Programs & Examples On #Prolog

Prolog is the most commonly used logic programming language. It supports non-deterministic programming through chronological backtracking and pattern matching through unification.

Prolog "or" operator, query

you can 'invoke' alternative bindings on Y this way:

...registered(X, Y), (Y=ct101; Y=ct102; Y=ct103).

Note the parenthesis are required to keep the correct execution control flow. The ;/2 it's the general or operator. For your restricted use you could as well choice the more idiomatic

...registered(X, Y), member(Y, [ct101,ct102,ct103]).

that on backtracking binds Y to each member of the list.

edit I understood with a delay your last requirement. If you want that Y match all 3 values the or is inappropriate, use instead

...registered(X, ct101), registered(X, ct102), registered(X, ct103).

or the more compact

...findall(Y, registered(X, Y), L), sort(L, [ct101,ct102,ct103]).

findall/3 build the list in the very same order that registered/2 succeeds. Then I use sort to ensure the matching.

...setof(Y, registered(X, Y), [ct101,ct102,ct103]).

setof/3 also sorts the result list

'if' in prolog?

Prolog predicates 'unify' -

So, in an imperative langauge I'd write

function bazoo(integer foo)
   if(foo == 5)

In Prolog I'd write

bazoo(5) :-  doSomething.
bazoo(Foo) :- Foo =/= 5, doSomeOtherThing.

which, when you understand both styles, is actually a lot clearer.
"I'm bazoo for the special case when foo is 5"
"I'm bazoo for the normal case when foo isn't 5"

How to import functions from different js file in a Vue+webpack+vue-loader project

I like the answer of Anacrust, though, by the fact "console.log" is executed twice, I would like to do a small update for src/mylib.js:

let test = {
  foo () { return 'foo' },
  bar () { return 'bar' },
  baz () { return 'baz' }

export default test

All other code remains the same...

batch file Copy files with certain extensions from multiple directories into one directory

Brandon, short and sweet. Also flexible.

set dSource=C:\Main directory\sub directory
set dTarget=D:\Documents
set fType=*.doc
for /f "delims=" %%f in ('dir /a-d /b /s "%dSource%\%fType%"') do (
    copy /V "%%f" "%dTarget%\" 2>nul

Hope this helps.

I would add some checks after the copy (using '||') but i'm not sure how "copy /v" reacts when it encounters an error.

you may want to try this:

copy /V "%%f" "%dTarget%\" 2>nul|| echo En error occured copying "%%F".&& exit /b 1

As the copy line. let me know if you get something out of it (in no position to test a copy failure atm..)

Remove all newlines from inside a string

As mentioned by @john, the most robust answer is:

string = "a\nb\rv"
new_string = " ".join(string.splitlines())

How can I lock a file using java (if possible)

If you can use Java NIO (JDK 1.4 or greater), then I think you're looking for java.nio.channels.FileChannel.lock()


How do I see if Wi-Fi is connected on Android?

Add this for JAVA:

public boolean CheckWifiConnection() {
        ConnectivityManager conMgr = (ConnectivityManager) getSystemService (Context.CONNECTIVITY_SERVICE);
        if (conMgr.getActiveNetworkInfo() != null
                && conMgr.getActiveNetworkInfo().isAvailable()
                && conMgr.getActiveNetworkInfo().isConnected()) {
            return true;
        } else {
            return false;

in Manifest file add the following permissions:

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

How to install OpenJDK 11 on Windows?

You can use Amazon Corretto. It is free to use multiplatform, production-ready distribution of the OpenJDK. It comes with long-term support that will include performance enhancements and security fixes. Check the installation instructions here.

You can also check Zulu from Azul.

One more thing I like to highlight here is both Amazon Corretto and Zulu are TCK Compliant. You can see the OpenJDK builds comparison here and here.

Swap DIV position with CSS only

In some cases you can just use the flex-box property order.

Very simple:

.flex-item {
    order: 2;


What's the difference between JavaScript and JScript?

Wikipedia has this to say about the differences.

In general JScript is an ActiveX scripting language that is probably interpreted as JavaScript by non-IE browsers.

Fast way to concatenate strings in nodeJS/JavaScript

The question is already answered, however when I first saw it I thought of NodeJS Buffer. But it is way slower than the +, so it is likely that nothing can be faster than + in string concetanation.

Tested with the following code:

function a(){
    var s = "hello";
    var p = "world";
    s = s + p;
    return s;

function b(){
    var s = new Buffer("hello");
    var p = new Buffer("world");
    s = Buffer.concat([s,p]);
    return s;

var times = 100000;

var t1 = new Date();
for( var i = 0; i < times; i++){

var t2 = new Date();
console.log("Normal took: " + (t2-t1) + " ms.");
for ( var i = 0; i < times; i++){

var t3 = new Date();

console.log("Buffer took: " + (t3-t2) + " ms.");


Normal took: 4 ms.
Buffer took: 458 ms.

How to resolve the "ADB server didn't ACK" error?

Try the following:

  • Close Eclipse.
  • Restart your phone.
  • End adb.exe process in Task Manager (Windows). In Mac, force close in Activity Monitor.
  • Issue kill and start command in \platform-tools\
    • C:\sdk\platform-tools>adb kill-server
    • C:\sdk\platform-tools>adb start-server
  • If it says something like 'started successfully', you are good.

How to determine if a point is in a 2D triangle?

One of the easiest ways to check if the area formed by the vertices of triangle (x1,y1),(x2,y2),(x3,y3) is positive or not.

Area can by calculated by the formula:

1/2 [x1(y2–y3) + x2(y3–y1) + x3(y1–y2)]

or python code can be written as:

def triangleornot(p1,p2,p3):
    return (1/ 2) [p1[0](p2[1]–p3[1]) + p2[0] (p3[1]–p1[1]) + p3[0] (p1[0]–p2[0])]

How to avoid 'undefined index' errors?

Same idea as Michael Waterfall

From CodeIgniter

// Lets you determine whether an array index is set and whether it has a value.
// If the element is empty it returns FALSE (or whatever you specify as the default value.)
function element($item, $array, $default = FALSE)
    if ( ! isset($array[$item]) OR $array[$item] == "")
        return $default;

    return $array[$item];

Can you style an html radio button to look like a checkbox?

Pure Vanilla CSS / HTML solution in 2021. It uses the CSS appearance: none; property.

Seems to be compatible with all major browsers at this time:

   appearance: none;
   border: 1px solid #d3d3d3;
   width: 30px;
   height: 30px;
   content: none;
   outline: none;
   margin: 0;
   box-shadow: rgba(0, 0, 0, 0.24) 0px 3px 8px;

input[type="radio"]:checked {
  appearance: none;
  outline: none;
  padding: 0;
  content: none;
  border: none;

  position: absolute;
  color: green !important;
  content: "\00A0\2713\00A0" !important;
  border: 1px solid #d3d3d3;
  font-weight: bolder;
  font-size: 21px;
<input type="radio" name="radio" checked>
<input type="radio" name="radio">
<input type="radio" name="radio">

Pass accepts header parameter to jquery ajax

In recent versions of jQuery, setting "dataType" to an appropriate value also sets the accepts header. For instance, dataType: "json" sets the accept header to Accept: application/json, text/javascript, */*; q=0.01.

How to test if a string contains one of the substrings in a list, in pandas?

One option is just to use the regex | character to try to match each of the substrings in the words in your Series s (still using str.contains).

You can construct the regex by joining the words in searchfor with |:

>>> searchfor = ['og', 'at']
>>> s[s.str.contains('|'.join(searchfor))]
0    cat
1    hat
2    dog
3    fog
dtype: object

As @AndyHayden noted in the comments below, take care if your substrings have special characters such as $ and ^ which you want to match literally. These characters have specific meanings in the context of regular expressions and will affect the matching.

You can make your list of substrings safer by escaping non-alphanumeric characters with re.escape:

>>> import re
>>> matches = ['$money', 'x^y']
>>> safe_matches = [re.escape(m) for m in matches]
>>> safe_matches
['\\$money', 'x\\^y']

The strings with in this new list will match each character literally when used with str.contains.

How can I check if an array contains a specific value in php?

Use the in_array() function.

$array = array('kitchen', 'bedroom', 'living_room', 'dining_room');

if (in_array('kitchen', $array)) {
    echo 'this array contains kitchen';

Android Studio cannot resolve R in imported project?

just clean project and then sync your project with gradle file.

How to save an HTML5 Canvas as an image on a server?

I've worked on something similar. Had to convert canvas Base64-encoded image to Uint8Array Blob.

function b64ToUint8Array(b64Image) {
   var img = atob(b64Image.split(',')[1]);
   var img_buffer = [];
   var i = 0;
   while (i < img.length) {
   return new Uint8Array(img_buffer);

var b64Image = canvas.toDataURL('image/jpeg');
var u8Image  = b64ToUint8Array(b64Image);

var formData = new FormData();
formData.append("image", new Blob([ u8Image ], {type: "image/jpg"}));

var xhr = new XMLHttpRequest();"POST", "/api/upload", true);

How to populate a dropdownlist with json data in jquery?

To populate ComboBox with JSON, you can consider using the: jqwidgets combobox, too.

PANIC: Cannot find AVD system path. Please define ANDROID_SDK_ROOT (in windows 10)

In Korean version of Windows 10, this problem happened because my Windows user name was in Korean not in English. After the user name was made again in English, the problem was cleared.

How to use MySQL DECIMAL?

Although the answers above seems correct, just a simple explanation to give you an idea of how it works.

Suppose that your column is set to be DECIMAL(13,4). This means that the column will have a total size of 13 digits where 4 of these will be used for precision representation.

So, in summary, for that column you would have a max value of: 999999999.9999

HTML5 event handling(onfocus and onfocusout) using angular 2

<input name="date" type="text" (focus)="focusFunction()" (focusout)="focusOutFunction()">

works for me from Pardeep Jain

How to set up a cron job to run an executable every hour?

Did you mean the executable fails to run , if invoked from any other directory? This is rather a bug on the executable. One potential reason could be the executable requires some shared libraires from the installed folder. You may check environment variable LD_LIBRARY_PATH

Converting Pandas dataframe into Spark dataframe error

You need to make sure your pandas dataframe columns are appropriate for the type spark is inferring. If your pandas dataframe lists something like:
<class 'pandas.core.frame.DataFrame'>
RangeIndex: 5062 entries, 0 to 5061
Data columns (total 51 columns):
SomeCol                    5062 non-null object
Col2                       5062 non-null object

And you're getting that error try:

df[['SomeCol', 'Col2']] = df[['SomeCol', 'Col2']].astype(str)

Now, make sure .astype(str) is actually the type you want those columns to be. Basically, when the underlying Java code tries to infer the type from an object in python it uses some observations and makes a guess, if that guess doesn't apply to all the data in the column(s) it's trying to convert from pandas to spark it will fail.

java.lang.NoClassDefFoundError: javax/mail/Authenticator, whats wrong?

Add following to your maven dependency



How do I programmatically get the GUID of an application in .NET 2.0

Try the following code. The value you are looking for is stored on a GuidAttribute instance attached to the Assembly

using System.Runtime.InteropServices;

static void Main(string[] args)
    var assembly = typeof(Program).Assembly;
    var attribute = (GuidAttribute)assembly.GetCustomAttributes(typeof(GuidAttribute),true)[0];
    var id = attribute.Value;

How to get the browser language using JavaScript

The "JavaScript" way:

var lang = navigator.language || navigator.userLanguage; //no ?s necessary

Really you should be doing language detection on the server, but if it's absolutely necessary to know/use via JavaScript, it can be gotten.

Disable cache for some images

I know this topic is old, but it ranks very well in Google. I found out that putting this in your header works well;

<meta Http-Equiv="Cache-Control" Content="no-cache">
<meta Http-Equiv="Pragma" Content="no-cache">
<meta Http-Equiv="Expires" Content="0">
<meta Http-Equiv="Pragma-directive: no-cache">
<meta Http-Equiv="Cache-directive: no-cache">

Bootstrap full responsive navbar with logo or brand name text

I checked and it worked for me.

<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1" style="margin-top:100px;"><!--style with margin-top according to your need-->
        <ul class="nav navbar-nav navbar-right">
            <li><a href="#">About</a></li>
            <li><a href="#">Services</a></li>
            <li><a href="#">Contact</a></li>

How to Migrate to WKWebView?

Use some design patterns, you can mix UIWebView and WKWebView. The key point is to design a unique browser interface. But you should pay more attention to your app's current functionality, for example: if your app using NSURLProtocol to enhance network ability, using WKWebView you have no chance to do the same thing. Because NSURLProtocol only effects the current process, and WKWebView using muliti-process architecture, the networking staff is in a seperate process.

Received fatal alert: handshake_failure through SSLHandshakeException

This can also happend when the client needs to present a certificate. After the server lists the certificate chain, the following can happen:

3. Certificate Request The server will issue a certificate request from the client. The request will list all of the certificates the server accepts.

*** CertificateRequest
Cert Types: RSA
Cert Authorities:
<CN=blah, OU=blah, O=blah, L=blah, ST=blah, C=blah>
<CN=yadda, DC=yadda, DC=yadda>
<CN=moreblah, OU=moreblah, O=moreblah, C=moreblah>
<CN=moreyada, OU=moreyada, O=moreyada, C=moreyada>
... the rest of the request
*** ServerHelloDone

4. Client Certificate Chain This is the certificate the client is sending to the server.

*** Certificate chain
chain [0] = [
  Version: V3
  Subject: EMAILADDRESS=client's email, CN=client, OU=client's ou, O=client's Org, L=client's location, ST=client's state, C=client's Country
  Signature Algorithm: SHA1withRSA, OID = 1.2.840.113549.1.1.5
  ... the rest of the certificate
*** ClientKeyExchange, RSA PreMasterSecret, TLSv1    
... key exchange info 

If there isn't a certificate in the chain and the server requires one, you'll get the handshake error here. A likely cause is the path to your certificate wasn't found.

5. Certificate Verify The client asks the server to verify the certificate

*** CertificateVerify
... payload of verify check

This step will only happen if you are sending a certificate.

6. Finished The server will respond with a verify response

*** Finished
verify_data:  { 345, ... }

CSS table layout: why does table-row not accept a margin?

Have you tried setting the bottom margin to .row div, i.e. to your "cells"? When you work with actual HTML tables, you cannot set margins to rows, too - only to cells.

Abort Ajax requests using jQuery

You can't recall the request but you can set a timeout value after which the response will be ignored. See this page for jquery AJAX options. I believe that your error callback will be called if the timeout period is exceeded. There is already a default timeout on every AJAX request.

You can also use the abort() method on the request object but, while it will cause the client to stop listening for the event, it may probably will not stop the server from processing it.

What is the best way to calculate a checksum for a file that is on my machine?

Note that the above solutions will not tell you if your installation is correct only if your install.exe is correct (you can trust it to produce a correct install.)

You would need MD5 sums for each file/folder to test if the installed code has been messed with after the install completed.

WinMerg is useful to compare two installs (on two different machines perhaps) to see if one has been changed or why one is broken.

Changing color of Twitter bootstrap Nav-Pills

You can supply your own class to the nav-pills container with your custom color for your active link, that way you can create as many colors as you like without modifying the bootstrap default colors in other sections of your page. Try this:


<ul class="nav nav-pills red">
    <li class="active"><a href="#tab1" data-toggle="tab">Overview</a></li>
    <li><a href="#tab2" data-toggle="tab">Sample</a></li>
    <li><a href="#tab3" data-toggle="tab">Sample</a></li>

And here is the CSS for your custom color:

.red .active a,
.red .active a:hover {
    background-color: red;

Also, if you prefer to replace the default color for the .active item in your nav-pills you can modify the original like so:

.nav-pills > .active > a, .nav-pills > .active > a:hover {
    background-color: red;

Could not load file or assembly 'Microsoft.ReportViewer.WebForms'

Updating ReportViewer should works. Use below instruction to install updated ReportViewer from Nuget Package Manager console.

Install-Package Microsoft.ReportingServices.ReportViewerControl.WebForms

Just add below assembly reference in your aspx file.

Here, is the version number of the ReportViewerControl.WebForms that was installed in my VS. Please check Reference of the Solution to confirm the version number. No need to add PublicTokens (if multiple installation exists, it may creates trouble again).

How to overlay one div over another div

Here follows a simple solution 100% based on CSS. The "secret" is to use the display: inline-block in the wrapper element. The vertical-align: bottom in the image is a hack to overcome the 4px padding that some browsers add after the element.

Advice: if the element before the wrapper is inline they can end up nested. In this case you can "wrap the wrapper" inside a container with display: block - usually a good and old div.

.wrapper {_x000D_
    display: inline-block;_x000D_
    position: relative;_x000D_
.hover {_x000D_
    position: absolute;_x000D_
    top: 0;_x000D_
    left: 0;_x000D_
    right: 0;_x000D_
    bottom: 0;_x000D_
    background-color: rgba(0, 188, 212, 0);_x000D_
    transition: background-color 0.5s;_x000D_
.hover:hover {_x000D_
    background-color: rgba(0, 188, 212, 0.8);_x000D_
    // You can tweak with other background properties too (ie: background-image)..._x000D_
img {_x000D_
    vertical-align: bottom;_x000D_
<div class="wrapper">_x000D_
    <div class="hover"></div>_x000D_
    <img src="" />_x000D_

Sequence contains no matching element

For those of you who faced this issue while creating a controller through the context menu, reopening Visual Studio as an administrator fixed it.

Count character occurrences in a string in C++


#include <iostream>
 #include <string>
 using namespace std;

int WordOccurrenceCount( std::string const & str, std::string const & word )
       int count(0);
       std::string::size_type word_pos( 0 );
       while ( word_pos!=std::string::npos )
               word_pos = str.find(word, word_pos );
               if ( word_pos != std::string::npos )

         // start next search after this word 
                       word_pos += word.length();

       return count;

int main()

   string sting1="theeee peeeearl is in theeee riveeeer";
   string word1="e";
   cout<<word1<<" occurs "<<WordOccurrenceCount(sting1,word1)<<" times in ["<<sting1 <<"] \n\n";

   return 0;

android: stretch image in imageview to fit screen

to change pro-grammatically use :



to change from xml use:


How can I convert a string with dot and comma into a float in Python

Just remove the , with replace():


Pure CSS animation visibility with delay

You can play with delay prop of animation, just set visibility:visible after a delay, demo:

@keyframes delayedShow {_x000D_
  to {_x000D_
    visibility: visible;_x000D_
  visibility: hidden;_x000D_
  animation: 0s linear 2.3s forwards delayedShow ;_x000D_
So, Where are you?_x000D_
<div class="delayedShow">_x000D_
  Hey, I'm here!_x000D_

"SetPropertiesRule" warning message when starting Tomcat from Eclipse

I respect all the solutions given here.

But what I came to know after reading all these, we haven't observed that on which folder the struts.xml file or any configuration file which is necessary for the web application.


  1. copy the struts.xml file to the src folder of our project.
  2. click "file-->save all" in eclipse and go click "project-->clean".
  3. restart the server.

Hope the problem solved.

Detect whether there is an Internet connection available on Android

The getActiveNetworkInfo() method of ConnectivityManager returns a NetworkInfo instance representing the first connected network interface it can find or null if none of the interfaces are connected. Checking if this method returns null should be enough to tell if an internet connection is available or not.

private boolean isNetworkAvailable() {
    ConnectivityManager connectivityManager 
          = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnected();

You will also need:

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

in your android manifest.


Note that having an active network interface doesn't guarantee that a particular networked service is available. Network issues, server downtime, low signal, captive portals, content filters and the like can all prevent your app from reaching a server. For instance you can't tell for sure if your app can reach Twitter until you receive a valid response from the Twitter service.

How to find and replace with regex in excel

If you want a formula to do it then:

=IF(ISNUMBER(SEARCH("*texts are *",A1)),LEFT(A1,FIND("texts are ",A1) + 9) & "WORD",A1)

This will do it. Change `"WORD" To the word you want.

Where can I view Tomcat log files in Eclipse?

Another forum provided this answer:

Ahh, figured this out. The following system properties need to be set, so that the "" file can be picked up.

Assuming that the tomcat is located under an Eclipse project, add the following under the "Arguments" tab of its launch configuration:


How to check status of PostgreSQL server Mac OS X

It depends on where your postgresql server is installed. You use the pg_ctl to manually start the server like below.

pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start

image size (drawable-hdpi/ldpi/mdpi/xhdpi)

As of Octoer 2020, the dimensions for Launcher, ActionBar/Tab and Notification icons are:

enter image description here

A very good online tool to generate launcher icons :

Increase Tomcat memory settings

try setting this

CATALINA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 
-server -Xms1536m -Xmx1536m
-XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=256m 
-XX:MaxPermSize=256m -XX:+DisableExplicitGC"

in {$tomcat-folder}\bin\ (create it if necessary).

See for more details.

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":

Is it possible to send an array with the Postman Chrome extension?

this worked for me. to pass an array of Item object {ItemID,ColorID,SizeID,Quntity}

Postman data

Use 'class' or 'typename' for template parameters?

In response to Mike B, I prefer to use 'class' as, within a template, 'typename' has an overloaded meaning, but 'class' does not. Take this checked integer type example:

template <class IntegerType>
class smart_integer {
    typedef integer_traits<Integer> traits;
    IntegerType operator+=(IntegerType value){
        typedef typename traits::larger_integer_t larger_t;
        larger_t interm = larger_t(myValue) + larger_t(value); 
        if(interm > traits::max() || interm < traits::min())
            throw overflow();
        myValue = IntegerType(interm);

larger_integer_t is a dependent name, so it requires 'typename' to preceed it so that the parser can recognize that larger_integer_t is a type. class, on the otherhand, has no such overloaded meaning.

That... or I'm just lazy at heart. I type 'class' far more often than 'typename', and thus find it much easier to type. Or it could be a sign that I write too much OO code.

How to square all the values in a vector in R?

How about sapply (not really necessary for this simple case):

newData<- sapply(data, function(x) x^2)

How can I do width = 100% - 100px in CSS?

The short answer is you DON'T do this in CSS. Internet Explorer has support for something called CSS Expressions, but this isn't standard and is definitely not supported by other browsers like FireFox for instance.

You'd be better off doing this in JavaScript.

How to check if the key pressed was an arrow key in Java KeyListener?

Just to complete the answer (using the KeyEvent is the way to go) but up arrow is 38 and down arrow is 40 so:

    else if (e.getKeyCode()==38)
            //Up arrow key code
    else if (e.getKeyCode()==40)
            //down arrow key code

variable or field declared void

It for example happens in this case here:

void initializeJSP(unknownType Experiment);

Try using std::string instead of just string (and include the <string> header). C++ Standard library classes are within the namespace std::.

Could not find tools.jar. Please check that C:\Program Files\Java\jre1.8.0_151 contains a valid JDK installation

The problem is your gradle build is not finding the JAVA_HOME path or JDK folder. So, you could declare the path in like\Program Files\Java\[or yours jdk folder name].

Use this guide for using

Or (and I prefer this solution) include JAVA_HOME path in systmem variables and restart CMD.

enter image description here

'AND' vs '&&' as operator

For safety, I always parenthesise my comparisons and space them out. That way, I don't have to rely on operator precedence:

    ((i==0) && (b==2)) 
    ((c==3) && !(f==5)) 

Java ByteBuffer to String

There is simpler approach to decode a ByteBuffer into a String without any problems, mentioned by Andy Thomas.

String s = StandardCharsets.UTF_8.decode(byteBuffer).toString();

Detect if page has finished loading

That's called onload. DOM ready was actually created for the exact reason that onload waited on images. ( Answer taken from Matchu on a simmilar question a while ago. )

window.onload = function () { alert("It's loaded!") }

onload waits for all resources that are part of the document.

Link to a question where he explained it all:

Click me, you know you want to!

How can I create a war file of my project in NetBeans?

Simplest way is to Check the Output - Build tab: It would display the location of war file.
It will have something like:

Installing D:\Project\target\Tool.war to C:\Users\myname.m2\repository\com\tool\1.0\Tool-1.0.war

How can I do a BEFORE UPDATED trigger with sql server?

The updated or deleted values are stored in DELETED. we can get it by the below method in trigger

Full example,




How can I change IIS Express port for a site

.Net Core

For those who got here looking for this configuration in .Net core this resides in the lauchSettings.json. Just edit the port in the property "applicationUrl".

The file should look something like this:

  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:53950/", //Here
      "sslPort": 0
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "index.html",
      "environmentVariables": {
        "Hosting:Environment": "Development"

Or you can use the GUI by double clicking in the "Properties" of your project.

Note: I had to reopen VS to make it work.

LinearLayout not expanding inside a ScrollView

Can you provide your layout xml? Doing so would allow people to recreate the issue with minimal effort.

You might have to set


for the item that you want expanded

(WAMP/XAMP) send Mail using SMTP localhost

If any one of you are getting error like following after following answer given by Afwe Wef

 Warning: mail() [<a href='function.mail'>function.mail</a>]: SMTP server response:

 550 The address is not valid. in c:\wamp\www\email.php

Go to php.ini

; For Win32 only.
sendmail_from = [email protected]

Enter [email protected] as your email id which you used to configure the hMailserver in front of sendmail_from .

your problem will be solved.

Tested on Wamp server2.2(Apache 2.2.22, php 5.3.13) on windows 8

If you are also getting following error

"APPLICATION"   6364    "2014-03-24 13:13:33.979"   "SMTPDeliverer - Message 2: Relaying to host"
"APPLICATION"   6364    "2014-03-24 13:13:34.415"   "SMTPDeliverer - Message 2: Message could not be delivered. Scheduling it for later delivery in 60 minutes."
"APPLICATION"   6364    "2014-03-24 13:13:34.430"   "SMTPDeliverer - Message 2: Message delivery thread completed."

You might have forgot to change the port from 25 to 465

Best practice to return errors in ASP.NET Web API

You can use custom ActionFilter in Web Api to validate model:

public class DRFValidationFilters : ActionFilterAttribute

    public override void OnActionExecuting(HttpActionContext actionContext)
        if (!actionContext.ModelState.IsValid)
            actionContext.Response = actionContext.Request
                .CreateErrorResponse(HttpStatusCode.BadRequest, actionContext.ModelState);


    public override Task OnActionExecutingAsync(HttpActionContext actionContext,
        CancellationToken cancellationToken)

        return Task.Factory.StartNew(() =>
            if (!actionContext.ModelState.IsValid)
                actionContext.Response = actionContext.Request
                    .CreateErrorResponse(HttpStatusCode.BadRequest, actionContext.ModelState);

    public class AspirantModel
        public int AspirantId { get; set; }
        public string FirstName { get; set; }
        public string MiddleName { get; set; }
        public string LastName { get; set; }
        public string AspirantType { get; set; }
        [RegularExpression(@"^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$",
            ErrorMessage = "Not a valid Phone number")]
        public string MobileNumber { get; set; }
        public int StateId { get; set; }
        public int CityId { get; set; }
        public int CenterId { get; set; }

        public IHttpActionResult Create(AspirantModel aspirant)
            if (aspirant != null)

                return Conflict();

            return Ok();

Register CustomAttribute class in webApiConfig.cs config.Filters.Add(new DRFValidationFilters());

Could not load file or assembly 'CrystalDecisions.ReportAppServer.CommLayer, Version=13.0.2000.0

I had the same error after moving to a new laptop (Windows 10). In addition to setting Copy Local to true as mentioned above, I had to install the Crystal Reports 32-bit runtime engine for .Net Framework, even though everything else is set to run in a 64-bit environment. Hope that helps.

Windows Control Panel - Programs and Features

How do I make a JAR from a .java file?

This can be done without terminal, directly from IDE. Netbeans, for example.

  1. Create a separate project with packages (Create Project - Java - Java Class Library).
  2. Put your .java classes there.
  3. Build this project.
  4. Go to your project folder and find build and dist folders there.
  5. Find .jar file in your dist folder.
  6. Get your other project and add this .jar file to project libraries.
  7. You can now reference classes from this library and its methods directly from code, if import is automatically done for you.

Is it possible to delete an object's property in PHP?

This also works if you are looping over an object.


No need to use brackets.

Detect whether current Windows version is 32 bit or 64 bit

I use this:

@echo off
 echo 64 BIT
) else (
 echo 32 BIT

It works on Windows XP, tested it on Windows XP Professional Both 64 bit and 32 bit.

How to check a string against null in java?

You can check with String == null

This works for me

    String foo = null;
    if(foo == null){
        System.out.println("String is null");

Is it possible only to declare a variable without assigning any value in Python?

Why not just do this:

var = None

Python is dynamic, so you don't need to declare things; they exist automatically in the first scope where they're assigned. So, all you need is a regular old assignment statement as above.

This is nice, because you'll never end up with an uninitialized variable. But be careful -- this doesn't mean that you won't end up with incorrectly initialized variables. If you init something to None, make sure that's what you really want, and assign something more meaningful if you can.

Limiting the number of characters in a string, and chopping off the rest

Use this to cut off the non needed characters:

String.substring(0, maxLength); 


String aString ="123456789";
String cutString = aString.substring(0, 4);
// Output is: "1234" 

To ensure you are not getting an IndexOutOfBoundsException when the input string is less than the expected length do the following instead:

int maxLength = (inputString.length() < MAX_CHAR)?inputString.length():MAX_CHAR;
inputString = inputString.substring(0, maxLength);

If you want your integers and doubles to have a certain length then I suggest you use NumberFormat to format your numbers instead of cutting off their string representation.

From inside of a Docker container, how do I connect to the localhost of the machine?

The CGroups and Namespaces are playing major role in the Container Ecosystem.

Namespace provide a layer of isolation. Each container runs in a separate namespace and its access is limited to that namespace. The Cgroups controls the resource utilization of each container, whereas Namespace controls what a process can see and access the respective resource.

Here is the basic understanding of the solution approach you could follow,

Use Network Namespace

When a container spawns out of image, a network interface is defined and create. This gives the container unique IP address and interface.

$ docker run -it alpine ifconfig

By changing the namespace to host, cotainers networks does not remain isolated to its interface, the process will have access to host machines network interface.

$ docker run -it --net=host alpine ifconfig

If the process listens on ports, they'll be listened on the host interface and mapped to the container.

Use PID Namespace By changing the Pid namespace allows a container to interact with other process beyond its normal scope.

This container will run in its own namespace.

$ docker run -it alpine ps aux

By changing the namespace to the host, the container can also see all the other processes running on the system.

$ docker run -it --pid=host alpine ps aux

Sharing Namespace

This is a bad practice to do this in production because you are breaking out of the container security model which might open up for vulnerabilities, and easy access to eavesdropper. This is only for debugging tools and understating the loopholes in container security.

The first container is nginx server. This will create a new network and process namespace. This container will bind itself to port 80 of newly created network interface.

$ docker run -d --name http nginx:alpine

Another container can now reuse this namespace,

$ docker run --net=container:http mohan08p/curl curl -s localhost

Also, this container can see the interface with the processes in a shared container.

$ docker run --pid=container:http alpine ps aux

This will allow you give more privileges to containers without changing or restarting the application. In the similar way you can connect to mysql on host, run and debug your application. But, its not recommend to go by this way. Hope it helps.

How to use the DropDownList's SelectedIndexChanged event

I think this is the culprit:

cmd = new SqlCommand(query, con);

DataTable dt = Select(query);


ddtype.DataSource = dt;

I don't know what that code is supposed to do, but it looks like you want to create an SqlDataReader for that, as explained here and all over the web if you search for "SqlCommand DropDownList DataSource":

cmd = new SqlCommand(query, con);
ddtype.DataSource = cmd.ExecuteReader();

Or you can create a DataTable as explained here:

cmd = new SqlCommand(query, con);

SqlDataAdapter listQueryAdapter = new SqlDataAdapter(cmd);
DataTable listTable = new DataTable();

ddtype.DataSource = listTable;

Create a BufferedImage from file and make it TYPE_INT_ARGB

Create a BufferedImage from file and make it TYPE_INT_RGB

import java.awt.image.*;
import javax.imageio.*;
public class Main{
    public static void main(String args[]){
            BufferedImage img = new BufferedImage( 
                500, 500, BufferedImage.TYPE_INT_RGB );
            File f = new File("MyFile.png");
            int r = 5;
            int g = 25; 
            int b = 255;
            int col = (r << 16) | (g << 8) | b;
            for(int x = 0; x < 500; x++){
                for(int y = 20; y < 300; y++){
                    img.setRGB(x, y, col);
            ImageIO.write(img, "PNG", f); 
        catch(Exception e){ 

This paints a big blue streak across the top.

If you want it ARGB, do it like this:

        BufferedImage img = new BufferedImage( 
            500, 500, BufferedImage.TYPE_INT_ARGB );
        File f = new File("MyFile.png");
        int r = 255;
        int g = 10;
        int b = 57;
        int alpha = 255;
        int col = (alpha << 24) | (r << 16) | (g << 8) | b;
        for(int x = 0; x < 500; x++){
            for(int y = 20; y < 30; y++){
                img.setRGB(x, y, col);
        ImageIO.write(img, "PNG", f);
    catch(Exception e){

Open up MyFile.png, it has a red streak across the top.

How to avoid the "Circular view path" exception with Spring MVC test

Add the annotation @ResponseBody to your method return.

How can I call a WordPress shortcode within a template?

Try this:

Template Name: [contact us]

echo do_shortcode('[CONTACT-US-FORM]'); 

How to create a hidden <img> in JavaScript?

How about

<img style="display: none;" src="a.gif">

That will disable the display completely, and not leave a placeholder

How to implement the factory method pattern in C++ correctly

Factory Pattern

class Point
  static Point Cartesian(double x, double y);

And if you compiler does not support Return Value Optimization, ditch it, it probably does not contain much optimization at all...

Java 8 - Difference between Optional.flatMap and

You can refer below link to understand in detail (best explanation which I could find):

Both map and flatMap - accept Function. The return type of map() is a single value whereas flatMap is returning stream of values

<R> Stream<R> map(Function<? super T, ? extends R> mapper)

<R> Stream<R> flatMap(Function<? super T, ? extends Stream<? extends R>> mapper)

AppFabric installation failed because installer MSI returned with error code : 1603

So, I was having the same issue. The main reason I am installing Appfabric is to create a SharePoint 2013 development server.
What did not work:

  • Updating the Environmental Variable PSModulePath - did not work. Still recieved the 1603 error after running the setup agian.
  • tried to find the registry entries. Could not find them.

What worked for me to get Appfrabic installed was installing from the setup file via powershell. Woo hoo! It worked for me! This is the link I retrieved the commands from: Installing AppFabric 1.1 with PowerShell DSC results in modal dialog error

        Start-Process -FilePath 'c:\temp\SharePoint\pre\appfabric\setup.exe' -ArgumentList '/i cacheclient","cachingService","CacheAdmin /gac /l c:\temp\appfabric.log' -Wait | Write-verbose
        Start-Process -FilePath 'c:\temp\SharePoint\pre\AppFabric1.1-RTM-KB2671763-x64-ENU.exe' -ArgumentList '/quiet' -Wait | Write-verbose

I hope this helps others with the same issue.

How to "properly" create a custom object in JavaScript?

There are two models for implementing classes and instances in JavaScript: the prototyping way, and the closure way. Both have advantages and drawbacks, and there are plenty of extended variations. Many programmers and libraries have different approaches and class-handling utility functions to paper over some of the uglier parts of the language.

The result is that in mixed company you will have a mishmash of metaclasses, all behaving slightly differently. What's worse, most JavaScript tutorial material is terrible and serves up some kind of in-between compromise to cover all bases, leaving you very confused. (Probably the author is also confused. JavaScript's object model is very different to most programming languages, and in many places straight-up badly designed.)

Let's start with the prototype way. This is the most JavaScript-native you can get: there is a minimum of overhead code and instanceof will work with instances of this kind of object.

function Shape(x, y) {
    this.x= x;
    this.y= y;

We can add methods to the instance created by new Shape by writing them to the prototype lookup of this constructor function:

Shape.prototype.toString= function() {
    return 'Shape at '+this.x+', '+this.y;

Now to subclass it, in as much as you can call what JavaScript does subclassing. We do that by completely replacing that weird magic prototype property:

function Circle(x, y, r) {, x, y); // invoke the base class's constructor function to take co-ords
    this.r= r;
Circle.prototype= new Shape();

before adding methods to it:

Circle.prototype.toString= function() {
    return 'Circular '' with radius '+this.r;

This example will work and you will see code like it in many tutorials. But man, that new Shape() is ugly: we're instantiating the base class even though no actual Shape is to be created. It happens to work in this simple case because JavaScript is so sloppy: it allows zero arguments to be passed in, in which case x and y become undefined and are assigned to the prototype's this.x and this.y. If the constructor function were doing anything more complicated, it would fall flat on its face.

So what we need to do is find a way to create a prototype object which contains the methods and other members we want at a class level, without calling the base class's constructor function. To do this we are going to have to start writing helper code. This is the simplest approach I know of:

function subclassOf(base) {
    _subclassOf.prototype= base.prototype;
    return new _subclassOf();
function _subclassOf() {};

This transfers the base class's members in its prototype to a new constructor function which does nothing, then uses that constructor. Now we can write simply:

function Circle(x, y, r) {, x, y);
    this.r= r;
Circle.prototype= subclassOf(Shape);

instead of the new Shape() wrongness. We now have an acceptable set of primitives to built classes.

There are a few refinements and extensions we can consider under this model. For example here is a syntactical-sugar version:

Function.prototype.subclass= function(base) {
    var c= Function.prototype.subclass.nonconstructor;
    c.prototype= base.prototype;
    this.prototype= new c();
Function.prototype.subclass.nonconstructor= function() {};


function Circle(x, y, r) {, x, y);
    this.r= r;

Either version has the drawback that the constructor function cannot be inherited, as it is in many languages. So even if your subclass adds nothing to the construction process, it must remember to call the base constructor with whatever arguments the base wanted. This can be slightly automated using apply, but still you have to write out:

function Point() {
    Shape.apply(this, arguments);

So a common extension is to break out the initialisation stuff into its own function rather than the constructor itself. This function can then inherit from the base just fine:

function Shape() { this._init.apply(this, arguments); }
Shape.prototype._init= function(x, y) {
    this.x= x;
    this.y= y;

function Point() { this._init.apply(this, arguments); }
// no need to write new initialiser for Point!

Now we've just got the same constructor function boilerplate for each class. Maybe we can move that out into its own helper function so we don't have to keep typing it, for example instead of Function.prototype.subclass, turning it round and letting the base class's Function spit out subclasses:

Function.prototype.makeSubclass= function() {
    function Class() {
        if ('_init' in this)
            this._init.apply(this, arguments);
    Function.prototype.makeSubclass.nonconstructor.prototype= this.prototype;
    Class.prototype= new Function.prototype.makeSubclass.nonconstructor();
    return Class;
Function.prototype.makeSubclass.nonconstructor= function() {};


Shape= Object.makeSubclass();
Shape.prototype._init= function(x, y) {
    this.x= x;
    this.y= y;

Point= Shape.makeSubclass();

Circle= Shape.makeSubclass();
Circle.prototype._init= function(x, y, r) {, x, y);
    this.r= r;

...which is starting to look a bit more like other languages, albeit with slightly clumsier syntax. You can sprinkle in a few extra features if you like. Maybe you want makeSubclass to take and remember a class name and provide a default toString using it. Maybe you want to make the constructor detect when it has accidentally been called without the new operator (which would otherwise often result in very annoying debugging):

Function.prototype.makeSubclass= function() {
    function Class() {
        if (!(this instanceof Class))
            throw('Constructor called without "new"');

Maybe you want to pass in all the new members and have makeSubclass add them to the prototype, to save you having to write Class.prototype... quite so much. A lot of class systems do that, eg:

Circle= Shape.makeSubclass({
    _init: function(x, y, z) {, x, y);
        this.r= r;

There are a lot of potential features you might consider desirable in an object system and no-one really agrees on one particular formula.

The closure way, then. This avoids the problems of JavaScript's prototype-based inheritance, by not using inheritance at all. Instead:

function Shape(x, y) {
    var that= this;

    this.x= x;
    this.y= y;

    this.toString= function() {
        return 'Shape at '+that.x+', '+that.y;

function Circle(x, y, r) {
    var that= this;, x, y);
    this.r= r;

    var _baseToString= this.toString;
    this.toString= function() {
        return 'Circular '+_baseToString(that)+' with radius '+that.r;

var mycircle= new Circle();

Now every single instance of Shape will have its own copy of the toString method (and any other methods or other class members we add).

The bad thing about every instance having its own copy of each class member is that it's less efficient. If you are dealing with large numbers of subclassed instances, prototypical inheritance may serve you better. Also calling a method of the base class is slightly annoying as you can see: we have to remember what the method was before the subclass constructor overwrote it, or it gets lost.

[Also because there is no inheritance here, the instanceof operator won't work; you would have to provide your own mechanism for class-sniffing if you need it. Whilst you could fiddle the prototype objects in a similar way as with prototype inheritance, it's a bit tricky and not really worth it just to get instanceof working.]

The good thing about every instance having its own method is that the method may then be bound to the specific instance that owns it. This is useful because of JavaScript's weird way of binding this in method calls, which has the upshot that if you detach a method from its owner:

var ts= mycircle.toString;

then this inside the method won't be the Circle instance as expected (it'll actually be the global window object, causing widespread debugging woe). In reality this typically happens when a method is taken and assigned to a setTimeout, onclick or EventListener in general.

With the prototype way, you have to include a closure for every such assignment:

setTimeout(function() {
    mycircle.move(1, 1);
}, 1000);

or, in the future (or now if you hack Function.prototype) you can also do it with function.bind():

setTimeout(mycircle.move.bind(mycircle, 1, 1), 1000);

if your instances are done the closure way, the binding is done for free by the closure over the instance variable (usually called that or self, though personally I would advise against the latter as self already has another, different meaning in JavaScript). You don't get the arguments 1, 1 in the above snippet for free though, so you would still need another closure or a bind() if you need to do that.

There are lots of variants on the closure method too. You may prefer to omit this completely, creating a new that and returning it instead of using the new operator:

function Shape(x, y) {
    var that= {};

    that.x= x;
    that.y= y;

    that.toString= function() {
        return 'Shape at '+that.x+', '+that.y;

    return that;

function Circle(x, y, r) {
    var that= Shape(x, y);

    that.r= r;

    var _baseToString= that.toString;
    that.toString= function() {
        return 'Circular '+_baseToString(that)+' with radius '+r;

    return that;

var mycircle= Circle(); // you can include `new` if you want but it won't do anything

Which way is “proper”? Both. Which is “best”? That depends on your situation. FWIW I tend towards prototyping for real JavaScript inheritance when I'm doing strongly OO stuff, and closures for simple throwaway page effects.

But both ways are quite counter-intuitive to most programmers. Both have many potential messy variations. You will meet both (as well as many in-between and generally broken schemes) if you use other people's code/libraries. There is no one generally-accepted answer. Welcome to the wonderful world of JavaScript objects.

[This has been part 94 of Why JavaScript Is Not My Favourite Programming Language.]

Decimal precision and scale in EF Code First

[Column(TypeName = "decimal(18,2)")]

this will work with EF Core code first migrations as described here.

SQL Developer is returning only the date, not the time. How do I fix this?

Neither of these answers would work for me, not the Preferences NLS configuration option or the ALTER statement. This was the only approach that worked in my case:

dbms_session.set_nls('nls_date_format','''DD-MM-YYYY HH24:MI:SS''');

*added after the BEGIN statement

I am using PL/SQL Developer v9.03.1641

Hopefully this is of help to someone!

Ignore parent padding

Kinda late.But it just takes a bit of math.

.content {
  margin-top: 50px;
  background: #777;
  padding: 30px;
  padding-bottom: 0;
  font-size: 11px;
  border: 1px dotted #222;

.bottom-content {
  background: #999;
  width: 100%; /* you need this for it to work */
  margin-left: -30px; /* will touch very left side */
  padding-right: 60px; /* will touch very right side */

<div class='content'>

  <p>A paragraph</p>
  <p>Another paragraph.</p>
  <p>No more content</p>

  <div class='bottom-content'>
      I want this div to ignore padding.

I don't have Windows so I didn't test this in IE.

fiddle: fiddle example..

SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

JSON.parse() doesn't recognize That data as string. For example {objAskGrant:"Yes",objPass:"asdfasdf",objNameSurname:"asdfasdf adfasdf",objEmail:"[email protected]",objGsm:3241234123,objAdres:"asdfasdf",objTerms:"CheckIsValid"}

Which is like this: JSON.parse({objAskGrant:"Yes",objPass:"asdfasdf",objNameSurname:"asdfasdf adfasdf",objEmail:"[email protected]",objGsm:3241234123,objAdres:"asdfasdf",objTerms:"CheckIsValid"}); That will output SyntaxError: missing " ' " instead of "{" on line...

So correctly wrap all data like this: '{"objAskGrant":"Yes","objPass":"asdfasdf","objNameSurname":"asdfasdf adfasdf","objEmail":"[email protected]","objGsm":3241234123,"objAdres":"asdfasdf","objTerms":"CheckIsValid"}' Which works perfectly well for me.

And not like this: "{"objAskGrant":"Yes","objPass":"asdfasdf","objNameSurname":"asdfasdf adfasdf","objEmail":"[email protected]","objGsm":3241234123,"objAdres":"asdfasdf","objTerms":"CheckIsValid"}" Which give the present error you are experiencing.

Recursive search and replace in text files on Mac and Linux is a go utility (i.e. cross-platform), tested on OSX, that does recursive search-and-replace for text in files within a given directory, and confirms each replacement. It's new, so might be buggy.

Usage looks like:

$ ls test
a  d  d2 z
$ cat test/z
$ ./serp --root test --search hi --replace bye --pattern "*"                         
test/z: replace hi with bye? (y/[n]) y
$ cat test/z

SQL order string as number

If possible you should change the data type of the column to a number if you only store numbers anyway.

If you can't do that then cast your column value to an integer explicitly with

select col from yourtable
order by cast(col as unsigned)

or implicitly for instance with a mathematical operation which forces a conversion to number

select col from yourtable
order by col + 0

BTW MySQL converts strings from left to right. Examples:

string value  |  integer value after conversion
'1'           |  1
'ABC'         |  0   /* the string does not contain a number, so the result is 0 */
'123miles'    |  123 
'$123'        |  0   /* the left side of the string does not start with a number */

Enabling WiFi on Android Emulator

When using an AVD with API level 25 or higher, the emulator provides a simulated Wi-Fi access point ("AndroidWifi"), and Android automatically connects to it.

Source :

Formatting floats in a numpy array

You're confusing actual precision and display precision. Decimal rounding cannot be represented exactly in binary. You should try:

> np.set_printoptions(precision=2)
> np.array([5.333333])
array([ 5.33])

Forgot Oracle username and password, how to retrieve?

The usernames are shown in the dba_users's username column, there is a script you can run called:

alter user username identified by password

You can get more information here -

Using {% url ??? %} in django templates

The selected answer is out of date and no others worked for me (Django 1.6 and [apparantly] no registered namespace.)

For Django 1.5 and later (from the docs)

Warning Don’t forget to put quotes around the function path or pattern name!

With a named URL you could do:

(r'^login/', login_view, name='login'),
<a href="{% url 'login' %}">logout</a>

Just as easy if the view takes another parameter

def login(request, extra_param):
<a href="{% url 'login' 'some_string_containing_relevant_data' %}">login</a>

How to copy files from host to Docker container?

  1. Get container name or short container id:

    $ docker ps
  2. Get full container id:

    $ docker inspect -f   '{{.Id}}'  SHORT_CONTAINER_ID-or-CONTAINER_NAME
  3. Copy file:

    $ sudo cp path-file-host /var/lib/docker/aufs/mnt/FULL_CONTAINER_ID/PATH-NEW-FILE


$ docker ps


d8e703d7e303   solidleon/ssh:latest      /usr/sbin/sshd -D                      cranky_pare

$ docker inspect -f   '{{.Id}}' cranky_pare


$ docker inspect -f   '{{.Id}}' d8e703d7e303


$ sudo cp file.txt /var/lib/docker/aufs/mnt/**d8e703d7e3039a6df6d01bd7fb58d1882e592a85059eb16c4b83cf91847f88e5**/root/file.txt

Generate random string/characters in JavaScript

The problem with responses to "I need random strings" questions (in whatever language) is practically every solution uses a flawed primary specification of string length. The questions themselves rarely reveal why the random strings are needed, but I would challenge you rarely need random strings of length, say 8. What you invariably need is some number of unique strings, for example, to use as identifiers for some purpose.

There are two leading ways to get strictly unique strings: deterministically (which is not random) and store/compare (which is onerous). What do we do? We give up the ghost. We go with probabilistic uniqueness instead. That is, we accept that there is some (however small) risk that our strings won't be unique. This is where understanding collision probability and entropy are helpful.

So I'll rephrase the invariable need as needing some number of strings with a small risk of repeat. As a concrete example, let's say you want to generate a potential of 5 million IDs. You don't want to store and compare each new string, and you want them to be random, so you accept some risk of repeat. As example, let's say a risk of less than 1 in a trillion chance of repeat. So what length of string do you need? Well, that question is underspecified as it depends on the characters used. But more importantly, it's misguided. What you need is a specification of the entropy of the strings, not their length. Entropy can be directly related to the probability of a repeat in some number of strings. String length can't.

And this is where a library like EntropyString can help. To generate random IDs that have less than 1 in a trillion chance of repeat in 5 million strings using entropy-string:

import {Random, Entropy} from 'entropy-string'

const random = new Random()
const bits = Entropy.bits(5e6, 1e12)

const string = random.string(bits)


entropy-string uses a character set with 32 characters by default. There are other predefined characters sets, and you can specify your own characters as well. For example, generating IDs with the same entropy as above but using hex characters:

import {Random, Entropy, charSet16} from './entropy-string'

const random = new Random(charSet16)
const bits = Entropy.bits(5e6, 1e12)

const string = random.string(bits)


Note the difference in string length due to the difference in total number of characters in the character set used. The risk of repeat in the specified number of potential strings is the same. The string lengths are not. And best of all, the risk of repeat and the potential number of strings is explicit. No more guessing with string length.

How can I close a browser window without receiving the "Do you want to close this window" prompt?

For security reasons, a window can only be closed in JavaScript if it was opened by JavaScript. In order to close the window, you must open a new window with _self as the target, which will overwrite your current window, and then close that one (which you can do since it was opened via JavaScript).'', '_self', '');

How do I negate a condition in PowerShell?

You almost had it with Not. It should be:

if (-Not (Test-Path C:\Code)) {
    write "it doesn't exist!"

You can also use !: if (!(Test-Path C:\Code)){}

Just for fun, you could also use bitwise exclusive or, though it's not the most readable/understandable method.

if ((test-path C:\code) -bxor 1) {write "it doesn't exist!"}

Angular2 - Focusing a textbox on component load

Directive for autoFocus first field

import {_x000D_
} from "@angular/core";_x000D_
  selector: "[appFocusFirstEmptyInput]"_x000D_
export class FocusFirstEmptyInputDirective implements AfterViewInit {_x000D_
  constructor(private el: ElementRef) {}_x000D_
  ngAfterViewInit(): void {_x000D_
    const invalidControl = this.el.nativeElement.querySelector(".ng-untouched");_x000D_
    if (invalidControl) {_x000D_

Executing periodic actions in Python

Surprised to not find a solution using a generator for timing. I just designed this one for my own purposes.

This solution: single threaded, no object instantiation each period, uses generator for times, rock solid on timing down to precision of the time module (unlike several of the solutions I've tried from stack exchange).

Note: for Python 2.x, replace next(g) below with

import time

def do_every(period,f,*args):
    def g_tick():
        t = time.time()
        while True:
            t += period
            yield max(t - time.time(),0)
    g = g_tick()
    while True:

def hello(s):
    print('hello {} ({:.4f})'.format(s,time.time()))


Results in, for example:

hello foo (1421705487.5811)
hello foo (1421705488.5811)
hello foo (1421705489.5809)
hello foo (1421705490.5830)
hello foo (1421705491.5803)
hello foo (1421705492.5808)
hello foo (1421705493.5811)
hello foo (1421705494.5811)
hello foo (1421705495.5810)
hello foo (1421705496.5811)
hello foo (1421705497.5810)
hello foo (1421705498.5810)
hello foo (1421705499.5809)
hello foo (1421705500.5811)
hello foo (1421705501.5811)
hello foo (1421705502.5811)
hello foo (1421705503.5810)

Note that this example includes a simulation of the cpu doing something else for .3 seconds each period. If you changed it to be random each time it wouldn't matter. The max in the yield line serves to protect sleep from negative numbers in case the function being called takes longer than the period specified. In that case it would execute immediately and make up the lost time in the timing of the next execution.

How can get the text of a div tag using only javascript (no jQuery)

Actually you dont need to call document.getElementById() function to get access to your div.

You can use this object directly by id:

text = test.textContent || test.innerText;

UICollectionView Set number of columns

Here is the working code for Swift 3 or above, to have a two-columns layout :

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    sizeForItemAt indexPath: IndexPath) -> CGSize {
    let nbCol = 2
    let flowLayout = collectionViewLayout as! UICollectionViewFlowLayout
    let totalSpace = flowLayout.sectionInset.left
        + flowLayout.sectionInset.right
        + (flowLayout.minimumInteritemSpacing * CGFloat(nbCol - 1))
    let size = Int((collectionView.bounds.width - totalSpace) / CGFloat(nbCol))
    return CGSize(width: size, height: size)

Feel free to change "nbCol" to your desired number of columns.

Android Endless List

Just wanted to contribute a solution that I used for my app.

It is also based on the OnScrollListener interface, but I found it to have a much better scrolling performance on low-end devices, since none of the visible/total count calculations are carried out during the scroll operations.

  1. Let your ListFragment or ListActivity implement OnScrollListener
  2. Add the following methods to that class:

    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        //leave this empty
    public void onScrollStateChanged(AbsListView listView, int scrollState) {
        if (scrollState == SCROLL_STATE_IDLE) {
            if (listView.getLastVisiblePosition() >= listView.getCount() - 1 - threshold) {
                //load more list items:

    where currentPage is the page of your datasource that should be added to your list, and threshold is the number of list items (counted from the end) that should, if visible, trigger the loading process. If you set threshold to 0, for instance, the user has to scroll to the very end of the list in order to load more items.

  3. (optional) As you can see, the "load-more check" is only called when the user stops scrolling. To improve usability, you may inflate and add a loading indicator to the end of the list via listView.addFooterView(yourFooterView). One example for such a footer view:

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android=""
        android:padding="10dp" >
            android:layout_gravity="center_vertical" />
            android:text="@string/loading_text" />
  4. (optional) Finally, remove that loading indicator by calling listView.removeFooterView(yourFooterView) if there are no more items or pages.

How to run a command in the background on Windows?

Use the start command with the /b flag to run a command/application without opening a new window. For example, this runs dotnet run in the background:

start /b dotnet run

You can pass parameters to the command/application too. For example, I'm starting 3 instances of this C# project, with parameter values of x, y, and z:

enter image description here

To stop the program(s) running in the background: CTRL + BREAK

In my experience, this stops all of the background commands/programs you have started in that cmd instance.

According to the Microsoft docs:

CTRL+C handling is ignored unless the application enables CTRL+C processing. Use CTRL+BREAK to interrupt the application.

Set language for syntax highlighting in Visual Studio Code

In the very right bottom corner, left to the smiley there was the icon saying "Plain Text". When you click it, the menu with all languages appears where you can choose your desired language.


Virtual member call in a constructor

One important aspect of this question which other answers have not yet addressed is that it is safe for a base-class to call virtual members from within its constructor if that is what the derived classes are expecting it to do. In such cases, the designer of the derived class is responsible for ensuring that any methods which are run before construction is complete will behave as sensibly as they can under the circumstances. For example, in C++/CLI, constructors are wrapped in code which will call Dispose on the partially-constructed object if construction fails. Calling Dispose in such cases is often necessary to prevent resource leaks, but Dispose methods must be prepared for the possibility that the object upon which they are run may not have been fully constructed.

What are unit tests, integration tests, smoke tests, and regression tests?

Unit Testing: It always performs by developer after their development done to find out issue from their testing side before they make any requirement ready for QA.

Integration Testing: It means tester have to verify module to sub module verification when some data/function output are drive to one module to other module. Or in your system if using third party tool which using your system data for integrate.

Smoke Testing: tester performed to verify system for high-level testing and trying to find out show stopper bug before changes or code goes live.

Regression Testing: Tester performed regression for verification of existing functionality due to changes implemented in system for newly enhancement or changes in system.

Clicking at coordinates without identifying element

There is a way to do this. Using the ActionChains API you can move the mouse over a containing element, adjust by some offset (relative to the middle of that element) to put the "cursor" over the desired button (or other element), and then click at that location. Here's how to do it using webdriver in Python:

from selenium import webdriver
from selenium.webdriver.common.action_chains import ActionChains
browser = webdriver.Chrome()
elem = browser.find_element_by_selector(".some > selector")
ac = ActionChains(browser)
ac.move_to_element(elem).move_by_offset(x_offset, y_offset).click().perform()

Y'all are much to quick to dismiss the question. There are a number of reasons one might to need to click at a specific location, rather than on an element. In my case I have an SVG bar chart with an overlay element that catches all the clicks. I want to simulate a click over one of the bars, but since the overlay is there Selenium can't click on the element itself. This technique would also be valuable for imagemaps.

How to select the first row for each group in MySQL?

You should use some aggregate function to get the value of AnotherColumn that you want. That is, if you want the lowest value of AnotherColumn for each value of SomeColumn (either numerically or lexicographically), you can use:

SELECT SomeColumn, MIN(AnotherColumn)
FROM YourTable
GROUP BY SomeColumn

Some hopefully helpful links:

Incorrect string value: '\xF0\x9F\x8E\xB6\xF0\x9F...' MySQL

Change database charset and collation

    CHARACTER SET = utf8mb4
    COLLATE = utf8mb4_unicode_ci;

change specific table's charset and collation

    COLLATE utf8mb4_unicode_ci;

change connection charset in mysql driver





From this article

Can the Twitter Bootstrap Carousel plugin fade in and out on slide transition

Yes. Bootstrap uses CSS transitions so it can be done easily without any Javascript.

The CSS:

.carousel .item {-webkit-transition: opacity 3s; -moz-transition: opacity 3s; -ms-transition: opacity 3s; -o-transition: opacity 3s; transition: opacity 3s;}
.carousel .active.left {left:0;opacity:0;z-index:2;}
.carousel .next {left:0;opacity:1;z-index:1;}

I noticed however that the transition end event was firing prematurely with the default interval of 5s and a fade transition of 3s. Bumping the carousel interval to 8s provides a nice effect.

Very smooth.

Difference between dict.clear() and assigning {} in Python

One thing not mentioned is scoping issues. Not a great example, but here's the case where I ran into the problem:

def conf_decorator(dec):
    """Enables behavior like this:
        def f(): ...


        def f(): ...

        (assuming threaded is wrapped with this function.)
        Sends any accumulated kwargs to threaded.
    c_kwargs = {}
    def wrapped(f=None, **kwargs):
        if f:
            r = dec(f, **c_kwargs)
            c_kwargs = {}
            return r
            c_kwargs.update(kwargs) #<- UnboundLocalError: local variable 'c_kwargs' referenced before assignment
            return wrapped
    return wrapped

The solution is to replace c_kwargs = {} with c_kwargs.clear()

If someone thinks up a more practical example, feel free to edit this post.

How do I use InputFilter to limit characters in an EditText in Android?

Use this its work 100% your need and very simple.

android:digits="@string/myAlphaNumeric" />

In strings.xml

<string name="myAlphaNumeric">abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789</string>

"configuration file /etc/nginx/nginx.conf test failed": How do I know why this happened?

sudo nginx -t should test all files and return errors and warnings locations

How to Run Terminal as Administrator on Mac Pro

Add sudo to your command line, like:

$ sudo firebase init

Bloomberg BDH function with ISIN

The problem is that an isin does not identify the exchange, only an issuer.

Let's say your isin is US4592001014 (IBM), one way to do it would be:

  • get the ticker (in A1):

    =BDP("US4592001014 ISIN", "TICKER") => IBM
  • get a proper symbol (in A2)

    =BDP("US4592001014 ISIN", "PARSEKYABLE_DES") => IBM XX Equity

    where XX depends on your terminal settings, which you can check on CNDF <Go>.

  • get the main exchange composite ticker, or whatever suits your need (in A3):

  • and finally:

    =BDP(A1&" "&A3&" Equity", "LAST_PRICE") => the last price of IBM US Equity

Powershell Error "The term 'Get-SPWeb' is not recognized as the name of a cmdlet, function..."

Run this script from SharePoint 2010 Management Shell as Administrator.

Python Key Error=0 - Can't find Dict error in code

It only comes when your list or dictionary not available in the local function.

How do I check (at runtime) if one class is a subclass of another?

issubclass minimal runnable example

Here is a more complete example with some assertions:

#!/usr/bin/env python3

class Base:

class Derived(Base):

base = Base()
derived = Derived()

# Basic usage.
assert issubclass(Derived, Base)
assert not issubclass(Base, Derived)

# True for same object.
assert issubclass(Base, Base)

# Cannot use object of class.
    issubclass(derived, Base)
except TypeError:
    assert False

# Do this instead.
assert isinstance(derived, Base)

GitHub upstream.

Tested in Python 3.5.2.

Where is the <conio.h> header file on Linux? Why can't I find <conio.h>?

A popular Linux library which has similar functionality would be ncurses.

Error - "UNION operator must have an equal number of expressions" when using CTE for recursive selection

The problem lays here:

--This result set has 3 columns
select LOC_id,LOC_locatie,LOC_deelVan_LOC_id from tblLocatie t
where t.LOC_id = 1 -- 1 represents an example

union all

--This result set has 1 columns   
select t.LOC_locatie + '>' from tblLocatie t
inner join q parent on parent.LOC_id = t.LOC_deelVan_LOC_id

In order to use union or union all number of columns and their types should be identical cross all result sets.

I guess you should just add the column LOC_deelVan_LOC_id to your second result set

Python 3 string.join() equivalent?

str.join() works fine in Python 3, you just need to get the order of the arguments correct

>>> str.join('.', ('a', 'b', 'c'))

Check whether an input string contains a number in javascript

This is what you need.

      var hasNumber = /\d/;   
      hasNumber.test("ABC33SDF");  //true
      hasNumber.test("ABCSDF");  //false 

Best way to update an element in a generic List

You could do:

var matchingDog = AllDogs.FirstOrDefault(dog => dog.Id == "2"));

This will return the matching dog, else it will return null.

You can then set the property like follows:

if (matchingDog != null)
    matchingDog.Name = "New Dog Name";

Beautiful way to remove GET-variables with PHP?

Another solution... I find this function more elegant, it will also remove the trailing '?' if the key to remove is the only one in the query string.

 * Remove a query string parameter from an URL.
 * @param string $url
 * @param string $varname
 * @return string
function removeQueryStringParameter($url, $varname)
    $parsedUrl = parse_url($url);
    $query = array();

    if (isset($parsedUrl['query'])) {
        parse_str($parsedUrl['query'], $query);

    $path = isset($parsedUrl['path']) ? $parsedUrl['path'] : '';
    $query = !empty($query) ? '?'. http_build_query($query) : '';

    return $parsedUrl['scheme']. '://'. $parsedUrl['host']. $path. $query;


$urls = array(

foreach ($urls as $url) {
    echo $url. '<br/>';
    echo removeQueryStringParameter($url, 'test'). '<br/><br/>';

Will output:

» Run these tests on 3v4l

How to play a sound using Swift?

This is basic code to find and play an audio file in Swift.

Add your audio file to your Xcode and add the code below.

import AVFoundation

class ViewController: UIViewController {

   var audioPlayer = AVAudioPlayer() // declare globally

   override func viewDidLoad() {

        guard let sound = Bundle.main.path(forResource: "audiofilename", ofType: "mp3") else {
            print("Error getting the mp3 file from the main bundle.")
        do {
            audioPlayer = try AVAudioPlayer(contentsOf: URL(fileURLWithPath: sound))
        } catch {
            print("Audio file error.")

    @IBAction func notePressed(_ sender: UIButton) { // Button action

Why do I get "warning longer object length is not a multiple of shorter object length"?

I had a similar problem but it had to do with the structure and class of the object. I would check how dih_y2$MemberID is formatted.

Reading from memory stream to string

string result = Encoding.UTF8.GetString((stream as MemoryStream).ToArray());

DataSet panel (Report Data) in SSRS designer is gone

If you are using BIDS with SQL 2008 R2 you can only get the "Report Data" menu by clicking inside the actual report layout itself.

  1. Click inside the actual report layout.

  2. Now select "View" from the main menu bar.

  3. Now select "Report Data" which is the last item.

Use sed to replace all backslashes with forward slashes

Just use:

sed 's.\\./.g'

There's no reason to use / as the separator in sed. But if you really wanted to:

sed 's/\\/\//g'

Should black box or white box testing be the emphasis for testers?

  • Usually the white-box testing is not possible for testers. Thus the only viable answer for testers is to emphasize black-box approach.

  • However, with aspect-oriented-programming and design-by-contract methodology, when the testing goals are programmed into the target code as contracts (seen from the static view of a program), and/or when the testing temporal logic is programmed into the code as cross-cuts (dynamic view of the test logic), white-box testing would become not only possible but also a preferred take for testers. Given that said, it will need be an expertise-demanding take, the testers need to be not only good testers, but also good programmers or more than good programmers.

Find a string within a cell using VBA

you never change the value of rng so it always points to the initial cell

copy the Set rng = rng.Offset(1, 0) to a new line before loop

also, your InStr test will always fail
True is -1, but the return from InStr will be greater than 0 when the string is found. change the test to remove = True

new code:

Sub IfTest()
 'This should split the information in a table up into cells
 Dim Splitter() As String
 Dim LenValue As Integer     'Gives the number of characters in date string
 Dim LeftValue As Integer    'One less than the LenValue to drop the ")"
 Dim rng As Range, cell As Range
 Set rng = ActiveCell

Do While ActiveCell.Value <> Empty
    If InStr(rng, "%") Then
        ActiveCell.Offset(0, 0).Select
        Splitter = Split(ActiveCell.Value, "% Change")
        ActiveCell.Offset(0, 10).Select
        ActiveCell.Value = Splitter(1)
        ActiveCell.Offset(0, -1).Select
        ActiveCell.Value = "% Change"
        ActiveCell.Offset(1, -9).Select
        ActiveCell.Offset(0, 0).Select
        Splitter = Split(ActiveCell.Value, "(")
        ActiveCell.Offset(0, 9).Select
        ActiveCell.Value = Splitter(0)
        ActiveCell.Offset(0, 1).Select
        LenValue = Len(Splitter(1))
        LeftValue = LenValue - 1
        ActiveCell.Value = Left(Splitter(1), LeftValue)
        ActiveCell.Offset(1, -10).Select
    End If
Set rng = rng.Offset(1, 0)

End Sub

Swift: Sort array of objects alphabetically

With Swift 3, you can choose one of the following ways to solve your problem.

1. Using sorted(by:?) with a Movie class that does not conform to Comparable protocol

If your Movie class does not conform to Comparable protocol, you must specify in your closure the property on which you wish to use Array's sorted(by:?) method.

Movie class declaration:

import Foundation

class Movie: CustomStringConvertible {

    let name: String
    var date: Date
    var description: String { return name }

    init(name: String, date: Date = Date()) { = name = date



let avatarMovie = Movie(name: "Avatar")
let titanicMovie = Movie(name: "Titanic")
let piranhaMovie = Movie(name: "Piranha II: The Spawning")

let movies = [avatarMovie, titanicMovie, piranhaMovie]
let sortedMovies = movies.sorted(by: { $ < $ })
// let sortedMovies = movies.sorted { $ < $ } // also works


prints: [Avatar, Piranha II: The Spawning, Titanic]

2. Using sorted(by:?) with a Movie class that conforms to Comparable protocol

However, by making your Movie class conform to Comparable protocol, you can have a much concise code when you want to use Array's sorted(by:?) method.

Movie class declaration:

import Foundation

class Movie: CustomStringConvertible, Comparable {

    let name: String
    var date: Date
    var description: String { return name }

    init(name: String, date: Date = Date()) { = name = date

    static func ==(lhs: Movie, rhs: Movie) -> Bool {
        return ==

    static func <(lhs: Movie, rhs: Movie) -> Bool {
        return <



let avatarMovie = Movie(name: "Avatar")
let titanicMovie = Movie(name: "Titanic")
let piranhaMovie = Movie(name: "Piranha II: The Spawning")

let movies = [avatarMovie, titanicMovie, piranhaMovie]
let sortedMovies = movies.sorted(by: { $0 < $1 })
// let sortedMovies = movies.sorted { $0 < $1 } // also works
// let sortedMovies = movies.sorted(by: <) // also works


 prints: [Avatar, Piranha II: The Spawning, Titanic]

3. Using sorted() with a Movie class that conforms to Comparable protocol

By making your Movie class conform to Comparable protocol, you can use Array's sorted() method as an alternative to sorted(by:?).

Movie class declaration:

import Foundation

class Movie: CustomStringConvertible, Comparable {

    let name: String
    var date: Date
    var description: String { return name }

    init(name: String, date: Date = Date()) { = name = date

    static func ==(lhs: Movie, rhs: Movie) -> Bool {
        return ==

    static func <(lhs: Movie, rhs: Movie) -> Bool {
        return <



let avatarMovie = Movie(name: "Avatar")
let titanicMovie = Movie(name: "Titanic")
let piranhaMovie = Movie(name: "Piranha II: The Spawning")

let movies = [avatarMovie, titanicMovie, piranhaMovie]
let sortedMovies = movies.sorted()


 prints: [Avatar, Piranha II: The Spawning, Titanic]

Are SSL certificates bound to the servers ip address?

The SSL certificates are going to be bound to hostname rather than IP if they are setup in the standard way. Hence why it works at one site rather than the other.

Even if the servers share the same hostname they may well have two different certificates and hence WebSphere will have a certificate trust issue as it won't be able to recognise the certificate on the second server as it is different to the first.

Set a thin border using .css() in javascript

I'd recommend using a class instead of setting css properties. So instead of this:

$(this).css({"border-color": "#C1E0FF", 

Define a css class:

  border-color: #C1E0FF; 

And then change your javascript to:


Getting rid of bullet points from <ul>

Assuming that didn't work, you might want to combine the id-based selector with the li in order to apply the css to the li elements:

#otis li {
    list-style-type: none;


How do I show the schema of a table in a MySQL database?




How to fix the error "Windows SDK version 8.1" was not found?

I realize this post is a few years old, but I just wanted to extend this to anyone still struggling through this issue.

The company I work for still uses VS2015 so in turn I still use VS2015. I recently started working on a RPC application using C++ and found the need to download the Win32 Templates. Like many others I was having this "SDK 8.1 was not found" issue. i took the following corrective actions with no luck.

  • I found the SDK through Micrsoft at the following link as referenced above and downloaded it.
  • I located my VS2015 install in Apps & Features and ran the repair.
  • I completely uninstalled my VS2015 and reinstalled it.
  • I attempted to manually point my console app "Executable" and "Include" directories to the C:\Program Files (x86)\Microsoft SDKs\Windows Kits\8.1 and C:\Program Files (x86)\Microsoft SDKs\Windows\v8.1A\bin\NETFX 4.5.1 Tools.

None of the attempts above corrected the issue for me...

I then found this article on social MSDN

Finally what resolved the issue for me was:

  • Uninstalling and reinstalling VS2015.
  • Locating my installed "Windows Software Development Kit for Windows 8.1" and running the repair.
  • Checked my "C:\Program Files (x86)\Microsoft SDKs\Windows Kits\8.1" to verify the "DesignTime" folder was in fact there.
  • Opened VS created a Win32 Console application and comiled with no errors or issues

I hope this saves anyone else from almost 3 full days of frustration and loss of productivity.

How to test the `Mosquitto` server?

In separate terminal windows do the following:

  1. Start the broker:

  2. Start the command line subscriber:

    mosquitto_sub -v -t 'test/topic'
  3. Publish test message with the command line publisher:

    mosquitto_pub -t 'test/topic' -m 'helloWorld'

As well as seeing both the subscriber and publisher connection messages in the broker terminal the following should be printed in the subscriber terminal:

test/topic helloWorld

angular.service vs angular.factory

All the answers here seem to be around service and factory, and that's valid since that was what was being asked about. But it's also important to keep in mind that there are several others including provider(), value(), and constant().

The key to remember is that each one is a special case of the other. Each special case down the chain allowing you to do the same thing with less code. Each one also having some additional limitation.

To decide when to use which you just see which one allows you to do what you want in less code. Here is an image illustrating just how similar they are:

enter image description here

For a complete step by step breakdown and quick reference of when to use each you can visit the blog post where I got this image from:

How to pattern match using regular expression in Scala?

To expand a little on Andrew's answer: The fact that regular expressions define extractors can be used to decompose the substrings matched by the regex very nicely using Scala's pattern matching, e.g.:

val Process = """([a-cA-C])([^\s]+)""".r // define first, rest is non-space
for (p <- Process findAllIn "aha bah Cah dah") p match {
  case Process("b", _) => println("first: 'a', some rest")
  case Process(_, rest) => println("some first, rest: " + rest)
  // etc.

Global Variable from a different file Python

Just put your globals in the file you are importing.

PHP-FPM doesn't write to error log

This worked for me:

; Redirect worker stdout and stderr into main error log. If not set, stdout and
; stderr will be redirected to /dev/null according to FastCGI specs.
; Default Value: no
catch_workers_output = yes


The file to edit is the file that configure your desired pool. By default its: /etc/php-fpm.d/www.conf

onClick function of an input type="button" not working

You have to change the ID of the button to be different from the function name JSFiddle

var counter = 0;_x000D_
function moreFields() {_x000D_
  var newFields = document.getElementById('readroot').cloneNode(true);_x000D_ = '';_x000D_ = 'block';_x000D_
  var newField = newFields.childNodes;_x000D_
  for (var i = 0; i < newField.length; i++) {_x000D_
    var theName = newField[i].name_x000D_
    if (theName) newField[i].name = theName + counter;_x000D_
  var insertHere = document.getElementById('writeroot');_x000D_
  insertHere.parentNode.insertBefore(newFields, insertHere);_x000D_
window.onload = moreFields();
<div id="readroot" style="display: none">_x000D_
  <input type="button" value="Remove review" onclick="this.parentNode.parentNode.removeChild(this.parentNode);" />_x000D_
  <br />_x000D_
  <br />_x000D_
  <input name="cd" value="title" />_x000D_
  <select name="rankingsel">_x000D_
    <option value="excellent">Excellent</option>_x000D_
    <option value="good">Good</option>_x000D_
    <option value="ok">OK</option>_x000D_
    <option value="poor">Poor</option>_x000D_
    <option value="bad">Bad</option>_x000D_
  <br />_x000D_
  <br />_x000D_
  <textarea rows="5" cols="20" name="review">Short review</textarea>_x000D_
  <br />Radio buttons included to test them in Explorer:_x000D_
  <br />_x000D_
  <input type="radio" name="something" value="test1" />Test 1_x000D_
  <br />_x000D_
  <input type="radio" name="something" value="test2" />Test 2</div>_x000D_
<form method="post" action="index1.php"> <span id="writeroot"></span>_x000D_
  <input type="button" onclick="moreFields();" id="moreFieldsButton" value="Give me more fields!" />_x000D_
  <input type="submit" value="Send form" />_x000D_

how can I enable PHP Extension intl?

I was having same kind of problem with ldap, intl, curl php extensions. I've solved those issues by the following ways:

At first you've to check whether these extensions have been enabled in the php.ini file by removing semicolon (;) in front of the following lines:


Secondly, libeay32.dll, ibssh2.dll and ssleay32.dll files have to be loaded by php properly to function those extensions properly. These dll files are required by several php extensions (ie curl, ldap, intl etc). These files generally reside in the php installation directory [for my case it is C:\php directory]. Additionally, for intl extension to be enabled you're gonna need some other dll files to be loaded by php properly. The name of these files begin with icu (ie icudt57.dll icuin57.dll etc for php version 5.6). You'll also find these files in the php main installation directory.

There is a alternate way you can load these files from your httpd.conf (apache configuratio file) file instead of copying them to the apache's bin directory. This can be done by using the following technique:

Please note that my php version is 5.5.

LoadFile  "C:/php/icudt51.dll"
LoadFile  "C:/php/icuin51.dll"
LoadFile  "C:/php/icuio51.dll"
LoadFile  "C:/php/icule51.dll"
LoadFile  "C:/php/iculx51.dll"
LoadFile  "C:/php/icutest51.dll"
LoadFile  "C:/php/icutu51.dll"
LoadFile  "C:/php/icuuc51.dll"

LoadFile  "C:/php/libeay32.dll"
LoadFile  "C:/php/libssh2.dll"
LoadFile  "C:/php/ssleay32.dll"

 That's it.

How do you make a div follow as you scroll?

A better JQuery answer would be:

$('#ParentContainer').scroll(function() { 

You can also add a number after scrollTop i.e .scrollTop() + 5 to give it buff.

A good suggestion would also to limit the duration to 100 and go from default swing to linear easing.

$('#ParentContainer').scroll(function() { 

MVC ajax json post to controller action method

Below is how I got this working.

The Key point was: I needed to use the ViewModel associated with the view in order for the runtime to be able to resolve the object in the request.

[I know that that there is a way to bind an object other than the default ViewModel object but ended up simply populating the necessary properties for my needs as I could not get it to work]

  public ActionResult GetDataForInvoiceNumber(MyViewModel myViewModel)  
     var invoiceNumberQueryResult = _viewModelBuilder.HydrateMyViewModelGivenInvoiceDetail(myViewModel.InvoiceNumber, myViewModel.SelectedCompanyCode);
     return Json(invoiceNumberQueryResult, JsonRequestBehavior.DenyGet);

The JQuery script used to call this action method:

var requestData = {
         InvoiceNumber: $.trim(this.value),
         SelectedCompanyCode: $.trim($('#SelectedCompanyCode').val())

         url: '/en/myController/GetDataForInvoiceNumber',
         type: 'POST',
         data: JSON.stringify(requestData),
         dataType: 'json',
         contentType: 'application/json; charset=utf-8',
         error: function (xhr) {
            alert('Error: ' + xhr.statusText);
         success: function (result) {
         async: true,
         processData: false

How to reduce the image size without losing quality in PHP

You can resize and then use imagejpeg()

Don't pass 100 as the quality for imagejpeg() - anything over 90 is generally overkill and just gets you a bigger JPEG. For a thumbnail, try 75 and work downwards until the quality/size tradeoff is acceptable.

imagejpeg($tn, $save, 75);

How to install Visual C++ Build tools?

I just stumbled onto this issue accessing some Python libraries: Microsoft Visual C++ 14.0 is required. Get it with "Microsoft Visual C++ Build Tools". The latest link to that is actually here:

When you begin the installer, it will have several "options" enabled which will balloon the install size to 5gb. If you have Windows 10, you'll need to leave selected the "Windows 10 SDK" option as mentioned here.

enter image description here

I hope it helps save others time!

How to create an XML document using XmlDocument?

What about:

#region Using Statements
using System;
using System.Xml;

class Program {
    static void Main( string[ ] args ) {
        XmlDocument doc = new XmlDocument( );

        //(1) the xml declaration is recommended, but not mandatory
        XmlDeclaration xmlDeclaration = doc.CreateXmlDeclaration( "1.0", "UTF-8", null );
        XmlElement root = doc.DocumentElement;
        doc.InsertBefore( xmlDeclaration, root );

        //(2) string.Empty makes cleaner code
        XmlElement element1 = doc.CreateElement( string.Empty, "body", string.Empty );
        doc.AppendChild( element1 );

        XmlElement element2 = doc.CreateElement( string.Empty, "level1", string.Empty );
        element1.AppendChild( element2 );

        XmlElement element3 = doc.CreateElement( string.Empty, "level2", string.Empty );
        XmlText text1 = doc.CreateTextNode( "text" );
        element3.AppendChild( text1 );
        element2.AppendChild( element3 );

        XmlElement element4 = doc.CreateElement( string.Empty, "level2", string.Empty );
        XmlText text2 = doc.CreateTextNode( "other text" );
        element4.AppendChild( text2 );
        element2.AppendChild( element4 );

        doc.Save( "D:\\document.xml" );

(1) Does a valid XML file require an xml declaration?
(2) What is the difference between String.Empty and “” (empty string)?

The result is:

<?xml version="1.0" encoding="UTF-8"?>
    <level2>other text</level2>

But I recommend you to use LINQ to XML which is simpler and more readable like here:

#region Using Statements
using System;
using System.Xml.Linq;

class Program {
    static void Main( string[ ] args ) {
        XDocument doc = new XDocument( new XElement( "body", 
                                           new XElement( "level1", 
                                               new XElement( "level2", "text" ), 
                                               new XElement( "level2", "other text" ) ) ) );
        doc.Save( "D:\\document.xml" );

How can I add 1 day to current date?

If you want add a day (24 hours) to current datetime you can add milliseconds like this:

new Date( + ( 3600 * 1000 * 24))

How do I remove a substring from the end of a string in Python?

strip doesn't mean "remove this substring". x.strip(y) treats y as a set of characters and strips any characters in that set from both ends of x.

On Python 3.9 and newer you can use the removeprefix and removesuffix methods to remove an entire substring from either side of the string:

url = ''
url.removesuffix('.com')    # Returns 'abcdc'
url.removeprefix('abcdc.')  # Returns 'com'

The relevant Python Enhancement Proposal is PEP-616.

On Python 3.8 and older you can use endswith and slicing:

url = ''
if url.endswith('.com'):
    url = url[:-4]

Or a regular expression:

import re
url = ''
url = re.sub('\.com$', '', url)

Div 100% height works on Firefox but not in IE

I've been successful in getting this to work when I set the margins of the container to 0:

   margin: 0 px;

in addition to all your other styles

Postgres and Indexes on Foreign Keys and Primary Keys

Yes - for primary keys, no - for foreign keys (more in the docs).

\d <table_name>

in "psql" shows a description of a table including all its indexes.

Random string generation with upper case letters and digits

Simply use Python's builtin uuid:

If UUIDs are okay for your purposes, use the built-in uuid package.

One Line Solution:

import uuid; uuid.uuid4().hex.upper()[0:6]

In Depth Version:


import uuid
uuid.uuid4() #uuid4 => full random uuid
# Outputs something like: UUID('0172fc9a-1dac-4414-b88d-6b9a6feb91ea')

If you need exactly your format (for example, "6U1S75"), you can do it like this:

import uuid

def my_random_string(string_length=10):
    """Returns a random string of length string_length."""
    random = str(uuid.uuid4()) # Convert UUID format to a Python string.
    random = random.upper() # Make all characters uppercase.
    random = random.replace("-","") # Remove the UUID '-'.
    return random[0:string_length] # Return the random string.

print(my_random_string(6)) # For example, D9E50C

How to convert float to varchar in SQL Server

Try using the STR() function.

SELECT STR(float_field, 25, 5)

STR() Function

Another note: this pads on the left with spaces. If this is a problem combine with LTRIM:

SELECT LTRIM(STR(float_field, 25, 5))

How do I use the conditional operator (? :) in Ruby?

It is the ternary operator, and it works like in C (the parenthesis are not required). It's an expression that works like:

if_this_is_a_true_value ? then_the_result_is_this : else_it_is_this

However, in Ruby, if is also an expression so: if a then b else c end === a ? b : c, except for precedence issues. Both are expressions.


puts (if 1 then 2 else 3 end) # => 2

puts 1 ? 2 : 3                # => 2

x = if 1 then 2 else 3 end
puts x                        # => 2

Note that in the first case parenthesis are required (otherwise Ruby is confused because it thinks it is puts if 1 with some extra junk after it), but they are not required in the last case as said issue does not arise.

You can use the "long-if" form for readability on multiple lines:

question = if question.size > 20 then
  question.slice(0, 20) + "..."

HTML checkbox - allow to check only one checkbox

sapSet = mbo.getThisMboSet()
sapCount = sapSet.count()
saplist = []

if sapCount > 1:
   for i in range(sapCount):`enter code here`
     defaultCheck = sapSet.getMbo(i)
   defCount = saplist.count(1)
   if defCount > 1:
      errorgroup = " Please Note: you are allowed"
      errorkey = "  only One Default Account"
   if defCount < 1:
      errorgroup = " Please enter "
      errorkey = "  at leat One Default Account"

Undefined or null for AngularJS

My suggestion to you is to write your own utility service. You can include the service in each controller or create a parent controller, assign the utility service to your scope and then every child controller will inherit this without you having to include it.


var app = angular.module('plunker', []);

app.controller('MainCtrl', function($scope, Utils) {
    $scope.utils = Utils;

app.controller('ChildCtrl', function($scope, Utils) {
   $scope.undefined1 = Utils.isUndefinedOrNull(1);  // standard DI
   $scope.undefined2 = $scope.utils.isUndefinedOrNull(1);  // MainCtrl is parent


app.factory('Utils', function() {
  var service = {
     isUndefinedOrNull: function(obj) {
         return !angular.isDefined(obj) || obj===null;


  return service;

Or you could add it to the rootScope as well. Just a few options for extending angular with your own utility functions.

How can I print the contents of an array horizontally?

Just loop through the array and write the items to the console using Write instead of WriteLine:

foreach(var item in array)
    Console.Write(item.ToString() + " ");

As long as your items don't have any line breaks, that will produce a single line.

...or, as Jon Skeet said, provide a little more context to your question.

Switch focus between editor and integrated terminal in Visual Studio Code

As of version : 1.26.1 (linux), the shortcut is not set by default. To set the shortcut

  1. open keyboard shortcuts panel [ctrl + k , ctrl + s]
  2. Search for Focus Terminal

enter image description here

  1. Set your shortcut

For editor focus is already set by default.

enter image description here

Push eclipse project to GitHub with EGit

The key lies in when you create the project in eclipse.

First step, you create the Java project in eclipse. Right click on the project and choose Team > Share>Git.

In the Configure Git Repository dialog, ensure that you select the option to create the Repository in the parent folder of the project.. enter image description here Then you can push to github.

N.B: Eclipse will give you a warning about putting git repositories in your workspace. So when you create your project, set your project directory outside the default workspace.

Importing project into Netbeans

You may try creating a new project in netbeans and then copy and and paste the files into it. I usually experience this problem when the project wasn't created in netbeans.

What is difference between sleep() method and yield() method of multi threading?

sleep() causes the thread to definitely stop executing for a given amount of time; if no other thread or process needs to be run, the CPU will be idle (and probably enter a power saving mode).

yield() basically means that the thread is not doing anything particularly important and if any other threads or processes need to be run, they should. Otherwise, the current thread will continue to run.

AttributeError("'str' object has no attribute 'read'")

If you get a python error like this:

AttributeError: 'str' object has no attribute 'some_method'

You probably poisoned your object accidentally by overwriting your object with a string.

How to reproduce this error in python with a few lines of code:

#!/usr/bin/env python
import json
def foobar(json):
    msg = json.loads(json)

foobar('{"batman": "yes"}')

Run it, which prints:

AttributeError: 'str' object has no attribute 'loads'

But change the name of the variablename, and it works fine:

#!/usr/bin/env python
import json
def foobar(jsonstring):
    msg = json.loads(jsonstring)

foobar('{"batman": "yes"}')

This error is caused when you tried to run a method within a string. String has a few methods, but not the one you are invoking. So stop trying to invoke a method which String does not define and start looking for where you poisoned your object.

Remove '\' char from string c#

Why not simply this?

resultString = Regex.Replace(subjectString, @"\\", "");

Calculate cosine similarity given 2 sentence strings

Well, if you are aware of word embeddings like Glove/Word2Vec/Numberbatch, your job is half done. If not let me explain how this can be tackled. Convert each sentence into word tokens, and represent each of these tokens as vectors of high dimension (using the pre-trained word embeddings, or you could train them yourself even!). So, now you just don't capture their surface similarity but rather extract the meaning of each word which comprise the sentence as a whole. After this calculate their cosine similarity and you are set.

Moving matplotlib legend outside of the axis makes it cutoff by the figure box

Here is another, very manual solution. You can define the size of the axis and paddings are considered accordingly (including legend and tickmarks). Hope it is of use to somebody.

Example (axes size are the same!):

enter image description here


# Plot table

colmap = [(0,0,1) #blue
         ,(1,0,0) #red
         ,(0,1,0) #green
         ,(1,1,0) #yellow
         ,(1,0,1) #magenta
         ,(1,0.5,0.5) #pink
         ,(0.5,0.5,0.5) #gray
         ,(0.5,0,0) #brown
         ,(1,0.5,0) #orange

import matplotlib.pyplot as plt
import numpy as np

import collections
df = collections.OrderedDict()
df['labels']        = ['GWP100a\n[kgCO2eq]\n\nasedf\nasdf\nadfs','human\n[pts]','ressource\n[pts]'] 
df['all-petroleum long name'] = [3,5,2]
df['all-electric']  = [5.5, 1, 3]
df['HEV']           = [3.5, 2, 1]
df['PHEV']          = [3.5, 2, 1]

numLabels = len(df.values()[0])
numItems = len(df)-1
posX = np.arange(numLabels)+1
width = 1.0/(numItems+1)

fig = plt.figure(figsize=(2,2))
ax = fig.add_subplot(111)
for iiItem in range(1,numItems+1):*width, df.values()[iiItem], width, color=colmap[iiItem-1], label=df.keys()[iiItem])
ax.set(xticks=posX+width*(0.5*numItems), xticklabels=df['labels'])

# Change padding and margins, insert legend

fig.tight_layout() #tight margins
leg = ax.legend(loc='upper left', bbox_to_anchor=(1.02, 1), borderaxespad=0)
plt.draw() #to know size of legend

padLeft   = ax.get_position().x0 * fig.get_size_inches()[0]
padBottom = ax.get_position().y0 * fig.get_size_inches()[1]
padTop    = ( 1 - ax.get_position().y0 - ax.get_position().height ) * fig.get_size_inches()[1]
padRight  = ( 1 - ax.get_position().x0 - ax.get_position().width ) * fig.get_size_inches()[0]
dpi       = fig.get_dpi()
padLegend = ax.get_legend().get_frame().get_width() / dpi 

widthAx = 3 #inches
heightAx = 3 #inches
widthTot = widthAx+padLeft+padRight+padLegend
heightTot = heightAx+padTop+padBottom

# resize ipython window (optional)
posScreenX = 1366/2-10 #pixel
posScreenY = 0 #pixel
canvasPadding = 6 #pixel
canvasBottom = 40 #pixel
ipythonWindowSize = '{0}x{1}+{2}+{3}'.format(int(round(widthTot*dpi))+2*canvasPadding
plt.draw() #to resize ipython window. Has to be done BEFORE figure resizing!

# set figure size and ax position
ax.set_position([padLeft/widthTot, padBottom/heightTot, widthAx/widthTot, heightAx/heightTot])

How can I set an SQL Server connection string?

They are a number of things to worry about when connecting to SQL Server on another machine.

  • Host/IP address of the machine
  • Initial catalog (database name)
  • Valid username/password

Very often SQL Server may be running as a default instance which means you can simply specify the hostname/IP address, but you may encounter a scenario where it is running as a named instance (SQL Server Express Edition for instance). In this scenario you'll have to specify the hostname/instance name.

$(window).scrollTop() vs. $(document).scrollTop()

I've just had some of the similar problems with scrollTop described here.

In the end I got around this on Firefox and IE by using the selector $('*').scrollTop(0);

Not perfect if you have elements you don't want to effect but it gets around the Document, Body, HTML and Window disparity. If it helps...

NumPy array is not JSON serializable

Store as JSON a numpy.ndarray or any nested-list composition.

class NumpyEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, np.ndarray):
            return obj.tolist()
        return json.JSONEncoder.default(self, obj)

a = np.array([[1, 2, 3], [4, 5, 6]])
json_dump = json.dumps({'a': a, 'aa': [2, (2, 3, 4), a], 'bb': [2]}, cls=NumpyEncoder)

Will output:

(2, 3)
{"a": [[1, 2, 3], [4, 5, 6]], "aa": [2, [2, 3, 4], [[1, 2, 3], [4, 5, 6]]], "bb": [2]}

To restore from JSON:

json_load = json.loads(json_dump)
a_restored = np.asarray(json_load["a"])

Will output:

[[1 2 3]
 [4 5 6]]
(2, 3)

How do you add an array to another array in Ruby and not end up with a multi-dimensional result?

You've got a workable idea, but the #flatten! is in the wrong place -- it flattens its receiver, so you could use it to turn [1, 2, ['foo', 'bar']] into [1,2,'foo','bar'].

I'm doubtless forgetting some approaches, but you can concatenate:

a1.concat a2
a1 + a2              # creates a new array, as does a1 += a2

or prepend/append:

a1.push(*a2)         # note the asterisk
a2.unshift(*a1)      # note the asterisk, and that a2 is the receiver

or splice:

a1[a1.length, 0] = a2
a1[a1.length..0] = a2
a1.insert(a1.length, *a2)

or append and flatten:

(a1 << a2).flatten!  # a call to #flatten instead would return a new array

How do I get AWS_ACCESS_KEY_ID for Amazon?

It is very dangerous to create an access_key_id in "My Account ==> Security Credentials". Because the key has all authority. Please create "IAM" user and attach only some policies you need.

Creating an empty Pandas DataFrame, then filling it?

Initialize empty frame with column names

import pandas as pd

col_names =  ['A', 'B', 'C']
my_df  = pd.DataFrame(columns = col_names)

Add a new record to a frame

my_df.loc[len(my_df)] = [2, 4, 5]

You also might want to pass a dictionary:

my_dic = {'A':2, 'B':4, 'C':5}
my_df.loc[len(my_df)] = my_dic 

Append another frame to your existing frame

col_names =  ['A', 'B', 'C']
my_df2  = pd.DataFrame(columns = col_names)
my_df = my_df.append(my_df2)

Performance considerations

If you are adding rows inside a loop consider performance issues. For around the first 1000 records "my_df.loc" performance is better, but it gradually becomes slower by increasing the number of records in the loop.

If you plan to do thins inside a big loop (say 10M? records or so), you are better off using a mixture of these two; fill a dataframe with iloc until the size gets around 1000, then append it to the original dataframe, and empty the temp dataframe. This would boost your performance by around 10 times.

How to add one column into existing SQL Table

Its work perfectly

ALTER TABLE `products` ADD `LastUpdate` varchar(200) NULL;

But if you want more precise in table then you can try AFTER.

ALTER TABLE `products` ADD `LastUpdate` varchar(200) NULL AFTER `column_name`;

It will add LastUpdate column after specified column name (column_name).

Illegal access: this web application instance has been stopped already

If it's a local development tomcat launched from IDE, then restarting this IDE and rebuild project also helps.


You could also try to find if there is any running tomcat process in the background and kill it.

Modular multiplicative inverse function in Python

Many of the links above are broken as for 1/23/2017. I found this implementation:

How to force Sequential Javascript Execution?

If you don't insist on using pure Javascript, you can build a sequential code in Livescript and it looks pretty good. You might want to take a look at this example:

# application
    i = 3
    console.log td!, "start"
    <- :lo(op) ->
        console.log td!, "hi #{i}"
        <- wait-for \something
        if i is 0
            return op! # break
    <- sleep 1500ms
    <- :lo(op) ->
        console.log td!, "hello #{i}"
        if i is 3
            return op! # break
        <- sleep 1000ms
    <- sleep 0
    console.log td!, "heyy"

    a = 8
    <- :lo(op) ->
        console.log td!, "this runs in parallel!", a
        go \something
        if a is 0
            return op! # break
        <- sleep 500ms


0ms : start
2ms : hi 3
3ms : this runs in parallel! 8
3ms : hi 2
505ms : this runs in parallel! 7
505ms : hi 1
1007ms : this runs in parallel! 6
1508ms : this runs in parallel! 5
2009ms : this runs in parallel! 4
2509ms : hello 0
2509ms : this runs in parallel! 3
3010ms : this runs in parallel! 2
3509ms : hello 1
3510ms : this runs in parallel! 1
4511ms : hello 2
4511ms : heyy

How to stretch in width a WPF user control to its window?

You need to make sure your usercontrol hasn't set it's width in the usercontrol's xaml file. Just delete the Width="..." from it and you're good to go!

EDIT: This is the code I tested it with:


<UserControl x:Class="WpfApplication1.SOAnswerTest"
            <ColumnDefinition Name="LeftSideMenu" Width="100"/>
            <ColumnDefinition Name="Middle" Width="*"/>
            <ColumnDefinition Name="RightSideMenu" Width="90"/>
        <TextBlock Grid.Column="0">a</TextBlock>
        <TextBlock Grid.Column="1">b</TextBlock>
        <TextBlock Grid.Column="2">c</TextBlock>


<Window x:Class="WpfApplication1.Window1"
    Title="Window1" Height="300" Width="415">

        <local:SOAnswerTest Grid.Column="0" Grid.Row="5" Grid.ColumnSpan="2"/>

How can I turn a JSONArray into a JSONObject?

Can't you originally get the data as a JSONObject?

Perhaps parse the string as both a JSONObject and a JSONArray in the first place? Where is the JSON string coming from?

I'm not sure that it is possible to convert a JsonArray into a JsonObject.

I presume you are using the following from

    A JSONObject is an unordered collection of name/value pairs. Its external form is a string wrapped in curly braces with colons between the names and values, and commas between the values and names. The internal form is an object having get() and opt() methods for accessing the values by name, and put() methods for adding or replacing values by name. The values can be any of these types: Boolean, JSONArray, JSONObject, Number, and String, or the JSONObject.NULL object.

    A JSONArray is an ordered sequence of values. Its external form is a string wrapped in square brackets with commas between the values. The internal form is an object having get() and opt() methods for accessing the values by index, and put() methods for adding or replacing values. The values can be any of these types: Boolean, JSONArray, JSONObject, Number, and String, or the JSONObject.NULL object.

How can you create pop up messages in a batch script?

This is very simple beacuse i have created a couple lines of code that will do this for you

So set a variable as msg and then use this code. it popup in a VBS message box.


@echo off
echo %msg% >vbs.txt
copy vbs.txt vbs.vbs
del vbs.txt
start vbs.vbs
timeout /t 1
del vbs.vbs

This is just something i came up with it should work for most of your message needs and it also works with Spaces unlike some batch scripts

Abstraction vs Encapsulation in Java

OO Abstraction occurs during class level design, with the objective of hiding the implementation complexity of how the the features offered by an API / design / system were implemented, in a sense simplifying the 'interface' to access the underlying implementation.

The process of abstraction can be repeated at increasingly 'higher' levels (layers) of classes, which enables large systems to be built without increasing the complexity of code and understanding at each layer.

For example, a Java developer can make use of the high level features of FileInputStream without concern for how it works (i.e. file handles, file system security checks, memory allocation and buffering will be managed internally, and are hidden from consumers). This allows the implementation of FileInputStream to be changed, and as long as the API (interface) to FileInputStream remains consistent, code built against previous versions will still work.

Similarly, when designing your own classes, you will want to hide internal implementation details from others as far as possible.

In the Booch definition1, OO Encapsulation is achieved through Information Hiding, and specifically around hiding internal data (fields / members representing the state) owned by a class instance, by enforcing access to the internal data in a controlled manner, and preventing direct, external change to these fields, as well as hiding any internal implementation methods of the class (e.g. by making them private).

For example, the fields of a class can be made private by default, and only if external access to these was required, would a get() and/or set() (or Property) be exposed from the class. (In modern day OO languages, fields can be marked as readonly / final / immutable which further restricts change, even within the class).

Example where NO information hiding has been applied (Bad Practice):

class Foo {
   // BAD - NOT Encapsulated - code external to the class can change this field directly
   // Class Foo has no control over the range of values which could be set.
   public int notEncapsulated;

Example where field encapsulation has been applied:

class Bar {
   // Improvement - access restricted only to this class
   private int encapsulatedPercentageField;

   // The state of Bar (and its fields) can now be changed in a controlled manner
   public void setEncapsulatedField(int percentageValue) {
      if (percentageValue >= 0 && percentageValue <= 100) {
          encapsulatedPercentageField = percentageValue;
      // else throw ... out of range

Example of immutable / constructor-only initialization of a field:

class Baz {
   private final int immutableField;

   public void Baz(int onlyValue) {
      // ... As above, can also check that onlyValue is valid
      immutableField = onlyValue;
   // Further change of `immutableField` outside of the constructor is NOT permitted, even within the same class 

Re : Abstraction vs Abstract Class

Abstract classes are classes which promote reuse of commonality between classes, but which themselves cannot directly be instantiated with new() - abstract classes must be subclassed, and only concrete (non abstract) subclasses may be instantiated. Possibly one source of confusion between Abstraction and an abstract class was that in the early days of OO, inheritance was more heavily used to achieve code reuse (e.g. with associated abstract base classes). Nowadays, composition is generally favoured over inheritance, and there are more tools available to achieve abstraction, such as through Interfaces, events / delegates / functions, traits / mixins etc.

Re : Encapsulation vs Information Hiding

The meaning of encapsulation appears to have evolved over time, and in recent times, encapsulation can commonly also used in a more general sense when determining which methods, fields, properties, events etc to bundle into a class.

Quoting Wikipedia:

In the more concrete setting of an object-oriented programming language, the notion is used to mean either an information hiding mechanism, a bundling mechanism, or the combination of the two.

For example, in the statement

I've encapsulated the data access code into its own class

.. the interpretation of encapsulation is roughly equivalent to the Separation of Concerns or the Single Responsibility Principal (the "S" in SOLID), and could arguably be used as a synonym for refactoring.

[1] Once you've seen Booch's encapsulation cat picture you'll never be able to forget encapsulation - p46 of Object Oriented Analysis and Design with Applications, 2nd Ed

How to convert an ArrayList containing Integers to primitive int array?

Google Guava

Google Guava provides a neat way to do this by calling Ints.toArray.

List<Integer> list = ...;
int[] values = Ints.toArray(list);

How to set a ripple effect on textview or imageview on Android?

Add android:clickable="true" android:focusable="true"

For Ripple Effect


For Selectable Effect


For Button effect

android:adjustViewBounds="true" style="?android:attr/borderlessButtonStyle"

Why does an onclick property set with setAttribute fail to work in IE?

Or you could use jQuery and avoid all those issues:

var execBtn = $("<input>", {
       type: "button",
       id: "execBtn",
       value: "Execute"

jQuery will take care of all the cross-browser issues as well.

HTTP Status 405 - Request method 'POST' not supported (Spring MVC)

I found the problem that was causing the HTTP error.

In the setFalse() function that is triggered by the Save button my code was trying to submit the form that contained the button.

        function setFalse(){
            document.getElementById("hasId").value ="false";

when I remove the document.submitForm.submit(); it works:

        function setFalse(){
            document.getElementById("hasId").value ="false";

@Roger Lindsjö Thank you for spotting my error where I wasn't passing on the right parameter!

How to avoid .pyc files?

In 2.5, theres no way to suppress it, other than measures like not giving users write access to the directory.

In python 2.6 and 3.0 however, there may be a setting in the sys module called "dont_write_bytecode" that can be set to suppress this. This can also be set by passing the "-B" option, or setting the environment variable "PYTHONDONTWRITEBYTECODE"

Why is not Element in Typescript?

Using typescript, I use a custom interface that only applies to my function. Example use case.

  handleChange(event: { target: HTMLInputElement; }) {
    this.setState({ value: });

In this case, the handleChange will receive an object with target field that is of type HTMLInputElement.

Later in my code I can use

<input type='text' value={this.state.value} onChange={this.handleChange} />

A cleaner approach would be to put the interface to a separate file.

interface HandleNameChangeInterface {
  target: HTMLInputElement;

then later use the following function definition:

  handleChange(event: HandleNameChangeInterface) {
    this.setState({ value: });

In my usecase, it's expressly defined that the only caller to handleChange is an HTML element type of input text.

node: command not found

The problem is that your PATH does not include the location of the node executable.

You can likely run node as "/usr/local/bin/node".

You can add that location to your path by running the following command to add a single line to your bashrc file:

echo 'export PATH=$PATH:/usr/local/bin' >> $HOME/.bashrc

What exactly is std::atomic?

I understand that std::atomic<> makes an object atomic.

That's a matter of perspective... you can't apply it to arbitrary objects and have their operations become atomic, but the provided specialisations for (most) integral types and pointers can be used.

a = a + 12;

std::atomic<> does not (use template expressions to) simplify this to a single atomic operation, instead the operator T() const volatile noexcept member does an atomic load() of a, then twelve is added, and operator=(T t) noexcept does a store(t).

rsync error: failed to set times on "/foo/bar": Operation not permitted

The problem in my case was that the "receiver mountpoint" was incorrectly mounted. It was in read-only mode (for some extrange reason). It looked like rsync was copying the files, but it was not. I checked my fstab file and changed mount options to default, re-mount file system and execute rsync again. All fine then.

How to convert "Mon Jun 18 00:00:00 IST 2012" to 18/06/2012?

I hope following program will solve your problem

String dateStr = "Mon Jun 18 00:00:00 IST 2012";
DateFormat formatter = new SimpleDateFormat("E MMM dd HH:mm:ss Z yyyy");
Date date = (Date)formatter.parse(dateStr);

Calendar cal = Calendar.getInstance();
String formatedDate = cal.get(Calendar.DATE) + "/" + (cal.get(Calendar.MONTH) + 1) + "/" +         cal.get(Calendar.YEAR);
System.out.println("formatedDate : " + formatedDate);    

Spring MVC @PathVariable with dot (.) is getting truncated

As far as i know this issue appears only for the pathvariable at the end of the requestmapping.

We were able to solve that by defining the regex addon in the requestmapping.


How do I debug a stand-alone VBScript script?

Click the mse7.exe installed along with Office typically at \Program Files\Microsoft Office\OFFICE11.

This will open up the debugger, open the file and then run the debugger in the GUI mode.

check if command was successful in a batch file

Goodness I had a hard time finding the answer to this... Here it is:

cd thisDoesntExist
if %errorlevel% == 0 (
  echo Oh, I guess it does
  echo Huh.

Select query to get data from SQL Server

According to MSDN

result is the number of lines affected, and since your query is select no lines are affected (i.e. inserted, deleted or updated) anyhow.

If you want to return a single row of the query, use ExecuteScalar() instead of ExecuteNonQuery():

  int result = (int) (command.ExecuteScalar());

However, if you expect many rows to be returned, ExecuteReader() is the only option:

  using (SqlDataReader reader = command.ExecuteReader()) {
    while (reader.Read()) {
      int result = reader.GetInt32(0);


How do I set the icon for my application in visual studio 2008?

You add the .ico in your resource as bobobobo said and then in your main dialog's constructor you modify:

m_hIcon = AfxGetApp()->LoadIcon(ICON_ID_FROM_RESOURCE.H);