Programs & Examples On #Reactor

The reactor design pattern is an event handling pattern for handling service requests delivered concurrently to a service handler by one or more inputs. The service handler demultiplexes the incoming requests and dispatches them synchronously to the associated request handlers.

Maven:Non-resolvable parent POM and 'parent.relativePath' points at wrong local POM

The normal layout for a maven multi module project is:

+-- pom.xml
+-- module
    +-- pom.xml

Check that you use this layout.


  1. the relativePath looks strange. Instead of '..'


    try '../' instead:


    You can also remove relativePath if you use the standard layout. This is what I always do, and on the command line I can build as well the parent (and all modules) or only a single module.

  2. The module path may be wrong. In the parent you define the module as:


    You must specify the name of the folder of the child module, not an artifact identifier. If junitcategorizer.cutdetection is not the name of the folder than change it accordingly.

Hope that helps..

EDIT have a look at the other post, I answered there.

Plugin org.apache.maven.plugins:maven-clean-plugin:2.5 or one of its dependencies could not be resolved

I faced the same problem and was frustrated to see as to all options i tried and none of them work,

Turns out once you have configured everything correctly including settings.xml

just clear your local repository folder and try mvn commands. That greatly helped me

Hope this helps others

Launching Spring application Address already in use

I would suggest to kill the port number. It worked for me

netstat -ano | findstr :yourPortNumber taskkill /PID typeyourPIDhere /F

Why is Maven downloading the maven-metadata.xml every time?

It is possibly to use the flag -o,--offline "Work offline" to prevent that.

Like this:

maven compile -o

"Non-resolvable parent POM: Could not transfer artifact" when trying to refer to a parent pom from a child pom with ${parent.groupid}

I assume the question is already answered. If above solution doesn't help in solving the issue then can use below to solve the issue.

The issue occurs if sometimes your maven user settings is not reflecting correct settings.xml file.

To update the settings file go to Windows > Preferences > Maven > User Settings and update the settings.xml to it correct location.

Once this is doen re-build the project, these should solve the issue. Thanks.

Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.10:test

I had a similar problem, and the solution for me was quite different from what the other users posted.

The problem with me was related to the project I was working last year, which required a certain proxy on maven settings (located at <path to maven folder>\maven\conf\settings.xml and C:\Users\<my user>\.m2\settings.xml). The proxy was blocking the download of required external packages.

The solution was to put back the original file (settings.xml) on those places. Once things were restored, I was able to download the packages and everything worked.

Non-resolvable parent POM for Could not find artifact and 'parent.relativePath' points at wrong local POM

I faced the same issue. Setting relative path of the parent in module projects solved the issue.

Use <relativePath>../Parent Project Name/pom.xml</relativePath>

how to access downloads folder in android?

You need to set this permission in your manifest.xml file


Java: unable to find valid certification path to requested target

There is a lot of way to solve this...

One way is set the TrustStore certificates in a keystore file and put it in the path of the application, and set these system properties in the main method:

public static void main(String[] args) {
  System.setProperty("", "trust-store.jks");
  System.setProperty("", "TrustStore");

Other way is place the keystore as resource file inside the project jar file and load it:

public static SSLContext createSSLContext(String resourcePath, String pass) throws NoSuchAlgorithmException, KeyStoreException, IOException, CertificateException, UnrecoverableKeyException, KeyManagementException {
  // initialise the keystore
  final char[] password = pass.toCharArray();
  KeyStore ks = KeyStore.getInstance("JKS");
  ), password);

  // Setup the key manager factory.
  KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
  kmf.init(ks, password);

  // Setup the trust manager factory.
  TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509");

  SSLContext sslc = SSLContext.getInstance("TLS");
  sslc.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);
  return sslc;

public static void main(String[] args) {
    createSSLContext("/trust-store.jks", "TrustStore"));

In windows you can try this solution too:

I created the keystore file from a Certificate authority CA .crt file in this way:

keytool -import -alias ca -keystore trust-store.jks -storepass TrustStore -trustcacerts -file ca.crt


Get values from other sheet using VBA

That will be (for you very specific example)




So get a F1 click and read about Worksheets collection, which contains Worksheet objects, which in turn has a Cells collection, holding Cell objects...

What is the current choice for doing RPC in Python?

XML-RPC is part of the Python standard library:

Why and how to fix? IIS Express "The specified port is in use"

Just to add to this, I had the full IIS feature turned on for one of my machines and it seemed to cause this to happen intermittently.

I also got random complaints about needing Admin rights to bind sites after a while, I assume that somehow it was looking at the full IIS config (Which does require admin as it's not a per-user file).

If you are stuck and nothing else is helping (and you don't want to just choose another port) then check you have removed this if it is present.

Read all worksheets in an Excel workbook into an R list with data.frames

Updated answer using readxl (22nd June 2015)

Since posting this question the readxl package has been released. It supports both xls and xlsx format. Importantly, in contrast to other excel import packages, it works on Windows, Mac, and Linux without requiring installation of additional software.

So a function for importing all sheets in an Excel workbook would be:

read_excel_allsheets <- function(filename, tibble = FALSE) {
    # I prefer straight data.frames
    # but if you like tidyverse tibbles (the default with read_excel)
    # then just pass tibble = TRUE
    sheets <- readxl::excel_sheets(filename)
    x <- lapply(sheets, function(X) readxl::read_excel(filename, sheet = X))
    if(!tibble) x <- lapply(x,
    names(x) <- sheets

This could be called with:

mysheets <- read_excel_allsheets("foo.xls")

Old Answer

Building on the answer provided by @mnel, here is a simple function that takes an Excel file as an argument and returns each sheet as a data.frame in a named list.


importWorksheets <- function(filename) {
    # filename: name of Excel file
    workbook <- loadWorkbook(filename)
    sheet_names <- getSheets(workbook)
    names(sheet_names) <- sheet_names
    sheet_list <- lapply(sheet_names, function(.sheet){
        readWorksheet(object=workbook, .sheet)})

Thus, it could be called with:


Timestamp Difference In Hours for PostgreSQL

extract(hour from age(now(),links.created)) gives you a floor-rounded count of the hour difference.

Cannot delete directory with Directory.Delete(path, true)

I´ve solved with this millenary technique (you can leave the Thread.Sleep on his own in the catch)

bool deleted = false;
                Directory.Delete(rutaFinal, true);                    
                deleted = true;
            catch (Exception e)
                string mensaje = e.Message;
                if( mensaje == "The directory is not empty.")
        } while (deleted == false);

FileProvider - IllegalArgumentException: Failed to find configured root

My issue was that I had overlapping names in the file paths for different types, like this:

    path="." />
    path="." />

After I changed the names ("cached_files") to be unique, I got rid of the error. My guess is that those paths are stored in some HashMap or something which does not allow duplicates.

Sending emails with Javascript

You can use this free service:

  1. Include the script:

<script src=""></script>

  1. Send an email using:
  "[email protected]",
  "[email protected]",
  "This is a subject",
  "this is the body",

'mvn' is not recognized as an internal or external command,

Add maven directory /bin to System variables under the name Path.

To check this, you can echo %PATH%

How do I bind onchange event of a TextBox using JQuery?

You must change the event name from "change" to "onchange":

        $("input#tags").bind("onchange", autoFill);

or use the shortcut binder method change:


Note that the onchange event usually fires when the user leave the input, so for auto-complete you better use the keydown event.

getApplication() vs. getApplicationContext()

It seems to have to do with context wrapping. Most classes derived from Context are actually a ContextWrapper, which essentially delegates to another context, possibly with changes by the wrapper.

The context is a general abstraction that supports mocking and proxying. Since many contexts are bound to a limited-lifetime object such as an Activity, there needs to be a way to get a longer-lived context, for purposes such as registering for future notifications. That is achieved by Context.getApplicationContext(). A logical implementation is to return the global Application object, but nothing prevents a context implementation from returning a wrapper or proxy with a suitable lifetime instead.

Activities and services are more specifically associated with an Application object. The usefulness of this, I believe, is that you can create and register in the manifest a custom class derived from Application and be certain that Activity.getApplication() or Service.getApplication() will return that specific object of that specific type, which you can cast to your derived Application class and use for whatever custom purpose.

In other words, getApplication() is guaranteed to return an Application object, while getApplicationContext() is free to return a proxy instead.

Can you create nested WITH clauses for Common Table Expressions?

we can create nested cte.please see the below cte in example

;with cte_data as 
Select * from [HumanResources].[Department]
),cte_data1 as
Select * from [HumanResources].[Department]

select * from cte_data,cte_data1

VBA Excel sort range by specific column

If the starting cell of the range and of the key is static, the solution can be very simple:

Range(Selection, Selection.End(xlToRight)).Select
Range(Selection, Selection.End(xlDown)).Select
Selection.Sort key1:=Range("B3", Range("B3").End(xlDown)), _
order1:=xlAscending, Header:=xlNo

The matching wildcard is strict, but no declaration can be found for element 'tx:annotation-driven'

This is for others (like me :) ). Don't forget to add the spring tx jar/maven dependency. Also correct configuration in appctx is:



, by mistake wrong configuration which others may have


i.e., extra "/spring-tx-3.1.xsd"


in other words what is there in xmlns(namespace) should have proper mapping in schemaLocation (namespace vs schema).

namespace here is :

schema Doc Of namespace is :

this schema of namespace later is mapped in jar to locate the path of actual xsd located in org.springframework.transaction.config

AttributeError: 'module' object has no attribute 'urlopen'

This works in Python 2.x.

For Python 3 look in the docs:

import urllib.request

with urllib.request.urlopen("") as url:
    s =
    # I'm guessing this would output the html source code ?

@Autowired and static method

Use AppContext. Make sure you create a bean in your context file.

private final static Foo foo = AppContext.getApplicationContext().getBean(Foo.class);

public static void randomMethod() {

Lightweight Javascript DB for use in Node.js

I'm only familiar with Mongo and Couch, but there's also one named Persistence.

Get query from java.sql.PreparedStatement

If you only want to log the query, then add 'logger' and 'profileSQL' to the jdbc url:


Then you will get the SQL statement below:

2016-01-14 10:09:43  INFO MySQL - FETCH created: Thu Jan 14 10:09:43 CST 2016 duration: 1 connection: 19130945 statement: 999 resultset: 0
2016-01-14 10:09:43  INFO MySQL - QUERY created: Thu Jan 14 10:09:43 CST 2016 duration: 1 connection: 19130945 statement: 999 resultset: 0 message: SET sql_mode='NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES'
2016-01-14 10:09:43  INFO MySQL - FETCH created: Thu Jan 14 10:09:43 CST 2016 duration: 1 connection: 19130945 statement: 999 resultset: 0
2016-01-14 10:09:43  INFO MySQL - QUERY created: Thu Jan 14 10:09:43 CST 2016 duration: 2 connection: 19130945 statement: 13 resultset: 17 message: select 1
2016-01-14 10:09:43  INFO MySQL - FETCH created: Thu Jan 14 10:09:43 CST 2016 duration: 0 connection: 19130945 statement: 13 resultset: 17
2016-01-14 10:09:43  INFO MySQL - QUERY created: Thu Jan 14 10:09:43 CST 2016 duration: 1 connection: 19130945 statement: 15 resultset: 18 message: select @@session.tx_read_only
2016-01-14 10:09:43  INFO MySQL - FETCH created: Thu Jan 14 10:09:43 CST 2016 duration: 0 connection: 19130945 statement: 15 resultset: 18
2016-01-14 10:09:43  INFO MySQL - QUERY created: Thu Jan 14 10:09:43 CST 2016 duration: 2 connection: 19130945 statement: 14 resultset: 0 message: update sequence set seq=seq+incr where name='demo' and seq=4602
2016-01-14 10:09:43  INFO MySQL - FETCH created: Thu Jan 14 10:09:43 CST 2016 duration: 0 connection: 19130945 statement: 14 resultset: 0

The default logger is:


Mysql jdbc property list:

Executing <script> injected by innerHTML after AJAX call

Another thing to do is to load the page with a script such as:

<div id="content" onmouseover='myFunction();$(this).prop( 'onmouseover', null );'>
<script type="text/javascript">
function myFunction() {
  //do something

This will load the page, then run the script and remove the event handler when the function has been run. This will not run immediately after an ajax load, but if you are waiting for the user to enter the div element, this will work just fine.

PS. Requires Jquery

Getting Textbox value in Javascript

The ID you are trying is an serverside.

That is going to render in the browser differently.

try to get the ID by watching the html in the Browser.

var TestVar = document.getElementById('ctl00_ContentColumn_txt_model_code').value;

this may works.

Or do that ClientID method. That also works but ultimately the browser will get the same thing what i had written.

fitting data with numpy

Note that you can use the Polynomial class directly to do the fitting and return a Polynomial instance.

from numpy.polynomial import Polynomial

p =, y, 4)

p uses scaled and shifted x values for numerical stability. If you need the usual form of the coefficients, you will need to follow with

pnormal = p.convert(domain=(-1, 1))

What is the difference between "expose" and "publish" in Docker?

Basically, you have three options:

  1. Neither specify EXPOSE nor -p
  2. Only specify EXPOSE
  3. Specify EXPOSE and -p

1) If you specify neither EXPOSE nor -p, the service in the container will only be accessible from inside the container itself.

2) If you EXPOSE a port, the service in the container is not accessible from outside Docker, but from inside other Docker containers. So this is good for inter-container communication.

3) If you EXPOSE and -p a port, the service in the container is accessible from anywhere, even outside Docker.

The reason why both are separated is IMHO because:

  • choosing a host port depends on the host and hence does not belong to the Dockerfile (otherwise it would be depending on the host),
  • and often it's enough if a service in a container is accessible from other containers.

The documentation explicitly states:

The EXPOSE instruction exposes ports for use within links.

It also points you to how to link containers, which basically is the inter-container communication I talked about.

PS: If you do -p, but do not EXPOSE, Docker does an implicit EXPOSE. This is because if a port is open to the public, it is automatically also open to other Docker containers. Hence -p includes EXPOSE. That's why I didn't list it above as a fourth case.

Checking if a key exists in a JS object

map.has(key) is the latest ECMAScript 2015 way of checking the existance of a key in a map. Refer to this for complete details.

Android Reading from an Input stream efficiently

Possibly somewhat faster than Jaime Soriano's answer, and without the multi-byte encoding problems of Adrian's answer, I suggest:

File file = new File("/tmp/myfile");
try {
    FileInputStream stream = new FileInputStream(file);

    int count;
    byte[] buffer = new byte[1024];
    ByteArrayOutputStream byteStream =
        new ByteArrayOutputStream(stream.available());

    while (true) {
        count =;
        if (count <= 0)
        byteStream.write(buffer, 0, count);

    String string = byteStream.toString();
    System.out.format("%d bytes: \"%s\"%n", string.length(), string);
} catch (IOException e) {

jQuery set radio button

In your selector you seem to be attempting to fetch some nested element of your radio button with a given id. If you want to check a radio button, you should select this radio button in the selector and not something else:

$('input:radio[name="cols"]').attr('checked', 'checked');

This assumes that you have the following radio button in your markup:

<input type="radio" name="cols" value="1" />

If your radio button had an id:

<input type="radio" name="cols" value="1" id="myradio" />

you could directly use an id selector:

$('#myradio').attr('checked', 'checked');

How to use JavaScript source maps (.map files)?

  • How can a developer use it?

I didn't find answer for this in the comments, here is how can be used:

  1. Don't link your file in your index.html file (no need for that)
  2. Minifiacation tools (good ones) add a comment to your .min.js file:


which will connect your .map file.

When the min.js and files are ready...

  1. Chrome: Open dev-tools, navigate to Sources tab, You will see sources folder, where un-minified applications files are kept.

How Do I Make Glyphicons Bigger? (Change Size?)

try to use heading, no need extra css

<h1 class="glyphicon glyphicon-plus"></h1>

How do I unload (reload) a Python module?

For Python 2 use built-in function reload():


For Python 2 and 3.2–3.3 use reload from module imp:

import imp

But imp is deprecated since version 3.4 in favor of importlib, so use:

import importlib


from importlib import reload

Android Completely transparent Status Bar?

Works for Android KitKat and above (For those who want to transparent the status bar and don't manipulate the NavigationBar, because all of these answers will transparent the NavigationBar too!)

The easiest way to achieve it:

Put these 3 lines of code in the styles.xml (v19) -> if you don't know how to have this (v19), just write them in your default styles.xml and then use alt+enter to automatically create it:

<item name="android:windowFullscreen">false</item>
<item name="android:windowContentOverlay">@null</item>
<item name="android:fitsSystemWindows">false</item>

And now, go to your MainActivity Class and put this Method out of onCreate in the class:

public static void setWindowFlag(Activity activity, final int bits, boolean on) {

    Window win = activity.getWindow();
    WindowManager.LayoutParams winParams = win.getAttributes();
    if (on) {
        winParams.flags |= bits;
    } else {
        winParams.flags &= ~bits;

Then put this code in the onCreate method of the Activity:

if (Build.VERSION.SDK_INT >= 19 && Build.VERSION.SDK_INT < 21) {
        setWindowFlag(this, WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS, true);
    if (Build.VERSION.SDK_INT >= 19) {
        getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
    //make fully Android Transparent Status bar
    if (Build.VERSION.SDK_INT >= 21) {
        setWindowFlag(this, WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS, false);

That's it!

Access denied for user 'root'@'localhost' (using password: YES) after new installation on Ubuntu

I had to be logged into Ubuntu as root in order to access Mariadb as root. It may have something to do with that "Harden ..." that it prompts you to do when you first install. So:

$ sudo su
[sudo] password for user: yourubunturootpassword
# mysql -r root -p
Enter password: yourmariadbrootpassword

and you're in.

jquery, selector for class within id

You can use the class selector along with descendant selector

$("#my_id .my_class")

XMLHttpRequest blocked by CORS Policy

I believe sideshowbarker 's answer here has all the info you need to fix this. If your problem is just No 'Access-Control-Allow-Origin' header is present on the response you're getting, you can set up a CORS proxy to get around this. Way more info on it in the linked answer

how to set windows service username and password through commandline

This works:

sc.exe config "[servicename]" obj= "[.\username]" password= "[password]"

Where each of the [bracketed] items are replaced with the true arguments. (Keep the quotes, but don't keep the brackets.)

Just keep in mind that:

  • The spacing in the above example matters. obj= "foo" is correct; obj="foo" is not.
  • '.' is an alias to the local machine, you can specify a domain there (or your local computer name) if you wish.
  • Passwords aren't validated until the service is started
  • Quote your parameters, as above. You can sometimes get by without quotes, but good luck.

How can I escape a double quote inside double quotes?

Make use of $"string".

In this example, it would be,

dbload=$"load data local infile \"'gfpoint.csv'\" into table $dbtable FIELDS TERMINATED BY ',' ENCLOSED BY '\"' LINES TERMINATED BY \"'\n'\" IGNORE 1 LINES"

Note(from the man page):

A double-quoted string preceded by a dollar sign ($"string") will cause the string to be translated according to the current locale. If the current locale is C or POSIX, the dollar sign is ignored. If the string is translated and replaced, the replacement is double-quoted.

Phone number validation Android

Given the rules you specified:

upto length 13 and including character + infront.

(and also incorporating the min length of 10 in your code)

You're going to want a regex that looks like this:


With the min and max lengths encoded in the regex, you can drop those conditions from your if() block.

Off topic: I'd suggest that a range of 10 - 13 is too limiting for an international phone number field; you're almost certain to find valid numbers that are both longer and shorter than this. I'd suggest a range of 8 - 20 to be safe.

[EDIT] OP states the above regex doesn't work due to the escape sequence. Not sure why, but an alternative would be:


[EDIT 2] OP now adds that the + sign should be optional. In this case, the regex needs a question mark after the +, so the example above would now look like this:


How to obtain a QuerySet of all rows, with specific fields for each one of them?

We can select required fields over values.


"element.dispatchEvent is not a function" js error caught in firebug of FF3.0

Change the following line

$(document).ready(function() {


jQuery(document).ready(function($) {

Swift 3 URLSession.shared() Ambiguous reference to member 'dataTask(with:completionHandler:) error (bug)

In my case error was in NSURL

let url = NSURL(string: urlString)

In Swift 3 you must write just URL:

let url = URL(string: urlString)

Create a one to many relationship using SQL Server

This is a simple example of a classic Order example. Each Customer can have multiple Orders, and each Order can consist of multiple OrderLines.

You create a relation by adding a foreign key column. Each Order record has a CustomerID in it, that points to the ID of the Customer. Similarly, each OrderLine has an OrderID value. This is how the database diagram looks:

enter image description here

In this diagram, there are actual foreign key constraints. They are optional, but they ensure integrity of your data. Also, they make the structure of your database clearer to anyone using it.

I assume you know how to create the tables themselves. Then you just need to define the relationships between them. You can of course define constraints in T-SQL (as posted by several people), but they're also easily added using the designer. Using SQL Management Studio, you can right-click the Order table, click Design (I think it may be called Edit under 2005). Then anywhere in the window that opens right-click and select Relationships.

You will get another dialog, on the right there should be a grid view. One of the first lines reads "Tables and Columns Specification". Click that line, then click again on the little [...] button that appears on the right. You will get this dialog:

Foreign key constraint

The Order table should already be selected on the right. Select the Customer table on the left dropdown. Then in the left grid, select the ID column. In the right grid, select the CustomerID column. Close the dialog, and the next. Press Ctrl+S to save.

Having this constraint will ensure that no Order records can exist without an accompanying Customer record.

To effectively query a database like this, you might want to read up on JOINs.

Creating an array from a text file in Bash

This answer says to use

mapfile -t myArray < file.txt

I made a shim for mapfile if you want to use mapfile on bash < 4.x for whatever reason. It uses the existing mapfile command if you are on bash >= 4.x

Currently, only options -d and -t work. But that should be enough for that command above. I've only tested on macOS. On macOS Sierra 10.12.6, the system bash is 3.2.57(1)-release. So the shim can come in handy. You can also just update your bash with homebrew, build bash yourself, etc.

It uses this technique to set variables up one call stack.

How to amend a commit without changing commit message (reusing the previous one)?

Another (silly) possibility is to git commit --amend <<< :wq if you've got vi(m) as $EDITOR.


In a more general case:

N( A union B) = N(A) + N(B) - N(A intersect B) 
= COUNTIFS(A1:A196,"Yes",J1:J196,"Agree")+COUNTIFS(A1:A196,"No",J1:J196,"Agree")-A1:A196,"Yes",A1:A196,"No")

Angular2 - Radio Button Binding

Here is some code I use that works with Angular 7

(Note: In the past I sometimes used info provided by the answer of Anthony Brenelière, which I appreciate. But, at least for Angular 7, this part:


I found to be unnecessary.)

My solution here has three advantages:

  1. Consistent with the most commonly recommended solutions. So it is good for new projects.
  2. Also allows radio button code to be similar to Flex/ActionScript code. This is personally important because I am translating Flex code to Angular. Like Flex/ActionScript code it allows code to work on a radio button object to check or uncheck or find out if a radio button is checked.
  3. Unlike most solutions you will see, it is very object-based. One advantage is organization: It groups together data binding fields of a radio button, such as selected, enabled, visible, and possibly others.

Example HTML:

       <input type="radio" id="byAllRadioButton"

      <input type="radio" id="byNameRadioButton"

Example TypeScript:

 findByRadioButtonGroup : UIRadioButtonGroupModel
    = new UIRadioButtonGroupModel("findByRadioButtonGroup",
                                  (groupValue : any) => this.handleCriteriaRadioButtonChange(groupValue)

  byAllRadioButton : UIRadioButtonControlModel
    = new UIRadioButtonControlModel("byAllRadioButton",
    this.findByRadioButtonGroup) ;

  byNameRadioButton : UIRadioButtonControlModel
    = new UIRadioButtonControlModel("byNameRadioButton",
    this.findByRadioButtonGroup) ;

  private handleCriteriaRadioButtonChange = (groupValue : any) : void => {

    if ( this.byAllRadioButton.selected ) {

      // Do something

    } else if ( this.byNameRadioButton.selected ) {

      // Do something

    } else {
      throw new Error("No expected radio button selected");

Two classes are used:

Radio Button Group Class:

export class UIRadioButtonGroupModel {

  private _dataBindingValue : any;

  constructor(private readonly debugName : string,
              private readonly initialDataBindingValue : any = null,   // Can be null or unspecified
              private readonly notifyOfChangeHandler : Function = null       // Can be null or unspecified
  ) {

    this._dataBindingValue = initialDataBindingValue;

  public get dataBindingValue() : any {

    return this._dataBindingValue;

  public set dataBindingValue(val : any) {

    this._dataBindingValue = val;
    if (this.notifyOfChangeHandler != null) {
      MyAngularUtils.callLater(this.notifyOfChangeHandler, this._dataBindingValue);

  public unselectRadioButton(valueOfOneRadioButton : any) {

    // Warning: This method probably never or almost never should be needed.
    // Setting the selected radio button to unselected probably should be avoided, since
    // the result will be that no radio button will be selected.  That is
    // typically not how radio buttons work.  But we allow it here.
    // Be careful in its use.

    if (valueOfOneRadioButton == this._dataBindingValue) {
      console.warn("Setting radio button group value to null");
      this.dataBindingValue = null;


Radio Button Class

export class UIRadioButtonControlModel {

  public enabled : boolean = true;
  public visible : boolean = true;

  constructor(public readonly debugName : string,
              public readonly MY_DATA_BINDING_VALUE : any,
              private readonly group : UIRadioButtonGroupModel,
              ) {


  public get selected() : boolean {

    return ( == this.MY_DATA_BINDING_VALUE);

  public set selected(doSelectMe : boolean) {

    if (doSelectMe) { = this.MY_DATA_BINDING_VALUE;
    } else {;


Best implementation for hashCode method for a collection

It is better to use the functionality provided by Eclipse which does a pretty good job and you can put your efforts and energy in developing the business logic.

How to find a number in a string using JavaScript?

var regex = /\d+/g;_x000D_
var string = "you can enter 30%-20% maximum 500 choices";_x000D_
var matches = string.match(regex);  // creates array from matches_x000D_

How to change facet labels?

This solution is very close to what @domi has, but is designed to shorten the name by fetching first 4 letters and last number.


# simulate some data
xy <- data.frame(hospital = rep(paste("Hospital #", 1:3, sep = ""), each = 30),
                 value = rnorm(90))

shortener <- function(string) {
  abb <- substr(string, start = 1, stop = 4) # fetch only first 4 strings
  num <- gsub("^.*(\\d{1})$", "\\1", string) # using regular expression, fetch last number
  out <- paste(abb, num) # put everything together

ggplot(xy, aes(x = value)) +
  theme_bw() +
  geom_histogram() +
  facet_grid(hospital ~ ., labeller = labeller(hospital = shortener))

enter image description here

How can I install a CPAN module into a local directory?

Other answers already on Stackoverflow:

From perlfaq8:

How do I keep my own module/library directory?

When you build modules, tell Perl where to install the modules.

For Makefile.PL-based distributions, use the INSTALL_BASE option when generating Makefiles:

perl Makefile.PL INSTALL_BASE=/mydir/perl

You can set this in your configuration so modules automatically install in your private library directory when you use the shell:

% cpan
cpan> o conf makepl_arg INSTALL_BASE=/mydir/perl
cpan> o conf commit

For Build.PL-based distributions, use the --install_base option:

perl Build.PL --install_base /mydir/perl

You can configure to automatically use this option too:

% cpan
cpan> o conf mbuildpl_arg '--install_base /mydir/perl'
cpan> o conf commit

Python "expected an indented block"

#option = 1
#while option != 0:

print ("MENU")
print("please make a selection")
print("1. count")
print("0. quit")
option = int(input("MAKE Your Selection  "))
if option == 1:
    print("1. count up")
    print("2. count down")
    print("0. go back")
    option = int(input("MAKE Your Selection  "))
    if option == 1:
        x = int(input("please enter a number   "))
        for x in range(1, x, 1):
            print (x)

    elif option == 2:
        x = int(input("please enter a number   "))
        for x in range(x, 0, -1):
            print (x) 
    elif option == 0:
        print("invalid command")
    print ("H!111")

You can try this code! It works.

What's the difference between an element and a node in XML?

An xml document is made of nested elements. An element begins at its opening tag and ends at its closing tag. You're probably seen <body> and </body> in html. Everything between the opening and closing tags is the element's content. If an element is defined by a self-closing tag (eg. <br/>) then its content is empty.

Opening tags can also specify attributes, eg. <p class="rant">. In this example the attribute name is 'class' and its value 'rant'.

The XML language has no such thing as a 'node'. Read the spec, the word doesn't occur.

Some people use the word 'node' informally to mean element, which is confusing because some parsers also give the word a technical meaning (identifying 'text nodes' and 'element nodes'). The exact meaning depends on the parser, so the word is ill-defined unless you state what parser you are using. If you mean element, say 'element'.

How to implode array with key and value without foreach in PHP

You could use PHP's array_reduce as well,

$a = ['Name' => 'Last Name'];

function acc($acc,$k)use($a){ return $acc .= $k.":".$a[$k].",";}

$imploded = array_reduce(array_keys($a), "acc");

Android Studio Gradle Already disposed Module

For me this happened when i deleted a module and built a new one with the same package name Solution:

Clean & Restart Studio

How to change ReactJS styles dynamically?

Ok, finally found the solution.

Probably due to lack of experience with ReactJS and web development...

    var Task = React.createClass({
    render: function() {
      var percentage = this.props.children + '%';
        <div className="ui-progressbar-value ui-widget-header ui-corner-left" style={{width : percentage}}/>

I created the percentage variable outside in the render function.

How can I select an element with multiple classes in jQuery?

Just mention another case with element:

E.g. <div id="title1" class="A B C">

Just type: $("div#title1.A.B.C")

How to pick a new color for each plotted line within a figure in matplotlib?

I usually use the second one of these:

from matplotlib.pyplot import cm
import numpy as np

#variable n below should be number of curves to plot

#version 1:

for i,c in zip(range(n),color):
   plt.plot(x, y,c=c)

#or version 2:

for i in range(n):
   plt.plot(x, y,c=c)

Example of 2: example plot with iter,next color

The developers of this app have not set up this app properly for Facebook Login?

There are a bunch of possible things which could trigger this error:

In your case, you just need to add your facebook account into either tester, developer or admin of your facebook app as you want to use that account to test.

But if you see the error upon clicking connect to facebook(before you have chance to enter facebook credentials), then it means your current facebook account detected from cookie is not a valid tester/developer/admin account for your app. Your could either add your account in or just hit and sign out(to remove the undesired cookie).

Arrow operator (->) usage in C

The -> operator makes the code more readable than the * operator in some situations.

Such as: (quoted from the EDK II project)

  IN EFI_BLOCK_IO_PROTOCOL          *This,
  IN UINT32                         MediaId,
  IN EFI_LBA                        Lba,
  IN UINTN                          BufferSize,
  OUT VOID                          *Buffer

  /// The revision to which the block IO interface adheres. All future
  /// revisions must be backwards compatible. If a future version is not
  /// back wards compatible, it is not the same GUID.
  UINT64              Revision;
  /// Pointer to the EFI_BLOCK_IO_MEDIA data for this device.

  EFI_BLOCK_RESET     Reset;
  EFI_BLOCK_READ      ReadBlocks;
  EFI_BLOCK_WRITE     WriteBlocks;
  EFI_BLOCK_FLUSH     FlushBlocks;


The _EFI_BLOCK_IO_PROTOCOL struct contains 4 function pointer members.

Suppose you have a variable struct _EFI_BLOCK_IO_PROTOCOL * pStruct, and you want to use the good old * operator to call it's member function pointer. You will end up with code like this:


But with the -> operator, you can write like this:


Which looks better?

Hadoop "Unable to load native-hadoop library for your platform" warning

I had the same issue. It's solved by adding following lines in .bashrc:

export HADOOP_OPTS="-Djava.library.path=$HADOOP_HOME/lib"

Pandas/Python: Set value of one column based on value in another column

Note the tilda that reverses the selection. It uses pandas methods (i.e. is faster than if/else).

df.loc[(df['c1'] == 'Value'), 'c2'] = 10
df.loc[~(df['c1'] == 'Value'), 'c2'] = df['c3']

TS1086: An accessor cannot be declared in ambient context

If it's just a library that's causing this, this will avoid the problem just fine. Typescript can be a pain on the neck sometimes so set this value on your tsconfig.json file.

"compilerOptions": {
    "skipLibCheck": true

how to get param in method post spring mvc?

It also works if you change the content type

    <form method="POST"
    id="frmRegister" name="frmRegister"

In the controller also add the header value as follows:

    @RequestMapping(value = "/create_customer", method = RequestMethod.POST, headers = "Content-Type=application/x-www-form-urlencoded")

How to center and crop an image to always appear in square shape with CSS?

    <img class="crop" src=""/>

<img src=""/>

div {
    width: 200px;
    height: 200px;
    overflow: hidden;
    margin: 10px;
    position: relative;
.crop {
    position: absolute;
    left: -100%;
    right: -100%;
    top: -100%;
    bottom: -100%;
    margin: auto; 
    height: auto;
    width: auto;

How to render a DateTime in a specific format in ASP.NET MVC 3?

I use the following approach to inline format and display a date property from the model.

@Html.ValueFor(model => model.MyDateTime, "{0:dd/MM/yyyy}")

Otherwise when populating a TextBox or Editor you could do like @Darin suggested, decorated the attribute with a [DisplayFormat] attribute.

MySql Proccesslist filled with "Sleep" Entries leading to "Too many Connections"?

The above solutions like run a query

SET session wait_timeout=600;

Will only work until mysql is restarted. For a persistant solution, edit mysql.conf and add after [mysqld]:

interactive_timeout = 300

Where 300 is the number of seconds you want.

Passing arguments to angularjs filters

Extending on pkozlowski.opensource's answer and using javascript array's builtin filter method a prettified solution could be this:

.filter('weDontLike', function(){
    return function(items, name){
        return items.filter(function(item) {
            return != name;

Here's the jsfiddle link.

More on Array filter here.

Allowed memory size of X bytes exhausted

ini_set('memory_limit', '128M'); 


php.ini  =>  memory_limit = 128M


php_value memory_limit 128M

How to get all columns' names for all the tables in MySQL?

The question was :

Is there a fast way of getting all COLUMN NAMES from all tables in MySQL, without having to list all the tables?

SQL to get all information for each column

select * from information_schema.columns
where table_schema = 'your_db'
order by table_name,ordinal_position


select COLUMN_NAME from information_schema.columns
where table_schema = 'your_db'
order by table_name,ordinal_position

Is there a way to list all resources in AWS

The AWS-provided tools are not useful because they are not comprehensive.

In my own quest to mitigate this problem and pull a list of all of my AWS resources, I found this:

I have not tested it yet, but it looks legit.

Device not detected in Eclipse when connected with USB cable

Please check whether your device is shown in the Eclipse device tab in Window > Open Perspective. If its not shown there then you need to install drivers for the the device. Once the device is visible in the Devices tab then change the launch settings for manual target. Once you launch your app then it will allow you to choose from the real device or the virtual devices

-bash: export: `=': not a valid identifier

I faced the same error and did some research to only see that there could be different scenarios to this error. Let me share my findings.

Scenario 1: There cannot be spaces beside the = (equals) sign

$ export TEMP_ENV = example-value
-bash: export: `=': not a valid identifier
// this is the answer to the question

$ export TEMP_ENV =example-value
-bash: export: `=example-value': not a valid identifier

$ export TEMP_ENV= example-value
-bash: export: `example-value': not a valid identifier

Scenario 2: Object value assignment should not have spaces besides quotes

$ export TEMP_ENV={ "key" : "json example" } 
-bash: export: `:': not a valid identifier
-bash: export: `json example': not a valid identifier
-bash: export: `}': not a valid identifier

Scenario 3: List value assignment should not have spaces between values

$ export TEMP_ENV=[1,2 ,3 ]
-bash: export: `,3': not a valid identifier
-bash: export: `]': not a valid identifier

I'm sharing these, because I was stuck for a couple of hours trying to figure out a workaround. Hopefully, it will help someone in need.

How to get the device's IMEI/ESN programmatically in android?

I use the following code to get the IMEI or use Secure.ANDROID_ID as an alternative, when the device doesn't have phone capabilities:

 * Returns the unique identifier for the device
 * @return unique identifier for the device
public String getDeviceIMEI() {
    String deviceUniqueIdentifier = null;
    TelephonyManager tm = (TelephonyManager) this.getSystemService(Context.TELEPHONY_SERVICE);
    if (null != tm) {
        deviceUniqueIdentifier = tm.getDeviceId();
    if (null == deviceUniqueIdentifier || 0 == deviceUniqueIdentifier.length()) {
        deviceUniqueIdentifier = Settings.Secure.getString(this.getContentResolver(), Settings.Secure.ANDROID_ID);
    return deviceUniqueIdentifier;

Is there a rule-of-thumb for how to divide a dataset into training and validation sets?

Last year, I took Prof: Andrew Ng’s online machine learning course. His recommendation was:

Training: 60%

Cross validation: 20%

Testing: 20%


Your attempt wasn't that bad. You have to do it with LIKE, yes.

In the manual it says:

Use LIKE to create an empty table based on the definition of another table, including any column attributes and indexes defined in the original table.

So you do:

CREATE TABLE New_Users  LIKE Old_Users;

Then you insert with


But you can not do it in one statement.

How to plot a very simple bar chart (Python, Matplotlib) using input *.txt file?

First, what you are looking for is a column or bar diagram, not really a histogram. A histogram is made from a frequency distribution of a continuous variable that is separated into bins. Here you have a column against separate labels.

To make a bar diagram with matplotlib, use the method. Have a look at this page of the matplotlib documentation that explains very well with examples and source code how to do it.

If it is possible though, I would just suggest that for a simple task like this if you could avoid writing code that would be better. If you have any spreadsheet program this should be a piece of cake because that's exactly what they are for, and you won't have to 'reinvent the wheel'. The following is the plot of your data in Excel:

Bar diagram plot in Excel

I just copied your data from the question, used the text import wizard to put it in two columns, then I inserted a column diagram.

How can I get just the first row in a result set AFTER ordering?

An alternative way:

FROM bla
WHERE finalDate = (SELECT MAX(finalDate) FROM bla) AND
      rownum = 1

typedef fixed length array

Here's a short example of why typedef array can be confusingly inconsistent. The other answers provide a workaround.

#include <stdio.h>
typedef char type24[3];

int func(type24 a) {
        type24 b;
        printf("sizeof(a) is %zu\n",sizeof(a));
        printf("sizeof(b) is %zu\n",sizeof(b));
        return 0;

int main(void) {
        type24 a;
        return func(a);

This produces the output

sizeof(a) is 8
sizeof(b) is 3

because type24 as a parameter is a pointer. (In C, arrays are always passed as pointers.) The gcc8 compiler will issue a warning by default, thankfully.

How to check if an element is visible with WebDriver

Verifying ele is visible.

public static boolean isElementVisible(final By by)
    throws InterruptedException {
        boolean value = false;

        if (driver.findElements(by).size() > 0) {
            value = true;
        return value;

One liner for If string is not null or empty else

This may help:

public string NonBlankValueOf(string strTestString)
    return String.IsNullOrEmpty(strTestString)? "0": strTestString;

Best way to define error codes/strings in Java?

A little late but, I was just looking for a pretty solution for myself. If you have different kind of message error you can add simple, custom message factory so that you can specify more details and format that you'd like later.

public enum Error {
    DATABASE(0, "A database error has occured. "), 
    DUPLICATE_USER(1, "User already exists. ");
    private String description = "";
    public Error changeDescription(String description) {
        this.description = description;
        return this;

Error genericError = Error.DATABASE;
Error specific = Error.DUPLICATE_USER.changeDescription("(Call Admin)");

EDIT: ok, using enum here is a little dangerous since you alter particular enum permanently. I guess better would be to change to class and use static fields, but than you cannot use '==' anymore. So I guess it's a good example what not to do, (or do it only during initialization) :)

How does setTimeout work in Node.JS?

The only way to ensure code is executed is to place your setTimeout logic in a different process.

Use the child process module to spawn a new node.js program that does your logic and pass data to that process through some kind of a stream (maybe tcp).

This way even if some long blocking code is running in your main process your child process has already started itself and placed a setTimeout in a new process and a new thread and will thus run when you expect it to.

Further complication are at a hardware level where you have more threads running then processes and thus context switching will cause (very minor) delays from your expected timing. This should be neglible and if it matters you need to seriously consider what your trying to do, why you need such accuracy and what kind of real time alternative hardware is available to do the job instead.

In general using child processes and running multiple node applications as separate processes together with a load balancer or shared data storage (like redis) is important for scaling your code.

Is Safari on iOS 6 caching $.ajax results?

I found one workaround that makes me curious as to why it works. Before reading Tadej's answer concerning ASP.NET web service, I was trying to come up with something that would work.

And I'm not saying that it's a good solution, but I just wanted to document it here.

main page: includes a JavaScript function, checkStatus(). The method calls another method which uses a jQuery AJAX call to update the html content. I used setInterval to call checkStatus(). Of course, I ran into the caching problem.

Solution: use another page to call the update.

On the main page, I set a boolean variable, runUpdate, and added the following to the body tag:

<iframe src="helper.html" style="display: none; visibility: hidden;"></iframe>

In the of helper.html:

<meta http-equiv="refresh" content="5">
<script type="text/javascript">
    if (parent.runUpdate) { parent.checkStatus(); }

So, if checkStatus() is called from the main page, I get the cached content. If I call checkStatus from the child page, I get updated content.

'Java' is not recognized as an internal or external command

In case you are using a laptop and do not have the Pause\Break button. For windows 10 users with 20h2 and above:

1 WIN ? type "About your PC" ? scroll at the bottom ? Advanced system settings ? Environment variables or WIN+R ? shell:::{bb06c0e4-d293-4f75-8a90-cb05b6477eee} to open Classic System Properties ? on the left side ? Advanced system settings ? Environment variables

Also for Windows 10 and Windows 7:

1 WIN ? This PC ? properties ? Advanced system settings ? Environment variables

  1. In the System variables section click on New…
  2. In Variable name write: JAVA_HOME
  3. In Variable value write: C:\Program Files\Java\jdk-15.0.2\bin, press OK

I have taken steps 2-4 from Vijay Bhatt

Adding a new system variable in UI

There is a bit faster way to set a system variable. Run a console (terminal) as an administrator.

General command synax to add a new variable:

setx variableName value /M

In our example, we would need to set it as

setx JAVA_HOME "C:\Program Files\Java\jdk-15.0.2\bin" /M`

Like this: Adding a new system variable using admin console

/M - flag specifies to set the variable in the system environment. After command execution, you should see the message: SUCCESS: Specified value was saved.

How can I check that it is added?

  1. Close your active terminal;
  2. Open your favorite terminal;
  3. Type java -version.

You should see something similar to this: Result image

Notice: User variables can be created w/o having a root (administrator privileges), whereas to create System variable; You need to open a console as a root.

I have used C:\Program Files\Java\jdk-15.0.2\bin as an example, in your case, it could be different from mine.

How can I create C header files

  1. Open your favorite text editor
  2. Create a new file named whatever.h
  3. Put your function prototypes in it


Example whatever.h

int f(int a);

Note: include guards (preprocessor commands) added thanks to luke. They avoid including the same header file twice in the same compilation. Another possibility (also mentioned on the comments) is to add #pragma once but it is not guaranteed to be supported on every compiler.

Example whatever.c

#include "whatever.h"

int f(int a) { return a + 1; }

And then you can include "whatever.h" into any other .c file, and link it with whatever.c's object file.

Like this:


#include "whatever.h"

int main(int argc, char **argv)
    printf("%d\n", f(2)); /* prints 3 */
    return 0;

To compile it (if you use GCC):

$ gcc -c whatever.c -o whatever.o
$ gcc -c sample.c -o sample.o

To link the files to create an executable file:

$ gcc sample.o whatever.o -o sample

You can test sample:

$ ./sample

Add string in a certain position in Python

This seems very easy:

>>> hash = "355879ACB6"
>>> hash = hash[:4] + '-' + hash[4:]
>>> print hash

However if you like something like a function do as this:

def insert_dash(string, index):
    return string[:index] + '-' + string[index:]

print insert_dash("355879ACB6", 5)

C# Example of AES256 encryption using System.Security.Cryptography.Aes

public class AesCryptoService
    private static byte[] Key = Encoding.ASCII.GetBytes(@"qwr{@^h`h&_`50/ja9!'dcmh3!uw<&=?");
    private static byte[] IV = Encoding.ASCII.GetBytes(@"9/\~V).A,lY&=t2b");

    public static string EncryptStringToBytes_Aes(string plainText)
        if (plainText == null || plainText.Length <= 0)
            throw new ArgumentNullException("plainText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("IV");
        byte[] encrypted;

        using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
            aesAlg.Key = Key;
            aesAlg.IV = IV;
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.Padding = PaddingMode.PKCS7;

            ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

            using (MemoryStream msEncrypt = new MemoryStream())
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    encrypted = msEncrypt.ToArray();
        return Convert.ToBase64String(encrypted);

    public static string DecryptStringFromBytes_Aes(string Text)
        if (Text == null || Text.Length <= 0)
            throw new ArgumentNullException("cipherText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("IV");

        string plaintext = null;
        byte[] cipherText = Convert.FromBase64String(Text.Replace(' ', '+'));

        using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
            aesAlg.Key = Key;
            aesAlg.IV = IV;
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.Padding = PaddingMode.PKCS7;

            ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

            using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        plaintext = srDecrypt.ReadToEnd();


        return plaintext;

Another Repeated column in mapping for entity error

@Column(name = "COLUMN_NAME", nullable = false)
public Long getId() {
    return id;

@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, targetEntity = SomeCustomEntity.class)
@JoinColumn(name = "COLUMN_NAME", referencedColumnName = "COLUMN_NAME", nullable = false, updatable = false, insertable = false)
@org.hibernate.annotations.Cascade(value = org.hibernate.annotations.CascadeType.ALL)
public List<SomeCustomEntity> getAbschreibareAustattungen() {
    return abschreibareAustattungen;

If you have already mapped a column and have accidentaly set the same values for name and referencedColumnName in @JoinColumn hibernate gives the same stupid error


Caused by: org.hibernate.MappingException: Repeated column in mapping for entity: com.testtest.SomeCustomEntity column: COLUMN_NAME (should be mapped with insert="false" update="false")

C# find highest array value and index

This is not the most glamorous way but works.

(must have using System.Linq;)

 int maxValue = anArray.Max();
 int maxIndex = anArray.ToList().IndexOf(maxValue);

TypeError: can only concatenate list (not "str") to list

Let me fix your code

inventory=["sword", "potion", "armour", "bow"]
print("\ncommands: use (remove) and pickup (add)")
selection=input("choose a command [use/pickup]")

if selection == "use":
    inventory.remove(input("What do you want to use? "))
elif selection == "pickup":
    add=input("What do you want to pickup? ")
    newinv=inventory+[str(add)] #use '[str(add)]' or list(str(add))

The error is you are adding string and list, you should use list or [] to make the string become list type

What are all the common ways to read a file in Ruby?

content = `cat file`

I think this method is the most "uncommon" one. Maybe it is kind of tricky, but it works if cat is installed.

Truncate all tables in a MySQL database in one command?

I know this isn't exactly one command, but the desired result can be achieved from within phpMyAdmin by following these steps:

  1. Select (all) tables to be removed (Check All)
  2. Select "Drop" / "Truncate" from the "With selected:" list
  3. On the confirmation page ("Do you really want to:") copy the query (everything with the red background)
  4. Go at the top and click on SQL and write: "SET FOREIGN_KEY_CHECKS=0;" then paste the previously copied query
  5. Click "Go"

The idea is to quickly get all the tables from the database (which you do in 5 seconds and 2 clicks) but disable foreign key checks first. No CLI and no dropping the database and adding it again.

Python != operation vs "is not"

None is a singleton, therefore identity comparison will always work, whereas an object can fake the equality comparison via .__eq__().

Loop through files in a folder in matlab

At first, you must specify your path, the path that your *.csv files are in there

path = 'f:\project\dataset'

You can change it based on your system.


use dir function :

files = dir (strcat(path,'\*.csv'))

L = length (files);

for i=1:L
   % process the image in here

pwd also can be used.

How to copy a selection to the OS X clipboard

If the clipboard is enabled, you can copy a selected region to the clipboard by hitting "*y

To see if it is enabled, run vim --version and look for +clipboard or -clipboard. For example, it's not enabled by default on my 10.5.6 box:

% which vim
% vim --version
VIM - Vi IMproved 7.2 (2008 Aug 9, compiled Nov 11 2008 17:20:43)
Included patches: 1-22
Compiled by [email protected]
Normal version without GUI.  Features included (+) or not (-):
-clientserver -clipboard +cmdline_compl +cmdline_hist +cmdline_info +comments

If it had been compiled with +clipboard, I'd be able to use the "* register to access the system clipboard.

I downloaded the 7.2 source and compiled it (easy as tar xjf && cd vim72 && ./configure && make && sudo make install), and the clipboard was enabled:

% which vim
% vim --version
VIM - Vi IMproved 7.2 (2008 Aug 9, compiled Mar 24 2009 17:31:52)
Compiled by [email protected]
Normal version with GTK2 GUI.  Features included (+) or not (-):
+clientserver +clipboard +cmdline_compl +cmdline_hist +cmdline_info +comments

However, even after compiling, I couldn't copy to the clipboard when running vim in, only in

ProcessBuilder: Forwarding stdout and stderr of started processes without blocking the main thread

It's really surprising to me that the redirection methods in ProcessBuilder don't accept an OutputStream, only File. Yet another proof of forced boilerplate code that Java forces you to write.

That said, let's look at a list of comprehensive options:

  1. If you want the process output to simply be redirected to its parent's output stream, inheritIO will do the job.
  2. If you want the process output to go to a file, use redirect*(file).
  3. If you want the process output to go to a logger, you need to consume the process InputStream in a separate thread. See the answers that use a Runnable or CompletableFuture. You can also adapt the code below to do this.
  4. If you want to the process output to go to a PrintWriter, that may or may not be the stdout (very useful for testing), you can do the following:
static int execute(List<String> args, PrintWriter out) {
    ProcessBuilder builder = new ProcessBuilder()
    Process process = null;
    boolean complete = false;
    try {
        process = builder.start();
        redirectOut(process.getInputStream(), out)
                .orTimeout(TIMEOUT, TimeUnit.SECONDS);
        complete = process.waitFor(TIMEOUT, TimeUnit.SECONDS);
    } catch (IOException e) {
        throw new UncheckedIOException(e);
    } catch (InterruptedException e) {
        LOG.warn("Thread was interrupted", e);
    } finally {
        if (process != null && !complete) {
            LOG.warn("Process {} didn't finish within {} seconds", args.get(0), TIMEOUT);
            process = process.destroyForcibly();

    return process != null ? process.exitValue() : 1;

private static CompletableFuture<Void> redirectOut(InputStream in, PrintWriter out) {
    return CompletableFuture.runAsync(() -> {
        try (
                InputStreamReader inputStreamReader = new InputStreamReader(in);
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader)
        ) {
        } catch (IOException e) {
            LOG.error("Failed to redirect process output", e);

Advantages of the code above over the other answers thus far:

  1. redirectErrorStream(true) redirects the error stream to the output stream, so that we only have to bother with one.
  2. CompletableFuture.runAsync runs from the ForkJoinPool. Note that this code doesn't block by calling get or join on the CompletableFuture but sets a timeout instead on its completion (Java 9+). There's no need for CompletableFuture.supplyAsync because there's nothing really to return from the method redirectOut.
  3. BufferedReader.lines is simpler than using a while loop.

header location not working in my php code

Create config.php and put the code it will work

CodeIgniter activerecord, retrieve last insert id?

List of details which helps in requesting id and queries are

For fetching Last inserted Id :This will fetching the last records from the table


Fetching SQL query add this after modal request


Mismatched anonymous define() module

Be aware that some browser extensions can add code to the pages. In my case I had an "Emmet in all textareas" plugin that messed up with my requireJs. Make sure that no extra code is beign added to your document by inspecting it in the browser.

Truncate string in Laravel blade templates

Update for Laravel 7.*: Fluent Strings i.e a more fluent, object-oriented interface for working with string values, allowing you to chain multiple string operations together using a more readable syntax compared to traditional string operations.

limit Example :

$truncated = Str::of('The quick brown fox jumps over the lazy dog')->limit(20);


The quick brown fox...

words Example :

$string = Str::of('Perfectly balanced, as all things should be.')->words(3, ' >>>');


Perfectly balanced, as >>>

Update for Laravel 6.* : You require this package to work all laravel helpers composer require laravel/helpers

For using helper in controller, don't forget to include/use class as well

use Illuminate\Support\Str;

Laravel 5.8 Update

This is for handling characters from the string :

{!! Str::limit('Lorem ipsum dolor', 10, ' ...') !!}


Lorem ipsu ... 

This is for handling words from the string :

{!! Str::words('Lorem ipsum dolor', 2, ' ...') !!}


Lorem ipsum ... 

Here is the latest helper documentation for handling string Laravel Helpers

Max retries exceeded with URL in requests

just import time and add :


somewhere in the for loop, to avoid sending too many request to the server in a short time. the number 6 means: 6 seconds. keep testing numbers starting from 1, until you reach the minimum seconds that will help to avoid the problem.

How to convert a normal Git repository to a bare one?

First, backup your existing repo:

(a)  mkdir backup

(b)  cd backup

(c)  git clone non_bare_repo

Second, run the following:

git clone --bare -l non_bare_repo new_bare_repo

How to convert InputStream to FileInputStream

Long story short: Don't use FileInputStream as a parameter or variable type. Use the abstract base class, in this case InputStream instead.

How to use PHP string in mySQL LIKE query?

You have the syntax wrong; there is no need to place a period inside a double-quoted string. Instead, it should be more like

$query = mysql_query("SELECT * FROM table WHERE the_number LIKE '$prefix%'");

You can confirm this by printing out the string to see that it turns out identical to the first case.

Of course it's not a good idea to simply inject variables into the query string like this because of the danger of SQL injection. At the very least you should manually escape the contents of the variable with mysql_real_escape_string, which would make it look perhaps like this:

$sql = sprintf("SELECT * FROM table WHERE the_number LIKE '%s%%'",
$query = mysql_query($sql);

Note that inside the first argument of sprintf the percent sign needs to be doubled to end up appearing once in the result.

How to set thymeleaf th:field value from other variable

You could approach this method.

Instead of using th:field use html id & name. Set value using th:value

<input class="form-control"
           th:value="${}" id="clientName" name="clientName" />

Hope this will help you

jquery how to catch enter key and change event to tab

I know this is rather old, but I was looking for the same answer and found that the chosen solution did not obey the tabIndex. I have hence modified it to the following which works for me. Please note that maxTabNumber is a global variable that holds the maximum number of tabbable input fields

  $('input').on("keypress", function (e) {_x000D_
                if (e.keyCode == 13) {_x000D_
                    var inputs = $(this).parents("form").eq(0).find(":input");_x000D_
                    var idx = inputs.index(this);_x000D_
                    var tabIndex = parseInt($(this).attr("tabindex"));_x000D_
                    tabIndex = (tabIndex + 1) % (maxTabNumber + 1);_x000D_
                    if (tabIndex == 0) { tabIndex = 1; }_x000D_
                    $('[tabindex=' + tabIndex + ']').focus();_x000D_
                    $('[tabindex=' + tabIndex + ']').select();_x000D_
                    return false;_x000D_

How do I script a "yes" response for installing programs?

Although this may be more complicated/heavier-weight than you want, one very flexible way to do it is using something like Expect (or one of the derivatives in another programming language).

Expect is a language designed specifically to control text-based applications, which is exactly what you are looking to do. If you end up needing to do something more complicated (like with logic to actually decide what to do/answer next), Expect is the way to go.

Case objects vs Enumerations in Scala

Case objects already return their name for their toString methods, so passing it in separately is unnecessary. Here is a version similar to jho's (convenience methods omitted for brevity):

trait Enum[A] {
  trait Value { self: A => }
  val values: List[A]

sealed trait Currency extends Currency.Value
object Currency extends Enum[Currency] {
  case object EUR extends Currency
  case object GBP extends Currency
  val values = List(EUR, GBP)

Objects are lazy; by using vals instead we can drop the list but have to repeat the name:

trait Enum[A <: {def name: String}] {
  trait Value { self: A =>
    _values :+= this
  private var _values = List.empty[A]
  def values = _values

sealed abstract class Currency(val name: String) extends Currency.Value
object Currency extends Enum[Currency] {
  val EUR = new Currency("EUR") {}
  val GBP = new Currency("GBP") {}

If you don't mind some cheating, you can pre-load your enumeration values using the reflection API or something like Google Reflections. Non-lazy case objects give you the cleanest syntax:

trait Enum[A] {
  trait Value { self: A =>
    _values :+= this
  private var _values = List.empty[A]
  def values = _values

sealed trait Currency extends Currency.Value
object Currency extends Enum[Currency] {
  case object EUR extends Currency
  case object GBP extends Currency

Nice and clean, with all the advantages of case classes and Java enumerations. Personally, I define the enumeration values outside of the object to better match idiomatic Scala code:

object Currency extends Enum[Currency]
sealed trait Currency extends Currency.Value
case object EUR extends Currency
case object GBP extends Currency

No module named 'openpyxl' - Python 3.4 - Ubuntu

You have to install it explixitly using the python package manager as

  1. pip install openpyxl for Python 2
  2. pip3 install openpyxl for Python 3

Start ssh-agent on login

So I used to use the approaches described above, but I kind of prefer the agent to die when my last bash session ends. This is a bit longer than the other solutions, but its my preferred approach. The basic idea is that the first bash session starts the ssh-agent. Then each additional bash session checks for the config file (~/.ssh/.agent_env). If that is there and there is a session running then source the environment and create a hardlink to the socket file in /tmp (needs to be on the same filesystem as the original socket file). As bash sessions shut down each deletes its own hardlink. The last session to close will find that the hardlinks have 2 links (the hardlink and the original), removal of the processes own socket and killing of the process will result in 0, leaving a clean environment after the last bash session closes.

# Start ssh-agent to keep you logged in with keys, use `ssh-add` to log in
agent=`pgrep ssh-agent -u $USER` # get only your agents           
if [[ "$agent" == "" || ! -e ~/.ssh/.agent_env ]]; then
    # if no agents or environment file is missing create a new one
    # remove old agents / environment variable files
    kill $agent running
    rm ~/.ssh/.agent_env 

    # restart
    eval `ssh-agent` 
    echo 'export SSH_AUTH_SOCK'=$SSH_AUTH_SOCK >> ~/.ssh/.agent_env             
    echo 'export SSH_AGENT_PID'=$SSH_AGENT_PID >> ~/.ssh/.agent_env             

# create our own hardlink to the socket (with random name)           
source ~/.ssh/.agent_env                                                    
ln -T $SSH_AUTH_SOCK $MYSOCK                                                
export SSH_AUTH_SOCK=$MYSOCK                                                

    # if we are the last holder of a hardlink, then kill the agent
    nhard=`ls -l $SSH_AUTH_SOCK | awk '{print $2}'`                             
    if [[ "$nhard" -eq 2 ]]; then                                               
        rm ~/.ssh/.agent_env                                                    
        ssh-agent -k                                                            
    rm $SSH_AUTH_SOCK                                                           
trap end_agent EXIT                                                             
set +x              

grep's at sign caught as whitespace

After some time with Google I asked on the ask ubuntu chat room.

A user there was king enough to help me find the solution I was looking for and i wanted to share so that any following suers running into this may find it:

grep -P "(^|\s)abc(\s|$)" gives the result I was looking for. -P is an experimental implementation of perl regexps.

grepping for abc and then using filters like grep -v '@abc' (this is far from perfect...) should also work, but my patch does something similar.

mysql -> insert into tbl (select from another table) and some default values

INSERT INTO def (field_1, field_2, field3) 
('$field_1', (SELECT id_user from user_table where name = 'jhon'), '$field3')

How to choose multiple files using File Upload Control?

The FileUpload.AllowMultiple property in .NET 4.5 and higher will allow you the control to select multiple files.

Below 4.5 like 4.0(vs 2010) we can use jquery for multiple file upload in single control,using,2 js files: and

in aspx file upload tag,add like class="multi"

<asp:FileUpload ID="FileUpload1" class="multi" runat="server" />

If you want working example go to link download sample.

JRE 1.7 - java version - returns: java/lang/NoClassDefFoundError: java/lang/Object

If you install a 64-bit version without first installing 32-bit, this error will occur despite fixing all of the other issues. I have a brand new Dell i7 64-bit Windows 10 Pro machine running Java 8u71. After having added my %path% and %classpath% to environment variables and trying several other fixes, uninstalling 64-bit, installing 32-bit then reinstalling 64-bit fixed it.

Some of the issues, like not having your files unpacked, etc. that have been mentioned as possible causes may still be causing issues, but if you don't do this, as well, the other fixes won't work.

Send auto email programmatically

It might be an easiest way-

    String recipientList = mEditTextTo.getText().toString();
    String[] recipients = recipientList.split(",");

    String subject = mEditTextSubject.getText().toString();
    String message = mEditTextMessage.getText().toString();

    Intent intent = new Intent(Intent.ACTION_SEND);
    intent.putExtra(Intent.EXTRA_EMAIL, recipients);
    intent.putExtra(Intent.EXTRA_SUBJECT, subject);
    intent.putExtra(Intent.EXTRA_TEXT, message);

    startActivity(Intent.createChooser(intent, "Choose an email client"));

tkinter: how to use after method

You need to give a function to be called after the time delay as the second argument to after:

after(delay_ms, callback=None, *args)

Registers an alarm callback that is called after a given time.

So what you really want to do is this:

tiles_letter = ['a', 'b', 'c', 'd', 'e']

def add_letter():
    rand = random.choice(tiles_letter)
    tile_frame = Label(frame, text=rand)
    root.after(500, add_letter)
    tiles_letter.remove(rand)  # remove that tile from list of tiles

root.after(0, add_letter)  # add_letter will run as soon as the mainloop starts.

You also need to schedule the function to be called again by repeating the call to after inside the callback function, since after only executes the given function once. This is also noted in the documentation:

The callback is only called once for each call to this method. To keep calling the callback, you need to reregister the callback inside itself

Note that your example will throw an exception as soon as you've exhausted all the entries in tiles_letter, so you need to change your logic to handle that case whichever way you want. The simplest thing would be to add a check at the beginning of add_letter to make sure the list isn't empty, and just return if it is:

def add_letter():
    if not tiles_letter:
    rand = random.choice(tiles_letter)
    tile_frame = Label(frame, text=rand)
    root.after(500, add_letter)
    tiles_letter.remove(rand)  # remove that tile from list of tiles


Java 8 stream reverse order

How about this utility method?

public static <T> Stream<T> getReverseStream(List<T> list) {
    final ListIterator<T> listIt = list.listIterator(list.size());
    final Iterator<T> reverseIterator = new Iterator<T>() {
        public boolean hasNext() {
            return listIt.hasPrevious();

        public T next() {
            return listIt.previous();
            Spliterator.ORDERED | Spliterator.IMMUTABLE), false);

Seems to work with all cases without duplication.

Converting Float to Dollars and Cents

Personally, I like this much better (which, granted, is just a different way of writing the currently selected "best answer"):

money = float(1234.5)
print('$' + format(money, ',.2f'))

Or, if you REALLY don't like "adding" multiple strings to combine them, you could do this instead:

money = float(1234.5)
print('${0}'.format(format(money, ',.2f')))

I just think both of these styles are a bit easier to read. :-)

(of course, you can still incorporate an If-Else to handle negative values as Eric suggests too)

How to I say Is Not Null in VBA

Use Not IsNull(Fields!W_O_Count.Value)

When is it appropriate to use C# partial classes?

If you have a sufficiently large class that doesn't lend itself to effective refactoring, separating it into multiple files helps keep things organized.

For instance, if you have a database for a site containing a discussion forum and a products system, and you don't want to create two different providers classes (NOT the same thing as a proxy class, just to be clear), you can create a single partial class in different files, like

MyProvider.cs - core logic

MyProvider.Forum.cs - methods pertaining specifically to the forum

MyProvider.Product.cs - methods for products

It's just another way to keep things organized.

Also, as others have said, it's about the only way to add methods to a generated class without running the risk of having your additions destroyed the next time the class is regenerated. This comes in handy with template-generated (T4) code, ORMs, etc.

Plot multiple columns on the same graph in R

A very simple solution:

df <- read.csv("df.csv",sep=",",head=T)
x <- cbind(df$Xax,df$Xax,df$Xax,df$Xax)
y <- cbind(df$A,df$B,df$C,df$D)

please note it just plots the data and it does not plot any regression line.

Setting the default active profile in Spring-boot

Put this in the

public static void main(String[] args) throws UnknownHostException {
    SpringApplication app = new SpringApplication(App.class);
    SimpleCommandLinePropertySource source = new SimpleCommandLinePropertySource(args);
    if (!source.containsProperty("") &&
            !System.getenv().containsKey("SPRING_PROFILES_ACTIVE")) {


This is how it is done in JHipster

How to change the default message of the required field in the popover of form-control in bootstrap?

Combination of Mritunjay and Bartu's answers are full answer to this question. I copying the full example.

<input class="form-control" type="email"  required="" placeholder="username"
 oninvalid="this.setCustomValidity('Please Enter valid email')"


this.setCustomValidity('Please Enter valid email')" - Display the custom message on invalidated of the field

oninput="setCustomValidity('')" - Remove the invalidate message on validated filed.

Where is the Keytool application?

For me it turned out to be in c/Program Files/Java/jdk1.7.0_25/bin (Windows 8). A more general answer to this question is that it will most likely be in the bin sub directory of wherever your jdk is installed.

Why do I need to override the equals and hashCode methods in Java?

IMHO, it's as per the rule says - If two objects are equal then they should have same hash, i.e., equal objects should produce equal hash values.

Given above, default equals() in Object is == which does comparison on the address, hashCode() returns the address in integer(hash on actual address) which is again distinct for distinct Object.

If you need to use the custom Objects in the Hash based collections, you need to override both equals() and hashCode(), example If I want to maintain the HashSet of the Employee Objects, if I don't use stronger hashCode and equals I may endup overriding the two different Employee Objects, this happen when I use the age as the hashCode(), however I should be using the unique value which can be the Employee ID.

How to remove old and unused Docker images

How to remove a tagged image

  1. docker rmi the tag first

  2. docker rmi the image.

    # that can be done in one docker rmi call e.g.: # docker rmi <repo:tag> <imageid>

(this works Nov 2016, Docker version 1.12.2)


$ docker images 
REPOSITORY              TAG                 IMAGE ID            CREATED             SIZE
usrxx/the-application   16112805            011fd5bf45a2        12 hours ago        5.753 GB
usryy/the-application   vx.xx.xx            5af809583b9c        3 days ago          5.743 GB
usrzz/the-application   vx.xx.xx            eef00ce9b81f        10 days ago         5.747 GB
usrAA/the-application   vx.xx.xx            422ba91c71bb        3 weeks ago         5.722 GB
usrBB/the-application   v1.00.18            a877aec95006        3 months ago        5.589 GB

$ docker rmi usrxx/the-application:16112805 && docker rmi 011fd5bf45a2
$ docker rmi usryy/the-application:vx.xx.xx && docker rmi 5af809583b9c
$ docker rmi usrzz/the-application:vx.xx.xx eef00ce9b81f
$ docker rmi usrAA/the-application:vx.xx.xx 422ba91c71bb
$ docker rmi usrBB/the-application:v1.00.18 a877aec95006

e.g. Scripted remove anything older than 2 weeks.

IMAGESINFO=$(docker images --no-trunc --format '{{.ID}} {{.Repository}} {{.Tag}} {{.CreatedSince}}' |grep -E " (weeks|months|years)")
TAGS=$(echo "$IMAGESINFO" | awk '{ print $2 ":" $3 }' )
IDS=$(echo "$IMAGESINFO" | awk '{ print $1 }' )
echo remove old images TAGS=$TAGS IDS=$IDS
for t in $TAGS; do docker rmi $t; done
for i in $IDS; do docker rmi $i; done

Is there a way to remove the separator line from a UITableView?

In Swift:

tableView.separatorStyle = .None

How to ISO 8601 format a Date with Timezone Offset in JavaScript?

The below should work properly, and for all browsers (thanks to @MattJohnson for the tip)

Date.prototype.toIsoString = function() {_x000D_
    var tzo = -this.getTimezoneOffset(),_x000D_
        dif = tzo >= 0 ? '+' : '-',_x000D_
        pad = function(num) {_x000D_
            var norm = Math.floor(Math.abs(num));_x000D_
            return (norm < 10 ? '0' : '') + norm;_x000D_
    return this.getFullYear() +_x000D_
        '-' + pad(this.getMonth() + 1) +_x000D_
        '-' + pad(this.getDate()) +_x000D_
        'T' + pad(this.getHours()) +_x000D_
        ':' + pad(this.getMinutes()) +_x000D_
        ':' + pad(this.getSeconds()) +_x000D_
        dif + pad(tzo / 60) +_x000D_
        ':' + pad(tzo % 60);_x000D_
var dt = new Date();_x000D_

Setting query string using Fetch GET request

You can use #stringify from query string

import { stringify } from 'query-string';


Converting Secret Key into a String and Vice Versa

You don't want to use .toString().

Notice that SecretKey inherits from, which itself inherits from Serializable. So the key here (no pun intended) is to serialize the key into a ByteArrayOutputStream, get the byte[] array and store it into the db. The reverse process would be to get the byte[] array off the db, create a ByteArrayInputStream offf the byte[] array, and deserialize the SecretKey off it...

... or even simpler, just use the .getEncoded() method inherited from (which is a parent interface of SecretKey). This method returns the encoded byte[] array off Key/SecretKey, which you can store or retrieve from the database.

This is all assuming your SecretKey implementation supports encoding. Otherwise, getEncoded() will return null.


You should look at the Key/SecretKey javadocs (available right at the start of a google page):

Or this from CodeRanch (also found with the same google search):

Please initialize the log4j system properly. While running web service

You have to create your own in the classpath folder.

Perform Button click event when user press Enter key in Textbox

Codeproject has a complete solution for this:

and like the article says: "decide which solution best fits your needs"

=================== EDITED ANSWER ============================

The link mentioned above, talks about two ways of capturing the "Enter Key" event:

Javascript (bind the onKeyPress event to the object and create a javascript function to check which key was pressed and do your logic)

_Page_Load in code behind:_

 //Add the javascript so we know where we want the enter key press to go
if (!IsPostBack)
                   "doClick('" + btnSearch.ClientID + "',event)");
                  "doClick('" + btnSearch.ClientID + "',event)");

Javascript code:

<SCRIPT type=text/javascript>
    function doClick(buttonName,e)
        //the purpose of this function is to allow the enter key to 
        //point to the correct button to click.
        var key;

              key = window.event.keyCode;     //IE
              key = e.which;     //firefox

        if (key == 13)
            //Get the button the user wants to have clicked
            var btn = document.getElementById(buttonName);
            if (btn != null)
            { //If we find the button click it
                event.keyCode = 0

Panel Control

<asp:Panel ID="panSearch" runat="server" DefaultButton="btnSearch2" Width="100%" >
    <asp:TextBox ID="txtboxFirstName2" runat="server" ></asp:TextBox>


Notice that the Panel tag has a property called DefaultButton. You set this property to the button ID of the button you want to be clicked on an Enter key press event. So any text box inside of the Panel will direct its Enter key press to the button set in the DefaultButton property of the Panel

React-router v4 this.props.history.push(...) not working

I had similar symptoms, but my problem was that I was nesting BrowserRouter

Do not nest BrowserRouter, because the history object will refer to the nearest BrowserRouter parent. So when you do a history.push(targeturl) and that targeturl it's not in that particular BrowserRouter it won't match any of it's route, so it will not load any sub-component.


Nest the Switch without wrapping it with a BrowserRouter


Let's consider this App.js file

    <Route exact path="/nestedrouter" component={NestedRouter}  />
    <Route exact path="/target" component={Target}  />

Instead of doing this in the NestedRouter.js file

    <Route exact path="/nestedrouter/" component={NestedRouter}  />
    <Route exact path="/nestedrouter/subroute" component={SubRoute}  />

Simply remove the BrowserRouter from NestedRouter.js file

    <Route exact path="/nestedrouter/" component={NestedRouter}  />
    <Route exact path="/nestedrouter/subroute" component={SubRoute}  />

Remove non-ASCII characters from CSV

I tried all the solutions and nothing worked. The following, however, does:

tr -cd '\11\12\15\40-\176'

Which I found here:

My problem needed it in a series of piped programs, not directly from a file, so modify as needed.

Displaying the build date

it could be Assembly execAssembly = Assembly.GetExecutingAssembly(); var creationTime = new FileInfo(execAssembly.Location).CreationTime; // "2019-09-08T14:29:12.2286642-04:00"

How to recursively find and list the latest modified files in a directory with subdirectories and times

Ignoring hidden files — with nice & fast time stamp

Handles spaces in filenames well — not that you should use those!

$ find . -type f -not -path '*/\.*' -printf '%TY.%Tm.%Td %THh%TM %Ta %p\n' |sort -nr |head -n 10

2017.01.28 07h00 Sat ./recent
2017.01.21 10h49 Sat ./hgb
2017.01.16 07h44 Mon ./swx
2017.01.10 18h24 Tue ./update-stations
2017.01.09 10h38 Mon ./stations.json

More find galore can be found by following the link.

Find duplicate values in R

Here, I summarize a few ways which may return different results to your question, so be careful:

# First assign your "id"s to an R object.
# Here's a hypothetical example:
id <- c("a","b","b","c","c","c","d","d","d","d")

#To return ALL MINUS ONE duplicated values:
## [1] "b" "c" "c" "d" "d" "d"

#To return ALL duplicated values by specifying fromLast argument:
id[duplicated(id) | duplicated(id, fromLast=TRUE)]
## [1] "b" "b" "c" "c" "c" "d" "d" "d" "d"

#Yet another way to return ALL duplicated values, using %in% operator:
id[ id %in% id[duplicated(id)] ]
## [1] "b" "b" "c" "c" "c" "d" "d" "d" "d"

Hope these help. Good luck.

Python - How do you run a .py file?

On windows platform, you have 2 choices:

  1. In a command line terminal, type


  2. Open the python editor IDLE from the menu, and open, then press F5 to run it.

For your posted code, the error is at this line:

def main(url, out_folder="C:\asdf\"):

It should be:

def main(url, out_folder="C:\\asdf\\"):

How do I pass data to Angular routed components?

Some super smart person (tmburnell) that is not me suggests re-writing the route data:

let route = this.router.config.find(r => r.path === '/path'); = { entity: 'entity' };

As seen here in the comments.

I hope someone will find this useful

UTF-8 problems while reading CSV file with fgetcsv

Try this:

$handle = fopen ("specialchars.csv","r");
echo '<table border="1"><tr><td>First name</td><td>Last name</td></tr><tr>';
while ($data = fgetcsv ($handle, 1000, ";")) {
        $data = array_map("utf8_encode", $data); //added
        $num = count ($data);
        for ($c=0; $c < $num; $c++) {
            // output data
            echo "<td>$data[$c]</td>";
        echo "</tr><tr>";

What does DIM stand for in Visual Basic and BASIC?

DIM stands for Declaration In Memory DIM x As New Integer creates a space in memory where the variable x is stored

JSON formatter in C#?

I updated the old version, now it should support unquoted values such as integers and booleans.

I refactored the previous version and got the final version: The code is shorter and cleaner. Only require one extension method. The most important: fixed some bugs.

class JsonHelper
    private const string INDENT_STRING = "    ";
    public static string FormatJson(string str)
        var indent = 0;
        var quoted = false;
        var sb = new StringBuilder();
        for (var i = 0; i < str.Length; i++)
            var ch = str[i];
            switch (ch)
                case '{':
                case '[':
                    if (!quoted)
                        Enumerable.Range(0, ++indent).ForEach(item => sb.Append(INDENT_STRING));
                case '}':
                case ']':
                    if (!quoted)
                        Enumerable.Range(0, --indent).ForEach(item => sb.Append(INDENT_STRING));
                case '"':
                    bool escaped = false;
                    var index = i;
                    while (index > 0 && str[--index] == '\\')
                        escaped = !escaped;
                    if (!escaped)
                        quoted = !quoted;
                case ',':
                    if (!quoted)
                        Enumerable.Range(0, indent).ForEach(item => sb.Append(INDENT_STRING));
                case ':':
                    if (!quoted)
                        sb.Append(" ");
        return sb.ToString();

static class Extensions
    public static void ForEach<T>(this IEnumerable<T> ie, Action<T> action)
        foreach (var i in ie)

Publish to IIS, setting Environment Variable

After extensive googling I found a working solution, which consists of two steps.

The first step is to set system wide environment variable ASPNET_ENV to Production and Restart the Windows Server. After this, all web apps are getting the value 'Production' as EnvironmentName.

The second step (to enable value 'Staging' for staging web) was rather more difficult to get to work correctly, but here it is:

  1. Create new windows user, for example StagingPool on the server.
  2. For this user, create new user variable ASPNETCORE_ENVIRONMENT with value 'Staging' (you can do it by logging in as this user or through regedit)
  3. Back as admin in IIS manager, find the Application Pool under which the Staging web is running and in Advanced Settings set Identity to user StagingPool.
  4. Also set Load User Profile to true, so the environment variables are loaded. <- very important!
  5. Ensure the StagingPool has access rights to the web folder and Stop and Start the Application Pool.

Now the Staging web should have the EnvironmentName set to 'Staging'.

Update: In Windows 7+ there is a command that can set environment variables from CMD prompt also for a specified user. This outputs help plus samples:

>setx /?

How to convert 'binary string' to normal string in Python3?

Decode it.

>>> b'a string'.decode('ascii')
'a string'

To get bytes from string, encode it.

>>> 'a string'.encode('ascii')
b'a string'

React Router v4 - How to get current route?

There's a hook called useLocation in react-router v5, no need for HOC or other stuff, it's very succinctly and convenient.

import { useLocation } from 'react-router-dom';

const ExampleComponent: React.FC = () => {
  const location = useLocation();  

  return (
    <Router basename='/app'>
        <AppBar handleMenuIcon={this.handleMenuIcon} title={location.pathname} />

Set Background color programmatically

In my case it wasn't changing the color because I was setting the color in my xml resource.

After delete the line that set the color it worked perfectly programmatically

This is an example I did in a RecyclerView

final Drawable drawable = ContextCompat.getDrawable(mContext, R.drawable.ic_icon).mutate();

} else {

Angular CLI - Please add a @NgModule annotation when using latest

In my case, I created a new ChildComponent in Parentcomponent whereas both in the same module but Parent is registered in a shared module so I created ChildComponent using CLI which registered Child in the current module but my parent was registered in the shared module.

So register the ChildComponent in Shared Module manually.

Java Runtime.getRuntime(): getting output from executing a command line program

Besides using ProcessBuilder as suggested Senthil, be sure to read and implement all the recommendations of When Runtime.exec() won't.

How to assign string to bytes array

For converting from a string to a byte slice, string -> []byte:


For converting an array to a slice, [20]byte -> []byte:


For copying a string to an array, string -> [20]byte:

copy(arr[:], str)

Same as above, but explicitly converting the string to a slice first:

copy(arr[:], []byte(str))

  • The built-in copy function only copies to a slice, from a slice.
  • Arrays are "the underlying data", while slices are "a viewport into underlying data".
  • Using [:] makes an array qualify as a slice.
  • A string does not qualify as a slice that can be copied to, but it qualifies as a slice that can be copied from (strings are immutable).
  • If the string is too long, copy will only copy the part of the string that fits.

This code:

var arr [20]byte
copy(arr[:], "abc")
fmt.Printf("array: %v (%T)\n", arr, arr) the following output:

array: [97 98 99 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] ([20]uint8)

I also made it available at the Go Playground

Create an array of integers property in Objective-C

I'm just speculating:

I think that the variable defined in the ivars allocates the space right in the object. This prevents you from creating accessors because you can't give an array by value to a function but only through a pointer. Therefore you have to use a pointer in the ivars:

int *doubleDigits;

And then allocate the space for it in the init-method:

@synthesize doubleDigits;

- (id)init {
    if (self = [super init]) {
        doubleDigits = malloc(sizeof(int) * 10);
         * This works, but is dangerous (forbidden) because bufferDoubleDigits
         * gets deleted at the end of -(id)init because it's on the stack:
         * int bufferDoubleDigits[] = {1,2,3,4,5,6,7,8,9,10};
         * [self setDoubleDigits:bufferDoubleDigits];
         * If you want to be on the safe side use memcpy() (needs #include <string.h>)
         * doubleDigits = malloc(sizeof(int) * 10);
         * int bufferDoubleDigits[] = {1,2,3,4,5,6,7,8,9,10};
         * memcpy(doubleDigits, bufferDoubleDigits, sizeof(int) * 10);
    return self;

- (void)dealloc {
    [super dealloc];

In this case the interface looks like this:

@interface MyClass : NSObject {
    int *doubleDigits;
@property int *doubleDigits;


I'm really unsure wether it's allowed to do this, are those values really on the stack or are they stored somewhere else? They are probably stored on the stack and therefore not safe to use in this context. (See the question on initializer lists)

int bufferDoubleDigits[] = {1,2,3,4,5,6,7,8,9,10};
[self setDoubleDigits:bufferDoubleDigits];

proper hibernate annotation for byte[]

I have finally got this working. It expands on the solution from A. Garcia, however, since the problem lies in the hibernate type MaterializedBlob type just mapping Blob > bytea is not sufficient, we need a replacement for MaterializedBlobType which works with hibernates broken blob support. This implementation only works with bytea, but maybe the guy from the JIRA issue who wanted OID could contribute an OID implementation.

Sadly replacing these types at runtime is a pain, since they should be part of the Dialect. If only this JIRA enhanement gets into 3.6 it would be possible.

public class PostgresqlMateralizedBlobType extends AbstractSingleColumnStandardBasicType<byte[]> {
 public static final PostgresqlMateralizedBlobType INSTANCE = new PostgresqlMateralizedBlobType();

 public PostgresqlMateralizedBlobType() {
  super( PostgresqlBlobTypeDescriptor.INSTANCE, PrimitiveByteArrayTypeDescriptor.INSTANCE );

  public String getName() {
   return "materialized_blob";

Much of this could probably be static (does getBinder() really need a new instance?), but I don't really understand the hibernate internal so this is mostly copy + paste + modify.

public class PostgresqlBlobTypeDescriptor extends BlobTypeDescriptor implements SqlTypeDescriptor {
  public static final BlobTypeDescriptor INSTANCE = new PostgresqlBlobTypeDescriptor();

  public <X> ValueBinder<X> getBinder(final JavaTypeDescriptor<X> javaTypeDescriptor) {
   return new PostgresqlBlobBinder<X>(javaTypeDescriptor, this);
  public <X> ValueExtractor<X> getExtractor(final JavaTypeDescriptor<X> javaTypeDescriptor) {
   return new BasicExtractor<X>( javaTypeDescriptor, this ) {
    protected X doExtract(ResultSet rs, String name, WrapperOptions options) throws SQLException { 
      return (X)rs.getBytes(name);

public class PostgresqlBlobBinder<J> implements ValueBinder<J> {
 private final JavaTypeDescriptor<J> javaDescriptor;
 private final SqlTypeDescriptor sqlDescriptor;

 public PostgresqlBlobBinder(JavaTypeDescriptor<J> javaDescriptor, SqlTypeDescriptor sqlDescriptor) { 
  this.javaDescriptor = javaDescriptor; this.sqlDescriptor = sqlDescriptor;
 public final void bind(PreparedStatement st, J value, int index, WrapperOptions options) 
 throws SQLException {
  st.setBytes(index, (byte[])value);

Importing from a relative path in Python

Doing a relative import is absolulutely OK! Here's what little 'ol me does:

#first change the cwd to the script path
scriptPath = os.path.realpath(os.path.dirname(sys.argv[0]))

#append the relative location you want to import from

#import your module stored in '../common'

How can I initialize an ArrayList with all zeroes in Java?

The integer passed to the constructor represents its initial capacity, i.e., the number of elements it can hold before it needs to resize its internal array (and has nothing to do with the initial number of elements in the list).

To initialize an list with 60 zeros you do:

List<Integer> list = new ArrayList<Integer>(Collections.nCopies(60, 0));

If you want to create a list with 60 different objects, you could use the Stream API with a Supplier as follows:

List<Person> persons = Stream.generate(Person::new)

Disabling Controls in Bootstrap


<select id="xxx" name="xxx" class="input-medium" disabled>

ReferenceError: event is not defined error in Firefox

You're declaring (some of) your event handlers incorrectly:

$('.menuOption').click(function( event ){ // <---- "event" parameter here

    var categories = $(this).attr('rel');


You need "event" to be a parameter to the handlers. WebKit follows IE's old behavior of using a global symbol for "event", but Firefox doesn't. When you're using jQuery, that library normalizes the behavior and ensures that your event handlers are passed the event parameter.

edit — to clarify: you have to provide some parameter name; using event makes it clear what you intend, but you can call it e or cupcake or anything else.

Note also that the reason you probably should use the parameter passed in from jQuery instead of the "native" one (in Chrome and IE and Safari) is that that one (the parameter) is a jQuery wrapper around the native event object. The wrapper is what normalizes the event behavior across browsers. If you use the global version, you don't get that.

How to view instagram profile picture in full-size?

You can even set the prof. pic size to its high resolution that is '1080x1080'

replace "150x150" with 1080x1080 and remove /vp/ from the link.

Actual meaning of 'shell=True' in subprocess

The benefit of not calling via the shell is that you are not invoking a 'mystery program.' On POSIX, the environment variable SHELL controls which binary is invoked as the "shell." On Windows, there is no bourne shell descendent, only cmd.exe.

So invoking the shell invokes a program of the user's choosing and is platform-dependent. Generally speaking, avoid invocations via the shell.

Invoking via the shell does allow you to expand environment variables and file globs according to the shell's usual mechanism. On POSIX systems, the shell expands file globs to a list of files. On Windows, a file glob (e.g., "*.*") is not expanded by the shell, anyway (but environment variables on a command line are expanded by cmd.exe).

If you think you want environment variable expansions and file globs, research the ILS attacks of 1992-ish on network services which performed subprogram invocations via the shell. Examples include the various sendmail backdoors involving ILS.

In summary, use shell=False.

What is the purpose of the single underscore "_" variable in Python?

As far as the Python languages is concerned, _ has no special meaning. It is a valid identifier just like _foo, foo_ or _f_o_o_.

Any special meaning of _ is purely by convention. Several cases are common:

  • A dummy name when a variable is not intended to be used, but a name is required by syntax/semantics.

    # iteration disregarding content
    sum(1 for _ in some_iterable)
    # unpacking disregarding specific elements
    head, *_ = values
    # function disregarding its argument
    def callback(_): return True
  • Many REPLs/shells store the result of the last top-level expression to builtins._.

    The special identifier _ is used in the interactive interpreter to store the result of the last evaluation; it is stored in the builtins module. When not in interactive mode, _ has no special meaning and is not defined. [source]

    Due to the way names are looked up, unless shadowed by a global or local _ definition the bare _ refers to builtins._ .

    >>> 42
    >>> f'the last answer is {_}'
    'the last answer is 42'
    >>> _
    'the last answer is 42'
    >>> _ = 4  # shadow ``builtins._`` with global ``_``
    >>> 23
    >>> _

    Note: Some shells such as ipython do not assign to builtins._ but special-case _.

  • In the context internationalization and localization, _ is used as an alias for the primary translation function.


    Return the localized translation of message, based on the current global domain, language, and locale directory. This function is usually aliased as _() in the local namespace (see examples below).

tsconfig.json: Build:No inputs were found in config file

Ok, in 2021, with a <project>/src/index.ts file, the following worked for me:

If VS Code complains with No inputs were found in config file... then change the include to…

"include": ["./src/**/*.ts"]

Found the above as a comment of How to Write Node.js Applications in Typescript

Convert IQueryable<> type object to List<T> type?

Add the following:

using System.Linq

...and call ToList() on the IQueryable<>.

postgresql - replace all instances of a string within text field

You can use the replace function

UPDATE your_table SET field = REPLACE(your_field, 'cat','dog')

The function definition is as follows (got from here):

replace(string text, from text, to text)

and returns the modified text. You can also check out this sql fiddle.

Creating multiple log files of different content with log4j

Perhaps something like this?

<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="">
 <!-- general application log -->
 <appender name="MainLogFile" class="org.apache.log4j.FileAppender">
  <param name="File" value="server.log" />
  <param name="Threshold" value="INFO" />
  <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern" value="%-5p %t [%-40.40c] %x - %m%n"/>
 <!-- additional fooSystem logging -->
 <appender name="FooLogFile" class="org.apache.log4j.FileAppender">
  <param name="File" value="foo.log" />
  <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern" value="%-5p %t [%-40.40c] %x - %m%n"/>
 <!-- foo logging -->
 <logger name="">
  <level value="DEBUG"/>
  <appender-ref ref="FooLogFile"/>
 <!-- default logging -->
  <level value="INFO"/>
  <appender-ref ref="MainLogFile"/>

Thus, all info messages are written to server.log; by contrast, foo.log contains only messages, including debug-level messages.

Changing case in Vim

See the following methods:

 ~    : Changes the case of current character

 guu  : Change current line from upper to lower.

 gUU  : Change current LINE from lower to upper.

 guw  : Change to end of current WORD from upper to lower.

 guaw : Change all of current WORD to lower.

 gUw  : Change to end of current WORD from lower to upper.

 gUaw : Change all of current WORD to upper.

 g~~  : Invert case to entire line

 g~w  : Invert case to current WORD

 guG : Change to lowercase until the end of document.

Get selected value in dropdown list using JavaScript

I don't know if I'm the one that doesn't get the question right, but this just worked for me: Using an onchange() event in your html, eg.

<select id="numberToSelect" onchange="selectNum">
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>


function sele(){
    var strUser = numberToSelect.value;

This will give you whatever value is on the select dropdown per click

How do I find the index of a character in a string in Ruby?

index(substring [, offset]) ? fixnum or nil
index(regexp [, offset]) ? fixnum or nil

Returns the index of the first occurrence of the given substring or pattern (regexp) in str. Returns nil if not found. If the second parameter is present, it specifies the position in the string to begin the search.

"hello".index('e')             #=> 1
"hello".index('lo')            #=> 3
"hello".index('a')             #=> nil
"hello".index(?e)              #=> 1
"hello".index(/[aeiou]/, -3)   #=> 4

Check out ruby documents for more information.

Create dynamic URLs in Flask with url_for()

It takes keyword arguments for the variables:

url_for('add', variable=foo)

Move branch pointer to different commit without checkout

If you want to move a non-checked out branch to another commit, the easiest way is running the git branch command with -f option, which determines where the branch HEAD should be pointing to:

git branch -f

Be careful as this won't work if the branch you are trying to move is your current branch. To move a branch pointer, run the following command: git update-ref -m "reset: Reset to " refs/heads/

The git update-ref command updates the object name stored in a ref safely.

Hope, my answer helped you.The source of information is this snippet.

Unique random string generation

  • not sure Microsoft's link are randomly generated
  • have a look to new Guid().ToString()

Pipe to/from the clipboard in Bash script

A way to paste from clipboard to file without any tools except echo.

  1. Escape single quotes in the text you want to paste: replace all occurrences of ' with '\'' and copy the result to clipboard.
  2. Type echo -n '
  3. Press Shift+Insert
  4. Type ' > filename.txt
  5. Press Enter

Basically you're doing this:

echo -n 'copied text with single quotes escaped' > filename.txt

It works even if the copied text has new lines.

Removing all unused references from a project in Visual Studio projects

In a Visual Basic project there is support to remove "Unused References" (Project-->References-->Unused References). In C# there isn´t such a function.

The only way to do it in a C# project (without other tools) is to remove possible unused assemblies, compile the project and verify if any errors occur during compilation. If none errors occur you have removed a unused assembly. (See my post)

If you want to know which project (assembly) depends on other assemblies you can use NDepend.

Laravel migration default value

Put the default value in single quote and it will work as intended. An example of migration:


EDIT : in your case ->default('100.0');

How to get the cursor to change to the hand when hovering a <button> tag


so you need to add: cursor:pointer;

In your case use:

#more {
  font-family:Verdana, Geneva, sans-serif;

This will apply the curser to the element with the ID "more" (can be only used once). So in your HTML use

<input type="button" id="more" />

If you want to apply this to more than one button then you have more than one possibility:

using CLASS

.more {
  font-family:Verdana, Geneva, sans-serif;

and in your HTML use

<input type="button" class="more" value="first" />
<input type="button" class="more" value="second" />

or apply to a html context:

input[type=button] {
  font-family:Verdana, Geneva, sans-serif;

and in your HTML use

<input type="button" value="first" />
<input type="button" value="second" />

How can I strip all punctuation from a string in JavaScript using regex?

/[^A-Za-z0-9\s]/g should match all punctuation but keep the spaces. So you can use .replace(/\s{2,}/g, " ") to replace extra spaces if you need to do so. You can test the regex in

.replace(/[^A-Za-z0-9\s]/g,"").replace(/\s{2,}/g, " ")

Update: Will only work if the input is ANSI English.

SSRS the definition of the report is invalid

I was getting this error and tried most of the suggestions here. Finally I did a "Clean" on the report project and tried again. It finally worked!!

Creating threads - Task.Factory.StartNew vs new Thread()

Your first block of code tells CLR to create a Thread (say. T) for you which is can be run as background (use thread pool threads when scheduling T ). In concise, you explicitly ask CLR to create a thread for you to do something and call Start() method on thread to start.

Your second block of code does the same but delegate (implicitly handover) the responsibility of creating thread (background- which again run in thread pool) and the starting thread through StartNew method in the Task Factory implementation.

This is a quick difference between given code blocks. Having said that, there are few detailed difference which you can google or see other answers from my fellow contributors.

Ruby capitalize every word first letter

In Rails:

"kirk douglas".titleize => "Kirk Douglas"
#this also works for 'kirk_douglas'

w/o Rails:

"kirk douglas".split(/ |\_/).map(&:capitalize).join(" ")

def titleize(str)
  str.split(/ |\_/).map(&:capitalize).join(" ")

class String  
  def titleize
    self.split(/ |\_/).map(&:capitalize).join(" ")

w/o Rails (load rails's ActiveSupport to patch #titleize method to String)

require 'active_support/core_ext'
"kirk douglas".titleize #=> "Kirk Douglas"

(some) string use cases handled by #titleize

  • "kirk douglas"
  • "kirk_douglas"
  • "kirk-douglas"
  • "kirkDouglas"
  • "KirkDouglas"

#titleize gotchas

Rails's titleize will convert things like dashes and underscores into spaces and can produce other unexpected results, especially with case-sensitive situations as pointed out by @JamesMcMahon:

"hEy lOok".titleize #=> "H Ey Lo Ok"

because it is meant to handle camel-cased code like:

"kirkDouglas".titleize #=> "Kirk Douglas"

To deal with this edge case you could clean your string with #downcase first before running #titleize. Of course if you do that you will wipe out any camelCased word separations:

"kirkDouglas".downcase.titleize #=> "Kirkdouglas"

Bad File Descriptor with Linux Socket write() Bad File Descriptor C

The value you have passed as the file descriptor is not valid. It is either negative or does not represent a currently open file or socket.

So you have either closed the socket before calling write() or you have corrupted the value of 'sockfd' somewhere in your code.

It would be useful to trace all calls to close(), and the value of 'sockfd' prior to the write() calls.

Your technique of only printing error messages in debug mode seems to me complete madness, and in any case calling another function between a system call and perror() is invalid, as it may disturb the value of errno. Indeed it may have done so in this case, and the real underlying error may be different.


It’s the double colon operator :: (see list of parser tokens).

How to change the href for a hyperlink using jQuery

      this.href = this.href.replace(/^http:\/\/beta\.stackoverflow\.com/, 

Adding a column to a dataframe in R

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

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

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

Foreign key constraint may cause cycles or multiple cascade paths?

By the sounds of it you have an OnDelete/OnUpdate action on one of your existing Foreign Keys, that will modify your codes table.

So by creating this Foreign Key, you'd be creating a cyclic problem,

E.g. Updating Employees, causes Codes to changed by an On Update Action, causes Employees to be changed by an On Update Action... etc...

If you post your Table Definitions for both tables, & your Foreign Key/constraint definitions we should be able to tell you where the problem is...

Failed to resolve:

My issue got resolved with the help of following steps:

For gradle 3.0.0 and above version

  1. add google() below jcenter()
  2. Change the compileSdkVersion to 26 and buildToolsVersion to 26.0.2
  3. Change to in the file

How do I break a string in YAML over multiple lines?

You might not believe it, but YAML can do multi-line keys too:


SVN remains in conflict?

One more solution below,

If the entire folder is removed and SVNis throwing the error "admin file .svn is missing", the following will be used to resolve the conflict to working state.

svn resolve --accept working "file / directory name "

How do I read a large csv file with pandas?

You can try sframe, that have the same syntax as pandas but allows you to manipulate files that are bigger than your RAM.

UnsupportedClassVersionError: JVMCFRE003 bad major version in WebSphere AS 7

I was getting this error in websphere 8.5:

java.lang.UnsupportedClassVersionError: JVMCFRE003 bad major version; class=com/xxx/Whatever, offset=6

I had my project JDK level set at 1.7 in eclipse and was8 by default runs on JDK 1.6 so there was a clash. I had to install the optional SDK 1.7 to my websphere server and then the problem went away. I guess I could have also set my project level down to 1.6 in eclipse but I wanted to code to 1.7.

ng-if check if array is empty

Verify the length property of the array to be greater than 0:

<p ng-if="post.capabilities.items.length > 0">
   <span ng-repeat="topic in post.capabilities.items">

Arrays (objects) in JavaScript are truthy values, so your initial verification <p ng-if="post.capabilities.items"> evaluates always to true, even if the array is empty.

References with text in LaTeX

Have a look to this wiki: LaTeX/Labels and Cross-referencing:

The hyperref package automatically includes the nameref package, and a similarly named command. It inserts text corresponding to the section name, for example:

\section{MySecondSection} In section \nameref{marker} we defined...

Creating multiline strings in JavaScript

My extension to It expects comment in a form /*! any multiline comment */ where symbol ! is used to prevent removing by minification (at least for YUI compressor)

Function.prototype.extractComment = function() {
    var startComment = "/*!";
    var endComment = "*/";
    var str = this.toString();

    var start = str.indexOf(startComment);
    var end = str.lastIndexOf(endComment);

    return str.slice(start + startComment.length, -(str.length - end));


var tmpl = function() { /*!
 <div class="navbar-collapse collapse">
    <ul class="nav navbar-nav">

TypeError: $ is not a function WordPress

I was able to resolve this very easily my simply enqueuing jQuery wp_enqueue_script("jquery");

The type or namespace name 'DbContext' could not be found

Like the others have suggested:

  1. Add the correct references and directives. But it still doesn't work? Maybe you have the same problem I did:

Have a look below and see if you can tell me what is wrong:

public class PanelLengthContext : DBContext { } ??!

Make sure the class name is not misspelt - (case sensitivity)!

  • DbContext is the correct spelling.
  • this is how it should look:
  • check the spelling. don't waste 20 min of your life like i did. public class PanelLengthContext : DbContext {}


Pass accepts header parameter to jquery ajax

There two alternate ways to set accept header, which are as below:

1) setRequestHeader('Accept','application/json; charset=utf-8');

2) $.ajax({
    dataType: ($.browser.msie) ? "text" : "json",
    accepts: {
        text: "application/json"

how to use font awesome in own css?

Instructions for Drupal 8 / FontAwesome 5

Create a YOUR_THEME_NAME_HERE.THEME file and place it in your themes directory (ie. your_site_name/themes/your_theme_name)

Paste this into the file, it is PHP code to find the Search Block and change the value to the UNICODE for the FontAwesome icon. You can find other characters at this link

function YOUR_THEME_NAME_HERE_form_search_block_form_alter(&$form, &$form_state) {
  $form['keys']['#attributes']['placeholder'][] = t('Search');
  $form['actions']['submit']['#value'] = html_entity_decode('&#xf002;');

Open the CSS file of your theme (ie. your_site_name/themes/your_theme_name/css/styles.css) and then paste this in which will change all input submit text to FontAwesome. Not sure if this will work if you also want to add text in the input button though for just an icon it is fine.

Make sure you import FontAwesome, add this at the top of the CSS file

@import url('');

then add this in the CSS

input#edit-submit {
    font-family: 'Font Awesome\ 5 Free';
    background-color: transparent;
    border: 0;  


Add Google Font Effects

If you are using Google Web Fonts as well you can add also add effects to the icon (see more here You need to import a Google Web Font including the effect(s) you would like to use first in the CSS so it will be

@import url(',800&effect=3d-float');
@import url('');

Then go back to your .THEME file and add the class for the 3D Float Effect so the code will now add a class to the input. There are different effects available. So just choose the effect you like, change the CSS for the font import and the change the value FONT-EFFECT-3D-FLOAT int the code below to font-effect-WHATEVER_EFFECT_HERE. Note effects are still in Beta and don't work in all browsers so read here before you try it

function YOUR_THEME_NAME_HERE_form_search_block_form_alter(&$form, &$form_state) {
  $form['keys']['#attributes']['placeholder'][] = t('Search');
  $form['actions']['submit']['#value'] = html_entity_decode('&#xf002;');
  $form['actions']['submit']['#attributes']['class'][] = 'font-effect-3d-float';

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

I used it like this:

@media (max-width: 450px) {
  br {
    display: none;

nb: media query via Foundation nb2: this is useful if one of the editor intend to use
tags in his/her copy and you need to deal with it specifically under some conditions—on mobile for example.

How to form a correct MySQL connection string?

try creating connection string this way:

MySqlConnectionStringBuilder conn_string = new MySqlConnectionStringBuilder();
conn_string.Server = "";
conn_string.UserID = "a455555_test";
conn_string.Password = "a455555_me";
conn_string.Database = "xxxxxxxx";

using (MySqlConnection conn = new MySqlConnection(conn_string.ToString()))
using (MySqlCommand cmd = conn.CreateCommand())
{    //watch out for this SQL injection vulnerability below
     cmd.CommandText = string.Format("INSERT Test (lat, long) VALUES ({0},{1})",
                                    OSGconv.deciLat, OSGconv.deciLon);

long long in C/C++

your code compiles here fine (even with that line uncommented. had to change it to

num3 = 100000000000000000000;

to start getting the warning.

iPhone/iPad browser simulator?

For now i think best emulator is

It has real sizes and virtual keyboard (that is the most important thing) , zooming events...

Also has same things but it has time limit.

How can I find the first occurrence of a sub-string in a python string?

to implement this in algorithmic way, by not using any python inbuilt function . This can be implemented as

def find_pos(string,word):

    for i in range(len(string) - len(word)+1):
        if string[i:i+len(word)] == word:
            return i
    return 'Not Found'

string = "the dude is a cool dude"
word = 'dude1'
# output 4

Delete all items from a c++ std::vector

I think you should use std::vector::clear:



Doesn't clear destruct the elements held by the vector?

Yes it does. It calls the destructor of every element in the vector before returning the memory. That depends on what "elements" you are storing in the vector. In the following example, I am storing the objects them selves inside the vector:

class myclass


std::vector<myclass> myvector;
myvector.clear(); // calling clear will do the following:
// 1) invoke the deconstrutor for every myclass
// 2) size == 0 (the vector contained the actual objects).

If you want to share objects between different containers for example, you could store pointers to them. In this case, when clear is called, only pointers memory is released, the actual objects are not touched:

std::vector<myclass*> myvector;
myvector.clear(); // calling clear will do:
// 1) ---------------
// 2) size == 0 (the vector contained "pointers" not the actual objects).

For the question in the comment, I think getVector() is defined like this:

std::vector<myclass> getVector();

Maybe you want to return a reference:

// vector.getVector().clear() clears m_vector in this case
std::vector<myclass>& getVector(); 

Only on Firefox "Loading failed for the <script> with source"

I've just had the same issue - for me Privacy Badger on Firefox was the issue - not adblocker. Posting for posterity

Clear text field value in JQuery

If you want to clear the text field, use: