Programs & Examples On #Scalable

What is correct media query for IPad Pro?

This worked for me

/* Portrait */
@media only screen 
  and (min-device-width: 834px) 
  and (max-device-width: 834px) 
  and (orientation: portrait) 
  and (-webkit-min-device-pixel-ratio: 2) {


/* Landscape */
@media only screen 
  and (min-width: 1112px) 
  and (max-width: 1112px) 
  and (orientation: landscape) 
  and (-webkit-min-device-pixel-ratio: 2)


Ionic 2: Cordova is not available. Make sure to include cordova.js or run in a device/simulator (running in emulator)

The livereload plugin fails to serve cordova.js file and serves // mock cordova file during development.

FIX: You need go to node_modules/@ionic/app-scripts/dist/dev-server/serve-config.js

and replace

exports.ANDROID_PLATFORM_PATH = path.join('platforms', 'android', 'assets', 'www');


exports.ANDROID_PLATFORM_PATH = path.join('platforms', 'android', 'app', 'src', 'main', 'assets', 'www');

disable viewport zooming iOS 10+ safari?

Check for scale factor in touchove event then prevent touch event.

document.addEventListener('touchmove', function(event) {
    event = event.originalEvent || event;
    if(event.scale > 1) {
}, false);

This page didn't load Google Maps correctly. See the JavaScript console for technical details

There are 2 possibilities for this problem :

  1. you didn't enter the API KEY for map browser
  2. you didn't enabling the API Library especially for this Google Maps JavaScript API

just check on your Google developer console for that 2 items

Difference between Amazon EC2 and AWS Elastic Beanstalk

First off, EC2 and Elastic Compute Cloud are the same thing.

Next, AWS encompasses the range of Web Services that includes EC2 and Elastic Beanstalk. It also includes many others such as S3, RDS, DynamoDB, and all the others.


EC2 is Amazon's service that allows you to create a server (AWS calls these instances) in the AWS cloud. You pay by the hour and only what you use. You can do whatever you want with this instance as well as launch n number of instances.

Elastic Beanstalk

Elastic Beanstalk is one layer of abstraction away from the EC2 layer. Elastic Beanstalk will setup an "environment" for you that can contain a number of EC2 instances, an optional database, as well as a few other AWS components such as a Elastic Load Balancer, Auto-Scaling Group, Security Group. Then Elastic Beanstalk will manage these items for you whenever you want to update your software running in AWS. Elastic Beanstalk doesn't add any cost on top of these resources that it creates for you. If you have 10 hours of EC2 usage, then all you pay is 10 compute hours.

Running Wordpress

For running Wordpress, it is whatever you are most comfortable with. You could run it straight on a single EC2 instance, you could use a solution from the AWS Marketplace, or you could use Elastic Beanstalk.

What to pick?

In the case that you want to reduce system operations and just focus on the website, then Elastic Beanstalk would be the best choice for that. Elastic Beanstalk supports a PHP stack (as well as others). You can keep your site in version control and easily deploy to your environment whenever you make changes. It will also setup an Autoscaling group which can spawn up more EC2 instances if traffic is growing.

Here's the first result off of Google when searching for "elastic beanstalk wordpress":

FontAwesome icons not showing. Why?

You must use https for Only https on maxcdn support CORS

<link href="" rel="stylesheet" media="screen" />

HTML 5 Favicon - Support?

The answers provided (at the time of this post) are link only answers so I thought I would summarize the links into an answer and what I will be using.

When working to create Cross Browser Favicons (including touch icons) there are several things to consider.

The first (of course) is Internet Explorer. IE does not support PNG favicons until version 11. So our first line is a conditional comment for favicons in IE 9 and below:

<!--[if IE]><link rel="shortcut icon" href="path/to/favicon.ico"><![endif]-->

To cover the uses of the icon create it at 32x32 pixels. Notice the rel="shortcut icon" for IE to recognize the icon it needs the word shortcut which is not standard. Also we wrap the .ico favicon in a IE conditional comment because Chrome and Safari will use the .ico file if it is present, despite other options available, not what we would like.

The above covers IE up to IE 9. IE 11 accepts PNG favicons, however, IE 10 does not. Also IE 10 does not read conditional comments thus IE 10 won't show a favicon. With IE 11 and Edge available I don't see IE 10 in widespread use, so I ignore this browser.

For the rest of the browsers we are going to use the standard way to cite a favicon:

<link rel="icon" href="path/to/favicon.png">

This icon should be 196x196 pixels in size to cover all devices that may use this icon.

To cover touch icons on mobile devices we are going to use Apple's proprietary way to cite a touch icon:

<link rel="apple-touch-icon-precomposed" href="apple-touch-icon-precomposed.png">

Using rel="apple-touch-icon-precomposed" will not apply the reflective shine when bookmarked on iOS. To have iOS apply the shine use rel="apple-touch-icon". This icon should be sized to 180x180 pixels as that is the current size recommend by Apple for the latest iPhones and iPads. I have read Blackberry will also use rel="apple-touch-icon-precomposed".

As a note: Chrome for Android states:

The apple-touch-* are deprecated, and will be supported only for a short time. (Written as of beta for m31 of Chrome).

Custom Tiles for IE 11+ on Windows 8.1+

IE 11+ on Windows 8.1+ does offer a way to create pinned tiles for your site.

Microsoft recommends creating a few tiles at the following size:

Small: 128 x 128

Medium: 270 x 270

Wide: 558 x 270

Large: 558 x 558

These should be transparent images as we will define a color background next.

Once these images are created you should create an xml file called browserconfig.xml with the following code:

<?xml version="1.0" encoding="utf-8"?>
      <square70x70logo src="images/smalltile.png"/>
      <square150x150logo src="images/mediumtile.png"/>
      <wide310x150logo src="images/widetile.png"/>
      <square310x310logo src="images/largetile.png"/>

Save this xml file in the root of your site. When a site is pinned IE will look for this file. If you want to name the xml file something different or have it in a different location add this meta tag to the head:

<meta name="msapplication-config" content="path-to-browserconfig/custom-name.xml" />

For additional information on IE 11+ custom tiles and using the XML file visit Microsoft's website.

Putting it all together:

To put it all together the above code would look like this:

<!-- For IE 9 and below. ICO should be 32x32 pixels in size -->
<!--[if IE]><link rel="shortcut icon" href="path/to/favicon.ico"><![endif]-->

<!-- Touch Icons - iOS and Android 2.1+ 180x180 pixels in size. --> 
<link rel="apple-touch-icon-precomposed" href="apple-touch-icon-precomposed.png">

<!-- Firefox, Chrome, Safari, IE 11+ and Opera. 196x196 pixels in size. -->
<link rel="icon" href="path/to/favicon.png">

Windows Phone Live Tiles

If a user is using a Windows Phone they can pin a website to the start screen of their phone. Unfortunately, when they do this it displays a screenshot of your phone, not a favicon (not even the MS specific code referenced above). To make a "Live Tile" for Windows Phone Users for your website one must use the following code:

Here are detailed instructions from Microsoft but here is a synopsis:

Step 1

Create a square image for your website, to support hi-res screens create it at 768x768 pixels in size.

Step 2

Add a hidden overlay of this image. Here is example code from Microsoft:

<div id="TileOverlay" onclick="ToggleTileOverlay()" style='background-color: Highlight; height: 100%; width: 100%; top: 0px; left: 0px; position: fixed; color: black; visibility: hidden'>
  <img src="customtile.png" width="320" height="320" />
  <div style='margin-top: 40px'>
     Add text/graphic asking user to pin to start using the menu...

Step 3

You then can add thew following line to add a pin to start link:

<a href="javascript:ToggleTileOverlay()">Pin this site to your start screen</a>

Microsoft recommends that you detect windows phone and only show that link to those users since it won't work for other users.

Step 4

Next you add some JS to toggle the overlay visibility

function ToggleTileOverlay() {
 var newVisibility =     (document.getElementById('TileOverlay').style.visibility == 'visible') ? 'hidden' : 'visible';
 document.getElementById('TileOverlay').style.visibility =    newVisibility;

Note on Sizes

I am using one size as every browser will scale down the image as necessary. I could add more HTML to specify multiple sizes if desired for those with a lower bandwidth but I am already compressing the PNG files heavily using TinyPNG and I find this unnecessary for my purposes. Also, according to philippe_b's answer Chrome and Firefox have bugs that cause the browser to load all sizes of icons. Using one large icon may be better than multiple smaller ones because of this.

Further Reading

For those who would like more details see the links below:

What is initial scale, user-scalable, minimum-scale, maximum-scale attribute in meta tag?

This meta tag is used by all responsive web pages, that is those that are designed to layout well across device types - phone, tablet, and desktop. The attributes do what they say. However, as MDN's Using the viewport meta tag to control layout on mobile browsers indicates,

On high dpi screens, pages with initial-scale=1 will effectively be zoomed by browsers.

I've found that the following ensures that the page displays with zero zoom by default.

<meta name="viewport" content="width=device-width, initial-scale=0.86, maximum-scale=3.0, minimum-scale=0.86">

Error: [$injector:unpr] Unknown provider: $routeProvider

It looks like you forgot to include the ngRoute module in your dependency for myApp.

In Angular 1.2, they've made ngRoute optional (so you can use third-party route providers, etc.) and you have to explicitly depend on it in modules, along with including the separate file.

'use strict';

angular.module('myApp', ['ngRoute']).
    config(['$routeProvider', function($routeProvider) {
$routeProvider.otherwise({redirectTo: '/home'});

Map isn't showing on Google Maps JavaScript API v3 when nested in a div tag

I just want to add what worked for me, I added height and width to both divs and used bootstrap to make it responsive

   <div class="col-lg-1 mapContainer">
       <div id="map"></div>

        height: 100%;

in order for col-lg-1 to work add bootstrap reference located Here

Using Address Instead Of Longitude And Latitude With Google Maps API

You can parse the geolocation through the addresses. Create an Array with jquery like this:

//follow this structure
var addressesArray = [
  'Address Str.No, Postal Area/city'

//loop all the addresses and call a marker for each one
for (var x = 0; x < addressesArray.length; x++) {
  $.getJSON(''+addressesArray[x]+'&sensor=false', null, function (data) {
    var p = data.results[0].geometry.location
    var latlng = new google.maps.LatLng(, p.lng);
    //it will place marker based on the addresses, which they will be translated as geolocations.
    var aMarker= new google.maps.Marker({
      position: latlng,
      map: map

Also please note that Google limit your results if you don't have a business account with them, and you my get an error if you use too many addresses.

Show pop-ups the most elegant way

  • Create a 'popup' directive and apply it to the container of the popup content
  • In the directive, wrap the content in a absolute position div along with the mask div below it.
  • It is OK to move the 2 divs in the DOM tree as needed from within the directive. Any UI code is OK in the directives, including the code to position the popup in center of screen.
  • Create and bind a boolean flag to controller. This flag will control visibility.
  • Create scope variables that bond to OK / Cancel functions etc.

Editing to add a high level example (non functional)

<div id='popup1-content' popup='showPopup1'>

<div id='popup2-content' popup='showPopup2'>

.directive('popup', function() {
  var p = {
      link : function(scope, iElement, iAttrs){
           //code to wrap the div (iElement) with a abs pos div (parentDiv)
          // code to add a mask layer div behind 
          // if the parent is already there, then skip adding it again.
         //use jquery ui to make it dragable etc.
, function(newVal, oldVal){
               if(newVal === true){

  return p;

@Media min-width & max-width

If website on small devices behavior like desktop screen then you have to put this meta tag into header before

<meta name="viewport" content="width=device-width, initial-scale=1">

For media queries you can set this as

this will cover your all mobile/cellphone widths

 @media only screen and (min-width: 200px) and (max-width: 767px)  {
    //Put your CSS here for 200px to 767px width devices (cover all width between 200px to 767px //

For iPad and iPad pro you have to use

  @media only screen and (min-width: 768px) and (max-width: 1024px)  {
        //Put your CSS here for 768px to 1024px width devices(covers all width between 768px to 1024px //   

If you want to add css for Landscape mode you can add this

and (orientation : landscape)

  @media only screen and (min-width: 200px) and (max-width: 767px) and (orientation : portrait) {
        //Put your CSS here for 200px to 767px width devices (cover all mobile portrait width //        

Google Maps API Multiple Markers with Infowindows

function setMarkers(map,locations){

for (var i = 0; i < locations.length; i++)

 var loan = locations[i][0];
 var lat = locations[i][1];
 var long = locations[i][2];
 var add =  locations[i][3];

 latlngset = new google.maps.LatLng(lat, long);

 var marker = new google.maps.Marker({  
          map: map, title: loan , position: latlngset  

 marker.content = "<h3>Loan Number: " + loan +  '</h3>' + "Address: " + add;,'click', function(map,marker){



Then move var infowindow = new google.maps.InfoWindow() to the initialize() function:

function initialize() {

    var myOptions = {
      center: new google.maps.LatLng(33.890542, 151.274856),
      zoom: 8,
      mapTypeId: google.maps.MapTypeId.ROADMAP

    var map = new google.maps.Map(document.getElementById("default"),
    map.infowindow = new google.maps.InfoWindow();



Disable scrolling in all mobile devices

For future generations:

To prevent scrolling but keep the contextmenu, try

document.body.addEventListener('touchmove', function(e){ e.preventDefault(); });

It still prevents way more than some might like, but for most browsers the only default behaviour prevented should be scrolling.

For a more sophisticated solution that allows for scrollable elements within the nonscrollable body and prevents rubberband, have a look at my answer over here:

Google Maps API: open url by clicking on marker

    function loadMarkers(){
          {% for location in object_list %}
              var point = new google.maps.LatLng({{location.latitude}},{{location.longitude}});
              var marker = new google.maps.Marker({
              position: point,
              map: map,
              url: {{}},

          google.maps.event.addDomListener(marker, 'click', function() {
              window.location.href = this.url; });

          {% endfor %}

How to move a marker in Google Maps API

Here is the full code with no errors

        <!DOCTYPE html>
        <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
        <style type="text/css">
          html { height: 100% }
          body { height: 100%; margin: 0; padding: 0 }
          #map_canvas { height: 100% }

        height: 400px; 
        width: 500px;

        <script type="text/javascript">
        function initialize() {

            var myLatLng = new google.maps.LatLng( 17.3850, 78.4867 ),
                myOptions = {
                    zoom: 5,
                    center: myLatLng,
                    mapTypeId: google.maps.MapTypeId.ROADMAP
                map = new google.maps.Map( document.getElementById( 'map-canvas' ), myOptions ),
                marker = new google.maps.Marker( {icon: {
                    url: '',
                    // This marker is 20 pixels wide by 32 pixels high.
                    size: new google.maps.Size(20, 32),
                    // The origin for this image is (0, 0).
                    origin: new google.maps.Point(0, 0),
                    // The anchor for this image is the base of the flagpole at (0, 32).
                    anchor: new google.maps.Point(0, 32)
                }, position: myLatLng, map: map} );

            marker.setMap( map );
            moveBus( map, marker );


        function moveBus( map, marker ) {
            setTimeout(() => {
                marker.setPosition( new google.maps.LatLng( 12.3850, 77.4867 ) );
                map.panTo( new google.maps.LatLng( 17.3850, 78.4867 ) );
            }, 1000)



        <body onload="initialize()">
        <script type="text/javascript">

        <script src=""></script>
        <div id="map-canvas" style="height: 500px; width: 500px;"></div>


How do I automatically resize an image for a mobile site?

For me, it worked best to add this in image css: max-width:100%; and NOT specify image width and height in html parameters. This adjusted the width to fit in device screen while adjusting height automatically. Otherwise height might be distorted.

Best way to store chat messages in a database?

There's nothing wrong with saving the whole history in the database, they are prepared for that kind of tasks.

Actually you can find here in Stack Overflow a link to an example schema for a chat: example

If you are still worried for the size, you could apply some optimizations to group messages, like adding a buffer to your application that you only push after some time (like 1 minute or so); that way you would avoid having only 1 line messages

CSS: 100% font size - 100% of what?

Sorry if I'm late to the party, but in your edit you make a remark about font: 100% Georgia, which the other answers haven't responded to.

There is a difference between font: 100% Georgia and font-size:100%; font-family:'Georgia'. If that was all the shorthand method did, the font-size part would be meaningless. But it also sets a lot of properties to their default values: the line height becomes normal (or around 1.2), ditto for the style (non-italic) and weight (non-bold).

That's all. The other answers already mentioned everything else there was to mention.

jquery mobile background image

Just add !important tag to all css elements in Paolo's answer! Works fine for me JQM+phonegap


body {
    background: url(../images/background.jpg) !important;

What's the point of 'meta viewport user-scalable=no' in the Google Maps API

On many devices (such as the iPhone), it prevents the user from using the browser's zoom. If you have a map and the browser does the zooming, then the user will see a big ol' pixelated image with huge pixelated labels. The idea is that the user should use the zooming provided by Google Maps. Not sure about any interaction with your plugin, but that's what it's there for.

More recently, as @ehfeng notes in his answer, Chrome for Android (and perhaps others) have taken advantage of the fact that there's no native browser zooming on pages with a viewport tag set like that. This allows them to get rid of the dreaded 300ms delay on touch events that the browser takes to wait and see if your single touch will end up being a double touch. (Think "single click" and "double click".) However, when this question was originally asked (in 2011), this wasn't true in any mobile browser. It's just added awesomeness that fortuitously arose more recently.

Is there a way to use max-width and height for a background image?

You can do this with background-size:

html {
    background: url(images/bg.jpg) no-repeat center center fixed; 
    background-size: cover;

There are a lot of values other than cover that you can set background-size to, see which one works for you:


It works in all modern browsers:

How do you disable viewport zooming on Mobile Safari?

This one should be working on iphone etc.

<meta name="viewport" content="width=device-width, initial-scale=1 initial-scale=1.0, maximum-scale=1.0, user-scalable=no">

Android Webview - Webpage should fit the device screen

I had video in html string, and width of web view was larger that screen width and this is working for me.

Add these lines to HTML string.

<meta name="viewport" content="width=device-width">

Result after adding above code to HTML string:

<!DOCTYPE html>

<meta name="viewport" content="width=device-width">


Can I change the viewport meta tag in mobile safari on the fly?

in your <head>

<meta id="viewport"
      content="width=1024, height=768, initial-scale=0, minimum-scale=0.25" />

somewhere in your javascript

      "initial-scale=0.5; maximum-scale=1.0; user-scalable=0;");

... but good luck with tweaking it for your device, fiddling for hours... and i'm still not there!


Disable scrolling in an iPhone web application?

If you are using jquery 1.7+, this works well:

$("donotscrollme").on("touchmove", false);

SQL (MySQL) vs NoSQL (CouchDB)

One of the best options is to go for MongoDB(NOSql dB) that supports scalability.Stores large amounts of data nothing but bigdata in the form of documents unlike rows and tables in sql.This is fasters that follows sharding of the data.Uses replicasets to ensure data guarantee that maintains multiple servers having primary db server as the base. Language independent. Flexible to use

Maven parent pom vs modules pom

  1. An independent parent is the best practice for sharing configuration and options across otherwise uncoupled components. Apache has a parent pom project to share legal notices and some common packaging options.

  2. If your top-level project has real work in it, such as aggregating javadoc or packaging a release, then you will have conflicts between the settings needed to do that work and the settings you want to share out via parent. A parent-only project avoids that.

  3. A common pattern (ignoring #1 for the moment) is have the projects-with-code use a parent project as their parent, and have it use the top-level as a parent. This allows core things to be shared by all, but avoids the problem described in #2.

  4. The site plugin will get very confused if the parent structure is not the same as the directory structure. If you want to build an aggregate site, you'll need to do some fiddling to get around this.

  5. Apache CXF is an example the pattern in #2.

How to send a html email with the bash command "sendmail"?

To follow up on the previous answer using mail :

Often times one's html output is interpreted by the client mailer, which may not format things using a fixed-width font. Thus your nicely formatted ascii alignment gets all messed up. To send old-fashioned fixed-width the way the God intended, try this:

{ echo -e "<pre>"
echo "Descriptive text here."
cat <<EOF

This is the ending text.
} | mail -s "$(echo -e 'Your subject.\nContent-Type: text/html')" [email protected]

You don't necessarily need the "Descriptive text here." line, but I have found that sometimes the first line may, depending on its contents, cause the mail program to interpret the rest of the file in ways you did not intend. Try the script with simple descriptive text first, before fine tuning the output in the way that you want.

Sleep Command in T-SQL?

Here is a very simple piece of C# code to test the CommandTimeout with. It creates a new command which will wait for 2 seconds. Set the CommandTimeout to 1 second and you will see an exception when running it. Setting the CommandTimeout to either 0 or something higher than 2 will run fine. By the way, the default CommandTimeout is 30 seconds.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.Data.SqlClient;

namespace ConsoleApplication1
  class Program
    static void Main(string[] args)
      var builder = new SqlConnectionStringBuilder();
      builder.DataSource = "localhost";
      builder.IntegratedSecurity = true;
      builder.InitialCatalog = "master";

      var connectionString = builder.ConnectionString;

      using (var connection = new SqlConnection(connectionString))

        using (var command = connection.CreateCommand())
          command.CommandText = "WAITFOR DELAY '00:00:02'";
          command.CommandTimeout = 1;


What is a simple C or C++ TCP server and client example?

Although many year ago, clsocket seems a really nice small cross-platform (Windows, Linux, Mac OSX):

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 simulate a mouse click using JavaScript?

Here's a pure JavaScript function which will simulate a click (or any mouse event) on a target element:

function simulatedClick(target, options) {

  var event = target.ownerDocument.createEvent('MouseEvents'),
      options = options || {},
      opts = { // These are the default values, set up for un-modified left clicks
        type: 'click',
        canBubble: true,
        cancelable: true,
        view: target.ownerDocument.defaultView,
        detail: 1,
        screenX: 0, //The coordinates within the entire page
        screenY: 0,
        clientX: 0, //The coordinates within the viewport
        clientY: 0,
        ctrlKey: false,
        altKey: false,
        shiftKey: false,
        metaKey: false, //I *think* 'meta' is 'Cmd/Apple' on Mac, and 'Windows key' on Win. Not sure, though!
        button: 0, //0 = left, 1 = middle, 2 = right
        relatedTarget: null,

  //Merge the options with the defaults
  for (var key in options) {
    if (options.hasOwnProperty(key)) {
      opts[key] = options[key];

  //Pass in the options

  //Fire the event

Here's a working example:

You can simulate a click on any element in the DOM. Something like simulatedClick(document.getElementById('yourButtonId')) would work.

You can pass in an object into options to override the defaults (to simulate which mouse button you want, whether Shift/Alt/Ctrl are held, etc. The options it accepts are based on the MouseEvents API.

I've tested in Firefox, Safari and Chrome. Internet Explorer might need special treatment, I'm not sure.

Can I override and overload static methods in Java?

Parent class methods that are static are not part of a child class (although they are accessible), so there is no question of overriding it. Even if you add another static method in a subclass, identical to the one in its parent class, this subclass static method is unique and distinct from the static method in its parent class.

Checking if a list of objects contains a property with a specific value

using System.Linq;    
list.Where(x=> x.Name == nameToExtract);

Edit: misread question (now all matches)

Hash function for a string

Use boost::hash

#include <boost\functional\hash.hpp>


std::string a = "ABCDE";
size_t b = boost::hash_value(a);

How to display pie chart data values of each slice in chart.js

@Hung Tran's answer works perfect. As an improvement, I would suggest not showing values that are 0. Say you have 5 elements and 2 of them are 0 and rest of them have values, the solution above will show 0 and 0%. It is better to filter that out with a not equal to 0 check!

          var val =[i];
          var percent = String(Math.round(val/total*100)) + "%";

          if(val != 0) {
            ctx.fillText([i], model.x + x, model.y + y);
            // Display percent in another line, line break doesn't work for fillText
            ctx.fillText(percent, model.x + x, model.y + y + 15);

Updated code below:

var data = {
    datasets: [{
        data: [
        backgroundColor: [
        label: 'My dataset' // for legend
    labels: [

var pieOptions = {
  events: false,
  animation: {
    duration: 500,
    easing: "easeOutQuart",
    onComplete: function () {
      var ctx = this.chart.ctx;
      ctx.font = Chart.helpers.fontString(, 'normal',;
      ctx.textAlign = 'center';
      ctx.textBaseline = 'bottom'; (dataset) {

        for (var i = 0; i <; i++) {
          var model = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._model,
              total = dataset._meta[Object.keys(dataset._meta)[0]].total,
              mid_radius = model.innerRadius + (model.outerRadius - model.innerRadius)/2,
              start_angle = model.startAngle,
              end_angle = model.endAngle,
              mid_angle = start_angle + (end_angle - start_angle)/2;

          var x = mid_radius * Math.cos(mid_angle);
          var y = mid_radius * Math.sin(mid_angle);

          ctx.fillStyle = '#fff';
          if (i == 3){ // Darker text color for lighter background
            ctx.fillStyle = '#444';

          var val =[i];
          var percent = String(Math.round(val/total*100)) + "%";

          if(val != 0) {
            ctx.fillText([i], model.x + x, model.y + y);
            // Display percent in another line, line break doesn't work for fillText
            ctx.fillText(percent, model.x + x, model.y + y + 15);

var pieChartCanvas = $("#pieChart");
var pieChart = new Chart(pieChartCanvas, {
  type: 'pie', // or doughnut
  data: data,
  options: pieOptions

SELECT using 'CASE' in SQL

Try this.


How do I replace text in a selection?

You can use ctrl+F to find the text.
ctrl+h to enter the replacement text. Then ctrl+shift+h to replace the current selected text and move to next matched text.

This is for windows. But you can check in mac also for which you might want to check the key bindings under Preferences.

Change R default library path using .libPaths in fails to work

I generally try to keep all of my packages in one library, but if you want to add a library why not append the new library (which must already exist in your filesystem) to the existing library path?

.libPaths( c( .libPaths(), "~/userLibrary") )
 # obviously this would need to be a valid file directory in your OS
 # min just happened to be on a Mac that day

Or (and this will make the userLibrary the first place to put new packages):

.libPaths( c( "~/userLibrary" , .libPaths() ) )

Then I get (at least back when I wrote this originally):

> .libPaths()
[1] "/Library/Frameworks/R.framework/Versions/2.15/Resources/library"
[2] "/Users/user_name/userLibrary"  

The .libPaths function is a bit different than most other nongraphics functions. It works via side-effect. The functions Sys.getenv and Sys.setenv that report and alter the R environment variables have been split apart but .libPaths can either report or alter its target.

The information about the R startup process can be read at ?Startup help page and there is RStudio material at:

In your case it appears that RStudio is not respecting the settings or perhaps is overriding them by reading an .Rprofile setting from one of the RStudio defaults. It should also be mentioned that the result from this operation also appends the contents of calls to .Library and, which is further reason why an RStudio- (or any other IDE or network installed-) hosted R might exhibit different behavior.

Since Sys.getenv() returns the current system environment for the R process, you can see the library and other paths with:

Sys.getenv()[ grep("LIB|PATH", names(Sys.getenv())) ]

The two that matter for storing and accessing packages are (now different on a Linux box):

R_LIBS_SITE                          /usr/local/lib/R/site-library:/usr/lib/R/site-library:/usr/lib/R/library
R_LIBS_USER                          /home/david/R/x86_64-pc-linux-gnu-library/3.5.1/

How to send password securely over HTTP?

Using https sounds best option here (certificates are not that expensive nowadays). However if http is a requirement, you may use some encription - encript it on server side and decript in users browser (send key separately).

We have used that while implementing - encription is done on clients (sender/receiver) sides, so users data are not available on network nor server layer.

How to find the socket buffer size of linux

Whilst, as has been pointed out, it is possible to see the current default socket buffer sizes in /proc, it is also possible to check them using sysctl (Note: Whilst the name includes ipv4 these sizes also apply to ipv6 sockets - the ipv6 tcp_v6_init_sock() code just calls the ipv4 tcp_init_sock() function):

 sysctl net.ipv4.tcp_rmem
 sysctl net.ipv4.tcp_wmem

However, the default socket buffers are just set when the sock is initialised but the kernel then dynamically sizes them (unless set using setsockopt() with SO_SNDBUF). The actual size of the buffers for currently open sockets may be inspected using the ss command (part of the iproute package), which can also provide a bunch more info on sockets like congestion control parameter etc. E.g. To list the currently open TCP (t option) sockets and associated memory (m) information:

ss -tm

Here's some example output:

State       Recv-Q Send-Q        Local Address:Port        Peer Address:Port
ESTAB       0      0   

Here's a brief explanation of skmem (socket memory) - for more info you'll need to look at the kernel sources (e.g. sock.h):

rb:sk_rcvbuf          # current receive buffer size
tb:sk_sndbuf          # current transmit buffer size
w:sk_wmem_queued      # persistent transmit queue size

typescript - cloning object

I ended up doing:

public clone(): any {
  const result = new (<any>this.constructor);

  // some deserialization code I hade in place already...
  // which deep copies all serialized properties of the
  // object graph
  // result.deserialize(this)

  // you could use any of the usggestions in the other answers to
  // copy over all the desired fields / properties

  return result;


var cloneObj = new (<any>this.constructor());

from @Fenton gave runtime errors.

Typescript version: 2.4.2

List submodules in a Git repository

If there isn't any .gitmodules file, but a submodules configuration exists in .git/modules/:

find .git/modules/ -name config -exec grep url {} \;

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]')

How to enable support of CPU virtualization on Macbook Pro?

CPU Virtualization is enabled by default on all MacBooks with compatible CPUs (i7 is compatible). You can try to reset PRAM if you think it was disabled somehow, but I doubt it.

I think the issue might be in the old version of OS. If your MacBook is i7, then you better upgrade OS to something newer.

Best way to structure a tkinter application?

I advocate an object oriented approach. This is the template that I start out with:

# Use Tkinter for python 2, tkinter for python 3
import tkinter as tk

class MainApplication(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        tk.Frame.__init__(self, parent, *args, **kwargs)
        self.parent = parent

        <create the rest of your GUI here>

if __name__ == "__main__":
    root = tk.Tk()
    MainApplication(root).pack(side="top", fill="both", expand=True)

The important things to notice are:

  • I don't use a wildcard import. I import the package as "tk", which requires that I prefix all commands with tk.. This prevents global namespace pollution, plus it makes the code completely obvious when you are using Tkinter classes, ttk classes, or some of your own.

  • The main application is a class. This gives you a private namespace for all of your callbacks and private functions, and just generally makes it easier to organize your code. In a procedural style you have to code top-down, defining functions before using them, etc. With this method you don't since you don't actually create the main window until the very last step. I prefer inheriting from tk.Frame just because I typically start by creating a frame, but it is by no means necessary.

If your app has additional toplevel windows, I recommend making each of those a separate class, inheriting from tk.Toplevel. This gives you all of the same advantages mentioned above -- the windows are atomic, they have their own namespace, and the code is well organized. Plus, it makes it easy to put each into its own module once the code starts to get large.

Finally, you might want to consider using classes for every major portion of your interface. For example, if you're creating an app with a toolbar, a navigation pane, a statusbar, and a main area, you could make each one of those classes. This makes your main code quite small and easy to understand:

class Navbar(tk.Frame): ...
class Toolbar(tk.Frame): ...
class Statusbar(tk.Frame): ...
class Main(tk.Frame): ...

class MainApplication(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        tk.Frame.__init__(self, parent, *args, **kwargs)
        self.statusbar = Statusbar(self, ...)
        self.toolbar = Toolbar(self, ...)
        self.navbar = Navbar(self, ...)
        self.main = Main(self, ...)

        self.statusbar.pack(side="bottom", fill="x")
        self.toolbar.pack(side="top", fill="x")
        self.navbar.pack(side="left", fill="y")
        self.main.pack(side="right", fill="both", expand=True)

Since all of those instances share a common parent, the parent effectively becomes the "controller" part of a model-view-controller architecture. So, for example, the main window could place something on the statusbar by calling self.parent.statusbar.set("Hello, world"). This allows you to define a simple interface between the components, helping to keep coupling to a minimun.

how to empty recyclebin through command prompt?

You can use this PowerShell command.

Clear-RecycleBin -Force

Note: If you want a confirmation prompt, remove the -Force flag

How to delete duplicate rows in SQL Server?

Another way of removing dublicated rows without loosing information in one step is like following:

delete from dublicated_table t1 (nolock)
join (
    select t2.dublicated_field
    , min(len(t2.field_kept)) as min_field_kept
    from dublicated_table t2 (nolock)
    group by t2.dublicated_field having COUNT(*)>1
) t3 
on t1.dublicated_field=t3.dublicated_field 
    and len(t1.field_kept)=t3.min_field_kept

How to insert close button in popover for Bootstrap

Previous examples have two main drawbacks:

  1. The 'close' button needs in some way, to be aware of the ID of the referenced-element.
  2. The need of adding on the '' event, a 'click' listener to the close button; which is also not a good solution because of, you would then be adding such listener each time the 'popover' is shown.

Below is a solution which has not such drawbacks.

By the default, the 'popover' element is inserted immediately after the referenced-element in the DOM (then notice the referenced-element and the popover are immediate sibling elements). Thus, when the 'close' button is clicked, you can simply look for its closest 'div.popover' parent, and then look for the immediately preceding sibling element of such parent.

Just add the following code in the 'onclick' handler of the 'close button:



var genericCloseBtnHtml = '<button onclick="$(this).closest(\'div.popover\').popover(\'hide\');" type="button" class="close" aria-hidden="true">&times;</button>';

    placement: 'auto left',
    trigger: 'manual',
    html: true,
    title: 'Alert' + genericCloseBtnHtml,
    content: 'invalid email and/or password'

Wait .5 seconds before continuing code

Make a timer, that activates whatever code you want to when it ticks. Make sure the first line in the timer's code is:

timer.enabled = false

Replace timer with whatever you named your timer.

Then use this in your code:

timer.enabled = true
Dim allelements As HtmlElementCollection = WebBrowser1.Document.All
For Each webpageelement As HtmlElement In allelements
    If webpageelement.InnerText = "Sign Up" Then
    End If

JBoss AS 7: How to clean up tmp?

Files related for deployment (and others temporary items) are created in standalone/tmp/vfs (Virtual File System). You may add a policy at startup for evicting temporary files :


What does it mean when MySQL is in the state "Sending data"?

In this state:

The thread is reading and processing rows for a SELECT statement, and sending data to the client.

Because operations occurring during this this state tend to perform large amounts of disk access (reads).

That's why it takes more time to complete and so is the longest-running state over the lifetime of a given query.

Installing specific laravel version with composer create-project

From the composer help create-project command

The create-project command creates a new project from a given
package into a new directory. If executed without params and in a directory with a composer.json file it installs the packages for the current project.
You can use this command to bootstrap new projects or setup a clean
version-controlled installation for developers of your project.

You can also specify the version with the package name using = or : as separator.

To install unstable packages, either specify the version you want, or use the --stability=dev (where dev can be one of RC, beta, alpha or dev).

This command works:

composer create-project laravel/laravel=4.1.27 your-project-name --prefer-dist

This works with the * notation.

Why is there no ForEach extension method on IEnumerable?

One workaround is to write .ToList().ForEach(x => ...).


Easy to understand - reader only needs to know what ships with C#, not any additional extension methods.

Syntactic noise is very mild (only adds a little extranious code).

Doesn't usually cost extra memory, since a native .ForEach() would have to realize the whole collection, anyway.


Order of operations isn't ideal. I'd rather realize one element, then act on it, then repeat. This code realizes all elements first, then acts on them each in sequence.

If realizing the list throws an exception, you never get to act on a single element.

If the enumeration is infinite (like the natural numbers), you're out of luck.

Android Respond To URL in Intent

You might need to allow different combinations of data in your intent filter to get it to work in different cases (http/ vs https/, www. vs no www., etc).

For example, I had to do the following for an app which would open when the user opened a link to Google Drive forms (

Note that path prefix is optional.

            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.DEFAULT" />
            <category android:name="android.intent.category.BROWSABLE" />

            <data android:scheme="http" />
            <data android:scheme="https" />

            <data android:host="" />
            <data android:host="" />

            <data android:pathPrefix="/forms" />

Replace forward slash "/ " character in JavaScript string?

Try escaping the slash: someString.replace(/\//g, "-");

By the way - / is a (forward-)slash; \ is a backslash.

Unicode, UTF, ASCII, ANSI format differences

Going down your list:

  • "Unicode" isn't an encoding, although unfortunately, a lot of documentation imprecisely uses it to refer to whichever Unicode encoding that particular system uses by default. On Windows and Java, this often means UTF-16; in many other places, it means UTF-8. Properly, Unicode refers to the abstract character set itself, not to any particular encoding.
  • UTF-16: 2 bytes per "code unit". This is the native format of strings in .NET, and generally in Windows and Java. Values outside the Basic Multilingual Plane (BMP) are encoded as surrogate pairs. These used to be relatively rarely used, but now many consumer applications will need to be aware of non-BMP characters in order to support emojis.
  • UTF-8: Variable length encoding, 1-4 bytes per code point. ASCII values are encoded as ASCII using 1 byte.
  • UTF-7: Usually used for mail encoding. Chances are if you think you need it and you're not doing mail, you're wrong. (That's just my experience of people posting in newsgroups etc - outside mail, it's really not widely used at all.)
  • UTF-32: Fixed width encoding using 4 bytes per code point. This isn't very efficient, but makes life easier outside the BMP. I have a .NET Utf32String class as part of my MiscUtil library, should you ever want it. (It's not been very thoroughly tested, mind you.)
  • ASCII: Single byte encoding only using the bottom 7 bits. (Unicode code points 0-127.) No accents etc.
  • ANSI: There's no one fixed ANSI encoding - there are lots of them. Usually when people say "ANSI" they mean "the default locale/codepage for my system" which is obtained via Encoding.Default, and is often Windows-1252 but can be other locales.

There's more on my Unicode page and tips for debugging Unicode problems.

The other big resource of code is which contains more information than you'll ever be able to work your way through - possibly the most useful bit is the code charts.

JSON Array iteration in Android/Java

If you're using the Java implementation, which is open source, you can just make JSONArray implement the Iterable interface and add the following method to the class:

public Iterator iterator() {
    return this.myArrayList.iterator();

This will make all instances of JSONArray iterable, meaning that the for (Object foo : bar) syntax will now work with it (note that foo has to be an Object, because JSONArrays do not have a declared type). All this works because the JSONArray class is backed by a simple ArrayList, which is already iterable. I imagine that other open source implementations would be just as easy to change.

sorting and paging with gridview

More simple way...:

    Dim dt As DataTable = DirectCast(GridView1.DataSource, DataTable)
    Dim dv As New DataView(dt)

    If GridView1.Attributes("dir") = SortDirection.Ascending Then
        dv.Sort = e.SortExpression & " DESC" 
        GridView1.Attributes("dir") = SortDirection.Descending

        GridView1.Attributes("dir") = SortDirection.Ascending
        dv.Sort = e.SortExpression & " ASC"

    End If

    GridView1.DataSource = dv

How can I find the dimensions of a matrix in Python?

The correct answer is the following:

import numpy 

MVVM: Tutorial from start to finish?

My blog has a complete series of tutorial starting from scratch for WPF MVVM and WPF Prism. Have a look here:

Modelling an elevator using Object-Oriented Analysis and Design

First there is an elevator class. It has a direction (up, down, stand, maintenance), a current floor and a list of floor requests sorted in the direction. It receives request from this elevator.

Then there is a bank. It contains the elevators and receives the requests from the floors. These are scheduled to all active elevators (not in maintenance).

The scheduling will be like:

  • if available pick a standing elevator for this floor.
  • else pick an elevator moving to this floor.
  • else pick a standing elevator on an other floor.
  • else pick the elevator with the lowest load.

Each elevator has a set of states.

  • Maintenance: the elevator does not react to external signals (only to its own signals).
  • Stand: the elevator is fixed on a floor. If it receives a call. And the elevator is on that floor, the doors open. If it is on another floor, it moves in that direction.
  • Up: the elevator moves up. Each time it reaches a floor, it checks if it needs to stop. If so it stops and opens the doors. It waits for a certain amount of time and closes the door (unless someting is moving through them. Then it removes the floor from the request list and checks if there is another request. If so the elevator starts moving again. If not it enters the state stand.
  • Down: like up but in reverse direction.

There are additional signals:

  • alarm. The elevator stops. And if it is on a floor, the doors open, the request list is cleared, the requests moved back to the bank.
  • door open. Opens the doors if an elevator is on a floor and not moving.
  • door closes. Closed the door if they are open.

EDIT: Some elevators don't start at bottom/first_floor esp. in case of skyscrapers.

min_floor & max_floor are two additional attributes for Elevator.

Python: Total sum of a list of numbers with the for loop

for s in range(0,len(x)):
print sum   

How do you specify table padding in CSS? ( table, not cell padding )

Here's the thing you should understand about tables... They're not a tree of nested independent elements. They're a single compound element. While the individual TDs behave more or less like CSS block elements, the intermediate stuff (anything between the TABLE and TD, including TRs and TBODYs) is indivisible and doesn't fall into either inline nor block. No random HTML elements are allowed in that other-dimensional space, and the size of such other-dimensional space isn't configurable at all through CSS. Only the HTML cellspacing property can even get at it, and that property has no analog in CSS.

So, to solve your problem, I'd suggest either a DIV wrapper as another poster suggests, or if you absolutely must keep it contained in the table, you have this ugly junk:

    .padded tr.first td { padding-top:10px; }
    .padded tr.last td { padding-bottom:10px; }
    .padded td.first { padding-left:10px; }
    .padded td.last { padding-right:10px; }

<table class='padded'>
    <tr class='first'>
        <td class='first'>a</td><td>b</td><td class='last'>c</td>
        <td class='first'>d</td><td>e</td><td class='last'>f</td>
    <tr class='last'>
        <td class='first'>g</td><td>h</td><td class='last'>i</td>

How do I parse command line arguments in Bash?

Assume we create a shell script named as follow

until [ $# -eq 0 ]
  name=${1:1}; shift;
  if [[ -z "$1" || $1 == -* ]] ; then eval "export $name=true"; else eval "export $name=$1"; shift; fi  
echo "year=$year month=$month day=$day flag=$flag"

After we run the following command:

sh  -year 2017 -flag  -month 12 -day 22 

The output would be:

year=2017 month=12 day=22 flag=true

Adding system header search path to Xcode

To use quotes just for completeness.

"/Users/my/work/a project with space"/**

If not recursive, remove the /**

boolean in an if statement



var p=5;

p==5 ? true
p=="5" ?  true
p==="5" ? false

=== means same type also same value == just same value

enter image description here

Gradle task - pass arguments to Java application

You can find the solution in Problems passing system properties and parameters when running Java class via Gradle . Both involve the use of the args property

Also you should read the difference between passing with -D or with -P that is explained in the Gradle documentation

How to escape strings in SQL Server using PHP?

In order to escape single- and double-quotes, you have to double them up:

$value = 'This is a quote, "I said, 'Hi'"';

$value = str_replace( "'", "''", $value ); 

$value = str_replace( '"', '""', $value );

$query = "INSERT INTO TableName ( TextFieldName ) VALUES ( '$value' ) ";


and attribution: Escape Character In Microsoft SQL Server 2000

How to split a string in Java

From the documentation:

public String[] split(String regex,int limit) Splits this string around matches of the given regular expression. The array returned by this method contains each substring of this string that is terminated by another substring that matches the given expression or is terminated by the end of the string. The substrings in the array are in the order in which they occur in this string. If the expression does not match any part of the input then the resulting array has just one element, namely this string.

Basically you can do something like this:

String s = "123-456-789-123"; // The String to be split
String[] array = s.split("-"); // Split according to the hyphen and put them in an array
for(String subString : array){ // Cycle through the array



How do Python functions handle the types of the parameters that you pass in?

As Alex Martelli explains,

The normal, Pythonic, preferred solution is almost invariably "duck typing": try using the argument as if it was of a certain desired type, do it in a try/except statement catching all exceptions that could arise if the argument was not in fact of that type (or any other type nicely duck-mimicking it;-), and in the except clause, try something else (using the argument "as if" it was of some other type).

Read the rest of his post for helpful information.

Force IE compatibility mode off using tags

There is the "edge" mode.

      <meta http-equiv="X-UA-Compatible" content="IE=edge" />
      <title>My Web Page</title>
      <p>Content goes here.</p>

From the linked MSDN page:

Edge mode tells Windows Internet Explorer to display content in the highest mode available, which actually breaks the “lock-in” paradigm. With Internet Explorer 8, this is equivalent to IE8 mode. If a (hypothetical) future release of Internet Explorer supported a higher compatibility mode, pages set to Edge mode would appear in the highest mode supported by that version; however, those same pages would still appear in IE8 mode when viewed with Internet Explorer 8.

However, "edge" mode is not encouraged in production use:

It is recommended that Web developers restrict their use of Edge mode to test pages and other non-production uses because of the possible unexpected results of rendering page content in future versions of Windows Internet Explorer.

I honestly don't entirely understand why. But according to this, the best way to go at the moment is using IE=8.

How do you turn a Mongoose document into a plain object?

In some cases as @JohnnyHK suggested, you would want to get the Object as a Plain Javascript. as described in this Mongoose Documentation there is another alternative to query the data directly as object:

const docs = await Model.find().lean();

In addition if someone might want to conditionally turn to an object,it is also possible as an option argument, see find() docs at the third parameter:

const toObject = true;
const docs = await Model.find({},null,{lean:toObject});

its available on the fonctions: find(), findOne(), findById(), findOneAndUpdate(), and findByIdAndUpdate().

How to enable LogCat/Console in Eclipse for Android?

In the Window menu, open Show View -> Other ... and type log to find it.


<table border="1"></table>

should do the trick.

Make anchor link go some pixels above where it's linked to

The easiest solution:


#link {
    top:-120px; /* -(some pixels above) */


    <a href="#link">Link</a>
        <div id="link"></div> /*this div should placed inside a target div in the page*/

How can we generate getters and setters in Visual Studio?

In Visual Studio Community Edition 2015 you can select all the fields you want and then press Ctrl + . to automatically generate the properties.

You have to choose if you want to use the property instead of the field or not.

Generating sql insert into for Oracle

If you have an empty table the Export method won't work. As a workaround. I used the Table View of Oracle SQL Developer. and clicked on Columns. Sorted by Nullable so NO was on top. And then selected these non nullable values using shift + select for the range.

This allowed me to do one base insert. So that Export could prepare a proper all columns insert.

Add shadow to custom shape on Android

If you don't mind doing some custom drawing with the Canvas API, check out this answer about drop shadows. Here's a follow-up question to that one which fixes a problem in the original.

What is the list of valid @SuppressWarnings warning names in Java?

A new favorite for me is @SuppressWarnings("WeakerAccess") in IntelliJ, which keeps it from complaining when it thinks you should have a weaker access modifier than you are using. We have to have public access for some methods to support testing, and the @VisibleForTesting annotation doesn't prevent the warnings.

ETA: "Anonymous" commented, on the page @MattCampbell linked to, the following incredibly useful note:

You shouldn't need to use this list for the purpose you are describing. IntelliJ will add those SuppressWarnings for you automatically if you ask it to. It has been capable of doing this for as many releases back as I remember.

Just go to the location where you have the warning and type Alt-Enter (or select it in the Inspections list if you are seeing it there). When the menu comes up, showing the warning and offering to fix it for you (e.g. if the warning is "Method may be static" then "make static" is IntellJ's offer to fix it for you), instead of selecting "enter", just use the right arrow button to access the submenu, which will have options like "Edit inspection profile setting" and so forth. At the bottom of this list will be options like "Suppress all inspections for class", "Suppress for class", "Suppress for method", and occasionally "Suppress for statement". You probably want whichever one of these appears last on the list. Selecting one of these will add a @SuppressWarnings annotation (or comment in some cases) to your code suppressing the warning in question. You won't need to guess at which annotation to add, because IntelliJ will choose based on the warning you selected.

Best way to define error codes/strings in Java?

Using interface as message constant is generally a bad idea. It will leak into client program permanently as part of exported API. Who knows, that later client programmers might parse that error messages(public) as part of their program.

You will be locked forever to support this, as changes in string format will/may break client program.

How to do IF NOT EXISTS in SQLite

You can also set a Constraint on a Table with the KEY fields and set On Conflict "Ignore"

When an applicable constraint violation occurs, the IGNORE resolution algorithm skips the one row that contains the constraint violation and continues processing subsequent rows of the SQL statement as if nothing went wrong. Other rows before and after the row that contained the constraint violation are inserted or updated normally. No error is returned when the IGNORE conflict resolution algorithm is used.

SQLite Documentation

Return a value if no rows are found in Microsoft tSQL

DECLARE @col int; 
select @col = id  FROM site WHERE status = 1; 
select coalesce(@col,0);

Difference between $(document.body) and $('body')

They refer to the same element, the difference is that when you say document.body you are passing the element directly to jQuery. Alternatively, when you pass the string 'body', the jQuery selector engine has to interpret the string to figure out what element(s) it refers to.

In practice either will get the job done.

If you are interested, there is more information in the documentation for the jQuery function.

How to use JNDI DataSource provided by Tomcat in Spring?

In your spring class, You can inject a bean annotated like as

private DataSource dataSource;

and You add this in your context.xml

<beans:bean id="dbDataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
    <beans:property name="jndiName" value="java:comp/env/jdbc/MyLocalDB"/>

You can declare the JNDI resource in tomcat's server.xml using

<Resource name="jdbc/TestDB" 


back to context.xml de spring add this

<ResourceLink name="jdbc/MyLocalDB"
                type="javax.sql.DataSource" />

if, like this exmple you are injecting connection to database, make sure that MySQL jar is present in the tomcat lib directory, otherwise tomcat will not be able to create the MySQL database connection pool.

jQuery find and replace string

You could do something this way:

$(document.body).find('*').each(function() {
    if($(this).hasClass('lollypops')){ //class replacing..many ways to do this :)
    var tmp = $(this).children().remove(); //removing and saving children to a tmp obj
    var text = $(this).text(); //getting just current node text
    text = text.replace(/lollypops/g, "marshmellows"); //replacing every lollypops occurence with marshmellows
    $(this).text(text); //setting text
    $(this).append(tmp); //re-append 'foundlings'


How can I compare time in SQL Server?

Just change convert datetime to time that should do the trick:

SELECT timeEvent 
FROM tbEvents 
WHERE convert(time, startHour) >= convert(time, @startHour)

Are these methods thread safe?

The only problem with threads is accessing the same object from different threads without synchronization.

If each function only uses parameters for reading and local variables, they don't need any synchronization to be thread-safe.

Erase whole array Python

Note that list and array are different classes. You can do:

del mylist[:]

This will actually modify your existing list. David's answer creates a new list and assigns it to the same variable. Which you want depends on the situation (e.g. does any other variable have a reference to the same list?).


a = [1,2]
b = a
a = []


a = [1,2]
b = a
del a[:]

Print a and b each time to see the difference.

How do you add an SDK to Android Studio?

You have to put your SDK's in a given directory or .app directory. You have to do it in finder while you are out of the application i'm assuming, but personally I'd use terminal in Mac instead of doing it in the App itself or finder. According to Google:

On Windows and Mac, the individual tools and other SDK packages are saved within the Android Studio application directory. To access the tools directly, use a terminal to navigate into the application and locate the sdk/ directory. For example:

 Windows: \Users\<user>\AppData\Local\Android\android-studio\sdk\
 Mac: /Applications/Android\

Simplest/cleanest way to implement a singleton in JavaScript

The clearest answer should be this one from the book Learning JavaScript Design Patterns by Addy Osmani.

var mySingleton = (function () {

  // Instance stores a reference to the singleton
  var instance;

  function init() {

    // Singleton

    // Private methods and variables
    function privateMethod(){
        console.log( "I am private" );

    var privateVariable = "I'm also private";

    var privateRandomNumber = Math.random();

    return {

      // Public methods and variables
      publicMethod: function () {
        console.log( "The public can see me!" );

      publicProperty: "I am also public",

      getRandomNumber: function() {
        return privateRandomNumber;



  return {

    // Get the singleton instance if one exists
    // or create one if it doesn't
    getInstance: function () {

      if ( !instance ) {
        instance = init();

      return instance;



Replacing accented characters php

Adding a little bit to what Lizard said, it worked to display correctly on web page, but added some other codes to complete what I was looking for replacing my tags to search correctly into my database with special characters. Thanks in advance.

$unwanted_array = array(    'Š'=>'S', 'š'=>'s', 'Ž'=>'Z', 'ž'=>'z', 'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A', 'Ä'=>'A', 'Å'=>'A', 'Æ'=>'A', 'Ç'=>'C', 'È'=>'E', 'É'=>'E',
                            'Ê'=>'E', 'Ë'=>'E', 'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I', 'Ñ'=>'N', 'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O', 'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O', 'Ù'=>'U',
                            'Ú'=>'U', 'Û'=>'U', 'Ü'=>'U', 'Ý'=>'Y', 'Þ'=>'B', 'ß'=>'Ss', 'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a', 'æ'=>'a', 'ç'=>'c',
                            'è'=>'e', 'é'=>'e', 'ê'=>'e', 'ë'=>'e', 'ì'=>'i', 'í'=>'i', 'î'=>'i', 'ï'=>'i', 'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o', 'ô'=>'o', 'õ'=>'o',
                            'ö'=>'o', 'ø'=>'o', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'ý'=>'y', 'þ'=>'b', 'ÿ'=>'y', 
                            '&#225;'=>'a', '&#233;'=>'e', '&#237;'=>'i', '&#243;'=>'o', '&#250;'=>'u',  
                            '&#193;'=>'A', '&#201;'=>'E', '&#205;'=>'I', '&#211;'=>'O', '&#218;'=>'U',
                            '&#209;'=>'N', '&#241;'=>'n' );
$newtag = strtr( $newtag, $unwanted_array );

Warning about SSL connection when connecting to MySQL database

How about using SSL but turning off server verification (such as when in development mode on your own computer):


Get Current Session Value in JavaScript?

Another approach is in your chtml

<input type="hidden" id="hdnSession" data-value="@Request.RequestContext.HttpContext.Session['someKey']" />

  and the script is

var sessionValue= $("#hdnSession").data('value');

or you may access directly by

 jQuery(document).ready(function ($) {
        var value = '@Request.RequestContext.HttpContext.Session["someKey"]';

Inline labels in Matplotlib

Nice question, a while ago I've experimented a bit with this, but haven't used it a lot because it's still not bulletproof. I divided the plot area into a 32x32 grid and calculated a 'potential field' for the best position of a label for each line according the following rules:

  • white space is a good place for a label
  • Label should be near corresponding line
  • Label should be away from the other lines

The code was something like this:

import matplotlib.pyplot as plt
import numpy as np
from scipy import ndimage

def my_legend(axis = None):

    if axis == None:
        axis = plt.gca()

    N = 32
    Nlines = len(axis.lines)
    print Nlines

    xmin, xmax = axis.get_xlim()
    ymin, ymax = axis.get_ylim()

    # the 'point of presence' matrix
    pop = np.zeros((Nlines, N, N), dtype=np.float)    

    for l in range(Nlines):
        # get xy data and scale it to the NxN squares
        xy = axis.lines[l].get_xydata()
        xy = (xy - [xmin,ymin]) / ([xmax-xmin, ymax-ymin]) * N
        xy = xy.astype(np.int32)
        # mask stuff outside plot        
        mask = (xy[:,0] >= 0) & (xy[:,0] < N) & (xy[:,1] >= 0) & (xy[:,1] < N)
        xy = xy[mask]
        # add to pop
        for p in xy:
            pop[l][tuple(p)] = 1.0

    # find whitespace, nice place for labels
    ws = 1.0 - (np.sum(pop, axis=0) > 0) * 1.0 
    # don't use the borders
    ws[:,0]   = 0
    ws[:,N-1] = 0
    ws[0,:]   = 0  
    ws[N-1,:] = 0  

    # blur the pop's
    for l in range(Nlines):
        pop[l] = ndimage.gaussian_filter(pop[l], sigma=N/5)

    for l in range(Nlines):
        # positive weights for current line, negative weight for others....
        w = -0.3 * np.ones(Nlines, dtype=np.float)
        w[l] = 0.5

        # calculate a field         
        p = ws + np.sum(w[:, np.newaxis, np.newaxis] * pop, axis=0)
        plt.imshow(p, interpolation='nearest')

        pos = np.argmax(p)  # note, argmax flattens the array first 
        best_x, best_y =  (pos / N, pos % N) 
        x = xmin + (xmax-xmin) * best_x / N       
        y = ymin + (ymax-ymin) * best_y / N       

        axis.text(x, y, axis.lines[l].get_label(), 


x = np.linspace(0, 1, 101)
y1 = np.sin(x * np.pi / 2)
y2 = np.cos(x * np.pi / 2)
y3 = x * x
plt.plot(x, y1, 'b', label='blue')
plt.plot(x, y2, 'r', label='red')
plt.plot(x, y3, 'g', label='green')

And the resulting plot: enter image description here

How to select an option from drop down using Selenium WebDriver C#?

You just need to pass the value and enter key:


How to get Java Decompiler / JD / JD-Eclipse running in Eclipse Helios

Its should work for all version of eclipse even in Spring tool suit(STS). Here is the steps

Go to the URl Follow The link to download or click the bellow link to direct download Click Here to download

Download JD-Eclipse. Download and unzip the JD-Eclipse Update Site,

Launch Eclipse,

Click on "Help > Install New Software...",

Click on button "Add..." to add an new repository,

Enter "JD-Eclipse Update Site" and select the local site directory,

enter image description here

Select extracted folder and give any name. I have given JDA. and click ok.

enter image description here

Check "Java Decompiler Eclipse Plug-in",

enter image description here

Next, next, next... and restart Eclipse.

Parse string to DateTime in C#

Put the value of a human-readable string into a .NET DateTime with code like this:

DateTime.ParseExact("April 16, 2011 4:27 pm", "MMMM d, yyyy h:mm tt", null);


In my humble experience with postgres 9.6, cascade delete doesn't work in practice for tables that grow above a trivial size.

  • Even worse, while the delete cascade is going on, the tables involved are locked so those tables (and potentially your whole database) is unusable.
  • Still worse, it's hard to get postgres to tell you what it's doing during the delete cascade. If it's taking a long time, which table or tables is making it slow? Perhaps it's somewhere in the pg_stats information? It's hard to tell.

Uncaught TypeError: Cannot read property 'value' of null

Instead of document or $(document) to avoid JQuery, you can add a TimeOut to validate the objects. TimeOut is executed after loading all objects within the page and other events...

setTimeout(function () { 

var str = document.getElementById("cal_preview").value;
var str1 = document.getElementById("year").value;

}, 0);

How to set bootstrap navbar active class with Angular JS?

Just to add my two cents in the debate I have made a pure angular module (no jquery), and it will also work with hash urls containing data. (i.g. #/this/is/path?this=is&some=data)

You just add the module as a dependency and auto-active to one of the ancestors of the menu. Like this:

<ul auto-active>
    <li><a href="#/">main</a></li>
    <li><a href="#/first">first</a></li>
    <li><a href="#/second">second</a></li>
    <li><a href="#/third">third</a></li>

And the module look like this:

(function () {
    angular.module('autoActive', [])
        .directive('autoActive', ['$location', function ($location) {
        return {
            restrict: 'A',
            scope: false,
            link: function (scope, element) {
                function setActive() {
                    var path = $location.path();
                    if (path) {
                        angular.forEach(element.find('li'), function (li) {
                            var anchor = li.querySelector('a');
                            if (anchor.href.match('#' + path + '(?=\\?|$)')) {
                            } else {


                scope.$on('$locationChangeSuccess', setActive);

* (You can of course just use the directive part)

** It's also worth noticing that this doesn't work for empty hashes (i.g. or just it needs to have at least or just But this happens automatically with ngResource and the like.

Android, How to limit width of TextView (and add three dots at the end of text)?

Add These two lines in your text


jQuery Keypress Arrow Keys

Please refer the link from JQuery

It says

The keypress event is sent to an element when the browser registers keyboard input. This is similar to the keydown event, except that modifier and non-printing keys such as Shift, Esc, and delete trigger keydown events but not keypress events. Other differences between the two events may arise depending on platform and browser.

That means you can not use keypress in case of arrows.

vertical divider between two columns in bootstrap

With Bootstrap 4 you can use borders, avoiding writing other CSS.


And if you want space between content and border you can use padding. (in this example padding left 4px)



    <link href="" rel="stylesheet"/>_x000D_
    <div class="row">_x000D_
      <div class="offset-6 border-left pl-4">First</div>_x000D_
      <div class="offset-6 border-left pl-4">Second</div>_x000D_

How to select all instances of selected region in Sublime Text

Even though there are multiple answers, there is an issue using this approach. It selects all the text that matches, not only the whole words like variables.

As per "Sublime Text: Select all instances of a variable and edit variable name" and the answer in "Sublime Text: Select all instances of a variable and edit variable name", we have to start with a empty selection. That is, start using the shortcut Alt+F3 which would help selecting only the whole words.

How to make Google Fonts work in IE?

Google Fonts uses Web Open Font Format (WOFF), which is good, because it's the recommended font format by the W3C.

IE versions older than IE9 don't support Web Open Font Format (WOFF) because it didn't exist back then. To support < IE9, you need to serve your font in Embedded Open Type (EOT). To do this you will need to write your own @font-face css tag instead of using the embed script from Google. Also you need to convert the original WOFF file to EOT.

You can convert your WOFF to EOT over here by first converting it to TTF and then to EOT:

Then you can serve the EOT font like this:

@font-face {
    font-family: 'MyFont';
    src: url('myfont.eot');

Now it works in < IE9. However, modern browsers don't support EOT anymore, so now your fonts won't work in modern browsers. So you need to specify them both. The src property supports this by comma seperating the font urls and specefying the type:

src: url('myfont.woff') format('woff'),
     url('myfont.eot') format('embedded-opentype');

However, < IE9 doesn't understand this, it just graps the text between the first quote and the last quote, so it will actually get:

myfont.woff') format('woff'),
url('myfont.eot') format('embedded-opentype

as the URL to the font. We can fix this by first specifying a src with only one url which is the EOT format, then specifying a second src property that's meant for the modern browsers and < IE9 will not understand. Because < IE9 will not understand it it will ignore the tag so the EOT will still be working. The modern browsers will use the last specified font they support, so probably WOFF.

src: url('myfont.eot');
src: url('myfont.woff') format('woff');

So only because in the second src property you specify the format('woff'), < IE9 won't understand it (or actually it just can't find the font at the url myfont.woff') format('woff) and will keep using the first specified one (eot).

So now you got your Google Webfonts working for < IE9 and modern browsers!

For more information about different font type and browser support, read this perfect article by Alex Tatiyants:

How to make the Facebook Like Box responsive?

As of August 4 2015, the native facebook like box have a responsive code snippet available at Facebook Developers page.

You can generate your responsive Facebook likebox here

This is the best solution ever rather than hacking CSS.

ASP.NET Identity - HttpContext has no extension method for GetOwinContext

For Devs getting this error in Web API Project -

The GetOwinContext extension method is defined in System.Web.Http.Owin dll and one more package will be needed i.e. Microsoft.Owin.Host.SystemWeb. This package needs to be installed in your project from nuget.

Link To Package: OWIN Package Install Command -

Install-Package Microsoft.AspNet.WebApi.Owin    

Link To System.web Package : Package Install Command -

Install-Package Microsoft.Owin.Host.SystemWeb

In order to resolve this error you need to find why its occurring in your case. Please Cross check below points in your code -

  1. You must have reference to Microsoft.AspNet.Identity.Owin;

    using Microsoft.AspNet.Identity.Owin;

  2. Define GetOwinContext() Under HttpContext.Current as below -

     return _userManager1 ?? HttpContext.Current.GetOwinContext().GetUserManager<ApplicationUserManager>();


    return _signInManager ?? HttpContext.Current.GetOwinContext().Get<ApplicationSignInManager>();

Complete Code Where GetOwinContext() is used -

 public ApplicationSignInManager SignInManager
    return _signInManager ?? HttpContext.Current.GetOwinContext().Get<ApplicationSignInManager>();
    private set
     _signInManager = value;

Namespace's I'm Using in Code File where GetOwinContext() Is used

using AngularJSAuthentication.API.Entities;
using AngularJSAuthentication.API.Models;
using HomeCinema.Common;
using Microsoft.AspNet.Identity;
using Microsoft.AspNet.Identity.EntityFramework;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Web;
using Microsoft.AspNet.Identity.Owin;
using Microsoft.Owin.Security.DataProtection;

I got this error while moving my code from my one project to another.

C# with MySQL INSERT parameters

Try adjusting the code at "SqlDbType" to match your DB type if necessary and use this code:



comm.Parameters.AddWithValue("@person", Myname);

That should work but remember with Command.Parameters.Add(), you can define the specific SqlDbType and with Command.Parameters.AddWithValue(), it will try get the SqlDbType based on parameter value implicitly which can break sometimes if it can not implicitly convert the datatype.

Hope this helps.

Unable to find the wrapper "https" - did you forget to enable it when you configured PHP?

If you are using wamp server then go to icon click on this wamp server icon click on this

Then go to PHP then click on PHP extension there would be php_openssl need to activate from there and restart wamp server active php_openssl from here

Embed HTML5 YouTube video without iframe?

Because of the GDPR it makes no sense to use the iframe, you should rather use the object tag with the embed tag and also use the embed link.

<object width="100%" height="333">
  <param name="movie" value="">
  <embed src="" width="100%" height="333">

You should also activate the extended data protection mode function to receive the no cookie url.


flash does not have to be used

Nocookie, however, means that data is still being transmitted, namely the thumbnail that is loaded from YouTube. But at least data is no longer passed on to advertising networks (as example DoubleClick). And no user data is stored on your website by youtube.

Declaration of Methods should be Compatible with Parent Methods in PHP

childClass::customMethod() has different arguments, or a different access level (public/private/protected) than parentClass::customMethod().

How to check whether a Storage item is set?

The shortest way is to use default value, if key is not in storage:

var sValue = localStorage['my.token'] || ''; /* for strings */
var iValue = localStorage['my.token'] || 0; /* for integers */

Is there a way I can capture my iPhone screen as a video?

I've continued to research this item myself, and it does appear to remain beyond us at this point.

I even tried buying a Apple Composite AV Cable, but it doesn't capture screen, just video playing like YouTube, etc.

So I decided to go with the iShowU path and that has worked out well so far.

Thanks Guys!

Javascript require() function giving ReferenceError: require is not defined

RequireJS is a JavaScript file and module loader. It is optimized for in-browser use, but it can be used in other JavaScript environments, like Rhino and Node. Using a modular script loader like RequireJS will improve the speed and quality of your code.

IE 6+ .......... compatible ?
Firefox 2+ ..... compatible ?
Safari 3.2+ .... compatible ?
Chrome 3+ ...... compatible ?
Opera 10+ ...... compatible ?

Add this to your project:

and take a look at this

PHP - concatenate or directly insert variables in string

I use a dot(.) to concate string and variable. like this-

echo "Hello ".$var;

Sometimes, I use curly braces to concate string and variable that looks like this-

echo "Hello {$var}";

What does ${} (dollar sign and curly braces) mean in a string in Javascript?

You can also perform Implicit Type Conversions with template literals. Example:

let fruits = ["mango","orange","pineapple","papaya"];

console.log(`My favourite fruits are ${fruits}`);
// My favourite fruits are mango,orange,pineapple,papaya

Entity Framework 5 Updating a Record

There are some really good answers given already, but I wanted to throw in my two cents. Here is a very simple way to convert a view object into a entity. The simple idea is that only the properties that exist in the view model get written to the entity. This is similar to @Anik Islam Abhi's answer, but has null propagation.

public static T MapVMUpdate<T>(object updatedVM, T original)
    PropertyInfo[] originalProps = original.GetType().GetProperties();
    PropertyInfo[] vmProps = updatedVM.GetType().GetProperties();
    foreach (PropertyInfo prop in vmProps)
        PropertyInfo projectProp = originalProps.FirstOrDefault(x => x.Name == prop.Name);
        if (projectProp != null)
            projectProp.SetValue(original, prop.GetValue(updatedVM));
    return original;


  • Views don't need to have all the properties of the entity.
  • You never have to update code when you add remove a property to a view.
  • Completely generic


  • 2 hits on the database, one to load the original entity, and one to save it.

To me the simplicity and low maintenance requirements of this approach outweigh the added database call.

Python JSON encoding

The data you are encoding is a keyless array, so JSON encodes it with [] brackets. See for more information about that. The curly braces are used for lists with key/value pairs.


JSON is built on two structures:

A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array. An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.

An object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by , (comma).

An array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by , (comma).

Pods stuck in Terminating status

you can use awk :

kubectl get pods --all-namespaces | awk '{if ($4=="Terminating") print "oc delete pod " $2 " -n " $1 " --force --grace-period=0 ";}' | sh

List columns with indexes in PostgreSQL

A little bit modified answer of @cope360:

create table test (a int, b int, c int, constraint pk_test primary key(c, a, b));
select i.relname as index_name,
       ix.indisunique as is_unique,
       a.attname as column_name,
from pg_class c
       inner join pg_index ix on c.oid=ix.indrelid
       inner join pg_class i on ix.indexrelid=i.oid
       inner join pg_attribute a on a.attrelid=c.oid and a.attnum=any(ix.indkey)
where c.oid='public.test'::regclass::oid
order by array_position(ix.indkey, a.attnum) asc;

This will show the index columns in correct order:

index_name      is_unique  column_name
pk_test         true       c
pk_test         true       a
pk_test         true       b

What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it?

Array index out of bounds exception

That's how this type of exception looks when thrown in Eclipse. The number in red signifies the index you tried to access. So the code would look like this:


The error is thrown when you try to access an index which doesn't exist in that array. If an array has a length of 3,

int[] intArray = new int[3];

then the only valid indexes are:


If an array has a length of 1,

int[] intArray = new int[1];

then the only valid index is:


Any integer equal to the length of the array, or bigger than it: is out of bounds.

Any integer less than 0: is out of bounds;

P.S.: If you look to have a better understanding of arrays and do some practical exercises, there's a video here: tutorial on arrays in Java

Errors: "INSERT EXEC statement cannot be nested." and "Cannot use the ROLLBACK statement within an INSERT-EXEC statement." How to solve this?

My work around for this problem has always been to use the principle that single hash temp tables are in scope to any called procs. So, I have an option switch in the proc parameters (default set to off). If this is switched on, the called proc will insert the results into the temp table created in the calling proc. I think in the past I have taken it a step further and put some code in the called proc to check if the single hash table exists in scope, if it does then insert the code, otherwise return the result set. Seems to work well - best way of passing large data sets between procs.

How to check for Is not Null And Is not Empty string in SQL server?

WHERE NULLIF(your_column, '') IS NOT NULL

Nowadays (4.5 years on), to make it easier for a human to read, I would just use

WHERE your_column <> ''

While there is a temptation to make the null check explicit...

WHERE your_column <> '' 
      AND your_column IS NOT NULL @Martin Smith demonstrates in the accepted answer, it doesn't really add anything (and I personally shun SQL nulls entirely nowadays, so it wouldn't apply to me anyway!).

codeigniter model error: Undefined property

It solved throung second parameter in Model load:


first parameter is the model's filename, and second it defining the name of model to be used in the controller:

function alluser() 
$result = $this->User->showusers();

Text in HTML Field to disappear when clicked?

Use the placeholder attribute. The text disappears when the user starts typing. This is an example of a project I am working on:

<div class="" id="search-form">
    <input type="text" name="" value="" class="form-control" placeholder="Search..." >

Adding content to a linear layout dynamically?

LinearLayout layout = (LinearLayout)findViewById(;
View child = getLayoutInflater().inflate(R.layout.child, null);

MySql: Tinyint (2) vs tinyint(1) - what is the difference?

Query OK, 0 rows affected (0.04 sec)

mysql> INSERT INTO tin3 VALUES(1,12),(2,7),(4,101);
Query OK, 3 rows affected (0.02 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM tin3;
| id | val        |
|  1 | 0000000012 |
|  2 | 0000000007 |
|  4 | 0000000101 |
3 rows in set (0.00 sec)


mysql> SELECT LENGTH(val) FROM tin3 WHERE id=2;
| LENGTH(val) |
|          10 |
1 row in set (0.01 sec)

mysql> SELECT val+1 FROM tin3 WHERE id=2;
| val+1 |
|     8 |
1 row in set (0.00 sec)

$.focus() not working

if you use bootstrap + modal, this worked for me :

  $(myModal).on('', function() {

How can I check whether a variable is defined in Node.js?

Determine if property is existing (but is not a falsy value):

if (typeof query !== 'undefined' && query !== null){

Usually using

if (query){

is sufficient. Please note that:

if (!query){

doStuff() will execute even if query was an existing variable with falsy value (0, false, undefined or null)

Btw, there's a sexy coffeescript way of doing this:

if object?.property? then doStuff()

which compiles to:

if ((typeof object !== "undefined" && object !== null ? : void 0) != null) 


Should URL be case sensitive?

It is possible to make noncase sensitive URLs

RewriteEngine on
rewritemap lowercase int:tolower
RewriteCond $1 [A-Z]
RewriteRule ^/(.*)$ /${lowercase:$1} [R=301,L]

Making etc direct to

Python Requests requests.exceptions.SSLError: [Errno 8] _ssl.c:504: EOF occurred in violation of protocol

Reposting this here for others from the requests issue page:

Requests' does not support doing this before version 1. Subsequent to version 1, you are expected to subclass the HTTPAdapter, like so:

from requests.adapters import HTTPAdapter
from requests.packages.urllib3.poolmanager import PoolManager
import ssl

class MyAdapter(HTTPAdapter):
    def init_poolmanager(self, connections, maxsize, block=False):
        self.poolmanager = PoolManager(num_pools=connections,

When you've done that, you can do this:

import requests
s = requests.Session()
s.mount('https://', MyAdapter())

Any request through that session object will then use TLSv1.

Fitting empirical distribution to theoretical ones with Scipy (Python)?

It sounds like probability density estimation problem to me.

from scipy.stats import gaussian_kde
occurences = [0,0,0,0,..,1,1,1,1,...,2,2,2,2,...,47]
values = range(0,48)
kde = gaussian_kde(map(float, occurences))
p = kde(values)
p = p/sum(p)
print "P(x>=1) = %f" % sum(p[1:])

Also see

What's the main difference between Java SE and Java EE?

The biggest difference are the enterprise services (hence the ee) such as an application server supporting EJBs etc.

Uncaught Error: SECURITY_ERR: DOM Exception 18 when I try to set a cookie

Faced with the same situation playing with Javascript . Unfortunately Chrome doesn't allow to access javascript workers stored in a local file.

One kind of workaround below using a local storage is to running Chrome with --allow-file-access-from-files (with s at the end), but only one instance of Chrome is allowed, which is not too convenient for me. For this reason i'm using Chrome Canary, with file access allowed.

BTW in Firefox there is no such an issue.

Why is a "GRANT USAGE" created the first time I grant a user privileges?

I was trying to find the meaning of GRANT USAGE on *.* TO and found here. I can clarify that GRANT USAGE on *.* TO user IDENTIFIED BY PASSWORD password will be granted when you create the user with the following command (CREATE):

CREATE USER 'user'@'localhost' IDENTIFIED BY 'password'; 

When you grant privilege with GRANT, new privilege s will be added on top of it.

How to show the "Are you sure you want to navigate away from this page?" when changes committed?

To expand on Keith's already amazing answer:

Custom warning messages

To allow custom warning messages, you can wrap it in a function like this:

function preventNavigation(message) {
    var confirmOnPageExit = function (e) {
        // If we haven't been passed the event get the window.event
        e = e || window.event;

        // For IE6-8 and Firefox prior to version 4
        if (e)
            e.returnValue = message;

        // For Chrome, Safari, IE8+ and Opera 12+
        return message;
    window.onbeforeunload = confirmOnPageExit;

Then just call that function with your custom message:

preventNavigation("Baby, please don't go!!!");

Enabling navigation again

To re-enable navigation, all you need to do is set window.onbeforeunload to null. Here it is, wrapped in a neat little function that can be called anywhere:

function enableNavigation() {
    window.onbeforeunload = null;

Using jQuery to bind this to form elements

If using jQuery, this can easily be bound to all of the elements of a form like this:

$("#yourForm :input").change(function() {
    preventNavigation("You have not saved the form. Any \
        changes will be lost if you leave this page.");

Then to allow the form to be submitted:

$("#yourForm").on("submit", function(event) {

Dynamically-modified forms:

preventNavigation() and enableNavigation() can be bound to any other functions as needed, such as dynamically modifying a form, or clicking on a button that sends an AJAX request. I did this by adding a hidden input element to the form:

<input id="dummy_input" type="hidden" />

Then any time I want to prevent the user from navigating away, I trigger the change on that input to make sure that preventNavigation() gets executed:

function somethingThatModifiesAFormDynamically() {

    // Do something that modifies a form

    // ...
    // ...

best way to get folder and file list in Javascript

fs/promises and fs.Dirent

Here's an efficient, non-blocking ls program using Node's fast fs.Dirent objects and fs/promises module. This approach allows you to skip wasteful fs.exist or fs.stat calls on every path -

// main.js
import { readdir } from "fs/promises"
import { join } from "path"

async function* ls (path = ".")
{ yield path
  for (const dirent of await readdir(path, { withFileTypes: true }))
    if (dirent.isDirectory())
      yield* ls(join(path,
      yield join(path,

async function* empty () {}

async function toArray (iter = empty())
{ let r = []
  for await (const x of iter)
  return r

toArray(ls(".")).then(console.log, console.error)

Let's get some sample files so we can see ls working -

$ yarn add immutable     # (just some example package)
$ node main.js

For added explanation and other ways to leverage async generators, see this Q&A.

SQL Server - How to lock a table until a stored procedure finishes

Needed this answer myself and from the link provided by David Moye, decided on this and thought it might be of use to others with the same question:


  -- lock table "a" till end of transaction
  SELECT ...
  FROM a
  WHERE ...

  -- do some other stuff (including inserting/updating table "a")

  -- release lock

customize Android Facebook Login button

Proper and Cleanest way

After checking the answers below, it seems that they're kind of hacks that rely on editing the login button view to make it more suitable for your need.

Demo image

Being in the same position, I've succeeded to customize the facebook login button efficiently.

   app:fb_text="Facebook Connect"
   android:layout_centerHorizontal="true" />

and implement the onClickListener like so

FacebookLogin.setOnClickListener(new View.OnClickListener() {
   public void onClick(View view) {
      if (AccessToken.getCurrentAccessToken() != null){
      } else {
         mLoginManager.logInWithReadPermissions(MainActivity.this,              Arrays.asList("public_profile"));

You could find the whole source code on:

How to generate the "create table" sql statement for an existing table in postgreSQL

Generate the create table statement for a table in postgresql from linux commandline:

Create a table for a demo:

CREATE TABLE your_table(
    thekey   integer NOT NULL,  ticker   character varying(10) NOT NULL,
    date_val date,              open_val numeric(10,4) NOT NULL

pg_dump can output the table-create psql:

pg_dump -U your_user your_database -t your_table --schema-only

Which prints:

-- pre-requisite database and table configuration omitted
CREATE TABLE your_table (                                                                                                      
    thekey integer NOT NULL,                                                                                                   
    ticker character varying(10) NOT NULL,                                                                                     
    date_val date,                                                                                                             
    open_val numeric(10,4) NOT NULL                                                                                            
-- post-requisite database and table configuration omitted


pg_dump helps us get information about the database itself. -U stands for username. My pgadmin user has no password set, so I don't have to put in a password. The -t option means specify for one table. --schema-only means print only data about the table, and not the data in the table. Here is the exact command I use:

Get the table name and datatype information from postgresql with SQL:

CREATE TABLE your_table(  thekey integer NOT NULL,
                          ticker character varying(10) NOT NULL,
                          date_val date,
                          open_val numeric(10,4) NOT NULL

SELECT table_name, column_name, data_type 
FROM information_schema.columns 
WHERE table_name = 'your_table'; 

Which prints:

¦ table_name ¦ column_name ¦     data_type     ¦ 
¦ your_table ¦ thekey      ¦ integer           ¦ 
¦ your_table ¦ ticker      ¦ character varying ¦ 
¦ your_table ¦ date_val    ¦ date              ¦ 
¦ your_table ¦ open_val    ¦ numeric           ¦ 

Serial Port (RS -232) Connection in C++

Please take a look here:

1) You can use this with Windows (incl. MinGW) as well as Linux. Alternative you can only use the code as an example.

2) Step-by-step tutorial how to use serial ports on windows

3) You can use this literally on MinGW

Here's some very, very simple code (without any error handling or settings):

#include <windows.h>

/* ... */

// Open serial port
HANDLE serialHandle;


// Do some basic settings
DCB serialParams = { 0 };
serialParams.DCBlength = sizeof(serialParams);

GetCommState(serialHandle, &serialParams);
serialParams.BaudRate = baudrate;
serialParams.ByteSize = byteSize;
serialParams.StopBits = stopBits;
serialParams.Parity = parity;
SetCommState(serialHandle, &serialParams);

// Set timeouts
COMMTIMEOUTS timeout = { 0 };
timeout.ReadIntervalTimeout = 50;
timeout.ReadTotalTimeoutConstant = 50;
timeout.ReadTotalTimeoutMultiplier = 50;
timeout.WriteTotalTimeoutConstant = 50;
timeout.WriteTotalTimeoutMultiplier = 10;

SetCommTimeouts(serialHandle, &timeout);

Now you can use WriteFile() / ReadFile() to write / read bytes. Don't forget to close your connection:


Insert into ... values ( SELECT ... FROM ... )

To get only one value in a multi value INSERT from another table I did the following in SQLite3:

INSERT INTO column_1 ( val_1, val_from_other_table ) 
VALUES('val_1', (SELECT  val_2 FROM table_2 WHERE val_2 = something))

What is JNDI? What is its basic use? When is it used?

JNDI Overview

JNDI is an API specified in Java technology that provides naming and directory functionality to applications written in the Java programming language. It is designed especially for the Java platform using Java's object model. Using JNDI, applications based on Java technology can store and retrieve named Java objects of any type. In addition, JNDI provides methods for performing standard directory operations, such as associating attributes with objects and searching for objects using their attributes.

JNDI is also defined independent of any specific naming or directory service implementation. It enables applications to access different, possibly multiple, naming and directory services using a common API. Different naming and directory service providers can be plugged in seamlessly behind this common API. This enables Java technology-based applications to take advantage of information in a variety of existing naming and directory services, such as LDAP, NDS, DNS, and NIS(YP), as well as enabling the applications to coexist with legacy software and systems.

Using JNDI as a tool, you can build new powerful and portable applications that not only take advantage of Java's object model but are also well-integrated with the environment in which they are deployed.


A completely free agile software process tool

You can check out It's free for now because it's in beta and they say there is no time limit. It behaves very similar to AgileZen

I second the google doc, or you could use an online collaborative board that multiple people can edit.

Or you can host a more robust excel doc in skydrive from MS. I haven't tried that yet. is another one that I am playing with currently. It has unlimited collaborators, though I think you would probably have to invite them everytime?? with a free account.

Hope that helps!

How to return history of validation loss in Keras

Another option is CSVLogger: It creates a csv file appending the result of each epoch. Even if you interrupt training, you get to see how it evolved.

Mock HttpContext.Current in Test Init Method

Below Test Init will also do the job.

public void TestInit()
  HttpContext.Current = new HttpContext(new HttpRequest(null, "", null), new HttpResponse(null));
  YourControllerToBeTestedController = GetYourToBeTestedController();

PHP - Check if the page run on Mobile or Desktop browser

There is a very nice PHP library for detecting mobile clients here:

Using that it's quite easy to only display content for a mobile:

include 'Mobile_Detect.php';
$detect = new Mobile_Detect();

// Check for any mobile device.
if ($detect->isMobile()){
   // mobile content
else {
   // other content for desktops

How to use PHP OPCache?

I encountered this when setting up moodle. I added the following lines in the php.ini file.


opcache.enable = 1
opcache.memory_consumption = 128
opcache.max_accelerated_files = 4000
opcache.revalidate_freq = 60

; Required for Moodle
opcache.use_cwd = 1
opcache.validate_timestamps = 1
opcache.save_comments = 1
opcache.enable_file_override = 0

; If something does not work in Moodle
;opcache.revalidate_path = 1 ; May fix problems with include paths
;opcache.mmap_base = 0x20000000 ; (Windows only) fix OPcache crashes with event id 487

; Experimental for Moodle 2.6 and later
;opcache.fast_shutdown = 1
;opcache.enable_cli = 1 ; Speeds up CLI cron
;opcache.load_comments = 0 ; May lower memory use, might not be compatible with add-ons and other apps


intl.default_locale = en_utf8
intl.error_level = E_WARNING

intl ->

OpenSSL: PEM routines:PEM_read_bio:no start line:pem_lib.c:703:Expecting: TRUSTED CERTIFICATE

  1. Since you are on Windows, make sure that your certificate in Windows "compatible", most importantly that it doesn't have ^M in the end of each line

    If you open it it will look like this:


    To solve "this" open it with Write or Notepad++ and have it convert it to Windows "style"

  2. Try to run openssl x509 -text -inform DER -in server_cert.pem and see what the output is, it is unlikely that a private/secret key would be untrusted, trust only is needed if you exported the key from a keystore, did you?

Make XmlHttpRequest POST using JSON

If you use JSON properly, you can have nested object without any issue :

var xmlhttp = new XMLHttpRequest();   // new HttpRequest instance 
var theUrl = "/json-handler";"POST", theUrl);
xmlhttp.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
xmlhttp.send(JSON.stringify({ "email": "[email protected]", "response": { "name": "Tester" } }));

What is the difference between \r and \n?

\r is used to point to the start of a line and can replace the text from there, e.g.


Produces this output:


\n is for new line.

AngularJS passing data to $http.get request

You can pass params directly to $http.get() The following works fine

$http.get(user.details_path, {
    params: { user_id: }

CMD command to check connected USB devices

You could use wmic command:

wmic logicaldisk where drivetype=2 get <DeviceID, VolumeName, Description, ...>

Drivetype 2 indicates that its a removable disk.

How to move a marker in Google Maps API

You are using the correct API, but is the "marker" variable visible to the entire script. I don't see this marker variable declared globally.

Error: Local workspace file ('angular.json') could not be found

Check your folder structure where you are executing the command, you should run the command 'ng serve' where there should be a angular.json file in the structure.

angular.json file will be generated by default when we run the command

npm install -g '@angular/cli' ng new Project_name then cd project_folder then, run ng serve. it worked for me

How to use ternary operator in razor (specifically on HTML attributes)?


The important concept is that you are evaluating an expression in your Razor code. The best way to do this (if, for example, you are in a foreach loop) is using a generic method.

The syntax for calling a generic method in Razor is:


In this case, the expression is:

User.Identity.IsAuthenticated ? "auth" : "anon"

Therefore, the solution is:

@(User.Identity.IsAuthenticated ? "auth" : "anon")

This code can be used anywhere in Razor, not just for an html attribute.

See @Kyralessa 's comment for C# Razor Syntax Quick Reference (Phil Haack's blog).

How to use Regular Expressions (Regex) in Microsoft Excel both in-cell and loops

I needed to use this as a cell function (like SUM or VLOOKUP) and found that it was easy to:

  1. Make sure you are in a Macro Enabled Excel File (save as xlsm).
  2. Open developer tools Alt + F11
  3. Add Microsoft VBScript Regular Expressions 5.5 as in other answers
  4. Create the following function either in workbook or in its own module:

    Function REGPLACE(myRange As Range, matchPattern As String, outputPattern As String) As Variant
        Dim regex As New VBScript_RegExp_55.RegExp
        Dim strInput As String
        strInput = myRange.Value
        With regex
            .Global = True
            .MultiLine = True
            .IgnoreCase = False
            .Pattern = matchPattern
        End With
        REGPLACE = regex.Replace(strInput, outputPattern)
    End Function
  5. Then you can use in cell with =REGPLACE(B1, "(\w) (\d+)", "$1$2") (ex: "A 243" to "A243")

Extracting extension from filename in Python

This is a direct string representation techniques : I see a lot of solutions mentioned, but I think most are looking at split. Split however does it at every occurrence of "." . What you would rather be looking for is partition.

string = "folder/to_path/filename.ext"
extension = string.rpartition(".")[-1]

How to install pip3 on Windows?

On Windows pip3 should be in the Scripts path of your Python installation:



where python

to find out where your Python executable(s) is/are located. The result should look like this:




You can check if pip3 works with this absolute path:


if yes, add C:\path\to\python\Scripts to your environmental variable PATH .

Batch file: Find if substring is in string (not in a file)

You can pipe the source string to findstr and check the value of ERRORLEVEL to see if the pattern string was found. A value of zero indicates success and the pattern was found. Here is an example:

: Y.CMD - Test if pattern in string
: P1 - the pattern
: P2 - the string to check
@echo off

echo.%2 | findstr /C:"%1" 1>nul

if errorlevel 1 (
  echo. got one - pattern not found
) ELSE (
  echo. got zero - found pattern

When this is run in CMD.EXE, we get:

C:\DemoDev>y pqrs "abc def pqr 123"
 got one - pattern not found

C:\DemoDev>y pqr "abc def pqr 123" 
 got zero - found pattern

Razor View Without Layout


    Layout = null;

to get rid of the layout specified in _ViewStart.

Hide header in stack navigator React navigation

You can hide StackNavigator header like this:

const Stack = createStackNavigator();
function StackScreen() {
    return (
            screenOptions={{ headerShown: false }}>
            <Stack.Screen name="Login" component={Login} />
            <Stack.Screen name="Training" component={Training} />
            <Stack.Screen name="Course" component={Course} />
            <Stack.Screen name="Signup" component={Signup} />

How to group by month from Date field using sql

Try the Following Code

SELECT  Closing_Date = DATEADD(MONTH, DATEDIFF(MONTH, 0, Closing_Date), 0), 
        COUNT(Status) TotalCount 
FROM    MyTable
WHERE   Closing_Date >= '2012-02-01' 
AND     Closing_Date <= '2012-12-31'
AND     Defect_Status1 IS NOT NULL
GROUP BY DATEADD(MONTH, DATEDIFF(MONTH, 0, Closing_Date), 0), Category;

Execute JavaScript code stored as a string

new Function('alert("Hello")')();

I think this is the best way.

Extract substring in Bash

Here's a prefix-suffix solution (similar to the solutions given by JB and Darron) that matches the first block of digits and does not depend on the surrounding underscores:

s1="${str#"${str%%[[:digit:]]*}"}"   # strip off non-digit prefix from str
s2="${s1%%[^[:digit:]]*}"            # strip off non-digit suffix from s1
echo "$s2"                           # 12345

Copy files on Windows Command Line with Progress

If you want to copy files and see a "progress" I suggest the script below in Batch that I used from another script as a base

I used a progress bar and a percentage while the script copies the game files Nuclear throne:

@echo off
title NTU Installer
setlocal EnableDelayedExpansion

@echo Iniciando instalacao...
if not exist "C:\NTU" (
    md "C:\NTU
if not exist "C:\NTU\Profile" (
    md "C:\NTU\Profile"
ping -n 5 localhost >nul

for %%f in (*.*) do set/a vb+=1
set "barra="
::loop da barra
for /l %%i in (1,1,70) do set "barra=!barra!Û"
rem barra vaiza para ser preenchida
set "resto="
rem loop da barra vazia
for /l %%i in (1,1,110) do set "resto=!resto!"
set i=0
rem carregameno de arquivos
for %%f in (*.*) do (
    >>"log_ntu.css" (
        copy "%%f" "C:\NTU">nul
        echo Copiado:%%f
    set /a i+=1,percent=i*100/vb,barlen=70*percent/100
    for %%a in (!barlen!) do echo  !percent!%% /                         
    echo Instalado:[%%f] / Complete:[!percent!%%/100%]
    ping localhost -n 1.9  >nul
xcopy /e "Profile" "C:\NTU\Profile">"log_profile.css"              

@echo Criando atalho na area de trabalho...
copy "NTU.lnk" "C:\Users\%username%\Desktop">nul
ping localhost -n 4  >nul

@echo Arquivos instalados!

JavaScript module pattern with example

In order to approach to Modular design pattern, you need to understand these concept first:

Immediately-Invoked Function Expression (IIFE):

(function() {
      // Your code goes here 

There are two ways you can use the functions. 1. Function declaration 2. Function expression.

Here are using function expression.

What is namespace? Now if we add the namespace to the above piece of code then

var anoyn = (function() {

What is closure in JS?

It means if we declare any function with any variable scope/inside another function (in JS we can declare a function inside another function!) then it will count that function scope always. This means that any variable in outer function will be read always. It will not read the global variable (if any) with the same name. This is also one of the objective of using modular design pattern avoiding naming conflict.

var scope = "I am global";
function whatismyscope() {
    var scope = "I am just a local";
    function func() {return scope;}
    return func;

Now we will apply these three concepts I mentioned above to define our first modular design pattern:

var modularpattern = (function() {
    // your module code goes here
    var sum = 0 ;

    return {
        add:function() {
            sum = sum + 1;
            return sum;
        reset:function() {
            return sum = 0;    
alert(modularpattern.add());    // alerts: 1
alert(modularpattern.add());    // alerts: 2
alert(modularpattern.reset());  // alerts: 0

jsfiddle for the code above.

The objective is to hide the variable accessibility from the outside world.

Hope this helps. Good Luck.

Redirecting 404 error with .htaccess via 301 for SEO etc

I came up with the solution and posted it on my blog

here is the htaccess code also

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule . / [L,R=301]

but I posted other solutions on my blog too, it depends what you need really

Adding a column to a dataframe in R

That is a pretty standard use case for apply():

R> vec <- 1:10
R> DF <- data.frame(start=c(1,3,5,7), end=c(2,6,7,9))
R> DF$newcol <- apply(DF,1,function(row) mean(vec[ row[1] : row[2] ] ))
  start end newcol
1     1   2    1.5
2     3   6    4.5
3     5   7    6.0
4     7   9    8.0

You can also use plyr if you prefer but here is no real need to go beyond functions from base R.

How can I download a specific Maven artifact in one command line?

The usage from the official documentation:

For my case, see the answer below:

mvn dependency:get -Dartifact=$2:$3:$4:$5 -DremoteRepositories=$1 -Dtransitive=false
mvn dependency:copy -Dartifact=$2:$3:$4:$5 -DremoteRepositories=$1 -Dtransitive=false -DoutputDirectory=$6

#mvn dependency:get -Dartifact=com.huya.mtp:hynswup:1.0.88-SNAPSHOT:jar -DremoteRepositories= -Dtransitive=false
#mvn dependency:copy -Dartifact=com.huya.mtp:hynswup:1.0.88-SNAPSHOT:jar -DremoteRepositories= -Dtransitive=false -DoutputDirectory=.

Use the command mvn dependency:get to download the specific artifact and use the command mvn dependency:copy to copy the downloaded artifact to the destination directory -DoutputDirectory.

Flask Value error view function did not return a response

You are not returning a response object from your view my_form_post. The function ends with implicit return None, which Flask does not like.

Make the function my_form_post return an explicit response, for example

return 'OK'

at the end of the function.

Collections.sort with multiple fields

Use Comparator interface with methods introduced in JDK1.8: comparing and thenComparing, or more concrete methods: comparingXXX and thenComparingXXX.

For example, if we wanna sort a list of persons by their id firstly, then age, then name:

            Comparator<Person> comparator = Comparator.comparingLong(Person::getId)

Unit test naming best practices


For test method names, I personally find using verbose and self-documented names very useful (alongside Javadoc comments that further explain what the test is doing).

Flutter command not found

In Mac, There are two options to solve this issue.

Option 1: Adding the flutter SDK path permanently(it will work in any terminal session)

Download the flutter SDK and extract in any location and then you have to add the below line in $HOME/.bash_profile file(hidden folder as default).

export PATH="$PATH:[where flutter sdk downloaded and extracted]/flutter/bin"

for eg:export PATH="$PATH:~/development/tools/flutter/bin"

Option 2: If you are facing any difficulties with Option 1, then this is much simpler but you have to do this simple step whenever you restart your system/terminal.

Step 1: Go to the path where flutter SDK downloaded and extracted (eg: cd ~/Development/tools/)

Step 2: Enter this command

export PATH='pwd'/flutter/bin:$PATH

That's it. Type "flutter doctor" to check this issue gets resolved. Happy Coding. Server returned HTTP response code: 500

Change the content-type to "application/x-www-form-urlencoded", i solved the problem.

Print "\n" or newline characters as part of the output on terminal

If you're in control of the string, you could also use a 'Raw' string type:

>>> string = r"abcd\n"
>>> print(string)

Add a row number to result set of a SQL query

The typical pattern would be as follows, but you need to actually define how the ordering should be applied (since a table is, by definition, an unordered bag of rows):

SELECT t.A, t.B, t.C, number = ROW_NUMBER() OVER (ORDER BY t.A)
  FROM dbo.tableZ AS t

Not sure what the variables in your question are supposed to represent (they don't match).

Converting a UNIX Timestamp to Formatted Date String

You can do like as.....

$originalDate = "1585876500";

echo $newDate = date("Y-m-d h:i:sa", date($originalDate));

How to construct a WebSocket URI relative to the page URI?

On localhost you should consider context path.

function wsURL(path) {
    var protocol = (location.protocol === 'https:') ? 'wss://' : 'ws://';
    var url = protocol +;
    if(location.hostname === 'localhost') {
        url += '/' + location.pathname.split('/')[1]; // add context path
    return url + path;

VBScript - How to make program wait until process has finished?

You need to tell the run to wait until the process is finished. Something like:

const DontWaitUntilFinished = false, ShowWindow = 1, DontShowWindow = 0, WaitUntilFinished = true
set oShell = WScript.CreateObject("WScript.Shell")
command = "cmd /c C:\windows\system32\wscript.exe <path>\myScript.vbs " & args
oShell.Run command, DontShowWindow, WaitUntilFinished

In the script itself, start Excel like so. While debugging start visible:

File = "c:\test\myfile.xls" """C:\Program Files\Microsoft Office\Office14\EXCEL.EXE"" " & File, 1, true

Join two sql queries

Here's what worked for me:

select visits, activations, simulations, simulations/activations
   as sims_per_visit, activations/visits*100
   as adoption_rate, simulations/activations*100
   as completion_rate, duration/60
   as minutes, m1 as month, Wk1 as week, Yr1 as year 

    (select count(*) as visits, year(stamp) as Yr1, week(stamp) as Wk1, month(stamp)
    as m1 from sessions group by week(stamp), year(stamp)) as t3


    (select count(*) as activations, year(stamp) as Yr2, week(stamp) as Wk2,
    month(stamp) as m2 from sessions where activated='1' group by week(stamp),
    year(stamp)) as t4


    (select count(*) as simulations, year(stamp) as Yr3 , week(stamp) as Wk3,
    month(stamp) as m3 from sessions where simulations>'0' group by week(stamp),
    year(stamp)) as t5


    (select avg(duration) as duration, year(stamp) as Yr4 , week(stamp) as Wk4,
    month(stamp) as m4 from sessions where activated='1' group by week(stamp),
    year(stamp)) as t6
where Yr1=Yr2 and Wk1=Wk2 and Wk1=Wk3 and Yr1=Yr3 and Yr1=Yr4 and Wk1=Wk4

I used joins, not unions (I needed different columns for each query, a join puts it all in the same column) and I dropped the quotation marks (compared to what Liam was doing) because they were giving me errors.

Thanks! I couldn't have pulled that off without this page! PS: Sorry I don't know how you're getting your statements formatted with colors. etc.

How to upgrade all Python packages with pip

Windows PowerShell solution

pip freeze | %{$_.split('==')[0]} | %{pip install --upgrade $_}

How to update value of a key in dictionary in c#?

Try this simple function to add an dictionary item if it does not exist or update when it exists:

    public void AddOrUpdateDictionaryEntry(string key, int value)
        if (dict.ContainsKey(key))
            dict[key] = value;
            dict.Add(key, value);

This is the same as dict[key] = value.

Visual Studio 2017 error: Unable to start program, An operation is not legal in the current state

For me the issue was signing into my Google account on the debug Chrome window. This had been working fine for me until I signed in. Once I signed out of that instance of Chrome AND choose to delete all of my settings via the checkbox, the debugger worked fine again.

My non-debugging instance of Chrome was still signed into Google and unaffected. The main issue is that my lovely plugins are gone from the debug version, but at least I can step through client code again.

How to get the scroll bar with CSS overflow on iOS

Edit following the comment left, kindly, by kritzikratzi:

[Starting] with ios 5beta a new property -webkit-overflow-scrolling: touch can be added which should result in the expected behaviour.

Some, but very little, further reading:

Original answer, left for posterity.

Unfortunately neither overflow: auto, or scroll, produces scrollbars on the iOS devices, apparently due to the screen-width that would be taken up such useful mechanisms.

Instead, as you've found, users are required to perform the two-finger swipe in order to scroll the overflow-ed content. The only reference, since I'm unable to find the manual for the phone itself, I could find is here: iPhone 101: Two-fingered scrolling.

The only work-around I can think of for this, is if you could possibly use some JavaScript, and maybe jQTouch, to create your own scroll-bars for overflow elements. Alternatively you could use @media queries to remove the overflow and show the content in full, as an iPhone user this gets my vote, if only for the sheer simplicity. For example:

<link rel="stylesheet" href="handheld.css" media="only screen and (max-device width:480px)" />

The preceding code comes from A List Apart, from the same article linked-to above (I'm not sure why they left of the type="text/css", but I assume there are reasons.

How to select a div element in the code-behind page?

If you want to find the control from code behind you have to use runat="server" attribute on control. And then you can use Control.FindControl.

<div class="tab-pane active" id="portlet_tab1" runat="server">

Control myControl1 = FindControl("portlet_tab1");
    //do stuff

If you use runat server and your control is inside the ContentPlaceHolder you have to know the ctrl name would not be portlet_tab1 anymore. It will render with the ctrl00 format.

Something like: #ctl00_ContentPlaceHolderMain_portlet_tab1. You will have to modify name if you use jquery.

You can also do it using jQuery on client side without using the runat-server attribute:

<script type='text/javascript'>



Is it possible to ping a server from Javascript?

You can run the DOS ping.exe command from javaScript using the folowing:

function ping(ip)
    var input = "";
    var WshShell = new ActiveXObject("WScript.Shell");
    var oExec = WshShell.Exec("c:/windows/system32/ping.exe " + ip);

    while (!oExec.StdOut.AtEndOfStream)
            input += oExec.StdOut.ReadLine() + "<br />";
    return input;

Is this what was asked for, or am i missing something?

Adding Permissions in AndroidManifest.xml in Android Studio?

Put these two line in your AndroidMainfest

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 

How to convert integer to char in C?

To convert integer to char only 0 to 9 will be converted. As we know 0's ASCII value is 48 so we have to add its value to the integer value to convert in into the desired character hence

int i=5;
char c = i+'0';

What is char ** in C?

It is a pointer to a pointer, so yes, in a way it's a 2D character array. In the same way that a char* could indicate an array of chars, a char** could indicate that it points to and array of char*s.

How to know when a web page was last updated?

In general, there is no way to know when something on another site has been changed. If the site offers an RSS feed, you should try that. If the site does not offer an RSS feed (or if the RSS feed doesn't include the information you're looking for), then you have to scrape and compare.

Perl regular expression (using a variable as a search string with Perl operator characters included)

Use \Q to autoescape any potentially problematic characters in your variable.

if($text_to_search =~ m/\Q$search_string/) print "wee";

belongs_to through associations

Just use has_one instead of belongs_to in your :through, like this:

class Choice
  belongs_to :user
  belongs_to :answer
  has_one :question, :through => :answer

Unrelated, but I'd be hesitant to use validates_uniqueness_of instead of using a proper unique constraint in your database. When you do this in ruby you have race conditions.

How to remove the left part of a string?

def remove_prefix(text, prefix):
    return text[len(prefix):] if text.startswith(prefix) else text

How do I make a transparent canvas in html5?

I believe you are trying to do exactly what I just tried to do: I want two stacked canvases... the bottom one has a static image and the top one contains animated sprites. Because of the animation, you need to clear the background of the top layer to transparent at the start of rendering every new frame. I finally found the answer: it's not using globalAlpha, and it's not using a rgba() color. The simple, effective answer is:


Why does the arrow (->) operator in C exist?

Beyond historical (good and already reported) reasons, there's is also a little problem with operators precedence: dot operator has higher priority than star operator, so if you have struct containing pointer to struct containing pointer to struct... These two are equivalent:



But the second is clearly more readable. Arrow operator has the highest priority (just as dot) and associates left to right. I think this is clearer than use dot operator both for pointers to struct and struct, because we know the type from the expression without have to look at the declaration, that could even be in another file.

Use string in switch case in java

String value = someMethod();
switch(0) {
    if ("apple".equals(value)) {
    if ("carrot".equals(value)) {
    if ("mango".equals(value)) {
    if ("orance".equals(value)) {

Returning value that was passed into a method

Even more useful, if you have multiple parameters you can access any/all of them with:

_mock.Setup(x => x.DoSomething(It.IsAny<string>(),It.IsAny<string>(),It.IsAny<string>())
     .Returns((string a, string b, string c) => string.Concat(a,b,c));

You always need to reference all the arguments, to match the method's signature, even if you're only going to use one of them.

How to develop Android app completely using python?

You could try BeeWare - as described on their website:

Write your apps in Python and release them on iOS, Android, Windows, MacOS, Linux, Web, and tvOS using rich, native user interfaces. One codebase. Multiple apps.

Gives you want you want now to write Android Apps in Python, plus has the advantage that you won't need to learn yet another framework in future if you end up also wanting to do something on one of the other listed platforms.

Here's the Tutorial for Android Apps.

Oracle Installer:[INS-13001] Environment does not meet minimum requirements

To prevent this dialog box from appearing, do the following:

  1. Right click on the setup.exe for the Oracle 11g 32-bit client, and select Properties.
  2. Select the Compatibility tab, and set the Compatibility mode to Windows 7. Click OK to close the Properties tab.
  3. Double click setup.exe to install the client.

How to run function in AngularJS controller on document ready?

See this post How to execute angular controller function on page load?
For fast lookup:

// register controller in html
<div data-ng-controller="myCtrl" data-ng-init="init()"></div>

// in controller
$scope.init = function () {
    // check if there is query in url
    // and fire search in case its value is not empty

This way, You don't have to wait till document is ready.

How to parse dates in multiple formats using SimpleDateFormat

Implemented the same in scala, Please help urself with converting to Java, the core logic and functions used stays the same.

import java.text.SimpleDateFormat
import org.apache.commons.lang.time.DateUtils

object MultiDataFormat {
  def main(args: Array[String]) {

val dates =Array("2015-10-31","26/12/2015","19-10-2016")

val possibleDateFormats:Array[String] = Array("yyyy-MM-dd","dd/MM/yyyy","dd-MM-yyyy")

val sdf =  new SimpleDateFormat("yyyy-MM-dd") //change it as per the requirement
  for (date<-dates) {
    val outputDate = DateUtils.parseDateStrictly(date, possibleDateFormats)
    System.out.println("inputDate ==> " + date + ", outputDate ==> " +outputDate + " " + sdf.format(outputDate) )



Cross join does not combine the rows, if you have 100 rows in each table with 1 to 1 match, you get 10.000 results, Innerjoin will only return 100 rows in the same situation.

These 2 examples will return the same result:

Cross join

select * from table1 cross join table2 where = table2.fk_id

Inner join

select * from table1 join table2 on = table2.fk_id

Use the last method

intellij idea - Error: java: invalid source release 1.9

In Project Structure in Project SDK: modify SDK to 11 or higher and in Project language level: modify to 11 - Local variable syntax for lambda parameters

How to make bootstrap 3 fluid layout without horizontal scrollbar

This was introduced in v3.1.0:

Commit #62736046 added ".container-fluid variation for full-width containers and layouts".

IF a cell contains a string

SEARCH does not return 0 if there is no match, it returns #VALUE!. So you have to wrap calls to SEARCH with IFERROR.

For example...

=IF(IFERROR(SEARCH("cat", A1), 0), "cat", "none")



Here, IFERROR returns the value from SEARCH when it works; the given value of 0 otherwise.

Storing Data in MySQL as JSON

JSON is a valid datatype in PostgreSQL database as well. However, MySQL database has not officially supported JSON yet. But it's baking:

I also agree that there are many valid cases that some data is better be serialized to a string in a database. The primary reason might be when it's not regularly queried, and when it's own schema might change - you don't want to change the database schema corresponding to that. The second reason is when the serialized string is directly from external sources, you may not want to parse all of them and feed in the database at any cost until you use any. So I'll be waiting for the new MySQL release to support JSON since it'll be easier for switching between different database then.

Get loop counter/index using for…of syntax in JavaScript

Solution for small array collections:

for (var obj in arr) {
    var i = Object.keys(arr).indexOf(obj);

arr - ARRAY, obj - KEY of current element, i - COUNTER/INDEX

Notice: Method keys() is not available for IE version <9, you should use Polyfill code.

Parse time of format hh:mm:ss

String time = "12:32:22";
String[] values = time.split(":");

This will take your time and split it where it sees a colon and put the value in an array, so you should have 3 values after this.

Then loop through string array and convert each one. (with Integer.parseInt)

Password masking console application

Complete solution, vanilla C# .net 3.5+

Cut & Paste :)

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;

    namespace ConsoleReadPasswords
        class Program
            static void Main(string[] args)

                string password = Orb.App.Console.ReadPassword();

                Console.WriteLine("Sorry - I just can't keep a secret!");
                Console.WriteLine("Your password was:\n<Password>{0}</Password>", password);


    namespace Orb.App
        /// <summary>
        /// Adds some nice help to the console. Static extension methods don't exist (probably for a good reason) so the next best thing is congruent naming.
        /// </summary>
        static public class Console
            /// <summary>
            /// Like System.Console.ReadLine(), only with a mask.
            /// </summary>
            /// <param name="mask">a <c>char</c> representing your choice of console mask</param>
            /// <returns>the string the user typed in </returns>
            public static string ReadPassword(char mask)
                const int ENTER = 13, BACKSP = 8, CTRLBACKSP = 127;
                int[] FILTERED = { 0, 27, 9, 10 /*, 32 space, if you care */ }; // const

                var pass = new Stack<char>();
                char chr = (char)0;

                while ((chr = System.Console.ReadKey(true).KeyChar) != ENTER)
                    if (chr == BACKSP)
                        if (pass.Count > 0)
                            System.Console.Write("\b \b");
                    else if (chr == CTRLBACKSP)
                        while (pass.Count > 0)
                            System.Console.Write("\b \b");
                    else if (FILTERED.Count(x => chr == x) > 0) { }


                return new string(pass.Reverse().ToArray());

            /// <summary>
            /// Like System.Console.ReadLine(), only with a mask.
            /// </summary>
            /// <returns>the string the user typed in </returns>
            public static string ReadPassword()
                return Orb.App.Console.ReadPassword('*');

Mvn install or Mvn package


package: take the compiled code and package it in its distributable format, such as a JAR.

install: install the package into the local repository, for use as a dependency in other projects locally

So the answer to your question is, it depends on whether you want it in installed into your local repo. Install will also run package because it's higher up in the goal phase stack.

SQL Server format decimal places with commas

If you are using SQL Azure Reporting Services, the "format" function is unsupported. This is really the only way to format a tooltip in a chart in SSRS. So the workaround is to return a column that has a string representation of the formatted number to use for the tooltip. So, I do agree that SQL is not the place for formatting. Except in cases like this where the tool does not have proper functions to handle display formatting.

In my case I needed to show a number formatted with commas and no decimals (type decimal 2) and ended up with this gem of a calculated column in my dataset query:

,Fmt_DDS=reverse(stuff(reverse(CONVERT(varchar(25),cast(SUM(kv.DeepDiveSavingsEst) as money),1)), 1, 3, ''))

It works, but is very ugly and non-obvious to whoever maintains the report down the road. Yay Cloud!

Run Function After Delay

$(document).ready(function() {

  // place this within dom ready function
  function showpanel() {     

 // use setTimeout() to execute
 setTimeout(showpanel, 1000)


For more see here

How to use log levels in java

This tip shows how to use Logger in any java application. Logger needs to configure Formatter and Handler. There are many types of handlers and formatters present. In this example FileHandler is used to store all the log messages in a log file. And Simple formatter is used to format the log messages in human readable form.

package MyProject;

import java.util.logging.FileHandler;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.logging.SimpleFormatter;

public class MyLogger {

  public static void main(String[] args) {

    Logger logger = Logger.getLogger("MyLog");
    FileHandler fh;

    try {

      // This block configure the logger with handler and formatter
      fh = new FileHandler("c:\\MyLogFile.log", true);
      SimpleFormatter formatter = new SimpleFormatter();

      // the following statement is used to log any messages   
      logger.log(Level.WARNING,"My first log");

    } catch (SecurityException e) {
    } catch (IOException e) {



some more examples you can find here

How to extract an assembly from the GAC?

Open RUN then type %windir%\assembly\GAC_MSIL, this will open your dlls in folders' view you can then navigate to your dll named folder and open it, you will find your dll file and copy it easily

how to use #ifdef with an OR condition?

Like this

#if defined(LINUX) || defined(ANDROID)

Iterating Through a Dictionary in Swift

Here is an alternative for that experiment (Swift 3.0). This tells you exactly which kind of number was the largest.

let interestingNumbers = [
"Prime": [2, 3, 5, 7, 11, 13],
"Fibonacci": [1, 1, 2, 3, 5, 8],
"Square": [1, 4, 9, 16, 25],

var largest = 0
var whichKind: String? = nil

for (kind, numbers) in interestingNumbers {
    for number in numbers {
    if number > largest {
        whichKind = kind
        largest = number



Converting float to char*

char array[10];
sprintf(array, "%f", 3.123);

sprintf: (from MSDN)

bootstrap 4 row height

Use the sizing utility classes...

  • h-50 = height 50%
  • h-100 = height 100%

 <div class="container">
        <div class="row">
            <div class="col-md-8 col-lg-6 B">
                <div class="card card-inverse card-primary">
                    <img src="" class="img-fluid" alt="Responsive image">
            <div class="col-md-4 col-lg-3 G">
                <div class="row h-100">
                    <div class="col-md-6 col-lg-6 B h-50 pb-3">
                        <div class="card card-inverse card-success h-100">

                    <div class="col-md-6 col-lg-6 B h-50 pb-3">
                        <div class="card card-inverse bg-success h-100">

                    <div class="col-md-12 h-50">
                        <div class="card card-inverse bg-danger h-100">


Or, for an unknown number of child columns, use flexbox and the cols will fill height. See the d-flex flex-column on the row, and h-100 on the child cols.

<div class="container">
    <div class="row">
        <div class="col-md-8 col-lg-6 B">
            <div class="card card-inverse card-primary">
                <img src="" class="img-fluid" alt="Responsive image">
        <div class="col-md-4 col-lg-3 G ">
            <div class="row d-flex flex-column h-100">
                <div class="col-md-6 col-lg-6 B h-100">
                    <div class="card bg-success h-100">

                <div class="col-md-6 col-lg-6 B h-100">
                    <div class="card bg-success h-100">

                <div class="col-md-12 h-100">
                    <div class="card bg-danger h-100">


bad operand types for binary operator "&" java

Because & has a lesser priority than ==.

Your code is equivalent to a[0] & (1 == 0), and unless a[0] is a boolean this won't compile...

You need to:

(a[0] & 1) == 0

etc etc.

(yes, Java does hava a boolean & operator -- a non shortcut logical and)

How to align checkboxes and their labels consistently cross-browsers

I've never had a problem with doing it like this:

    <input type="checkbox" id="cb" /> <label for="cb">Label text</label>

List of all special characters that need to be escaped in a regex

According to the String Literals / Metacharacters documentation page, they are:


Also it would be cool to have that list refereed somewhere in code, but I don't know where that could be...

What is the difference between #include <filename> and #include "filename"?

#include <filename>

is used when you want to use the header file of the C/C++ system or compiler libraries. These libraries can be stdio.h, string.h, math.h, etc.

#include "path-to-file/filename"

is used when you want to use your own custom header file which is in your project folder or somewhere else.

For more information about preprocessors and header. Read C - Preprocessors.

How to create a vector of user defined size but with no predefined values?

With the constructor:

// create a vector with 20 integer elements
std::vector<int> arr(20);

for(int x = 0; x < 20; ++x)
   arr[x] = x;

Pointer to class data member "::*"

I think you'd only want to do this if the member data was pretty large (e.g., an object of another pretty hefty class), and you have some external routine which only works on references to objects of that class. You don't want to copy the member object, so this lets you pass it around.

How do I get a YouTube video thumbnail from the YouTube API?

You can get the Video Entry which contains the URL to the video's thumbnail. There's example code in the link. Or, if you want to parse XML, there's information here. The XML returned has a media:thumbnail element, which contains the thumbnail's URL.

How can I get a value from a map?

How can I get the value from the map, which is passed as a reference to a function?

Well, you can pass it as a reference. The standard reference wrapper that is.

typedef std::map<std::string, std::string> MAP;
// create your map reference type
using map_ref_t = std::reference_wrapper<MAP>;

// use it 
void function(map_ref_t map_r)
    // get to the map from inside the
    // std::reference_wrapper
    // see the alternatives behind that link
    MAP & the_map = map_r;
    // take the value from the map
    // by reference
    auto & value_r = the_map["key"];
    // change it, "in place"
    value_r = "new!";

And the test.

    void test_ref_to_map() {

    MAP valueMap;
    valueMap["key"] = "value";
    // pass it by reference
    // check that the value has changed
    assert( "new!" == valueMap["key"] );

I think this is nice and simple. Enjoy ...