Programs & Examples On #Mkmapview

MKMapView is part of Apple's Map Kit framework for developing location-aware iOS applications, and provides an embeddable map interface. Effective iOS 6, the Map Kit framework uses Apple's own map service. In iOS 5.1 and earlier, the framework uses the Google Mobile Maps service.

Show Current Location and Update Location in MKMapView in Swift

you have to override CLLocationManager.didUpdateLocations

 func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {

    let userLocation:CLLocation = locations[0] as CLLocation

    let location = CLLocationCoordinate2D(latitude: userLocation.coordinate.latitude, longitude: userLocation.coordinate.longitude)

    let span = MKCoordinateSpanMake(0.5, 0.5)

    let region = MKCoordinateRegion (center:  location,span: span)

    mapView.setRegion(region, animated: true)

you also have to add NSLocationWhenInUseUsageDescription and NSLocationAlwaysUsageDescription to your plist setting Result as value

Zooming MKMapView to fit annotation pins?

@"I'm not sure if this is because of some other factors in my implementation, but I find that showAnnotations doesn't do as close a zoom/fit of the annotations as the manual implementation does, so I've stuck with the manual one. – Ted Avery Apr 17 at 0:35"

I had the same problem, but then I tried doing showAnnotations twice (like below), and for some reason, it worked.

[mapView showAnnotations:yourAnnotationArray animated:YES]; [mapView showAnnotations:yourAnnotationArray animated:YES];

Exception is never thrown in body of corresponding try statement

A catch-block in a try statement needs to catch exactly the exception that the code inside the try {}-block can throw (or a super class of that).

try {
    //do something that throws ExceptionA, e.g.
    throw new ExceptionA("I am Exception Alpha!");
catch(ExceptionA e) {
    //do something to handle the exception, e.g.
    System.out.println("Message: " + e.getMessage());

What you are trying to do is this:

try {
    throw new ExceptionB("I am Exception Bravo!");
catch(ExceptionA e) {
    System.out.println("Message: " + e.getMessage());

This will lead to an compiler error, because your java knows that you are trying to catch an exception that will NEVER EVER EVER occur. Thus you would get: exception ExceptionA is never thrown in body of corresponding try statement.

How can I stop "property does not exist on type JQuery" syntax errors when using Typescript?

You could cast it to <any> or extend the jquery typing to add your own method.


//Or add your own custom methods (Assuming this is added by yourself as a part of custom plugin)

interface JQuery {

Comparing two arrays of objects, and exclude the elements who match values into new array in JS

The same result can be achieved using Lodash.

var result1 = [_x000D_
    {id:1, name:'Sandra', type:'user', username:'sandra'},_x000D_
    {id:2, name:'John', type:'admin', username:'johnny2'},_x000D_
    {id:3, name:'Peter', type:'user', username:'pete'},_x000D_
    {id:4, name:'Bobby', type:'user', username:'be_bob'}_x000D_
var result2 = [_x000D_
    {id:2, name:'John', email:'[email protected]'},_x000D_
    {id:4, name:'Bobby', email:'[email protected]'}_x000D_
var result3 = _(result1) _x000D_
        .differenceBy(result2, 'id', 'name')_x000D_
        .map(_.partial(_.pick, _, 'id', 'name'))_x000D_
<script src=""></script>

You can get the desired result applying a difference between both arrays using the properties "id" and "name" as a way to "link" elements between them. If any of those properties are different, the elements are considered different (improbably in your case because id seems to be unique).

Lastly, you have to map the result in order to "omit" the undesired properties of the object.

Hope it helps.

Communication between tabs or windows

I've created a library sysend.js, it's very small, you can check its source code. The library don't have any external dependencies.

You can use it for communication between tabs/windows in same browser and domain. The library use BroadcastChannel, if supported, or storage event from localStorage.

API is very simple:

sysend.on('foo', function(message) {
sysend.broadcast('foo', {message: 'Hello'});
sysend.broadcast('foo', "hello");
sysend.broadcast('foo'); // empty notification

when your brower support BroadcastChannel it sent literal object (but it's in fact auto-serialized by browser) and if not it's serialized to JSON first and deserialized on other end.

Recent version also have helper API to create proxy for Cross-Domain communication. (it require single html file on target domain).

Here is demo.


New version also support Cross-Domain communication, if you include special proxy.html file on target domain and call proxy function from source domain:


(proxy.html it's very simple html file, that only have one script tag with the library).

If you want two way communication you need to do the same on other domain.

NOTE: If you will implement same functionality using localStorage, there is issue in IE. Storage event is sent to the same window, which triggered the event and for other browsers it's only invoked for other tabs/windows.

Fatal error: Call to undefined function mb_strlen()

For me the following command did the trick

sudo apt install php-mbstring

How do you create a Marker with a custom icon for google maps API v3?


    var marker = new google.maps.Marker({
      position: map.getCenter(),
      icon: '',
      map: map

from here

How to center the text in PHPExcel merged cell

When using merged columns, I got it centered by using PHPExcel_Style_Alignment::HORIZONTAL_CENTER_CONTINUOUS instead of PHPExcel_Style_Alignment::HORIZONTAL_CENTER

what is the use of annotations @Id and @GeneratedValue(strategy = GenerationType.IDENTITY)? Why the generationtype is identity?

In a Object Relational Mapping context, every object needs to have a unique identifier. You use the @Id annotation to specify the primary key of an entity.

The @GeneratedValue annotation is used to specify how the primary key should be generated. In your example you are using an Identity strategy which

Indicates that the persistence provider must assign primary keys for the entity using a database identity column.

There are other strategies, you can see more here.

What difference does .AsNoTracking() make?

No Tracking LINQ to Entities queries

Usage of AsNoTracking() is recommended when your query is meant for read operations. In these scenarios, you get back your entities but they are not tracked by your context.This ensures minimal memory usage and optimal performance


  1. Improved performance over regular LINQ queries.
  2. Fully materialized objects.
  3. Simplest to write with syntax built into the programming language.


  1. Not suitable for CUD operations.
  2. Certain technical restrictions, such as: Patterns using DefaultIfEmpty for OUTER JOIN queries result in more complex queries than simple OUTER JOIN statements in Entity SQL.
  3. You still can’t use LIKE with general pattern matching.

More info available here:

Performance considerations for Entity Framework

Entity Framework and NoTracking

How do I change Eclipse to use spaces instead of tabs?

As an augmentation to the other answers, on Mac OS X, the "Preferences" menu is under Eclipse, not Window (unlike Windows/Linux Eclipse distributions). Everything else is still the same as pointed out by other answers past this point.

IE: Java Formatter available under:

Eclipse >      | # Not Window!
Preferences >  |
Java >         |
Code Style >   |
Formatter      |

From here, edit the formatter and the tab policy can be set under "Indentation".

django no such table:

If you are using latest version of django 2.x or 1.11.x then you have to first create migrations ,

python makemigrations

After that you just have to run migrate command for syncing database .

python migrate --run-syncdb

These will sync your database and python models and also second command will print all sql behind it.

How to center a component in Material-UI and make it responsive?

With other answers used, xs='auto' did a trick for me.

<Grid container
    style={{ minHeight: "100vh" }}>

    <Grid item xs='auto'>
            buttonText="Log in with Google"

C++, How to determine if a Windows Process is running?

You can use GetExitCodeProcess. It will return STILL_ACTIVE (259) if the process is still running (or if it happened to exit with that exit code :( ).

How do I sort a vector of pairs based on the second element of the pair?

For something reusable:

template<template <typename> class P = std::less >
struct compare_pair_second {
    template<class T1, class T2> bool operator()(const std::pair<T1, T2>& left, const std::pair<T1, T2>& right) {
        return P<T2>()(left.second, right.second);

You can use it as

std::sort(foo.begin(), foo.end(), compare_pair_second<>());


std::sort(foo.begin(), foo.end(), compare_pair_second<std::less>());

How to check if a map contains a key in Go?

    var d map[string]string
    value, ok := d["key"]
    if ok {
        fmt.Println("Key Present ", value)
    } else {
        fmt.Println(" Key Not Present ")

What is the best way to implement "remember me" for a website?

I would store a user ID and a token. When the user comes back to the site, compare those two pieces of information against something persistent like a database entry.

As for security, just don't put anything in there that will allow someone to modify the cookie to gain extra benefits. For example, don't store their user groups or their password. Anything that can be modified that would circumvent your security should not be stored in the cookie.

How to create a notification with NotificationCompat.Builder?

You can try this code this works fine for me:

    NotificationCompat.Builder mBuilder= new NotificationCompat.Builder(this);

    Intent i = new Intent(noti.this, Xyz_activtiy.class);
    PendingIntent pendingIntent= PendingIntent.getActivity(this,0,i,0);

    mBuilder.setContentTitle("New notification title");
    mBuilder.setContentText("Notification text");

    NotificationManager notificationManager= (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);

How can I loop over entries in JSON?

Actually, to query the team_name, just add it in brackets to the last line. Apart from that, it seems to work on Python 2.7.3 on command line.

from urllib2 import urlopen
import json

url = ''
response = urlopen(url)
json_obj = json.load(response)

for i in json_obj['team']:
    print i['team_name']

Is there a standardized method to swap two variables in Python?

Does not work for multidimensional arrays, because references are used here.

import numpy as np

# swaps
data = np.random.random(2)
data[0], data[1] = data[1], data[0]

# does not swap
data = np.random.random((2, 2))
data[0], data[1] = data[1], data[0]

See also Swap slices of Numpy arrays

Python SQLite: database is locked

I'm presuming you are actually using sqlite3 even though your code says otherwise. Here are some things to check:

  1. That you don't have a hung process sitting on the file (unix: $ fuser cache.db should say nothing)
  2. There isn't a cache.db-journal file in the directory with cache.db; this would indicate a crashed session that hasn't been cleaned up properly.
  3. Ask the database shell to check itself: $ sqlite3 cache.db "pragma integrity_check;"
  4. Backup the database $ sqlite3 cache.db ".backup cache.db.bak"
  5. Remove cache.db as you probably have nothing in it (if you are just learning) and try your code again
  6. See if the backup works $ sqlite3 cache.db.bak ".schema"

Failing that, read Things That Can Go Wrong and How to Corrupt Your Database Files

Cast Double to Integer in Java

You need to explicitly get the int value using method intValue() like this:

Double d = 5.25;
Integer i = d.intValue(); // i becomes 5


double d = 5.25;
int i = (int) d;

No provider for Http StaticInjectorError

Add these two file in your app.module.ts

import { FileTransfer } from '@ionic-native/file-transfer';
import { File } from '@ionic-native/file';

after that declare these to in provider..

providers: [

This is work for me.

Getting "java.nio.file.AccessDeniedException" when trying to write to a folder

Delete .android folder cache files, Also delete the build folder manually from a directory and open android studio and run again.

enter image description here

Html.fromHtml deprecated in Android N

Compare of the flags of fromHtml().

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

<h4>Heading H4</h4>

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

<blockquote>This is a blockquote</blockquote>

Text after blockquote
Text before div

<div>This is a div</div>

Text after div


How do you fade in/out a background color using jquery?

To fade between 2 colors using only simple javascript:

function Blend(a, b, alpha) {
  var aa = [
        parseInt('0x' + a.substring(1, 3)), 
        parseInt('0x' + a.substring(3, 5)), 
        parseInt('0x' + a.substring(5, 7))

  var bb = [
        parseInt('0x' + b.substring(1, 3)), 
        parseInt('0x' + b.substring(3, 5)), 
        parseInt('0x' + b.substring(5, 7))

  r = '0' + Math.round(aa[0] + (bb[0] - aa[0])*alpha).toString(16);
  g = '0' + Math.round(aa[1] + (bb[1] - aa[1])*alpha).toString(16);
  b = '0' + Math.round(aa[2] + (bb[2] - aa[2])*alpha).toString(16);

  return '#'
        + r.substring(r.length - 2)
        + g.substring(g.length - 2)
        + b.substring(b.length - 2);

function fadeText(cl1, cl2, elm){
  var t = [];
  var steps = 100;
  var delay = 3000;

  for (var i = 0; i < steps; i++) {
    (function(j) {
         t[j] = setTimeout(function() {
          var a  = j/steps;
          var color = Blend(cl1,cl2,a);
 = color;
         }, j*delay/steps);

  return t;

var cl1 = "#ffffff";
var cl2 = "#c00000";
var elm = document.getElementById("note");
T  = fadeText(cl1,cl2,elm);


How to create a BKS (BouncyCastle) format Java Keystore that contains a client certificate chain

Detailed Step by Step instructions I followed to achieve this

  • Download bouncycastle JAR from or take it from the "doc" folder.
  • Configure BouncyCastle for PC using one of the below methods.
    • Adding the BC Provider Statically (Recommended)
      • Copy the bcprov-ext-jdk15on-1.46.jar to each
        • D:\tools\jdk1.5.0_09\jre\lib\ext (JDK (bundled JRE)
        • D:\tools\jre1.5.0_09\lib\ext (JRE)
        • C:\ (location to be used in env variable)
      • Modify the file under
        • D:\tools\jdk1.5.0_09\jre\lib\security
        • D:\tools\jre1.5.0_09\lib\security
        • and add the following entry
          • security.provider.7=org.bouncycastle.jce.provider.BouncyCastleProvider
      • Add the following environment variable in "User Variables" section
        • CLASSPATH=%CLASSPATH%;c:\bcprov-ext-jdk15on-1.46.jar
    • Add bcprov-ext-jdk15on-1.46.jar to CLASSPATH of your project and Add the following line in your code
      • Security.addProvider(new BouncyCastleProvider());
  • Generate the Keystore using Bouncy Castle
    • Run the following command
      • keytool -genkey -alias myproject -keystore C:/myproject.keystore -storepass myproject -storetype BKS -provider org.bouncycastle.jce.provider.BouncyCastleProvider
    • This generates the file C:\myproject.keystore
    • Run the following command to check if it is properly generated or not
      • keytool -list -keystore C:\myproject.keystore -storetype BKS
  • Configure BouncyCastle for TOMCAT

    • Open D:\tools\apache-tomcat-6.0.35\conf\server.xml and add the following entry

      • <Connector port="8443" keystorePass="myproject" alias="myproject" keystore="c:/myproject.keystore" keystoreType="BKS" SSLEnabled="true" clientAuth="false" protocol="HTTP/1.1" scheme="https" secure="true" sslProtocol="TLS" sslImplementationName="org.bouncycastle.jce.provider.BouncyCastleProvider"/>
    • Restart the server after these changes.

  • Configure BouncyCastle for Android Client
    • No need to configure since Android supports Bouncy Castle Version 1.46 internally in the provided "android.jar".
    • Just implement your version of HTTP Client ( can be found below) and set the following in code
      • SSLSocketFactory.setHostnameVerifier(SSLSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER);
    • If you don't do this, it gives an exception as below
      • hostname in certificate didn't match: <> !=
    • In production mode, change the above code to
      • SSLSocketFactory.setHostnameVerifier(SSLSocketFactory.STRICT_HOSTNAME_VERIFIER);



import org.apache.http.conn.ClientConnectionManager;
import org.apache.http.conn.scheme.PlainSocketFactory;
import org.apache.http.conn.scheme.Scheme;
import org.apache.http.conn.scheme.SchemeRegistry;
import org.apache.http.conn.ssl.SSLSocketFactory;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.SingleClientConnManager;

import com.arisglobal.aglite.activity.R;

import android.content.Context;

public class MyHttpClient extends DefaultHttpClient {

    final Context context;

    public MyHttpClient(Context context) {
        this.context = context;

    protected ClientConnectionManager createClientConnectionManager() {
        SchemeRegistry registry = new SchemeRegistry();

        registry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));

        // Register for port 443 our SSLSocketFactory with our keystore to the ConnectionManager
        registry.register(new Scheme("https", newSslSocketFactory(), 443));
        return new SingleClientConnManager(getParams(), registry);

    private SSLSocketFactory newSslSocketFactory() {
        try {
            // Get an instance of the Bouncy Castle KeyStore format
            KeyStore trusted = KeyStore.getInstance("BKS");

            // Get the raw resource, which contains the keystore with your trusted certificates (root and any intermediate certs)
            InputStream in = context.getResources().openRawResource(R.raw.aglite);
            try {
                // Initialize the keystore with the provided trusted certificates.
                // Also provide the password of the keystore
                trusted.load(in, "aglite".toCharArray());
            } finally {

            // Pass the keystore to the SSLSocketFactory. The factory is responsible for the verification of the server certificate.
            SSLSocketFactory sf = new SSLSocketFactory(trusted);

            // Hostname verification from certificate
            return sf;
        } catch (Exception e) {
            throw new AssertionError(e);

How to invoke the above code in your Activity class:

DefaultHttpClient client = new MyHttpClient(getApplicationContext());
HttpResponse response = client.execute(...);

C# SQL Server - Passing a list to a stored procedure

The typical pattern in this situation is to pass the elements in a comma delimited list, and then in SQL split that out into a table you can use. Most people usually create a specified function for doing this like:

 INSERT INTO <SomeTempTable>
 SELECT item FROM dbo.SplitCommaString(@myParameter)

And then you can use it in other queries.

Is Constructor Overriding Possible?

What you describe isn't overriding. If you don't specify a default constructor, the compiler will create a default constructor. If it's a subclass, it will call the default parent constructor(super()), it will also initialize all instance variables to a default value determined by the type's default value(0 for numeric types, false for booleans, or null for objects).

Overriding happens when a subclass has the same name, number/type of parameters, and the same return type as an instance method of the superclass. In this case, the subclass will override the superclass's method. Information on overriding here.

CSS/HTML: Create a glowing border around an Input Field

You better use Twitter Bootstrap which contains all of this nice stuff inside. Particularly here is exactly what you want.

In addition, you can use different themes built for Twitter Bootstrap from this website

How to convert hex to ASCII characters in the Linux shell?

As per @Randal comment, you can use perl, e.g.

$ printf 5a5a5a5a | perl -lne 'print pack "H*", $_'

and other way round:

$ printf ZZZZ | perl -lne 'print unpack "H*", $_'

Another example with file:

$ printf 5a5a5a5a | perl -lne 'print pack "H*", $_' > file.bin
$ perl -lne 'print unpack "H*", $_' < file.bin

Compiling C++ on remote Linux machine - "clock skew detected" warning

Replace the watch battery in your computer. I have seen this error message when the coin looking battery on the motherboard was in need of replacement.

.ssh directory not being created

As a slight improvement over the other answers, you can do the mkdir and chmod as a single operation using mkdir's -m switch.

$ mkdir -m 700 ${HOME}/.ssh


From a Linux system

$ mkdir --help
Usage: mkdir [OPTION]... DIRECTORY...
Create the DIRECTORY(ies), if they do not already exist.

Mandatory arguments to long options are mandatory for short options too.
  -m, --mode=MODE   set file mode (as in chmod), not a=rwx - umask

Print the address or pointer for value in C

To print address in pointer to pointer:


to dereference once and print the second address:


You can always verify with debugger, if you are on linux use ddd and display memory, or just plain gdb, you will see the memory address so you can compare with the values in your pointers.

jQuery UI Alert Dialog as a replacement for alert()

Use this code syntax.

   $("<div></div>").html("YOUR MESSAGE").dialog(); 

this works but it append a node to the DOM. You can use a class and then or first remove all elements with that class. ex:

function simple_alert(msg)

OnItemClickListener using ArrayAdapter for ListView

you can use this way...

listView.setOnItemClickListener(new OnItemClickListener() {

        public void onItemClick(AdapterView<?> parent, View view,
                final int position, long id) {

          String main = listView.getSelectedItem().toString();

ASP.NET / C#: DropDownList SelectedIndexChanged in server control not firing

Is Viewstate turned on?

Edit: Perhaps you should reconsider overriding the rendering function

  protected override void RenderContents(HtmlTextWriter output)

and instead add the dropdownlists to the control and render the control using the default RenderContents.

Edit: See the answer from Dennis which I alluded to in my previous comment:

Controls.Add ( ddlCountries );
Controls.Add ( ddlStates );

submitting a form when a checkbox is checked

Submit form when your checkbox is checked

$(document).ready(function () {   
                if( $(".yourcheckboxclass").is(":checked") )

                    alert("Please select !!!");
                    return false;
                return false;

No restricted globals

/* eslint no-restricted-globals:0 */

is another alternate approach

How to base64 encode image in linux bash / shell

If you need input from termial, try this

lc=`echo -n "xxx_${yyy}_iOS" |  base64`

-n option will not input "\n" character to base64 command.

Random float number generation

#include <cstdint>
#include <cstdlib>
#include <ctime>

using namespace std;

/* single precision float offers 24bit worth of linear distance from 1.0f to 0.0f */
float getval() {
    /* rand() has min 16bit, but we need a 24bit random number. */
    uint_least32_t r = (rand() & 0xffff) + ((rand() & 0x00ff) << 16);
    /* 5.9604645E-8 is (1f - 0.99999994f), 0.99999994f is the first value less than 1f. */
    return (double)r * 5.9604645E-8;

int main()

I couldn't post two answers, so here is the second solution. log2 random numbers, massive bias towards 0.0f but it's truly a random float 1.0f to 0.0f.

#include <cstdint>
#include <cstdlib>
#include <ctime>

using namespace std;

float getval () {
    union UNION {
        uint32_t i;
        float f;
    } r;
    /* 3 because it's 0011, the first bit is the float's sign.
     * Clearing the second bit eliminates values > 1.0f.
    r.i = (rand () & 0xffff) + ((rand () & 0x3fff) << 16);
    return r.f;

int main ()
    srand (time (NULL));

What is the difference between public, private, and protected?

PHP manual has a good read on the question here.

The visibility of a property or method can be defined by prefixing the declaration with the keywords public, protected or private. Class members declared public can be accessed everywhere. Members declared protected can be accessed only within the class itself and by inherited and parent classes. Members declared as private may only be accessed by the class that defines the member.

How do I check if a string contains a specific word?

You could use regular expressions as it's better for word matching compared to strpos, as mentioned by other users. A strpos check for are will also return true for strings such as: fare, care, stare, etc. These unintended matches can simply be avoided in regular expression by using word boundaries.

A simple match for are could look something like this:

$a = 'How are you?';

if (preg_match('/\bare\b/', $a)) {
    echo 'true';

On the performance side, strpos is about three times faster. When I did one million compares at once, it took preg_match 1.5 seconds to finish and for strpos it took 0.5 seconds.

Edit: In order to search any part of the string, not just word by word, I would recommend using a regular expression like

$a = 'How are you?';
$search = 'are y';
if(preg_match("/{$search}/i", $a)) {
    echo 'true';

The i at the end of regular expression changes regular expression to be case-insensitive, if you do not want that, you can leave it out.

Now, this can be quite problematic in some cases as the $search string isn't sanitized in any way, I mean, it might not pass the check in some cases as if $search is a user input they can add some string that might behave like some different regular expression...

Also, here's a great tool for testing and seeing explanations of various regular expressions Regex101

To combine both sets of functionality into a single multi-purpose function (including with selectable case sensitivity), you could use something like this:

function FindString($needle,$haystack,$i,$word)
{   // $i should be "" or "i" for case insensitive
    if (strtoupper($word)=="W")
    {   // if $word is "W" then word search instead of string in string search.
        if (preg_match("/\b{$needle}\b/{$i}", $haystack)) 
            return true;
        if(preg_match("/{$needle}/{$i}", $haystack)) 
            return true;
    return false;
    // Put quotes around true and false above to return them as strings instead of as bools/ints.

One more thing to take in mind, is that \b will not work in different languages other than english.

The explanation for this and the solution is taken from here:

\b represents the beginning or end of a word (Word Boundary). This regex would match apple in an apple pie, but wouldn’t match apple in pineapple, applecarts or bakeapples.

How about “café”? How can we extract the word “café” in regex? Actually, \bcafé\b wouldn’t work. Why? Because “café” contains non-ASCII character: é. \b can’t be simply used with Unicode such as ??????, ??, ????? and .

When you want to extract Unicode characters, you should directly define characters which represent word boundaries.

The answer: (?<=[\s,.:;"']|^)UNICODE_WORD(?=[\s,.:;"']|$)

So in order to use the answer in PHP, you can use this function:

function contains($str, array $arr) {
    // Works in Hebrew and any other unicode characters
    // Thanks
    // Thanks
    if (preg_match('/(?<=[\s,.:;"\']|^)' . $word . '(?=[\s,.:;"\']|$)/', $str)) return true;

And if you want to search for array of words, you can use this:

function arrayContainsWord($str, array $arr)
    foreach ($arr as $word) {
        // Works in Hebrew and any other unicode characters
        // Thanks
        // Thanks
        if (preg_match('/(?<=[\s,.:;"\']|^)' . $word . '(?=[\s,.:;"\']|$)/', $str)) return true;
    return false;

As of PHP 8.0.0 you can now use str_contains

    if (str_contains('abc', '')) {
        echo "Checking the existence of the empty string will always 
        return true";

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

First, create a empty DataFrame with column names, after that, inside the for loop, you must define a dictionary (a row) with the data to append:

df = pd.DataFrame(columns=['A'])
for i in range(5):
    df = df.append({'A': i}, ignore_index=True)
0  0
1  1
2  2
3  3
4  4

If you want to add a row with more columns, the code will looks like this:

df = pd.DataFrame(columns=['A','B','C'])
for i in range(5):
    df = df.append({'A': i,
                    'B': i * 2,
                    'C': i * 3,
    A   B   C
0   0   0   0
1   1   2   3
2   2   4   6
3   3   6   9
4   4   8   12


Volatile vs Static in Java

In simple terms,

  1. static : static variables are associated with the class, rather than with any object. Every instance of the class shares a class variable, which is in one fixed location in memory

  2. volatile: This keyword is applicable to both class and instance variables.

Using volatile variables reduces the risk of memory consistency errors, because any write to a volatile variable establishes a happens-before relationship with subsequent reads of that same variable. This means that changes to a volatile variable are always visible to other threads

Have a look at this article by Javin Paul to understand volatile variables in a better way.

enter image description here

In absence of volatile keyword, the value of variable in each thread's stack may be different. By making the variable as volatile, all threads will get same value in their working memory and memory consistency errors have been avoided.

Here the term variable can be either static (class) variable or instance (object) variable.

Regarding your query :

Anyway a static variable value is also going to be one value for all threads, then why should we go for volatile?

If I need instance variable in my application, I can't use static variable. Even in case of static variable, consistency is not guaranteed due to Thread cache as shown in the diagram.

Using volatile variables reduces the risk of memory consistency errors, because any write to a volatile variable establishes a happens-before relationship with subsequent reads of that same variable. This means that changes to a volatile variable are always visible to other threads.

What's more, it also means that when a thread reads a volatile variable, it sees not just the latest change to the volatile, but also the side effects of the code that led up the change => memory consistency errors are still possible with volatile variables. To avoid side effects, you have to use synchronized variables. But there is a better solution in java.

Using simple atomic variable access is more efficient than accessing these variables through synchronized code

Some of the classes in the java.util.concurrent package provide atomic methods that do not rely on synchronization.

Refer to this high level concurrency control article for more details.

Especially have a look at Atomic variables.

Related SE questions:

Volatile Vs Atomic

Volatile boolean vs AtomicBoolean

Difference between volatile and synchronized in Java

Open JQuery Datepicker by clicking on an image w/ no input field

The jQuery documentation says that the datePicker needs to be attached to a SPAN or a DIV when it is not associated with an input box. You could do something like this:

<img src='someimage.gif' id="datepickerImage" />
<div id="datepicker"></div>

<script type="text/javascript">
 $(document).ready(function() {
            changeMonth: true,
            changeYear: true,
    .click(function() {

    $("#datepickerImage").click(function() {

Module 'tensorflow' has no attribute 'contrib'

I used tensorflow 1.8 to train my model and there is no problem for now. Tensorflow 2.0 alpha is not suitable with object detection API

What does AngularJS do better than jQuery?


You go around making your webpage, and keep on putting {{data bindings}} whenever you feel you would have dynamic data. Angular will then provide you a $scope handler, which you can populate (statically or through calls to the web server).

This is a good understanding of data-binding. I think you've got that down.

DOM Manipulation

For simple DOM manipulation, which doesnot involve data manipulation (eg: color changes on mousehover, hiding/showing elements on click), jQuery or old-school js is sufficient and cleaner. This assumes that the model in angular's mvc is anything that reflects data on the page, and hence, css properties like color, display/hide, etc changes dont affect the model.

I can see your point here about "simple" DOM manipulation being cleaner, but only rarely and it would have to be really "simple". I think DOM manipulation is one the areas, just like data-binding, where Angular really shines. Understanding this will also help you see how Angular considers its views.

I'll start by comparing the Angular way with a vanilla js approach to DOM manipulation. Traditionally, we think of HTML as not "doing" anything and write it as such. So, inline js, like "onclick", etc are bad practice because they put the "doing" in the context of HTML, which doesn't "do". Angular flips that concept on its head. As you're writing your view, you think of HTML as being able to "do" lots of things. This capability is abstracted away in angular directives, but if they already exist or you have written them, you don't have to consider "how" it is done, you just use the power made available to you in this "augmented" HTML that angular allows you to use. This also means that ALL of your view logic is truly contained in the view, not in your javascript files. Again, the reasoning is that the directives written in your javascript files could be considered to be increasing the capability of HTML, so you let the DOM worry about manipulating itself (so to speak). I'll demonstrate with a simple example.

This is the markup we want to use. I gave it an intuitive name.

<div rotate-on-click="45"></div>

First, I'd just like to comment that if we've given our HTML this functionality via a custom Angular Directive, we're already done. That's a breath of fresh air. More on that in a moment.

Implementation with jQuery

live demo here (click).

function rotate(deg, elem) {
    webkitTransform: 'rotate('+deg+'deg)', 
    mozTransform: 'rotate('+deg+'deg)', 
    msTransform: 'rotate('+deg+'deg)', 
    oTransform: 'rotate('+deg+'deg)', 
    transform: 'rotate('+deg+'deg)'    

function addRotateOnClick($elems) {
  $elems.each(function(i, elem) {
    var deg = 0;
    $(elem).click(function() {
      deg+= parseInt($(this).attr('rotate-on-click'), 10);
      rotate(deg, this);


Implementation with Angular

live demo here (click).

app.directive('rotateOnClick', function() {
  return {
    restrict: 'A',
    link: function(scope, element, attrs) {
      var deg = 0;
      element.bind('click', function() {
        deg+= parseInt(attrs.rotateOnClick, 10);
          webkitTransform: 'rotate('+deg+'deg)', 
          mozTransform: 'rotate('+deg+'deg)', 
          msTransform: 'rotate('+deg+'deg)', 
          oTransform: 'rotate('+deg+'deg)', 
          transform: 'rotate('+deg+'deg)'    

Pretty light, VERY clean and that's just a simple manipulation! In my opinion, the angular approach wins in all regards, especially how the functionality is abstracted away and the dom manipulation is declared in the DOM. The functionality is hooked onto the element via an html attribute, so there is no need to query the DOM via a selector, and we've got two nice closures - one closure for the directive factory where variables are shared across all usages of the directive, and one closure for each usage of the directive in the link function (or compile function).

Two-way data binding and directives for DOM manipulation are only the start of what makes Angular awesome. Angular promotes all code being modular, reusable, and easily testable and also includes a single-page app routing system. It is important to note that jQuery is a library of commonly needed convenience/cross-browser methods, but Angular is a full featured framework for creating single page apps. The angular script actually includes its own "lite" version of jQuery so that some of the most essential methods are available. Therefore, you could argue that using Angular IS using jQuery (lightly), but Angular provides much more "magic" to help you in the process of creating apps.

This is a great post for more related information: How do I “think in AngularJS” if I have a jQuery background?

General differences.

The above points are aimed at the OP's specific concerns. I'll also give an overview of the other important differences. I suggest doing additional reading about each topic as well.

Angular and jQuery can't reasonably be compared.

Angular is a framework, jQuery is a library. Frameworks have their place and libraries have their place. However, there is no question that a good framework has more power in writing an application than a library. That's exactly the point of a framework. You're welcome to write your code in plain JS, or you can add in a library of common functions, or you can add a framework to drastically reduce the code you need to accomplish most things. Therefore, a more appropriate question is:

Why use a framework?

Good frameworks can help architect your code so that it is modular (therefore reusable), DRY, readable, performant and secure. jQuery is not a framework, so it doesn't help in these regards. We've all seen the typical walls of jQuery spaghetti code. This isn't jQuery's fault - it's the fault of developers that don't know how to architect code. However, if the devs did know how to architect code, they would end up writing some kind of minimal "framework" to provide the foundation (achitecture, etc) I discussed a moment ago, or they would add something in. For example, you might add RequireJS to act as part of your framework for writing good code.

Here are some things that modern frameworks are providing:

  • Templating
  • Data-binding
  • routing (single page app)
  • clean, modular, reusable architecture
  • security
  • additional functions/features for convenience

Before I further discuss Angular, I'd like to point out that Angular isn't the only one of its kind. Durandal, for example, is a framework built on top of jQuery, Knockout, and RequireJS. Again, jQuery cannot, by itself, provide what Knockout, RequireJS, and the whole framework built on top them can. It's just not comparable.

If you need to destroy a planet and you have a Death Star, use the Death star.

Angular (revisited).

Building on my previous points about what frameworks provide, I'd like to commend the way that Angular provides them and try to clarify why this is matter of factually superior to jQuery alone.

DOM reference.

In my above example, it is just absolutely unavoidable that jQuery has to hook onto the DOM in order to provide functionality. That means that the view (html) is concerned about functionality (because it is labeled with some kind of identifier - like "image slider") and JavaScript is concerned about providing that functionality. Angular eliminates that concept via abstraction. Properly written code with Angular means that the view is able to declare its own behavior. If I want to display a clock:



Yes, we need to go to JavaScript to make that mean something, but we're doing this in the opposite way of the jQuery approach. Our Angular directive (which is in it's own little world) has "augumented" the html and the html hooks the functionality into itself.

MVW Architecure / Modules / Dependency Injection

Angular gives you a straightforward way to structure your code. View things belong in the view (html), augmented view functionality belongs in directives, other logic (like ajax calls) and functions belong in services, and the connection of services and logic to the view belongs in controllers. There are some other angular components as well that help deal with configuration and modification of services, etc. Any functionality you create is automatically available anywhere you need it via the Injector subsystem which takes care of Dependency Injection throughout the application. When writing an application (module), I break it up into other reusable modules, each with their own reusable components, and then include them in the bigger project. Once you solve a problem with Angular, you've automatically solved it in a way that is useful and structured for reuse in the future and easily included in the next project. A HUGE bonus to all of this is that your code will be much easier to test.

It isn't easy to make things "work" in Angular.

THANK GOODNESS. The aforementioned jQuery spaghetti code resulted from a dev that made something "work" and then moved on. You can write bad Angular code, but it's much more difficult to do so, because Angular will fight you about it. This means that you have to take advantage (at least somewhat) to the clean architecture it provides. In other words, it's harder to write bad code with Angular, but more convenient to write clean code.

Angular is far from perfect. The web development world is always growing and changing and there are new and better ways being put forth to solve problems. Facebook's React and Flux, for example, have some great advantages over Angular, but come with their own drawbacks. Nothing's perfect, but Angular has been and is still awesome for now. Just as jQuery once helped the web world move forward, so has Angular, and so will many to come.

How to set a maximum execution time for a mysql query?

You can find the answer on this other S.O. question:

MySQL - can I limit the maximum time allowed for a query to run?

a cron job that runs every second on your database server, connecting and doing something like this:

  • Find all connections with a query time larger than your maximum desired time
  • Run KILL [process id] for each of those processes

C++ error: "Array must be initialized with a brace enclosed initializer"

The syntax to statically initialize an array uses curly braces, like this:

int array[10] = { 0 };

This will zero-initialize the array.

For multi-dimensional arrays, you need nested curly braces, like this:

int cipher[Array_size][Array_size]= { { 0 } };

Note that Array_size must be a compile-time constant for this to work. If Array_size is not known at compile-time, you must use dynamic initialization. (Preferably, an std::vector).

subquery in codeigniter active record

->where() support passing any string to it and it will use it in the query.

You can try using this:

$this->db->where('`id` NOT IN (SELECT `id_cer` FROM `revokace`)', NULL, FALSE);

The ,NULL,FALSE in the where() tells CodeIgniter not to escape the query, which may mess it up.

UPDATE: You can also check out the subquery library I wrote.

$sub = $this->subquery->start_subquery('where_in');
$this->subquery->end_subquery('id', FALSE);

Installing Git on Eclipse

It's Very Easy To Install By Following Below Steps In Eclipse JUNO version

Help-->Eclipse Marketplace-->Find: beside Textbox u can type "Egit"-->select Egit-git team provider intall button-->follow next steps and finally click finish

How to use stringstream to separate comma separated strings

#include <iostream>
#include <sstream>

std::string input = "abc,def,ghi";
std::istringstream ss(input);
std::string token;

while(std::getline(ss, token, ',')) {
    std::cout << token << '\n';


GitHub - List commits by author

If the author has a GitHub account, just click the author's username from anywhere in the commit history, and the commits you can see will be filtered down to those by that author:

Screenshot showing where to click to filter down commits

You can also click the 'n commits' link below their name on the repo's "contributors" page:

Another screenshot

Alternatively, you can directly append ?author=<theusername> or ?author=<emailaddress> to the URL. For example, or[email protected] both give me:

Screenshot with only Dave Methvin's commits

For authors without a GitHub account, only filtering by email address will work, and you will need to manually add ?author=<emailaddress> to the URL - the author's name will not be clickable from the commits list.

You can also get the list of commits by a particular author from the command line using

git log --author=[your git name]


git log --author=Prem

Package opencv was not found in the pkg-config search path

Hi first of all i would like you to use 'Synaptic Package Manager'. You just need to goto the ubuntu software center and search for synaptic package manager.. The beauty of this is that all the packages you need are easily available here. Second it will automatically configures all your paths. Now install this then search for opencv packages over there if you found the package with the green box then its installed but else the package is not in the right place so you need to reinstall it but from package manager this time. If installed then you can do this only, you just need to fill the OpenCV_DIR variable with the path of opencv (containing the OpenCVConfig.cmake file)

    export OpenCV_DIR=<path_of_opencv>

Oracle JDBC intermittent Connection Issue

Disabling SQL Net Banners saved us.

How do I vertical center text next to an image in html/css?

There are a couple of options:

  • You can use line-height and make sure it is tall as the containing element
  • Use display: table-cell and vertical align: middle

My preferred option would be the first one, if it's a short space, or the latter otherwise.

Instagram API: How to get all user media?

Instagram developer console has provided the solution for it.

To use this in PHP, here is the code snippet,

** Add this code snippet after your first curl call
** assume the response of the first call is stored in $userdata
** $access_token have your access token

$maximumNumberOfPost = 33; // it can be 20, depends on your instagram application
$no_of_images = 50 // Enter the number of images you want

if ($no_of_images > $maximumNumberOfPost) {

    $ImageArray = [];
    $next_url = $userdata->pagination->next_url;
    while ($no_of_images > $maximumNumberOfPost) {
           $originalNumbersOfImage = $no_of_images;
           $no_of_images = $no_of_images - $maximumNumberOfPost;
           $next_url = str_replace("count=" . $originalNumbersOfImage, "count=" . $no_of_images, $next_url);
           $chRepeat = curl_init();
           curl_setopt_array($chRepeat, [
                             CURLOPT_URL => $next_url,
                             CURLOPT_HTTPHEADER => [
                                    "Authorization: Bearer $access_token"
                              CURLOPT_RETURNTRANSFER => true
            $userRepeatdata = curl_exec($chRepeat);
            if ($userRepeatdata) {
                      $userRepeatdata = json_decode($userRepeatdata);
                      $next_url = $userRepeatdata->pagination->next_url;
                     if (isset($userRepeatdata->data) && $userRepeatdata->data) {
                          $ImageArray = $userRepeatdata->data;


Using the Jersey client to do a POST operation

Starting from Jersey 2.x, the MultivaluedMapImpl class is replaced by MultivaluedHashMap. You can use it to add form data and send it to the server:

    WebTarget webTarget ="");
    MultivaluedMap<String, String> formData = new MultivaluedHashMap<String, String>();
    formData.add("key1", "value1");
    formData.add("key2", "value2");
    Response response = webTarget.request().post(Entity.form(formData));

Note that the form entity is sent in the format of "application/x-www-form-urlencoded".

Auto-Submit Form using JavaScript

Try this,

HtmlElement head = _windowManager.ActiveBrowser.Document.GetElementsByTagName("head")[0];
HtmlElement scriptEl = _windowManager.ActiveBrowser.Document.CreateElement("script");
IHTMLScriptElement element = (IHTMLScriptElement)scriptEl.DomElement;
element.text = "window.onload = function() { document.forms[0].submit(); }";
strAdditionalHeader = "";

Xcode Debugger: view value of variable

I agree with other posters that Xcode as a developing environment should include an easy way to debug variables. Well, good news, there IS one!

After searching and not finding a simple answer/tutorial on how to debug variables in Xcode I went to explore with Xcode itself and found this (at least for me) very useful discovery.

How to easily debug your variables in Xcode 4.6.3

In the main screen of Xcode make sure to see the bottom Debug Area by clicking the upper-right corner button showed in the screenshot.

Debug Area button

Debug Area in Xcode 4.6.3

Now set a Breakpoint – the line in your code where you want your program to pause, by clicking the border of your Code Area.


Now in the Debug Area look for this buttons and click the one in the middle. You will notice your area is now divided in two.

Split Debug Area

Should look like this

Now run your application.

When the first Breakpoint is reached during the execution of your program you will see on the left side all your variables available at that breakpoint.

Search Field

You can expand the left arrows on the variable for a greater detail. And even use the search field to isolate that variable you want and see it change on real time as you "Step into" the scope of the Breakpoint.

Step Into

On the right side of your Debug Area you can send to print the variables as you desire using the mouse's right-button click over the desired variable.

Contextual Menu

As you can see, that contextual menu is full of very interesting debugging options. Such as Watch that has been already suggested with typed commands or even Edit Value… that changes the runtime value of your variable!

How to put a UserControl into Visual Studio toolBox

The issue with my designer was 32 vs 64 bit issue. I could add the control to tool box after following the instructions in Cannot add Controls from 64-bit Assemblies to the Toolbox or Use in Designers Within the Visual Studio IDE MS KB article.

Java Enum Methods - return opposite direction enum

For those lured here by title: yes, you can define your own methods in your enum. If you are wondering how to invoke such non-static method, you do it same way as with any other non-static method - you invoke it on instance of type which defines or inherits that method. In case of enums such instances are simply ENUM_CONSTANTs.

So all you need is EnumType.ENUM_CONSTANT.methodName(arguments).

Now lets go back to problem from question. One of solutions could be

public enum Direction {


    private Direction opposite;

    static {
        NORTH.opposite = SOUTH;
        SOUTH.opposite = NORTH;
        EAST.opposite = WEST;
        WEST.opposite = EAST;

    public Direction getOppositeDirection() {
        return opposite;


Now Direction.NORTH.getOppositeDirection() will return Direction.SOUTH.

Here is little more "hacky" way to illustrate @jedwards comment but it doesn't feel as flexible as first approach since adding more fields or changing their order will break our code.

public enum Direction {

    // cached values to avoid recreating such array each time method is called
    private static final Direction[] VALUES = values();

    public Direction getOppositeDirection() {
        return VALUES[(ordinal() + 2) % 4]; 

Which UUID version to use?

If you want a random number, use a random number library. If you want a unique identifier with effectively 0.00...many more 0s here...001% chance of collision, you should use UUIDv1. See Nick's post for UUIDv3 and v5.

UUIDv1 is NOT secure. It isn't meant to be. It is meant to be UNIQUE, not un-guessable. UUIDv1 uses the current timestamp, plus a machine identifier, plus some random-ish stuff to make a number that will never be generated by that algorithm again. This is appropriate for a transaction ID (even if everyone is doing millions of transactions/s).

To be honest, I don't understand why UUIDv4 exists... from reading RFC4122, it looks like that version does NOT eliminate possibility of collisions. It is just a random number generator. If that is true, than you have a very GOOD chance of two machines in the world eventually creating the same "UUID"v4 (quotes because there isn't a mechanism for guaranteeing U.niversal U.niqueness). In that situation, I don't think that algorithm belongs in a RFC describing methods for generating unique values. It would belong in a RFC about generating randomness. For a set of random numbers:

chance_of_collision = 1 - (set_size! / (set_size - tries)!) / (set_size ^ tries)

Determining the path that a yum package installed to

I don't know about yum, but rpm -ql will list the files in a particular .rpm file. If you can find the package file on your system you should be good to go.

How to disable <br> tags inside <div> by css?

or hide any br that follows the p tag, which are obviously not wanted

p + br {
    display: none;

How to create a delay in Swift?

Try the following implementation in Swift 3.0

func delayWithSeconds(_ seconds: Double, completion: @escaping () -> ()) {
    DispatchQueue.main.asyncAfter(deadline: .now() + seconds) { 


delayWithSeconds(1) {
   //Do something

Removing double quotes from variables in batch file creates problems with CMD environment

You have an extra double quote at the end, which is adding it back to the end of the string (after removing both quotes from the string).


set widget="a very useful item"
set widget
set widget=%widget:"=%
set widget


widget="a very useful item"
widget=a very useful item

Note: To replace Double Quotes " with Single Quotes ' do the following:

set widget=%widget:"='%

Note: To replace the word "World" (not case sensitive) with BobB do the following:

set widget="Hello World!"
set widget=%widget:world=BobB%
set widget


widget="Hello BobB!"

As far as your initial question goes (save the following code to a batch file .cmd or .bat and run):

SET BathFileAndPath=%~0
ECHO %BathFileAndPath%
ECHO "%BathFileAndPath%"
ECHO %~0


"C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd"
C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd
"C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd"
C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd
"C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd"
Press any key to continue . . .

%0 is the Script Name and Path.
%1 is the first command line argument, and so on.

Open button in new window?

<input type="button" onclick="; return false;" value="click me" />

How can I use/create dynamic template to compile dynamic Component with Angular 2.0?

This is the example of dynamic Form controls generated from server.

This example is dynamic Form controls is in add component (This is where you can get the Formcontrols from the server). If you see addcomponent method you can see the Forms Controls. In this example I am not using angular material,but It works (I am using @ work). This is target to angular 6, but works in all previous version.

Need to add JITComplierFactory for AngularVersion 5 and above.



Is there a way to specify how many characters of a string to print out using printf()?

In C++ it is easy.

std::copy(someStr.c_str(), someStr.c_str()+n, std::ostream_iterator<char>(std::cout, ""));

EDIT: It is also safer to use this with string iterators, so you don't run off the end. I'm not sure what happens with printf and string that are too short, but I'm guess this may be safer.

What is the simplest way to swap each pair of adjoining chars in a string with Python?

Here's one way...

>>> s = '2134'
>>> def swap(c, i, j):
...  c = list(c)
...  c[i], c[j] = c[j], c[i]
...  return ''.join(c)
>>> swap(s, 0, 1)

Is there an ignore command for git like there is for svn?

You have two ways of ignoring files:

  • .gitignore in any folder will ignore the files as specified in the file for that folder. Using wildcards is possible.
  • .git/info/exclude holds the global ignore pattern, similar to the global-ignores in subversions configuration file.

Undoing a git rebase

Let's say I rebase master to my feature branch and I get 30 new commits which break something. I've found that often it's easiest to just remove the bad commits.

git rebase -i HEAD~31

Interactive rebase for the last 31 commits (it doesn't hurt if you pick way too many).

Simply take the commits that you want to get rid of and mark them with "d" instead of "pick". Now the commits are deleted effectively undoing the rebase (if you remove only the commits you just got when rebasing).

Node Express sending image files as API response

a proper solution with streams and error handling is below:

const fs = require('fs')
const stream = require('stream')

app.get('/report/:chart_id/:user_id',(req, res) => {
  const r = fs.createReadStream('path to file') // or any other way to get a readable stream
  const ps = new stream.PassThrough() // <---- this makes a trick with stream error handling
   ps, // <---- this makes a trick with stream error handling
   (err) => {
    if (err) {
      console.log(err) // No such file or any other kind of error
      return res.sendStatus(400); 
  ps.pipe(res) // <---- this makes a trick with stream error handling

with Node older then 10 you will need to use pump instead of pipeline.

numpy: most efficient frequency counts for unique values in an array

I was also interested in this, so I did a little performance comparison (using perfplot, a pet project of mine). Result:

y = np.bincount(a)
ii = np.nonzero(y)[0]
out = np.vstack((ii, y[ii])).T

is by far the fastest. (Note the log-scaling.)

enter image description here

Code to generate the plot:

import numpy as np
import pandas as pd
import perfplot
from scipy.stats import itemfreq

def bincount(a):
    y = np.bincount(a)
    ii = np.nonzero(y)[0]
    return np.vstack((ii, y[ii])).T

def unique(a):
    unique, counts = np.unique(a, return_counts=True)
    return np.asarray((unique, counts)).T

def unique_count(a):
    unique, inverse = np.unique(a, return_inverse=True)
    count = np.zeros(len(unique),, inverse, 1)
    return np.vstack((unique, count)).T

def pandas_value_counts(a):
    out = pd.value_counts(pd.Series(a))
    out = np.stack([out.keys().values, out.values]).T
    return out
    setup=lambda n: np.random.randint(0, 1000, n),
    kernels=[bincount, unique, itemfreq, unique_count, pandas_value_counts],
    n_range=[2 ** k for k in range(26)],

How to fix Invalid byte 1 of 1-byte UTF-8 sequence

You have a library that needs to be erased Like the following library

   implementation 'org.apache.maven.plugins:maven-surefire-plugin:2.4.3'

How to read data from a file in Lua

Try this:


-- see if the file exists
function file_exists(file)
  local f =, "rb")
  if f then f:close() end
  return f ~= nil

-- get all lines from a file, returns an empty 
-- list/table if the file does not exist
function lines_from(file)
  if not file_exists(file) then return {} end
  lines = {}
  for line in io.lines(file) do 
    lines[#lines + 1] = line
  return lines

-- tests the functions above
local file = 'test.lua'
local lines = lines_from(file)

-- print all line numbers and their contents
for k,v in pairs(lines) do
  print('line[' .. k .. ']', v)

How do I view the SQL generated by the Entity Framework?

You can do the following:

IQueryable query = from x in appEntities
             where == 32
             select x;

var sql = ((System.Data.Objects.ObjectQuery)query).ToTraceString();

or in EF6:

var sql = ((System.Data.Entity.Core.Objects.ObjectQuery)query)

That will give you the SQL that was generated.

Parse error: Syntax error, unexpected end of file in my PHP code

I had the same error, but I had it fixed by modifying the php.ini file.

Find your php.ini file see Dude, where's my php.ini?

then open it with your favorite editor.

Look for a short_open_tag property, and apply the following change:

; short_open_tag = Off ; previous value
short_open_tag = On ; new value

C# elegant way to check if a property's property is null

Assuming you have empty values of types one approach would be this:

var x = (((objectA ?? A.Empty).PropertyOfB ?? B.Empty).PropertyOfC ?? C.Empty).PropertyOfString;

I'm a big fan of C# but a very nice thing in new Java (1.7?) is the .? operator:

 var x = objectA.?PropertyOfB.?PropertyOfC.?PropertyOfString;

How to change title of Activity in Android?

If you want to set title in Java file, then write in your activity onCreate

setTitle("Your Title");

if you want to in Manifest then write

        android:label="Your Title" >
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />

$ is not a function - jQuery error

In Wordpress jQuery.noConflict() is called on the jQuery file it includes (scroll to the bottom of the file it's including for jQuery to see this), which means $ doesn't work, but jQuery does, so your code should look like this:

<script type="text/javascript">
  jQuery(function($) {
    for(var i=0; i <= 20; i++) 
      $("ol li:nth-child(" + i + ")").addClass('olli' + i);

Convert form data to JavaScript object with jQuery

I wouldn't use this on a live site due to XSS attacks and probably plenty of other issues, but here's a quick example of what you could do:

    var arr = $(this).serializeArray();
    var json = "";
    jQuery.each(arr, function(){
        jQuery.each(this, function(i, val){
            if (i=="name") {
                json += '"' + val + '":';
            } else if (i=="value") {
                json += '"' + val.replace(/"/g, '\\"') + '",';
    json = "{" + json.substring(0, json.length - 1) + "}";
    // do something with json
    return false;

How to select count with Laravel's fluent query builder?

You can use an array in the select() to define more columns and you can use the DB::raw() there with aliasing it to followers. Should look like this:

$query = DB::table('category_issue')
    ->select(array('issues.*', DB::raw('COUNT(issue_subscriptions.issue_id) as followers')))
    ->where('category_id', '=', 1)
    ->join('issues', 'category_issue.issue_id', '=', '')
    ->left_join('issue_subscriptions', '', '=', 'issue_subscriptions.issue_id')
    ->order_by('followers', 'desc')

Is there a way to get element by XPath using JavaScript in Selenium WebDriver?

You can use document.evaluate:

Evaluates an XPath expression string and returns a result of the specified type if possible.

It is w3-standardized and whole documented:

function getElementByXpath(path) {_x000D_
  return document.evaluate(path, document, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null).singleNodeValue;_x000D_
console.log( getElementByXpath("//html[1]/body[1]/div[1]") );

There's also a great introduction on mozilla developer network:

Alternative version, using XPathEvaluator:

function getElementByXPath(xpath) {_x000D_
  return new XPathEvaluator()_x000D_
    .evaluate(document, XPathResult.FIRST_ORDERED_NODE_TYPE)_x000D_
console.log( getElementByXPath("//html[1]/body[1]/div[1]") );

How to generate and validate a software license key?

I've used Crypkey in the past. It's one of many available.

You can only protect software up to a point with any licensing scheme.

How to style the UL list to a single line

ul li{
  display: inline;

For more see the basic list options and a basic horizontal list at listamatic. (thanks to Daniel Straight below for the links).

Also, as pointed out in the comments, you probably want styling on the ul and whatever elements go inside the li's and the li's themselves to get things to look nice.

Make multiple-select to adjust its height to fit options without scroll bar

The way a select box is rendered is determined by the browser itself. So every browser will show you the height of the option list box in another height. You can't influence that. The only way you can change that is to make an own select from the scratch.

What are the most useful Intellij IDEA keyboard shortcuts?

Within the tool: "Help -> Default Keymap Reference" (as suggested by krosenvold)

On the Internet: "IntelliJ IDEA Developers Documentation"

Windows, Linux and Mac keyboard shortcut reference cards for versions 8, 7, 6, 5, and 4.5.

(I knew I had seen and used these reference "cards" before! ;-)

One of my favorites (not shown on the JetBrains cards) is "Ctrl+Shift+{Up or Down Arrow}" to move lines/methods up and down in the source code.

See also "Intellij Idea Keyboard Shortcuts" page on Ward's Wiki.

Metadata file '.dll' could not be found

My instance of the problem was caused by a common project that had a duplicate class name in it (under a different filename). It is strange that Visual Studio could not detect that and instead just blew up the build process.

How to run batch file from network share without "UNC path are not supported" message?

I needed to be able to just Windows Explorer browse through the server share, then double-click launch the batch file. @dbenham led me to an easier solution for my scenario (without the popd worries):

:: Capture UNC or mapped-drive path script was launched from
set NetPath=%~dp0

:: Assumes that setup.exe is in the same UNC path

:: Note that NetPath has a trailing backslash ("\")
robocopy.exe "%NetPath%Custom" /copyall "C:\Program Files (x86)\WP\Custom Templates"
Regedit.exe /s %NetPath%..\WPX5\Custom\Migrate.reg

:: I am not sure if WPX5 was typo, so use ".." for parent directory
set NetPath=
pause Invalid postback or callback argument

If you have code in your Page_Load() event. Try adding this:

if (!Page.IsPostBack)
//your code here 

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

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


Convert decimal to binary in python

I agree with @aaronasterling's answer. However, if you want a non-binary string that you can cast into an int, then you can use the canonical algorithm:

def decToBin(n):
    if n==0: return ''
        return decToBin(n/2) + str(n%2)

HttpListener Access Denied

By default Windows defines the following prefix that is available to everyone: http://+:80/Temporary_Listen_Addresses/

So you can register your HttpListener via:

Prefixes.Add("http://+:80/Temporary_Listen_Addresses/" + Guid.NewGuid().ToString("D") + "/";

This sometimes causes problems with software such as Skype which will try to utilise port 80 by default.

Should I use .done() and .fail() for new jQuery AJAX code instead of success and error

When we are going to migrate JQuery from 1.x to 2x or 3.x in our old existing application , then we will use .done,.fail instead of success,error as JQuery up gradation is going to be deprecated these methods.For example when we make a call to server web methods then server returns promise objects to the calling methods(Ajax methods) and this promise objects contains .done,.fail..etc methods.Hence we will the same for success and failure response. Below is the example(it is for POST request same way we can construct for request type like GET...)

            type: "POST",
            url: url,
            data: '{"name" :"sheo"}',
            contentType: "application/json; charset=utf-8",
            async: false,
            cache: false
            }).done(function (Response) {
                  //do something when get response            })
           .fail(function (Response) {
                    //do something when any error occurs.

How to convert String to DOM Document object in java?

Either escape the double quotes with \

String xmlString = "<element attribname=\"value\" attribname1=\"value1\"> pcdata</element>"

or use single quotes instead

String xmlString = "<element attribname='value' attribname1='value1'> pcdata</element>"

What is the iOS 5.0 user agent string?

I found a more complete listing at user agent string. BTW, this site has more than just iOS user agent strings. Also, the home page will "break down" the user agent string of your current browser for you.

Android, How to create option Menu

The previous answers have covered the traditional menu used in android. Their is another option you can use if you are looking for an alternative

Pulley menu is an alternate to the traditional Menu which allows user to select any option for an activity intuitively. The menu is revealed by dragging the screen downwards and in that gesture user can also select any of the options.

How to display a jpg file in Python?

Don't forget to include

import Image

In order to show it use this :'pathToFile').show()

How can I combine two HashMap objects containing the same types?

You could use Collection.addAll() for other types, e.g. List, Set, etc. For Map, you can use putAll.

'Must Override a Superclass Method' Errors after importing a project into Eclipse

The answer by Paul worked for me partially. I still had one error then. So, in addition to that, I also had to go to Properties-> Project Facets and there set the Java version from 1.5 to 1.6.

Maybe that helps.

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at

The server at needs to output the following header:


Where is your website address. You should check your settings on to see if you can enable this - if not their technical support would probably be the best way to resolve this. However to answer your question, you need the remote site to allow your site to access AJAX responses client side.

Key Presses in Python

There's a solution:

import pyautogui
for i in range(1000):

How do files get into the External Dependencies in Visual Studio C++?

The External Dependencies folder is populated by IntelliSense: the contents of the folder do not affect the build at all (you can in fact disable the folder in the UI).

You need to actually include the header (using a #include directive) to use it. Depending on what that header is, you may also need to add its containing folder to the "Additional Include Directories" property and you may need to add additional libraries and library folders to the linker options; you can set all of these in the project properties (right click the project, select Properties). You should compare the properties with those of the project that does build to determine what you need to add.

Finding the position of the max element

Or, written in one line:

std::cout << std::distance(sampleArray.begin(),std::max_element(sampleArray.begin(), sampleArray.end()));

How to develop or migrate apps for iPhone 5 screen resolution?

You can use the Auto Layout feature and create the design using iPhone 5 screen resolution and it will work for the both 4" and 3.5" devices, but in this case you should have a enough knowledge of layout manager.


In case anyone still hunting the cause of this hateful issue, there comes a solution to nail the causing file. from Drupal community.

And I quote:



function drupal_load(). It is a short function. Find following line: include_once DRUPAL_ROOT . '/' . $filename; Temporarily replace it by

include_once DRUPAL_ROOT . '/' . $filename;
$value = ob_get_contents();
if ($value !== '') {
  $filename = check_plain($filename);
  $value = check_plain($value);
  print "File '$filename' produced unforgivable content: '$value'.";

Will #if RELEASE work like #if DEBUG does in C#?


While in debug configuration there is a DEBUG defined constant (automatically defined by Visual Studio) while there is no such constant defined for release mode. Check your project settings under build.

Selecting [Define DEBUG constant] under Project -> Build is like including #define DEBUG at the beginning of every file.

If you want to define a RELEASE constant for the release configuration go to:

  • Project Properties -> Build
  • Select Release Mode
  • in the Conditional compilation symbols textbox enter: RELEASE

Angular2 change detection: ngOnChanges not firing for nested object

Here's an example using IterableDiffer with ngDoCheck. IterableDiffer is especially useful if you need to track changes over time as it lets you do things like iterate over only added/changed/removed values etc.

A simple example not using all advantages of IterableDiffer, but it works and shows the principle:

export class FeedbackMessagesComponent implements DoCheck {
  messages: UserFeedback[] = [];
  // Example UserFeedback instance { message = 'Ooops', type = Notice }

  display = 'none';

  private _iterableDiffer: IterableDiffer<UserFeedback>;

  constructor(private _iterableDiffers: IterableDiffers) {
    this._iterableDiffer = this._iterableDiffers.find([]).create(null);

  ngDoCheck(): void {
    const changes = this._iterableDiffer.diff(this.messages);

    if (changes) {
      // Here you can do stuff like changes.forEachRemovedItem()

      // We know contents of this.messages was changed so update visibility:
      this.display = this.messages.length > 0 ? 'block' : 'none';

This will now automatically show/hide depending on myMessagesArray count:


java.lang.OutOfMemoryError: bitmap size exceeds VM budget - Android

This explanation might help:

"Fast Tips:

1) NEVER call System.gc() yourself. This has been propagated as a fix here, and it doesn't work. Do not do it. If you noticed in my explanation, before getting an OutOfMemoryError, the JVM already runs a garbage collection so there is no reason to do one again (its slowing your program down). Doing one at the end of your activity is just covering up the problem. It may causes the bitmap to be put on the finalizer queue faster, but there is no reason you couldn't have simply called recycle on each bitmap instead.

2) Always call recycle() on bitmaps you don't need anymore. At the very least, in the onDestroy of your activity go through and recycle all the bitmaps you were using. Also, if you want the bitmap instances to be collected from the dalvik heap faster, it doesn't hurt to clear any references to the bitmap.

3) Calling recycle() and then System.gc() still might not remove the bitmap from the Dalvik heap. DO NOT BE CONCERNED about this. recycle() did its job and freed the native memory, it will just take some time to go through the steps I outlined earlier to actually remove the bitmap from the Dalvik heap. This is NOT a big deal because the large chunk of native memory is already free!

4) Always assume there is a bug in the framework last. Dalvik is doing exactly what its supposed to do. It may not be what you expect or what you want, but its how it works. "

How to set child process' environment variable in Makefile

I would re-write the original target test, taking care the needed variable is defined IN THE SAME SUB-PROCESS as the application to launch:

    ( NODE_ENV=test mocha --harmony --reporter spec test )

svn : how to create a branch from certain revision of trunk

$ svn copy \ \
   -m "Creating a private branch of /calc/trunk."

Where 192 is the revision you specify

You can find this information from the SVN Book, specifically here on the page about svn copy

How to specify the default error page in web.xml?

You can also do something like that:



For error code 403 it will return the page 403.html, and for any other error code it will return the page error.html.

Best way to get child nodes

firstElementChild might not be available in IE<9 (only firstChild)

on IE<9 firstChild is the firstElementChild because MS DOM (IE<9) is not storing empty text nodes. But if you do so on other browsers they will return empty text nodes...

my solution


this will give the firstchild even on IE<9

How to measure time elapsed on Javascript?

The Date documentation states that :

The JavaScript date is based on a time value that is milliseconds since midnight January 1, 1970, UTC

Click on start button then on end button. It will show you the number of seconds between the 2 clicks.

The milliseconds diff is in variable timeDiff. Play with it to find seconds/minutes/hours/ or what you need

var startTime, endTime;_x000D_
function start() {_x000D_
  startTime = new Date();_x000D_
function end() {_x000D_
  endTime = new Date();_x000D_
  var timeDiff = endTime - startTime; //in ms_x000D_
  // strip the ms_x000D_
  timeDiff /= 1000;_x000D_
  // get seconds _x000D_
  var seconds = Math.round(timeDiff);_x000D_
  console.log(seconds + " seconds");_x000D_
<button onclick="start()">Start</button>_x000D_
<button onclick="end()">End</button>

OR another way of doing it for modern browser

Using which returns a value representing the time elapsed since the time origin. This value is a double with microseconds in the fractional.

The time origin is a standard time which is considered to be the beginning of the current document's lifetime.

var startTime, endTime;_x000D_
function start() {_x000D_
  startTime =;_x000D_
function end() {_x000D_
  endTime =;_x000D_
  var timeDiff = endTime - startTime; //in ms _x000D_
  // strip the ms _x000D_
  timeDiff /= 1000; _x000D_
  // get seconds _x000D_
  var seconds = Math.round(timeDiff);_x000D_
  console.log(seconds + " seconds");_x000D_
<button onclick="start()">Start</button>_x000D_
<button onclick="end()">End</button>

Decimal precision and scale in EF Code First

Apparently, you can override the DbContext.OnModelCreating() method and configure the precision like this:

protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder)
    modelBuilder.Entity<Product>().Property(product => product.Price).Precision = 10;
    modelBuilder.Entity<Product>().Property(product => product.Price).Scale = 2;

But this is pretty tedious code when you have to do it with all your price-related properties, so I came up with this:

    protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder)
        var properties = new[]
            modelBuilder.Entity<Product>().Property(product => product.Price),
            modelBuilder.Entity<Order>().Property(order => order.OrderTotal),
            modelBuilder.Entity<OrderDetail>().Property(detail => detail.Total),
            modelBuilder.Entity<Option>().Property(option => option.Price)

        properties.ToList().ForEach(property =>
            property.Precision = 10;
            property.Scale = 2;


It's good practice that you call the base method when you override a method, even though the base implementation does nothing.

Update: This article was also very helpful.

How to find SQL Server running port?

SQL Server 2000 Programs | MS SQL Server | Client Network Utility | Select TCP_IP then Properties

SQL Server 2005 Programs | SQL Server | SQL Server Configuration Manager | Select Protocols for MSSQLSERVER or select Client Protocols and right click on TCP/IP

Can a website detect when you are using Selenium with chromedriver?

It sounds like they are behind a web application firewall. Take a look at modsecurity and OWASP to see how those work.

In reality, what you are asking is how to do bot detection evasion. That is not what Selenium WebDriver is for. It is for testing your web application not hitting other web applications. It is possible, but basically, you'd have to look at what a WAF looks for in their rule set and specifically avoid it with selenium if you can. Even then, it might still not work because you don't know what WAF they are using.

You did the right first step, that is, faking the user agent. If that didn't work though, then a WAF is in place and you probably need to get more tricky.

Point taken from other answer. Make sure your user agent is actually being set correctly first. Maybe have it hit a local web server or sniff the traffic going out.

How (and why) to use display: table-cell (CSS)

It's even easier to use parent > child selector relationship so the inner div do not need to have their css classes to be defined explicitly:

.display-table {_x000D_
    display: table; _x000D_
.display-table > div { _x000D_
    display: table-row; _x000D_
.display-table > div > div { _x000D_
    display: table-cell;_x000D_
    padding: 5px;_x000D_
<div class="display-table">_x000D_
        <div>0, 0</div>_x000D_
        <div>0, 1</div>_x000D_
        <div>1, 0</div>_x000D_
        <div>1, 1</div>_x000D_

Can't install any package with node npm

For future reference, this can also happen if npm is down. That's how I found this question. Wish the first npm task was a server status check so there was a clearer error message.

How to check if a value exists in a dictionary (python)

In Python 3, you can use

"one" in d.values()

to test if "one" is among the values of your dictionary.

In Python 2, it's more efficient to use

"one" in d.itervalues()


Note that this triggers a linear scan through the values of the dictionary, short-circuiting as soon as it is found, so this is a lot less efficient than checking whether a key is present.

Javascript - Append HTML to container element without innerHTML

alnafie has a great answer for this question. I wanted to give an example of his code for reference:

var childNumber = 3;_x000D_
function addChild() {_x000D_
  var parent = document.getElementById('i-want-more-children');_x000D_
  var newChild = '<p>Child ' + childNumber + '</p>';_x000D_
  parent.insertAdjacentHTML('beforeend', newChild);_x000D_
body {_x000D_
  text-align: center;_x000D_
button {_x000D_
  background: rgba(7, 99, 53, .1);_x000D_
  border: 3px solid rgba(7, 99, 53, 1);_x000D_
  border-radius: 5px;_x000D_
  color: rgba(7, 99, 53, 1);_x000D_
  cursor: pointer;_x000D_
  line-height: 40px;_x000D_
  font-size: 30px;_x000D_
  outline: none;_x000D_
  padding: 0 20px;_x000D_
  transition: all .3s;_x000D_
button:hover {_x000D_
  background: rgba(7, 99, 53, 1);_x000D_
  color: rgba(255,255,255,1);_x000D_
p {_x000D_
  font-size: 20px;_x000D_
  font-weight: bold;_x000D_
<button type="button" onclick="addChild()">Append Child</button>_x000D_
<div id="i-want-more-children">_x000D_
  <p>Child 1</p>_x000D_
  <p>Child 2</p>_x000D_

Hopefully this is helpful to others.

What is the difference between putting a property on application.yml or bootstrap.yml in spring boot?

Just my 2 Cents here ..

Bootstrap.yml or is used to fetch the config from Spring Cloud Server.

For Example, in My file I have the following Config

On starting the application , It tries to fetch the configuration for the service by connecting to http://localhost:8888 and looks at present in Spring Cloud Config server

You can validate the same from logs of Calcuation-Service when you start it up

INFO 10988 --- [ restartedMain] c.c.c.ConfigServicePropertySourceLocator : Fetching config from server at : http://localhost:8888

Splitting a C++ std::string using tokens, e.g. ";"

There are several libraries available solving this problem, but the simplest is probably to use Boost Tokenizer:

#include <iostream>
#include <string>
#include <boost/tokenizer.hpp>
#include <boost/foreach.hpp>

typedef boost::tokenizer<boost::char_separator<char> > tokenizer;

std::string str("denmark;sweden;india;us");
boost::char_separator<char> sep(";");
tokenizer tokens(str, sep);

BOOST_FOREACH(std::string const& token, tokens)
    std::cout << "<" << *tok_iter << "> " << "\n";

Combine two tables that have no common fields

    null as path, 
    null as Description 

    path as cid, 
    Description from zmw_t_path;

Best way to change the background color for an NSView

An easy, efficient solution is to configure the view to use a Core Animation layer as its backing store. Then you can use -[CALayer setBackgroundColor:] to set the background color of the layer.

- (void)awakeFromNib {
   self.wantsLayer = YES;  // NSView will create a CALayer automatically

- (BOOL)wantsUpdateLayer {
   return YES;  // Tells NSView to call `updateLayer` instead of `drawRect:`

- (void)updateLayer {
   self.layer.backgroundColor = [NSColor colorWithCalibratedRed:0.227f 

That’s it!

Error: "setFile(null,false) call failed" when using log4j

Have a look at the error - 'log4j:ERROR setFile(null,false) call failed. logs (Access is denied)'

It seems there's a log file named as 'logs' to which access is denied i.e it is not having sufficient permissions to write logs. Try by giving write permissions to the 'logs' log file. Hope it helps.

TypeError: Missing 1 required positional argument: 'self'

Works and is simpler than every other solution I see here :


This is great if you don't need to reuse a class instance. Tested on Python 3.7.3.


You need to replace it as WHERE clockDate = { fn CURRENT_DATE() } AND userName = 'test'. Please remove extra ")" from { fn CURRENT_DATE() })

EntityType has no key defined error

You don't have to use key attribute all the time. Make sure the mapping file properly addressed the key

this.HasKey(t => t.Key);
this.Property(p => p.Key)

and don't forget to add the mapping in the Repository's OnModelCreating

modelBuilder.Configurations.Add(new PacketHistoryMap());

Git checkout: updating paths is incompatible with switching branches

After having tried most of what I could read in this thread without success, I stumbled across this one: Remote branch not showing up in "git branch -r"

It turned out that my .git/config file was incorrect. After doing a simple fix all branches showed up.

Going from

[remote "origin"]
    url =
    fetch = +refs/heads/master:refs/remotes/origin/master


[remote "origin"]
    url =
    fetch = +refs/heads/*:refs/remotes/origin/*

Did the trick

An unhandled exception of type 'System.TypeInitializationException' occurred in EntityFramework.dll

In static class, if you are getting information from xml or reg, class tries to initialize all properties. therefore, you should control if the config variable is there otherwise properties will not initialize so the class.

Check xml referance variable is there, Check reg referance variable is is there, Make sure you handle if they are not there.

proper name for python * operator?

I believe it's most commonly called the "splat operator." Unpacking arguments is what it does.

utf-8 special characters not displaying

This is really annoying problem to fix but you can try these.

First of all, make sure the file is actually saved in UTF-8 format.

Then check that you have <meta http-equiv="Content-Type" content="text/html;charset=UTF-8"> in your HTML header.

You can also try calling header('Content-Type: text/html; charset=utf-8'); at the beginning of your PHP script or adding AddDefaultCharset UTF-8 to your .htaccess file.

Initializing data.frames()

> df <- data.frame(matrix(ncol = 300, nrow = 100))
> dim(df)
[1] 100 300

How to enable Ad Hoc Distributed Queries

If ad hoc updates to system catalog is "not supported", or if you get a "Msg 5808" then you will need to configure with override like this:

EXEC sp_configure 'show advanced options', 1
RECONFIGURE with override
EXEC sp_configure 'ad hoc distributed queries', 1
RECONFIGURE with override

Why is this printing 'None' in the output?

Because of double print function. I suggest you to use return instead of print inside the function definition.

def lyrics():
    return "The very first line"


def lyrics():
    print("The very first line")

What is the best way to left align and right align two div tags?

<div style="float: left;">Left Div</div>
<div style="float: right;">Right Div</div>

Assign output of a program to a variable using a MS batch file

In addition to the answer, you can't directly use output redirection operators in the set part of for loop (e.g. if you wanna hide stderror output from a user and provide a nicer error message). Instead, you have to escape them with a caret character (^):

for /f %%O in ('some-erroring-command 2^> nul') do (echo %%O)

Reference: Redirect output of command in for loop of batch script

Error creating bean with name 'entityManagerFactory

This sounds like a ClassLoader conflict. I'd bet you have the javax.persistence api 1.x on the classpath somewhere, whereas Spring is trying to access ValidationMode, which was only introduced in JPA 2.0.

Since you use Maven, do mvn dependency:tree, find the artifact:


And remove it from your setup. (See Excluding Dependencies)

AFAIK there is no such general distribution for JPA 2, but you can use this Hibernate-specific version:


OK, since that doesn't work, you still seem to have some JPA-1 version in there somewhere. In a test method, add this code:


See where that points you and get rid of that artifact.

Ahh, now I finally see the problem. Get rid of this:


and replace it with


On a different note, you should set all test libraries (spring-test, easymock etc.) to


How do I prevent a form from being resized by the user?

If you want to prevent resize by dragging sizegrips and by the maximize button and by maximize by doubleclick on the header text, than insert the following code in the load event of the form:

    Me.FormBorderStyle = Windows.Forms.FormBorderStyle.FixedSingle ' Prevent size grips
    Me.MaximumSize = Me.Size ' Prevent maximize (also by doubleclick of header text)

Of course all choices of a formborderstyle beginning with Fixed will do.

How to host google web fonts on my own server?

The contents of the CSS file (from the include URL) depends on what browser I view it from. For example, when browsing to using Chrome, the file only contained WOFF links. Using Internet Explorer (below), it included both EOT and WOFF. I pasted all the links into my browser to download them.

@font-face {
  font-family: 'Open Sans';
  font-style: normal;
  font-weight: 400;
  src: url(;
  src: local('Open Sans'), local('OpenSans'), url( format('embedded-opentype'), url( format('woff');

When you host your own web fonts, you need to correctly link to each font type, deal with legacy browser bugs, etc. When you use Google Web Fonts (hosted by Google), Google automatically links to the correct font types for that browser.

Recommended Fonts for Programming?

I've been using Anonymous, but I'll need to check out some of these other fonts.

In Java 8 how do I transform a Map<K,V> to another Map<K,V> using a lambda?

Here is another way that gives you access to the key and the value at the same time, in case you have to do some kind of transformation.

Map<String, Integer> pointsByName = new HashMap<>();
Map<String, Integer> maxPointsByName = new HashMap<>();

Map<String, Double> gradesByName = pointsByName.entrySet().stream()
        .map(entry -> new AbstractMap.SimpleImmutableEntry<>(
                entry.getKey(), ((double) entry.getValue() /
                        maxPointsByName.get(entry.getKey())) * 100d))
        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

Process escape sequences in a string in Python

The correct thing to do is use the 'string-escape' code to decode the string.

>>> myString = "spam\\neggs"
>>> decoded_string = bytes(myString, "utf-8").decode("unicode_escape") # python3 
>>> decoded_string = myString.decode('string_escape') # python2
>>> print(decoded_string)

Don't use the AST or eval. Using the string codecs is much safer.

Updates were rejected because the tip of your current branch is behind hint: its remote counterpart. Integrate the remote changes (e.g

You need to merge the remote branch into your current branch by running git pull.

If your local branch is already up-to-date, you may also need to run git pull --rebase.

A quick google search also turned up this same question asked by another SO user: Cannot push to GitHub - keeps saying need merge. More details there.

How to render a DateTime object in a Twig template

You can use date filter:

{{ game.gameDate|date("m/d/Y") }}

What does the error "JSX element type '...' does not have any construct or call signatures" mean?

If you are using material-ui, go to type definition of the component, which is being underlined by TypeScript. Most likely you will see something like this

export { default } from './ComponentName';

You have 2 options to resolve the error:

1.Add .default when using the component in JSX:

import ComponentName from './ComponentName'

const Component = () => <ComponentName.default />

2.Rename the component, which is being exported as "default", when importing:

import { default as ComponentName } from './ComponentName'

const Component = () => <ComponentName />

This way you don't need to specify .default every time you use the component.

How can I create a copy of an object in Python?

Shallow copy with copy.copy()

#!/usr/bin/env python3

import copy

class C():
    def __init__(self):
        self.x = [1]
        self.y = [2]

# It copies.
c = C()
d = copy.copy(c)
d.x = [3]
assert c.x == [1]
assert d.x == [3]

# It's shallow.
c = C()
d = copy.copy(c)
d.x[0] = 3
assert c.x == [3]
assert d.x == [3]

Deep copy with copy.deepcopy()

#!/usr/bin/env python3
import copy
class C():
    def __init__(self):
        self.x = [1]
        self.y = [2]
c = C()
d = copy.deepcopy(c)
d.x[0] = 3
assert c.x == [1]
assert d.x == [3]


Tested on Python 3.6.5.

When to use Common Table Expression (CTE)

Perhaps its more meaningful to think of a CTE as a substitute for a view used for a single query. But doesn't require the overhead, metadata, or persistence of a formal view. Very useful when you need to:

  • Create a recursive query.
  • Use the CTE's resultset more than once in your query.
  • Promote clarity in your query by reducing large chunks of identical subqueries.
  • Enable grouping by a column derived in the CTE's resultset

Here's a cut-and-paste example to play with:

WITH [cte_example] AS (
SELECT 1 AS [myNum], 'a num' as [label]
SELECT [myNum]+1,[label]
FROM [cte_example]
WHERE [myNum] <=  10
SELECT * FROM [cte_example]
SELECT SUM([myNum]), 'sum_all' FROM [cte_example]
SELECT SUM([myNum]), 'sum_odd' FROM [cte_example] WHERE [myNum] % 2 = 1
SELECT SUM([myNum]), 'sum_even' FROM [cte_example] WHERE [myNum] % 2 = 0;


querying WHERE condition to character length?

I think you want this:

select *
from dbo.table
where DATALENGTH(column_name) = 3

comparing 2 strings alphabetically for sorting purposes

"a".localeCompare("b") should actually return -1 since a sorts before b

How to override the path of PHP to use the MAMP path?

If you have to type


in your command line then add


to your PATH to be able to call php from anywhere.

How to get a path to a resource in a Java JAR file

You need to understand the path within the jar file.
Simply refer to it relative. So if you have a file (myfile.txt), located in foo.jar under the \src\main\resources directory (maven style). You would refer to it like:


If you dump your jar using jar -tvf myjar.jar you will see the output and the relative path within the jar file, and use the FORWARD SLASHES.

How to extend / inherit components?


Component inheritance is supported since 2.3.0-rc.0


So far, the most convenient for me is to keep template & styles into separate *html & *.css files and specify those through templateUrl and styleUrls, so it's easy reusable.

@Component {
    selector: 'my-panel',
    templateUrl: 'app/components/panel.html', 
    styleUrls: ['app/components/panel.css']
export class MyPanelComponent extends BasePanelComponent

php random x digit number

Please not that rand() does not generate a cryptographically secure value according to the docs:

This function does not generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a cryptographically secure value, consider using random_int(), random_bytes(), or openssl_random_pseudo_bytes() instead.

Instead it is better to use random_int(), available on PHP 7 (See:

So to extend @Marcus's answer, you should use:

function generateSecureRandomNumber($digits): int {
   return random_int(pow(10, $digits - 1), pow(10, $digits) - 1);

function generateSecureRandomNumberWithPadding($digits): string {
   $randomNumber = random_int(0, pow(10, $digits) - 1);
   return str_pad($randomNumber, $digits, '0', STR_PAD_LEFT);

Note that using rand() is fine if you don't need a secure random number.

With ng-bind-html-unsafe removed, how do I inject HTML?

You can create your own simple unsafe html binding, of course if you use user input it could be a security risk.

App.directive('simpleHtml', function() {
  return function(scope, element, attr) {
    scope.$watch(attr.simpleHtml, function (value) {

How to increase scrollback buffer size in tmux?

Open tmux configuration file with the following command:

vim ~/.tmux.conf

In the configuration file add the following line:

set -g history-limit 5000

Log out and log in again, start a new tmux windows and your limit is 5000 now.

Does overflow:hidden applied to <body> work on iPhone Safari?

Some solutions listed here had some strange glitches when stretching the elastic scrolling. To fix that I used:

body.lock-position {
  height: 100%;
  overflow: hidden;
  width: 100%;
  position: fixed;


Tools to get a pictorial function call graph of code

Dynamic analysis methods

Here I describe a few dynamic analysis methods.

Dynamic methods actually run the program to determine the call graph.

The opposite of dynamic methods are static methods, which try to determine it from the source alone without running the program.

Advantages of dynamic methods:

  • catches function pointers and virtual C++ calls. These are present in large numbers in any non-trivial software.

Disadvantages of dynamic methods:

  • you have to run the program, which might be slow, or require a setup that you don't have, e.g. cross-compilation
  • only functions that were actually called will show. E.g., some functions could be called or not depending on the command line arguments.


Test program:

int f2(int i) { return i + 2; }
int f1(int i) { return f2(2) + i + 1; }
int f0(int i) { return f1(1) + f2(2); }
int pointed(int i) { return i; }
int not_called(int i) { return 0; }

int main(int argc, char **argv) {
    int (*f)(int);
    f = pointed;
    if (argc == 1)
    if (argc == 2)
    return 0;


sudo apt-get install -y kcachegrind valgrind

# Compile the program as usual, no special flags.
gcc -ggdb3 -O0 -o main -std=c99 main.c

# Generate a callgrind.out.<PID> file.
valgrind --tool=callgrind ./main

# Open a GUI tool to visualize callgrind data.
kcachegrind callgrind.out.1234

You are now left inside an awesome GUI program that contains a lot of interesting performance data.

On the bottom right, select the "Call graph" tab. This shows an interactive call graph that correlates to performance metrics in other windows as you click the functions.

To export the graph, right click it and select "Export Graph". The exported PNG looks like this:

From that we can see that:

  • the root node is _start, which is the actual ELF entry point, and contains glibc initialization boilerplate
  • f0, f1 and f2 are called as expected from one another
  • pointed is also shown, even though we called it with a function pointer. It might not have been called if we had passed a command line argument.
  • not_called is not shown because it didn't get called in the run, because we didn't pass an extra command line argument.

The cool thing about valgrind is that it does not require any special compilation options.

Therefore, you could use it even if you don't have the source code, only the executable.

valgrind manages to do that by running your code through a lightweight "virtual machine". This also makes execution extremely slow compared to native execution.

As can be seen on the graph, timing information about each function call is also obtained, and this can be used to profile the program, which is likely the original use case of this setup, not just to see call graphs: How can I profile C++ code running on Linux?

Tested on Ubuntu 18.04.

gcc -finstrument-functions + etrace

-finstrument-functions adds callbacks, etrace parses the ELF file and implements all callbacks.

I couldn't get it working however unfortunately: Why doesn't `-finstrument-functions` work for me?

Claimed output is of format:

\-- main
|   \-- Crumble_make_apple_crumble
|   |   \-- Crumble_buy_stuff
|   |   |   \-- Crumble_buy
|   |   |   \-- Crumble_buy
|   |   |   \-- Crumble_buy
|   |   |   \-- Crumble_buy
|   |   |   \-- Crumble_buy
|   |   \-- Crumble_prepare_apples
|   |   |   \-- Crumble_skin_and_dice
|   |   \-- Crumble_mix
|   |   \-- Crumble_finalize
|   |   |   \-- Crumble_put
|   |   |   \-- Crumble_put
|   |   \-- Crumble_cook
|   |   |   \-- Crumble_put
|   |   |   \-- Crumble_bake

Likely the most efficient method besides specific hardware tracing support, but has the downside that you have to recompile the code.

Selenium and xPath - locating a link by containing text

I think the problem is here:

[contains(text()='Some text')]

To break this down,

  1. The [] are a conditional that operates on each individual node in that node set -- each span node in your case. It matches if any of the individual nodes it operates on match the conditions inside the brackets.
  2. text() is a selector that matches all of the text nodes that are children of the context node -- it returns a node set.
  3. contains is a function that operates on a string. If it is passed a node set, the node set is converted into a string by returning the string-value of the node in the node-set that is first in document order.

You should try to change this to

[text()[contains(.,'Some text')]]

  1. The outer [] are a conditional that operates on each individual node in that node set text() is a selector that matches all of the text nodes that are children of the context node -- it returns a node set.

  2. The inner [] are a conditional that operates on each node in that node set.

  3. contains is a function that operates on a string. Here it is passed an individual text node (.).

JPA CascadeType.ALL does not delete orphans

According to Java Persistence with Hibernate, cascade orphan delete is not available as a JPA annotation.

It is also not supported in JPA XML.

Making view resize to its parent when added with addSubview

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

myChildeView.autoresizingMask = (UIViewAutoresizingFlexibleWidth |

Also, you may need to call

myParentView.autoresizesSubviews = YES;

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

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

myParentView.clipsToBounds = YES;

PHP 7: Missing VCRUNTIME140.dll

I got same error and found that my Microsoft Visual C++ is 32 bit and Windows is 64 bit. I tried to install WAMP 7 32 bit and the problem was solved.

Maybe we need to install WAMP 32 bit if Visual Studio is 32 bit. And vice versa.

PhpMyAdmin not working on localhost

when I started xampp on my windows 10 there were many options available, unfortunately every one of them failed. I ll list them so that you don't go through all of them again.


1) i installed xampp initially in a different drive and not c because of UAC issues so i uninstalled Xampp and installed it again in c (didn't work) 2) while reinstalling i deactivated the antivirus as setup said that some installing might not end up properly(realized it doesn't matter :) lmao) 3) i tried to change ports several times of xampp from 80 to some different number like 8080 etc. still nothing happened 4) i then tried using firefox as it is believed that internet explorer or internet edge is not a good browser for xampp 5) after that i went to config file i.e inside phpmyadmin folder and did some crap as were given in the instructions. Failure it was 6) then i closed laptop and went to sleep(XD srry leave this point) 7) then i tried searching for windows web services in the services.msc to disable it. i couldn't find it


On eighth time i got success.This is what i did 8)In control panel, where you have actions , modules PIDs, Ports you will see Services under which you will see gray boxes which are actually checkboxes but are empty initially. i checked it so that xampp services start and apache services start. now you will see them ticked. After that just change the port of xampp and apache to 80.

I hope it helps. cheers ;)

NodeJS: How to get the server's port?

Requiring the http module was never necessary.

An additional import of http is not necessary in Express 3 or 4. Assigning the result of listen() is enough.

var server = require('express')();

server.get('/', function(req, res) {
  res.send("Hello Foo!");

var listener = server.listen(3000);
console.log('Your friendly Express server, listening on port %s', listener.address().port);
// Your friendly Express server, listening on port 3000

Again, this is tested in Express 3.5.1 & 4.0.0. Importing http was never necessary. The listen method returns an http server object.

object==null or null==object?

This trick supposed to prevent v = null kind of typos.

But Java allows only boolean expressions as if() conditions so that trick does not make much sense, compiler will find those typos anyway.

It is still valuable trick for C/C++ code though.

How to use executeReader() method to retrieve the value of just one cell

It is not recommended to use DataReader and Command.ExecuteReader to get just one value from the database. Instead, you should use Command.ExecuteScalar as following:

String sql = "SELECT ColumnNumber FROM learer WHERE = " + index;
SqlCommand cmd = new SqlCommand(sql,conn);
learerLabel.Text = (String) cmd.ExecuteScalar();

Here is more information about Connecting to database and managing data.

Mysql - How to quit/exit from stored procedure

To handle this situation in a portable way (ie will work on all databases because it doesn’t use MySQL label Kung fu), break the procedure up into logic parts, like this:

CREATE PROCEDURE SP_Reporting(IN tablename VARCHAR(20))
     IF tablename IS NOT NULL THEN
         CALL SP_Reporting_2(tablename);
     END IF;

CREATE PROCEDURE SP_Reporting_2(IN tablename VARCHAR(20))
     #proceed with code

CSS: On hover show and hide different div's at the same time?

Have you tried somethig like this?

.showme{display: none;}
.showhim:hover .showme{display : block;}
.showhim:hover .hideme{display:none;}

<div class="showhim">HOVER ME
  <div class="showme">hai</div>
  <div class="hideme">bye</div>

I dont know any reason why it shouldn't be possible.

Understanding repr( ) function in Python

1) The result of repr('foo') is the string 'foo'. In your Python shell, the result of the expression is expressed as a representation too, so you're essentially seeing repr(repr('foo')).

2) eval calculates the result of an expression. The result is always a value (such as a number, a string, or an object). Multiple variables can refer to the same value, as in:

x = 'foo'
y = x

x and y now refer to the same value.

3) I have no idea what you meant here. Can you post an example, and what you'd like to see?

How to call JavaScript function instead of href in HTML

<a href="#" onclick="javascript:ShowOld(2367,146986,2)">

Declare an array in TypeScript

let arr1: boolean[] = [];



What is the coolest thing you can do in <10 lines of simple code? Help me inspire beginners!

When I first figured out the bash forkbomb, I thought it was really sweet. So simple, yet neat in what it can do:

:(){ :|:& };:

How can I check that two objects have the same set of property names?

Here is my attempt at validating JSON properties. I used @casey-foster 's approach, but added recursion for deeper validation. The third parameter in function is optional and only used for testing.

//compare json2 to json1
function isValidJson(json1, json2, showInConsole) {

    if (!showInConsole)
        showInConsole = false;

    var aKeys = Object.keys(json1).sort();
    var bKeys = Object.keys(json2).sort();

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

        if (showInConsole)
            console.log("---------" + JSON.stringify(aKeys[i]) + "  " + JSON.stringify(bKeys[i]))

        if (JSON.stringify(aKeys[i]) === JSON.stringify(bKeys[i])) {

            if (typeof json1[aKeys[i]] === 'object'){ // contains another obj

                if (showInConsole)
                    console.log("Entering " + JSON.stringify(aKeys[i]))

                if (!isValidJson(json1[aKeys[i]], json2[bKeys[i]], showInConsole)) 
                    return false; // if recursive validation fails

                if (showInConsole)
                    console.log("Leaving " + JSON.stringify(aKeys[i]))


        } else {

            console.warn("validation failed at " + aKeys[i]);
            return false; // if attribute names dont mactch



    return true;


Check if element at position [x] exists in the list

if (list.Count > desiredIndex && list[desiredIndex] != null)
    // logic

android TextView: setting the background color dynamically doesn't work

two ways to do that:

1.create color in colors.xml file like:

        <color name="white">#ffffff</color>

and use it int activity java class as:




What is the purpose of the "role" attribute in HTML?

Is this role attribute necessary?

Answer: Yes.

  • The role attribute is necessary to support Accessible Rich Internet Applications (WAI-ARIA) to define roles in XML-based languages, when the languages do not define their own role attribute.
  • Although this is the reason the role attribute is published by the Protocols and Formats Working Group, the attribute has more general use cases as well.

It provides you:

  • Accessibility
  • Device adaptation
  • Server-side processing
  • Complex data description,...etc.

From ND to 1D arrays

Use np.ravel (for a 1D view) or np.ndarray.flatten (for a 1D copy) or np.ndarray.flat (for an 1D iterator):

In [12]: a = np.array([[1,2,3], [4,5,6]])

In [13]: b = a.ravel()

In [14]: b
Out[14]: array([1, 2, 3, 4, 5, 6])

Note that ravel() returns a view of a when possible. So modifying b also modifies a. ravel() returns a view when the 1D elements are contiguous in memory, but would return a copy if, for example, a were made from slicing another array using a non-unit step size (e.g. a = x[::2]).

If you want a copy rather than a view, use

In [15]: c = a.flatten()

If you just want an iterator, use np.ndarray.flat:

In [20]: d = a.flat

In [21]: d
Out[21]: <numpy.flatiter object at 0x8ec2068>

In [22]: list(d)
Out[22]: [1, 2, 3, 4, 5, 6]

How to make Google Fonts work in IE?

I tried all the options from above and they didn't work. Then I located the google font (Over the Rainbow) in my folder (new) and used IE conditional below and it worked perfect.

<!--[if IE]>
<style type="text/css">
    @font-face {
    font-family: "Over the Rainbow";
    src: url("../new/over.ttf");
    src: local("Over the Rainbow"), url("../new/over.ttf");

I hope it will help

Why does dividing two int not yield the right value when assigned to double?

c is a double variable, but the value being assigned to it is an int value because it results from the division of two ints, which gives you "integer division" (dropping the remainder). So what happens in the line c=a/b is

  1. a/b is evaluated, creating a temporary of type int
  2. the value of the temporary is assigned to c after conversion to type double.

The value of a/b is determined without reference to its context (assignment to double).

Can I return the 'id' field after a LINQ insert?

After you commit your object into the db the object receives a value in its ID field.


myObject.Field1 = "value";

// Db is the datacontext

// You can retrieve the id from the object
int id = myObject.ID;

Python popen command. Wait until the command is finished

You can you use subprocess to achieve this.

import subprocess

#This command could have multiple commands separated by a new line \n
some_command = "export PATH=$PATH:// \n customupload abc.txt"

p = subprocess.Popen(some_command, stdout=subprocess.PIPE, shell=True)

(output, err) = p.communicate()  

#This makes the wait possible
p_status = p.wait()

#This will give you the output of the command being executed
print "Command output: " + output

Change a Django form field to a hidden field

You can just use css :

#id_fieldname, label[for="id_fieldname"] {_x000D_
  position: absolute;_x000D_
  display: none_x000D_

This will make the field and its label invisible.

How do I clear my local working directory in Git?

To reset a specific file as git status suggests:

git checkout <filename>

To reset a folder

git checkout <foldername>/*

Using braces with dynamic variable names in PHP

i have a solution for dynamically created variable value and combined all value in a variable.

    for($i=1; $i<=4; $i++){
        $a = $_POST['a'.$i];
        $r .= $a;
    echo $r;

How to unset a JavaScript variable?

The delete operator removes a property from an object. It cannot remove a variable. So the answer to the question depends on how the global variable or property is defined.

(1) If it is created with var, it cannot be deleted.

For example:

var g_a = 1; //create with var, g_a is a variable 
delete g_a; //return false
console.log(g_a); //g_a is still 1

(2) If it is created without var, it can be deleted.

g_b = 1; //create without var, g_b is a property 
delete g_b; //return true
console.log(g_b); //error, g_b is not defined

Technical Explanation

1. Using var

In this case the reference g_a is created in what the ECMAScript spec calls "VariableEnvironment" that is attached to the current scope - this may be the a function execution context in the case of using var inside a function (though it may be get a little more complicated when you consider let) or in the case of "global" code the VariableEnvironment is attached to the global object (often window).

References in the VariableEnvironment are not normally deletable - the process detailed in ECMAScript 10.5 explains this in detail, but suffice it to say that unless your code is executed in an eval context (which most browser-based development consoles use), then variables declared with var cannot be deleted.

2. Without Using var

When trying to assign a value to a name without using the var keyword, Javascript tries to locate the named reference in what the ECMAScript spec calls "LexicalEnvironment", and the main difference is that LexicalEnvironments are nested - that is a LexicalEnvironment has a parent (what the ECMAScript spec calls "outer environment reference") and when Javascript fails to locate the reference in a LexicalEnvironment, it looks in the parent LexicalEnvironment (as detailed in 10.3.1 and The top level LexicalEnvironment is the "global environment", and that is bound to the global object in that its references are the global object's properties. So if you try to access a name that was not declared using a var keyword in the current scope or any outer scopes, Javascript will eventually fetch a property of the window object to serve as that reference. As we've learned before, properties on objects can be deleted.


  1. It is important to remember that var declarations are "hoisted" - i.e. they are always considered to have happened in the beginning of the scope that they are in - though not the value initialization that may be done in a var statement - that is left where it is. So in the following code, a is a reference from the VariableEnvironment and not the window property and its value will be 10 at the end of the code:

    function test() { a = 5; var a = 10; }
  2. The above discussion is when "strict mode" is not enabled. Lookup rules are a bit different when using "strict mode" and lexical references that would have resolved to window properties without "strict mode" will raise "undeclared variable" errors under "strict mode". I didn't really understand where this is specified, but its how browsers behave.

Test process.env with Jest

In my opinion, it's much cleaner and easier to understand if you extract the retrieval of environment variables into a utility (you probably want to include a check to fail fast if an environment variable is not set anyway), and then you can just mock the utility.

// util.js
exports.getEnv = (key) => {
    const value = process.env[key];
    if (value === undefined) {
      throw new Error(`Missing required environment variable ${key}`);
    return value;

// app.test.js
const util = require('./util');

util.getEnv.mockImplementation(key => `fake-${key}`);

test('test', () => {...});

What can MATLAB do that R cannot do?

Support for interactive graphics is much better in matlab than in R. I hate matlab as a language, but I get jealous when I see how its users can explore data with mouse operations, while I'm busy repeating commands with new values for xlim etc. Matlab also handles multi-panel plots much better than any of the R methods for the task. Generally, R graphics has a 1960s feel. It's fine for publication, but not the best solution for interactive exploration of data.

How to include External CSS and JS file in Laravel 5

I think that the right way is this one:

<script type="text/javascript" src="{{ URL::asset('js/jquery.js') }}"></script>

Here I have a js directory in the laravel's app/public folder. There I have a jquery.js file. The function URL::asset() produces the necessary url for you. Same for the css:

<link rel="stylesheet" href="{{ URL::asset('css/somestylesheet.css') }}" />

Hope this helps.

Keep in mind that the old mehods:

{{ Form::script() }}


{{ Form::style() }}

are deprecated and will not work in Laravel 5!

How to create a responsive image that also scales up in Bootstrap 3

Not sure if it helps you still... but I had to do a small trick to make the image bigger but keeping it responsive

@media screen and (max-width: 368px) {
        min-height: 150px;


Hope it helps P.S. The max width can be anything you like

What are the differences between git remote prune, git prune, git fetch --prune, etc

I don't blame you for getting frustrated about this. The best way to look at is this. There are potentially three versions of every remote branch:

  1. The actual branch on the remote repository
    (e.g., remote repo at, refs/heads/master)
  2. Your snapshot of that branch locally (stored under refs/remotes/...)
    (e.g., local repo, refs/remotes/origin/master)
  3. And a local branch that might be tracking the remote branch
    (e.g., local repo, refs/heads/master)

Let's start with git prune. This removes objects that are no longer being referenced, it does not remove references. In your case, you have a local branch. That means there's a ref named random_branch_I_want_deleted that refers to some objects that represent the history of that branch. So, by definition, git prune will not remove random_branch_I_want_deleted. Really, git prune is a way to delete data that has accumulated in Git but is not being referenced by anything. In general, it doesn't affect your view of any branches.

git remote prune origin and git fetch --prune both operate on references under refs/remotes/... (I'll refer to these as remote references). It doesn't affect local branches. The git remote version is useful if you only want to remove remote references under a particular remote. Otherwise, the two do exactly the same thing. So, in short, git remote prune and git fetch --prune operate on number 2 above. For example, if you deleted a branch using the git web GUI and don't want it to show up in your local branch list anymore (git branch -r), then this is the command you should use.

To remove a local branch, you should use git branch -d (or -D if it's not merged anywhere). FWIW, there is no git command to automatically remove the local tracking branches if a remote branch disappears.

spring PropertyPlaceholderConfigurer and context:property-placeholder

Following worked for me:
<context:property-placeholder location="file:src/resources/spring/"/>

Somehow "classpath:xxx" is not picking the file.

Declare a dictionary inside a static class

You can use the static/class constructor to initialize your dictionary:

public static class ErrorCode
    public const IDictionary<string, string> ErrorCodeDic;
    public static ErrorCode()
        ErrorCodeDic = new Dictionary<string, string>()
            { {"1", "User name or password problem"} };

Specifying ssh key in ansible playbook file

The variable name you're looking for is ansible_ssh_private_key_file.

You should set it at 'vars' level:

  • in the inventory file:

    myHost ansible_ssh_private_key_file=~/.ssh/mykey1.pem
    myOtherHost ansible_ssh_private_key_file=~/.ssh/mykey2.pem
  • in the host_vars:

    # hosts_vars/myHost.yml
    ansible_ssh_private_key_file: ~/.ssh/mykey1.pem
    # hosts_vars/myOtherHost.yml
    ansible_ssh_private_key_file: ~/.ssh/mykey2.pem
  • in a group_vars file if you use the same key for a group of hosts

  • in the vars section of your play:

    - hosts: myHost
      remote_user: ubuntu
        - vars.yml
        ansible_ssh_private_key_file: "{{ key1 }}"
        - name: Echo a hello message
          command: echo hello

Inventory documentation

How to see which flags -march=native will activate?

It should be (-### is similar to -v):

echo | gcc -### -E - -march=native 

To show the "real" native flags for gcc.

You can make them appear more "clearly" with a command:

gcc -### -E - -march=native 2>&1 | sed -r '/cc1/!d;s/(")|(^.* - )//g'

and you can get rid of flags with -mno-* with:

gcc -### -E - -march=native 2>&1 | sed -r '/cc1/!d;s/(")|(^.* - )|( -mno-[^\ ]+)//g'

What is the boundary in multipart/form-data?

multipart/form-data contains boundary to separate name/value pairs. The boundary acts like a marker of each chunk of name/value pairs passed when a form gets submitted. The boundary is automatically added to a content-type of a request header.

The form with enctype="multipart/form-data" attribute will have a request header Content-Type : multipart/form-data; boundary --- WebKit193844043-h (browser generated vaue).

The payload passed looks something like this:

Content-Type: multipart/form-data; boundary=---WebKitFormBoundary7MA4YWxkTrZu0gW

    Content-Disposition: form-data; name=”file”; filename=”captcha”

    Content-Disposition: form-data; name=”action”


On the webservice side, it's consumed in @Consumes("multipart/form-data") form.

Beware, when testing your webservice using chrome postman, you need to check the form data option(radio button) and File menu from the dropdown box to send attachment. Explicit provision of content-type as multipart/form-data throws an error. Because boundary is missing as it overrides the curl request of post man to server with content-type by appending the boundary which works fine.

See RFC1341 sec7.2 The Multipart Content-Type