

If you are using logging ( to format or redirect your ERROR, NOTICE, and DEBUG messages, you can redirect the WARNINGS from the warning system to the logging system:


See and

In my case, I was formatting all the exceptions with the logging system, but warnings (e.g. scikit-learn) were not affected.

How to run Visual Studio post-build events for debug build only

In Visual Studio 2012 you have to use (I think in Visual Studio 2010, too)

if $(Configuration) == Debug xcopy

$(ConfigurationName) was listed as a macro, but it wasn't assigned.

Enter image description here

Compare: Macros for Build Commands and Properties

Simple insecure two-way data "obfuscation"?

I've been using the accepted answer by Mark Brittingham and its has helped me a lot. Recently I had to send encrypted text to a different organization and that's where some issues came up. The OP does not require these options but since this is a popular question I'm posting my modification (Encrypt and Decrypt functions borrowed from here):

  1. Different IV for every message - Concatenates IV bytes to the cipher bytes before obtaining the hex. Of course this is a convention that needs to be conveyed to the parties receiving the cipher text.
  2. Allows two constructors - one for default RijndaelManaged values, and one where property values can be specified (based on mutual agreement between encrypting and decrypting parties)

Here is the class (test sample at the end):

/// <summary>
/// Based on
/// Uses UTF8 Encoding
/// </summary>
public class AnotherAES : IDisposable
    private RijndaelManaged rijn;

    /// <summary>
    /// Initialize algo with key, block size, key size, padding mode and cipher mode to be known.
    /// </summary>
    /// <param name="key">ASCII key to be used for encryption or decryption</param>
    /// <param name="blockSize">block size to use for AES algorithm. 128, 192 or 256 bits</param>
    /// <param name="keySize">key length to use for AES algorithm. 128, 192, or 256 bits</param>
    /// <param name="paddingMode"></param>
    /// <param name="cipherMode"></param>
    public AnotherAES(string key, int blockSize, int keySize, PaddingMode paddingMode, CipherMode cipherMode)
        rijn = new RijndaelManaged();
        rijn.Key = Encoding.UTF8.GetBytes(key);
        rijn.BlockSize = blockSize;
        rijn.KeySize = keySize;
        rijn.Padding = paddingMode;
        rijn.Mode = cipherMode;

    /// <summary>
    /// Initialize algo just with key
    /// Defaults for RijndaelManaged class: 
    /// Block Size: 256 bits (32 bytes)
    /// Key Size: 128 bits (16 bytes)
    /// Padding Mode: PKCS7
    /// Cipher Mode: CBC
    /// </summary>
    /// <param name="key"></param>
    public AnotherAES(string key)
        rijn = new RijndaelManaged();
        byte[] keyArray = Encoding.UTF8.GetBytes(key);
        rijn.Key = keyArray;

    /// <summary>
    /// Based on
    /// Encrypt a string using RijndaelManaged encryptor.
    /// </summary>
    /// <param name="plainText">string to be encrypted</param>
    /// <param name="IV">initialization vector to be used by crypto algorithm</param>
    /// <returns></returns>
    public byte[] Encrypt(string plainText, byte[] IV)
        if (rijn == null)
            throw new ArgumentNullException("Provider not initialized");

        // Check arguments.
        if (plainText == null || plainText.Length <= 0)
            throw new ArgumentNullException("plainText cannot be null or empty");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("IV cannot be null or empty");
        byte[] encrypted;

        // Create a decrytor to perform the stream transform.
        using (ICryptoTransform encryptor = rijn.CreateEncryptor(rijn.Key, IV))
            // Create the streams used for encryption.
            using (MemoryStream msEncrypt = new MemoryStream())
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                        //Write all data to the stream.
                    encrypted = msEncrypt.ToArray();
        // Return the encrypted bytes from the memory stream.
        return encrypted;
    }//end EncryptStringToBytes

    /// <summary>
    /// Based on
    /// </summary>
    /// <param name="cipherText">bytes to be decrypted back to plaintext</param>
    /// <param name="IV">initialization vector used to encrypt the bytes</param>
    /// <returns></returns>
    public string Decrypt(byte[] cipherText, byte[] IV)
        if (rijn == null)
            throw new ArgumentNullException("Provider not initialized");

        // Check arguments.
        if (cipherText == null || cipherText.Length <= 0)
            throw new ArgumentNullException("cipherText cannot be null or empty");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("IV cannot be null or empty");

        // Declare the string used to hold the decrypted text.
        string plaintext = null;

        // Create a decrytor to perform the stream transform.
        using (ICryptoTransform decryptor = rijn.CreateDecryptor(rijn.Key, IV))
            // Create the streams used for decryption.
            using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        // Read the decrypted bytes from the decrypting stream and place them in a string.
                        plaintext = srDecrypt.ReadToEnd();

        return plaintext;
    }//end DecryptStringFromBytes

    /// <summary>
    /// Generates a unique encryption vector using RijndaelManaged.GenerateIV() method
    /// </summary>
    /// <returns></returns>
    public byte[] GenerateEncryptionVector()
        if (rijn == null)
            throw new ArgumentNullException("Provider not initialized");

        //Generate a Vector
        return rijn.IV;
    }//end GenerateEncryptionVector

    /// <summary>
    /// Based on
    /// Generate a unique string given number of bytes required.
    /// This string can be used as IV. IV byte size should be equal to cipher-block byte size. 
    /// Allows seeing IV in plaintext so it can be passed along a url or some message.
    /// </summary>
    /// <param name="numBytes"></param>
    /// <returns></returns>
    public static string GetUniqueString(int numBytes)
        char[] chars = new char[62];
        chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".ToCharArray();
        byte[] data = new byte[1];
        using (RNGCryptoServiceProvider crypto = new RNGCryptoServiceProvider())
            data = new byte[numBytes];
        StringBuilder result = new StringBuilder(numBytes);
        foreach (byte b in data)
            result.Append(chars[b % (chars.Length)]);
        return result.ToString();
    }//end GetUniqueKey()

    /// <summary>
    /// Converts a string to byte array. Useful when converting back hex string which was originally formed from bytes.
    /// </summary>
    /// <param name="hex"></param>
    /// <returns></returns>
    public static byte[] StringToByteArray(String hex)
        int NumberChars = hex.Length;
        byte[] bytes = new byte[NumberChars / 2];
        for (int i = 0; i < NumberChars; i += 2)
            bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
        return bytes;
    }//end StringToByteArray

    /// <summary>
    /// Dispose RijndaelManaged object initialized in the constructor
    /// </summary>
    public void Dispose()
        if (rijn != null)
    }//end Dispose()
}//end class


Here is the test sample:

class Program
    string key;
    static void Main(string[] args)
        Program p = new Program();

        //get 16 byte key (just demo - typically you will have a predetermined key)
        p.key = AnotherAES.GetUniqueString(16);

        string plainText = "Hello World!";

        string hex = p.Encrypt(plainText);

        string roundTrip = p.Decrypt(hex);

        Console.WriteLine("Round Trip: {0}", roundTrip);

    string Encrypt(string plainText)
        Console.WriteLine("\nSending (encrypt side)...");
        Console.WriteLine("Plain Text: {0}", plainText);
        Console.WriteLine("Key: {0}", key);
        string hex = string.Empty;
        string ivString = AnotherAES.GetUniqueString(16);
        Console.WriteLine("IV: {0}", ivString);
        using (AnotherAES aes = new AnotherAES(key))
            //encrypting side
            byte[] IV = Encoding.UTF8.GetBytes(ivString);

            //get encrypted bytes (IV bytes prepended to cipher bytes)
            byte[] encryptedBytes = aes.Encrypt(plainText, IV);
            byte[] encryptedBytesWithIV = IV.Concat(encryptedBytes).ToArray();

            //get hex string to send with url
            //this hex has both IV and ciphertext
            hex = BitConverter.ToString(encryptedBytesWithIV).Replace("-", "");
            Console.WriteLine("sending hex: {0}", hex);

        return hex;

    string Decrypt(string hex)
        Console.WriteLine("\nReceiving (decrypt side)...");
        Console.WriteLine("received hex: {0}", hex);
        string roundTrip = string.Empty;
        Console.WriteLine("Key " + key);
        using (AnotherAES aes = new AnotherAES(key))
            //get bytes from url
            byte[] encryptedBytesWithIV = AnotherAES.StringToByteArray(hex);

            byte[] IV = encryptedBytesWithIV.Take(16).ToArray();

            Console.WriteLine("IV: {0}", System.Text.Encoding.Default.GetString(IV));

            byte[] cipher = encryptedBytesWithIV.Skip(16).ToArray();

            roundTrip = aes.Decrypt(cipher, IV);
        return roundTrip;

enter image description here

unable to dequeue a cell with identifier Cell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard

Just drag a cell (as you did for TableViewController) and add in to it just by releasing the cell on TableViewController. Click on the cell and.Go to its attributes inspector and set its identifier as "Cell".Hope it works.

Don't forget you want Identifier on the Attributes Inspector.

(NOT the "Restoration ID" on the "Identity Inspector" !)

How does spring.jpa.hibernate.ddl-auto property exactly work in Spring?

For the record, the spring.jpa.hibernate.ddl-auto property is Spring Data JPA specific and is their way to specify a value that will eventually be passed to Hibernate under the property it knows,

The values create, create-drop, validate, and update basically influence how the schema tool management will manipulate the database schema at startup.

For example, the update operation will query the JDBC driver's API to get the database metadata and then Hibernate compares the object model it creates based on reading your annotated classes or HBM XML mappings and will attempt to adjust the schema on-the-fly.

The update operation for example will attempt to add new columns, constraints, etc but will never remove a column or constraint that may have existed previously but no longer does as part of the object model from a prior run.

Typically in test case scenarios, you'll likely use create-drop so that you create your schema, your test case adds some mock data, you run your tests, and then during the test case cleanup, the schema objects are dropped, leaving an empty database.

In development, it's often common to see developers use update to automatically modify the schema to add new additions upon restart. But again understand, this does not remove a column or constraint that may exist from previous executions that is no longer necessary.

In production, it's often highly recommended you use none or simply don't specify this property. That is because it's common practice for DBAs to review migration scripts for database changes, particularly if your database is shared across multiple services and applications.

How do I get a plist as a Dictionary in Swift?

You can use that, I create a simple extension for Dictionary in github

extension Dictionary {
        Load a Plist file from the app bundle into a new dictionary

        :param: File name
        :return: Dictionary<String, AnyObject>?
    static func loadPlistFromProject(filename: String) -> Dictionary<String, AnyObject>? {

        if let path = NSBundle.mainBundle().pathForResource("GameParam", ofType: "plist") {
            return NSDictionary(contentsOfFile: path) as? Dictionary<String, AnyObject>
        println("Could not find file: \(filename)")
        return nil

And you can use that for load

  Example function for load Files Plist

  :param: Name File Plist
func loadPlist(filename: String) -> ExampleClass? {
    if let dictionary = Dictionary<String, AnyObject>.loadPlistFromProject(filename) {
        let stringValue = (dictionary["name"] as NSString)
        let intergerValue = (dictionary["score"] as NSString).integerValue
        let doubleValue = (dictionary["transition"] as NSString).doubleValue

        return ExampleClass(stringValue: stringValue, intergerValue: intergerValue, doubleValue: doubleValue)
    return nil

Difference between System.DateTime.Now and System.DateTime.Today

DateTime.Today is DateTime.Now with time set to zero.

It is important to note that there is a difference between a DateTime value, which represents the number of ticks that have elapsed since midnight of January 1, 0000, and the string representation of that DateTime value, which expresses a date and time value in a culture-specific-specific format:

DateTime.Now.Ticks is the actual time stored by .net (essentially UTC time), the rest are just representations (which are important for display purposes).

If the Kind property is DateTimeKind.Local it implicitly includes the time zone information of the local computer. When sending over a .net web service, DateTime values are by default serialized with time zone information included, e.g. 2008-10-31T15:07:38.6875000-05:00, and a computer in another time zone can still exactly know what time is being referred to.

So, using DateTime.Now and DateTime.Today is perfectly OK.

You usually start running into trouble when you begin confusing the string representation with the actual value and try to "fix" the DateTime, when it isn't broken.

Laravel - Pass more than one variable to view

Use compact

function view($view)
    $ms = Person::where('name', '=', 'Foo Bar')->first();

    $persons = Person::order_by('list_order', 'ASC')->get();
    return View::make('users', compact('ms','persons'));

os.walk without digging into directories below

Since Python 3.5 you can use os.scandir instead of os.listdir. Instead of strings you get an iterator of DirEntry objects in return. From the docs:

Using scandir() instead of listdir() can significantly increase the performance of code that also needs file type or file attribute information, because DirEntry objects expose this information if the operating system provides it when scanning a directory. All DirEntry methods may perform a system call, but is_dir() and is_file() usually only require a system call for symbolic links; DirEntry.stat() always requires a system call on Unix but only requires one for symbolic links on Windows.

You can access the name of the object via which is then equivalent to the output of os.listdir

Strange Characters in database text: Ã, Ã, ¢, â‚ €,

This is surely an encoding problem. You have a different encoding in your database and in your website and this fact is the cause of the problem. Also if you ran that command you have to change the records that are already in your tables to convert those character in UTF-8.

Update: Based on your last comment, the core of the problem is that you have a database and a data source (the CSV file) which use different encoding. Hence you can convert your database in UTF-8 or, at least, when you get the data that are in the CSV, you have to convert them from UTF-8 to latin1.

You can do the convertion following this articles:

How to use PHP OPCache?

I am going to drop in my two cents for what I use opcache.

I have made an extensive framework with a lot of fields and validation methods and enums to be able to talk to my database.

Without opcache

When using this script without opcache and I push 9000 requests in 2.8 seconds to the apache server it maxes out at 90-100% cpu for 70-80 seconds until it catches up with all the requests.

Total time taken: 76085 milliseconds(76 seconds)

With opcache enabled

With opcache enabled it runs at 25-30% cpu time for about 25 seconds and never passes 25% cpu use.

Total time taken: 26490 milliseconds(26 seconds)

I have made an opcache blacklist file to disable the caching of everything except the framework which is all static and doesnt need changing of functionality. I choose explicitly for just the framework files so that I could develop without worrying about reloading/validating the cache files. Having everything cached saves a second on the total of the requests 25546 milliseconds

This significantly expands the amount of data/requests I can handle per second without the server even breaking a sweat.

How to write the code for the back button?

<input type="submit" <a href="#" onclick="history.back();">"Back"</a>

Is invalid HTML due to the unclosed input element.

<a href="#" onclick="history.back(1);">"Back"</a>

is enough

Sending a JSON to server and retrieving a JSON in return, without JQuery

Sending and receiving data in JSON format using POST method

// Sending and receiving data in JSON format using POST method
var xhr = new XMLHttpRequest();
var url = "url";"POST", url, true);
xhr.setRequestHeader("Content-Type", "application/json");
xhr.onreadystatechange = function () {
    if (xhr.readyState === 4 && xhr.status === 200) {
        var json = JSON.parse(xhr.responseText);
        console.log( + ", " + json.password);
var data = JSON.stringify({"email": "[email protected]", "password": "101010"});

Sending and receiving data in JSON format using GET method

// Sending a receiving data in JSON format using GET method
var xhr = new XMLHttpRequest();
var url = "url?data=" + encodeURIComponent(JSON.stringify({"email": "[email protected]", "password": "101010"}));"GET", url, true);
xhr.setRequestHeader("Content-Type", "application/json");
xhr.onreadystatechange = function () {
    if (xhr.readyState === 4 && xhr.status === 200) {
        var json = JSON.parse(xhr.responseText);
        console.log( + ", " + json.password);

Handling data in JSON format on the server-side using PHP

// Handling data in JSON format on the server-side using PHP
header("Content-Type: application/json");
// build a PHP variable from JSON sent using POST method
$v = json_decode(stripslashes(file_get_contents("php://input")));
// build a PHP variable from JSON sent using GET method
$v = json_decode(stripslashes($_GET["data"]));
// encode the PHP variable to JSON and send it back on client-side
echo json_encode($v);

The limit of the length of an HTTP Get request is dependent on both the server and the client (browser) used, from 2kB - 8kB. The server should return 414 (Request-URI Too Long) status if an URI is longer than the server can handle.

Note Someone said that I could use state names instead of state values; in other words I could use xhr.readyState === xhr.DONE instead of xhr.readyState === 4 The problem is that Internet Explorer uses different state names so it's better to use state values.

Ctrl+click doesn't work in Eclipse Juno

Go to

Window -> Preferences -> General -> Editors -> Text Editors -> Hyperlinking

and be sure that

Enable on demand hyperlink style navigation

is checked.

java : non-static variable cannot be referenced from a static context Error

You probably want to add "static" to the declaration of con2.

In Java, things (both variables and methods) can be properties of the class (which means they're shared by all objects of that type), or they can be properties of the object (a different one in each object of the same class). The keyword "static" is used to indicate that something is a property of the class.

"Static" stuff exists all the time. The other stuff only exists after you've created an object, and even then each individual object has its own copy of the thing. And the flip side of this is key in this case: static stuff can't access non-static stuff, because it doesn't know which object to look in. If you pass it an object reference, it can do stuff like "thingie.con2", but simply saying "con2" is not allowed, because you haven't said which object's con2 is meant.

WAMP Server ERROR "Forbidden You don't have permission to access /phpmyadmin/ on this server."

Change httpd.conf file as follows:


<Directory />
    AllowOverride none
    Require all denied


<Directory />
    AllowOverride none
    Require all granted

CSS body background image fixed to full screen even when zooming in/out

Use Directly like this

     background: url(../img/beach.jpg) no-repeat fixed 100% 100%;

or call CSS separately like

    background-image: url(../img/beach.jpg);
    -moz-background-size: cover;
    -webkit-background-size: cover;
    -o-background-size: cover;
    background-size: cover;

Launch Minecraft from command line - username and password as prefix

This answer is going to briefly explain how the native files are handled on the latest launcher.

As of 4/29/2017 the Minecraft launcher for Windows extracts all native files and places them info %APPDATA%\Local\Temp{random folder}. That folder is temporary and is deleted once the javaw.exe process finishes (when Minecraft is closed). The location of that temporary folder must be provided in the launch arguments as the value of


Also, the latest launcher (2.0.847) does not show you the launch arguments so if you need to check them yourself you can do so under the Task Manager (simply enable the Command Line tab and expand it) or by using the WMIC utility as explained here.

Hope this helps some people who are still interested in doing this in 2017.