Programs & Examples On #Add

Addition is a mathematical operation that represents combining collections of objects together into a larger collection. It is signified by the plus sign (+).

How to add hours to current time in python

Import datetime and timedelta:

>>> from datetime import datetime, timedelta
>>> str( + timedelta(hours=9))[11:19]

But the better way is:

>>> ( + timedelta(hours=9)).strftime('%H:%M:%S')

You can refer strptime and strftime behavior to better understand how python processes dates and time field

How to add new column to MYSQL table?

your table:

q1 | q2 | q3 | q4 | q5

you can also do

ALTER TABLE yourtable ADD q6 VARCHAR( 255 ) after q5

How to add text to an existing div with jquery

$(function () {_x000D_
  $('#Add').click(function () {_x000D_
<script src=""></script>_x000D_
 <div id="Content">_x000D_
    <button id="Add">Add<button>_x000D_

momentJS date string add 5 days

To get an actual working example going that returns what one would expect:

var startdate = "20.03.2014";
var new_date = moment(startdate, "DD.MM.YYYY");
var thing = new_date.add(5, 'days').format('DD/MM/YYYY');

Add onclick event to newly added element in JavaScript

Short answer: you want to set the handler to a function:

elemm.onclick = function() { alert('blah'); };

Slightly longer answer: you'll have to write a few more lines of code to get that to work consistently across browsers.

The fact is that even the sligthly-longer-code that might solve that particular problem across a set of common browsers will still come with problems of its own. So if you don't care about cross-browser support, go with the totally short one. If you care about it and absolutely only want to get this one single thing working, go with a combination of addEventListener and attachEvent. If you want to be able to extensively create objects and add and remove event listeners throughout your code, and want that to work across browsers, you definitely want to delegate that responsibility to a library such as jQuery.

Add JavaScript object to JavaScript object

// Merge object2 into object1, recursively

$.extend( true, object1, object2 );

// Merge object2 into object1

$.extend( object1, object2 );

Add to python path mac os x

Setting the $PYTHONPATH environment variable does not seem to affect the Spyder IDE's iPython terminals on a Mac. However, Spyder's application menu contains a "PYTHONPATH manager." Adding my path here solved my problem. The "PYTHONPATH manager" is also persistent across application restarts.

This is specific to a Mac, because setting the PYTHONPATH environment variable on my Windows PC gives the expected behavior (modules are found) without using the PYTHONPATH manager in Spyder.

Datetime in C# add days

DateTime is immutable. That means you cannot change it's state and have to assign the result of an operation to a variable.

endDate = endDate.AddDays(addedDays);

Add text to textarea - Jquery

Just append() the text nodes:


How To Add An "a href" Link To A "div"?

Your solutions don't seem to be working for me, I have the following code. How to put link into the last two divs.

<html xmlns="" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office">

/* Import */
@import url(,400);
* {
  font-family: "Quicksand", sans-serif; 
  font-weight: bold; 
  text-align: center;  
  text-transform: uppercase; 
  -webkit-transition: all 0.25s ease; 
  -moz-transition: all 0.25s ease; 
  -ms-transition: all 0.25s ease; 
  -o-transition: all 0.025s ease; 

/* Colors */

#ora {
  background-color: #e67e22; 

#red {
  background-color: #e74c3c; 

#orab {
  background-color: white; 
  border: 5px solid #e67e22; 

#redb {
  background-color: white; 
  border: 5px solid #e74c3c; 
/* End of Colors */

.B {
  width: 240px; 
  height: 55px; 
  margin: auto; 
  line-height: 45px; 
  display: inline-block; 
  box-sizing: border-box; 
  -webkit-box-sizing: border-box; 
  -moz-box-sizing: border-box; 
  -ms-box-sizing: border-box; 
  -o-box-sizing: border-box; 

#orab:hover {
  background-color: #e67e22; 

#redb:hover {
  background-color: #e74c3c; 
#whib:hover {
  background-color: #ecf0f1; 

/* End of Border

.invert:hover {
  -webkit-filter: invert(1);
  -moz-filter: invert(1);
  -ms-filter: invert(1);
  -o-filter: invert(1);
<h1>Flat and Modern Buttons</h1>
<h2>Border Stylin'</h2> 

<div class="B bo" id="orab">See the movies list</div></a>
<div class="B bo" id="redb">Avail a free rental day</div>


What is the syntax for adding an element to a scala.collection.mutable.Map?

Create a mutable map without initial value:

scala> var d= collection.mutable.Map[Any, Any]()
d: scala.collection.mutable.Map[Any,Any] = Map()

Create a mutable map with initial values:

scala> var d= collection.mutable.Map[Any, Any]("a"->3,1->234,2->"test")
d: scala.collection.mutable.Map[Any,Any] = Map(2 -> test, a -> 3, 1 -> 234)

Update existing key-value:

scala> d("a")= "ABC"

Add new key-value:

scala> d(100)= "new element"

Check the updated map:

scala> d
res123: scala.collection.mutable.Map[Any,Any] = Map(2 -> test, 100 -> new element, a -> ABC, 1 -> 234)

How can I concatenate two arrays in Java?

Wow! lot of complex answers here including some simple ones that depend on external dependencies. how about doing it like this:

String [] arg1 = new String{"a","b","c"};
String [] arg2 = new String{"x","y","z"};

ArrayList<String> temp = new ArrayList<String>();
String [] concatedArgs = temp.toArray(new String[arg1.length+arg2.length]);

How to use ArrayList.addAll()?

Use Arrays class in Java which will return you an ArrayList :

final List<String> characters = Arrays.asList("+","-");

You will need a bit more work if you need a List<Character>.

cmd line rename file with date and time

ls | xargs -I % mv % %_`date +%d%b%Y`

One line is enough. ls all files/dirs under current dir and append date to each file.

Add a column to a table, if it does not already exist

When checking for a column in another database, you can simply include the database name:

  FROM   DatabaseName.sys.columns 
  WHERE  object_id = OBJECT_ID(N'[DatabaseName].[dbo].[TableName]') 
         AND name = 'ColumnName'

ListView with Add and Delete Buttons in each Row in android

on delete button click event

public void delete(View v){                

    ListView listview1;
    ArrayList<E> datalist;

    final int position = listview1.getPositionForView((View) v.getParent());


Git: add vs push vs commit

  • git add adds files to the Git index, which is a staging area for objects prepared to be commited.
  • git commit commits the files in the index to the repository, git commit -a is a shortcut to add all the modified tracked files to the index first.
  • git push sends all the pending changes to the remote repository to which your branch is mapped (eg. on GitHub).

In order to understand Git you would need to invest more effort than just glancing over the documentation, but it's definitely worth it. Just don't try to map Git commands directly to Subversion, as most of them don't have a direct counterpart.

Add to integers in a list

Here is an example where the things to add come from a dictionary

>>> L = [0, 0, 0, 0]
>>> things_to_add = ({'idx':1, 'amount': 1}, {'idx': 2, 'amount': 1})
>>> for item in things_to_add:
...     L[item['idx']] += item['amount']
>>> L
[0, 1, 1, 0]

Here is an example adding elements from another list

>>> L = [0, 0, 0, 0]
>>> things_to_add = [0, 1, 1, 0]
>>> for idx, amount in enumerate(things_to_add):
...     L[idx] += amount
>>> L
[0, 1, 1, 0]

You could also achieve the above with a list comprehension and zip

L[:] = [sum(i) for i in zip(L, things_to_add)]

Here is an example adding from a list of tuples

>>> things_to_add = [(1, 1), (2, 1)]
>>> for idx, amount in things_to_add:
...     L[idx] += amount
>>> L
[0, 1, 1, 0]

How to add an object to an ArrayList in Java

You have to use new operator here to instantiate. For example:

Contacts.add(new Data(name, address, contact));

Add a new item to recyclerview programmatically?

First add your item to mItems and then use:

mAdapter.notifyItemInserted(mItems.size() - 1);

this method is better than using:


in performance.

JList add/remove Item

The best and easiest way to clear a JLIST is:

myJlist.setListData(new String[0]);

How to convert a 3D point into 2D perspective projection?

All of the answers address the question posed in the title. However, I would like to add a caveat that is implicit in the text. Bézier patches are used to represent the surface, but you cannot just transform the points of the patch and tessellate the patch into polygons, because this will result in distorted geometry. You can, however, tessellate the patch first into polygons using a transformed screen tolerance and then transform the polygons, or you can convert the Bézier patches to rational Bézier patches, then tessellate those using a screen-space tolerance. The former is easier, but the latter is better for a production system.

I suspect that you want the easier way. For this, you would scale the screen tolerance by the norm of the Jacobian of the inverse perspective transformation and use that to determine the amount of tessellation that you need in model space (it might be easier to compute the forward Jacobian, invert that, then take the norm). Note that this norm is position-dependent, and you may want to evaluate this at several locations, depending on the perspective. Also remember that since the projective transformation is rational, you need to apply the quotient rule to compute the derivatives.

How to unzip gz file using Python

Maybe you want pass it to pandas also.

with'features_train.csv.gz') as f:

    features_train = pd.read_csv(f)


Constructors in Go

In Go, a constructor can be implemented using a function that returns a pointer to a modified structure.

type Colors struct {
    R   byte
    G   byte
    B   byte

// Constructor
func NewColors (r, g, b byte) *Colors {
    return &Color{R:r, G:g, B:b}

For weak dependencies and better abstraction, the constructor does not return a pointer to a structure, but an interface that this structure implements.

type Painter interface {
    paintMethod1() byte
    paintMethod2(byte) byte

type Colors struct {
    R byte
    G byte
    B byte

// Constructor return intreface
func NewColors(r, g, b byte) Painter {
    return &Color{R: r, G: g, B: b}

func (c *Colors) paintMethod1() byte {
    return c.R

func (c *Colors) paintMethod2(b byte) byte {
    return c.B = b

Angular2 RC5: Can't bind to 'Property X' since it isn't a known property of 'Child Component'

<create-report-card-form [currentReportCardCount]="providerData.reportCards.length" ...

In your HomeComponent template, you are trying to bind to an input on the CreateReportCardForm component that doesn't exist.

In CreateReportCardForm, these are your only three inputs:

@Input() public reportCardDataSourcesItems: SelectItem[];
@Input() public reportCardYearItems: SelectItem[];
@Input() errorMessages: Message[];

Add one for currentReportCardCount and you should be good to go.

How to use regex with find command?

You should use absolute directory path when applying find instruction with regular expression. In your example, the

find . -regex "[a-f0-9\-]\{36\}\.jpg"

should be changed into

find . -regex "./[a-f0-9\-]\{36\}\.jpg"

In most Linux systems, some disciplines in regular expression cannot be recognized by that system, so you have to explicitly point out -regexty like

find . -regextype posix-extended -regex "[a-f0-9\-]\{36\}\.jpg"

jQuery Combobox/select autocomplete?

This works great for me and I'm doing more, writing less with jQuery's example modified.

I defined the select object on my page, just like the jQuery ex. I took the text and pushed it to an array. Then I use the array as my source to my input autocomplete. tadaa.

$(function() {
   var mySource = [];
   $("#mySelect").children("option").map(function() {

      source: mySource,
      minLength: 3

Use RSA private key to generate public key?

openssl genrsa -out mykey.pem 1024

will actually produce a public - private key pair. The pair is stored in the generated mykey.pem file.

openssl rsa -in mykey.pem -pubout >

will extract the public key and print that out. Here is a link to a page that describes this better.

EDIT: Check the examples section here. To just output the public part of a private key:

openssl rsa -in key.pem -pubout -out pubkey.pem

To get a usable public key for SSH purposes, use ssh-keygen:

ssh-keygen -y -f key.pem >

Angular ForEach in Angular4/Typescript?

In Typescript use the For Each like below.

selectChildren(data, $event) {
let parentChecked = data.checked;
for(var obj in this.hierarchicalData)
        for (var childObj in obj )
            value.checked = parentChecked;


Just been doing that myself today... here is code I have working for me...

$data = array("a" => $a);
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "PUT");
curl_setopt($ch, CURLOPT_POSTFIELDS,http_build_query($data));

$response = curl_exec($ch);

if (!$response) 
    return false;


Best way to get value from Collection by index

You shouldn't. a Collection avoids talking about indexes specifically because it might not make sense for the specific collection. For example, a List implies some form of ordering, but a Set does not.

Collection<String> myCollection = new HashSet<String>();

for (String elem : myCollection) {
    System.out.println("elem = " + elem);

System.out.println("myCollection.toArray()[0] = " + myCollection.toArray()[0]);

gives me:

elem = World
elem = Hello
myCollection.toArray()[0] = World


myCollection = new ArrayList<String>();

for (String elem : myCollection) {
    System.out.println("elem = " + elem);

System.out.println("myCollection.toArray()[0] = " + myCollection.toArray()[0]);

gives me:

elem = Hello
elem = World
myCollection.toArray()[0] = Hello

Why do you want to do this? Could you not just iterate over the collection?

An App ID with Identifier '' is not available. Please enter a different string

This may only apply to the latest version of Xcode (7.3 D175), recently release:

Press the Try Again Button

After several hours of fiddling with Xcode build settings and starting the Certificate/App ID/Provisioning Profile dance from scratch, I ended up at the same place, same error message, App ID not available.

In frustration, I pressed the Try Again button thinking it was futile. But it worked.

Oracle SQL Developer: Failure - Test failed: The Network Adapter could not establish the connection?

I am answering this for the benefit of future community users. There were multiple issues. If you encounter this problem, I suggest you look for the following:

  • Make sure your tnsnames.ora is complete and has the databases you wish to connect to
  • Make sure you can tnsping the server you wish to connect to
  • On the server, make sure it will be open on the port you desire with the specific application you are using.

Once I did these three things, I solved my problem.

first-child and last-child with IE8

If your table is only 2 columns across, you can easily reach the second td with the adjacent sibling selector, which IE8 does support along with :first-child:

.editor td:first-child
    width: 150px; 

.editor td:first-child + td input,
.editor td:first-child + td textarea
    width: 500px;
    padding: 3px 5px 5px 5px;
    border: 1px solid #CCC; 

Otherwise, you'll have to use a JS selector library like jQuery, or manually add a class to the last td, as suggested by James Allardice.

AngularJS: ng-repeat list is not updated when a model element is spliced from the model array

If you add a $scope.$apply(); right after $scope.pluginsDisplayed.splice(index,1); then it works.

I am not sure why this is happening, but basically when AngularJS doesn't know that the $scope has changed, it requires to call $apply manually. I am also new to AngularJS so cannot explain this better. I need too look more into it.

I found this awesome article that explains it quite properly. Note: I think it might be better to use ng-click (docs) rather than binding to "mousedown". I wrote a simple app here (, source based on AngularJS. It is not very clean, but it might be of help.

How to determine SSL cert expiration date from a PEM encoded certificate?

For MAC OSX (El Capitan) This modification of Nicholas' example worked for me.

for pem in /path/to/certs/*.pem; do
    printf '%s: %s\n' \
        "$(date -jf "%b %e %H:%M:%S %Y %Z" "$(openssl x509 -enddate -noout -in "$pem"|cut -d= -f 2)" +"%Y-%m-%d")" \
done | sort

Sample Output:

2014-12-19: /path/to/certs/MDM_Certificate.pem
2015-11-13: /path/to/certs/MDM_AirWatch_Certificate.pem

macOS didn't like the --date= or --iso-8601 flags on my system.

curl : (1) Protocol https not supported or disabled in libcurl

Got the answer HERE for windows, it says there that:

curl -XPUT 'http://localhost:9200/api/twittervnext/tweet'

Woops, first try and already an error:

curl: (1) Protocol 'http not supported or disabled in libcurl

The reason for this error is kind of stupid, Windows doesn’t like it when you are using single quotes for commands. So the correct command is:

curl –XPUT "http://localhost:9200/api/twittervnext/tweet"

How to create a pivot query in sql server without aggregate function

SELECT [Period], [Account], [Value]
FROM TableName
) AS source
    FOR [Period] IN ([2000], [2001], [2002])
) as pvt

Another way,

      MAX(CASE WHEN Period = '2000' THEN Value ELSE NULL END) [2000],
      MAX(CASE WHEN Period = '2001' THEN Value ELSE NULL END) [2001],
      MAX(CASE WHEN Period = '2002' THEN Value ELSE NULL END) [2002]
FROM tableName
GROUP BY Account

Testing the type of a DOM element in JavaScript

I have another way of testing the same.

Element.prototype.typeof = "element";_x000D_
var element = document.body; // any dom element_x000D_
if (element && element.typeof == "element"){_x000D_
   return true; _x000D_
   // this is a dom element_x000D_
  return false; _x000D_
  // this isn't a dom element_x000D_

What is Node.js' Connect, Express and "middleware"?

[Update: As of its 4.0 release, Express no longer uses Connect. However, Express is still compatible with middleware written for Connect. My original answer is below.]

I'm glad you asked about this, because it's definitely a common point of confusion for folks looking at Node.js. Here's my best shot at explaining it:

  • Node.js itself offers an http module, whose createServer method returns an object that you can use to respond to HTTP requests. That object inherits the http.Server prototype.

  • Connect also offers a createServer method, which returns an object that inherits an extended version of http.Server. Connect's extensions are mainly there to make it easy to plug in middleware. That's why Connect describes itself as a "middleware framework," and is often analogized to Ruby's Rack.

  • Express does to Connect what Connect does to the http module: It offers a createServer method that extends Connect's Server prototype. So all of the functionality of Connect is there, plus view rendering and a handy DSL for describing routes. Ruby's Sinatra is a good analogy.

  • Then there are other frameworks that go even further and extend Express! Zappa, for instance, which integrates support for CoffeeScript, server-side jQuery, and testing.

Here's a concrete example of what's meant by "middleware": Out of the box, none of the above serves static files for you. But just throw in connect.static (a middleware that comes with Connect), configured to point to a directory, and your server will provide access to the files in that directory. Note that Express provides Connect's middlewares also; express.static is the same as connect.static. (Both were known as staticProvider until recently.)

My impression is that most "real" Node.js apps are being developed with Express these days; the features it adds are extremely useful, and all of the lower-level functionality is still there if you want it.

How can I open two pages from a single click without using JavaScript?

also you can open more than two page try this

`<a href="" target="_blank" onclick="'');'');">Click Here</a>`

Simplest way to wait some asynchronous tasks complete, in Javascript?

With deferred (another promise/deferred implementation) you can do:

// Setup 'pdrop', promise version of 'drop' method
var deferred = require('deferred');
mongoose.Collection.prototype.pdrop =

// Drop collections:['aaa','bbb','ccc'], function(name){
    return conn.collection(name).pdrop()(function () {
}).end(function () {
    console.log("all dropped");
}, null);

Which maven dependencies to include for spring 3.0?

You can add spring-context dependency for spring jars. You will get the following jars along with it.


Spring context dependencies

if you also want web components, you can use spring-webmvc dependency.


Spring webmvc dependencies

You can use whatever version of that you want. I have used 5.0.5.RELEASE here.

How to replace an entire line in a text file by line number

Let's suppose you want to replace line 4 with the text "different". You can use AWK like so:

awk '{ if (NR == 4) print "different"; else print $0}' input_file.txt > output_file.txt

AWK considers the input to be "records" divided into "fields". By default, one line is one record. NR is the number of records seen. $0 represents the current complete record (while $1 is the first field from the record and so on; by default the fields are words from the line).

So, if the current line number is 4, print the string "different" but otherwise print the line unchanged.

In AWK, program code enclosed in { } runs once on each input record.

You need to quote the AWK program in single-quotes to keep the shell from trying to interpret things like the $0.

EDIT: A shorter and more elegant AWK program from @chepner in the comments below:

awk 'NR==4 {$0="different"} { print }' input_file.txt

Only for record (i.e. line) number 4, replace the whole record with the string "different". Then for every input record, print the record.

Clearly my AWK skills are rusty! Thank you, @chepner.

EDIT: and see also an even shorter version from @Dennis Williamson:

awk 'NR==4 {$0="different"} 1' input_file.txt

How this works is explained in the comments: the 1 always evaluates true, so the associated code block always runs. But there is no associated code block, which means AWK does its default action of just printing the whole line. AWK is designed to allow terse programs like this.

How to unblock with mysqladmin flush hosts

You can easily restart your MySql service. This kicks the error off.

Command to list all files in a folder as well as sub-folders in windows

Following commands we can use for Linux or Mac. For Windows we can use below on git bash.

List all files, first level folders, and their contents

ls * -r

List all first-level subdirectories and files

file */*

Save file list to text

file */* *>> ../files.txt
file */* -r *>> ../files-recursive.txt

Get everything

find . -type f

Save everything to file

find . -type f > ../files-all.txt

How to set Bullet colors in UL/LI html lists via CSS without using any images or span tags

I use jQuery for this:

jQuery('li').wrapInner('<span class="li_content" />');

& with some CSS:

li { color: red; }
li span.li_content { color: black; }

maybe overkill, but handy if you're coding for a CMS and you don't want to ask your editors to put an extra span in every list-items.

How to copy a row and insert in same table with a autoincrement field in MySQL?

You can also pass in '0' as the value for the column to auto-increment, the correct value will be used when the record is created. This is so much easier than temporary tables.

Source: Copying rows in MySQL (see the second comment, by TRiG, to the first solution, by Lore)

jQuery load more data on scroll

Here is an example:

  1. On scrolling to the bottom, html elements are appeneded. This appending mechanism are only done twice, and then a button with powderblue color is appended at last.

<!DOCTYPE html>_x000D_
    <title>Demo: Lazy Loader</title>_x000D_
    <script src=""></script>_x000D_
        #myScroll {_x000D_
            border: 1px solid #999;_x000D_
        p {_x000D_
            border: 1px solid #ccc;_x000D_
            padding: 50px;_x000D_
            text-align: center;_x000D_
        .loading {_x000D_
            color: red;_x000D_
        .dynamic {_x000D_
  var counter=0;_x000D_
        $(window).scroll(function () {_x000D_
            if ($(window).scrollTop() == $(document).height() - $(window).height() && counter < 2) {_x000D_
        function appendData() {_x000D_
            var html = '';_x000D_
            for (i = 0; i < 10; i++) {_x000D_
                html += '<p class="dynamic">Dynamic Data :  This is test data.<br />Next line.</p>';_x000D_
   $('#myScroll').append('<button id="uniqueButton" style="margin-left: 50%; background-color: powderblue;">Click</button><br /><br />');_x000D_
    <div id="myScroll">_x000D_
            Contents will load here!!!.<br />_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_
        <p >This is test data.<br />Next line.</p>_x000D_

What is the mouse down selector in CSS?

I figured out that this behaves like a mousedown event:

button:active:hover {}

How to pass multiple parameter to @Directives (@Components) in Angular with TypeScript?

From the Documentation

As with components, you can add as many directive property bindings as you need by stringing them along in the template.

Add an input property to HighlightDirective called defaultColor:

@Input() defaultColor: string;


<p [myHighlight]="color" defaultColor="violet">
  Highlight me too!

Angular knows that the defaultColor binding belongs to the HighlightDirective because you made it public with the @Input decorator.

Either way, the @Input decorator tells Angular that this property is public and available for binding by a parent component. Without @Input, Angular refuses to bind to the property.

For your example

With many parameters

Add properties into the Directive class with @Input() decorator

    selector: '[selectable]'
export class SelectableDirective{
    private el: HTMLElement;

    @Input('selectable') option:any;   
    @Input('first') f;
    @Input('second') s;


And in the template pass bound properties to your li element

<li *ngFor = 'let opt of currentQuestion.options' 
    [selectable] = 'opt' 
    (selectedOption) = 'onOptionSelection($event)'>

Here on the li element we have a directive with name selectable. In the selectable we have two @Input()'s, f with name first and s with name second. We have applied these two on the li properties with name [first] and [second]. And our directive will find these properties on that li element, which are set for him with @Input() decorator. So selectable, [first] and [second] will be bound to every directive on li, which has property with these names.

With single parameter

    selector: '[selectable]'
export class SelectableDirective{
    private el: HTMLElement;

    @Input('selectable') option:any;   
    @Input('params') params;



<li *ngFor = 'let opt of currentQuestion.options' 
    [selectable] = 'opt' 
    [params]='{firstParam: 1, seconParam: 2, thirdParam: 3}'
    (selectedOption) = 'onOptionSelection($event)'>

Comparing the contents of two files in Sublime Text

You can actually compare files natively right in Sublime Text.

  1. Navigate to the folder containing them through Open Folder... or in a project
  2. Select the two files (ie, by holding Ctrl on Windows or ? on macOS) you want to compare in the sidebar
  3. Right click and select the Diff files... option.

How can I sort one set of data to match another set of data in Excel?

You can use VLOOKUP.

Assuming those are in columns A and B in Sheet1 and Sheet2 each, 22350 is in cell A2 of Sheet1, you can use:

=VLOOKUP(A2, Sheet2!A:B, 2, 0)

This will return you #N/A if there are no matches. Drag/Fill/Copy&Paste the formula to the bottom of your table and that should do it.

Row numbers in query result using Microsoft Access

Another way to assign a row number in a query is to use the DCount function.

SELECT *, DCount("[ID]","[mytable]","[ID]<=" & [ID]) AS row_id
FROM [mytable]
WHERE row_id=15

How do I update Anaconda?

This can update the Python instance only:

conda update python

Delete certain lines in a txt file via a batch file

If you have sed:

sed -e '/REFERENCE/d' -e '/ERROR/d' [FILENAME]

Where FILENAME is the name of the text file with the good & bad lines

.append(), prepend(), .after() and .before()

There is no extra advantage for each of them. It totally depends on your scenario. Code below shows their difference.

    Before inserts your html here
<div id="mainTabsDiv">
    Prepend inserts your html here
    <div id="homeTabDiv">
    <div id="aboutUsTabDiv">
            About Us
    <div id="contactUsTabDiv">
            Contact Us
    Append inserts your html here
After inserts your html here

Android how to use Environment.getExternalStorageDirectory()

As described in Documentation Environment.getExternalStorageDirectory() :

Environment.getExternalStorageDirectory() Return the primary shared/external storage directory.

This is an example of how to use it reading an image :

String fileName = "stored_image.jpg";
 String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
 String pathDir = baseDir + "/Android/data/com.mypackage.myapplication/";

 File f = new File(pathDir + File.separator + fileName);

          Log.d("Application", "The file " + file.getName() + " exists!";
          Log.d("Application", "The file no longer exists!";

Error #2032: Stream Error

Just to clarify my comment (it's illegible in a single line)

I think the best answer is the comment by Mike Chambers in this link ( by Hunter McMillen.

A note from Mike Chambers:

If you run into this using URLLoader, listen for the:

and in AIR :

It should give you some more information (such as the status code being returned from the server).

Using File.listFiles with FileNameExtensionFilter

Is there a specific reason you want to use FileNameExtensionFilter? I know this works..

private File[] getNewTextFiles() {
    return dir.listFiles(new FilenameFilter() {
        public boolean accept(File dir, String name) {
            return name.toLowerCase().endsWith(".txt");

How do I change the hover over color for a hover over table in Bootstrap?

Try Bootstrap’s .table-hover class to implement hoverable rows, for example

<table class="table table-hover">

JavaScript: How do I print a message to the error console?

If you are using Firebug and need to support IE, Safari or Opera as well, Firebug Lite adds console.log() support to these browsers.

How to change Java version used by TOMCAT?

There are several good answers on here but I wanted to add one since it may be helpful for users like me who have Tomcat installed as a service on a Windows machine.

Option 3 here:

Basically, open tomcatw.exe and point Tomcat to the version of the JVM you need to use then restart the service. Ensure your deployed applications still work as well.

How to select all records from one table that do not exist in another table?

See query:

        Table1 e
            INNER JOIN
        Table2 s ON =;

Conceptually would be: Fetching the matching records in subquery and then in main query fetching the records which are not in subquery.

How to set label size in Bootstrap

You'll have to do 2 things to make a Bootstrap label (or anything really) adjust sizes based on screen size:

  • Use a media query per display size range to adjust the CSS.
  • Override CSS sizing set by Bootstrap. You do this by making your CSS rules more specific than Bootstrap's. By default, Bootstrap sets .label { font-size: 75% }. So any extra selector on your CSS rule will make it more specific.

Here's an example CSS listing to accomplish what you are asking, using the default 4 sizes in Bootstrap:

@media (max-width: 767) {
    /* your custom css class on a parent will increase specificity */
    /* so this rule will override Bootstrap's font size setting */
    .autosized .label { font-size: 14px; }

@media (min-width: 768px) and (max-width: 991px) {
    .autosized .label { font-size: 16px; }

@media (min-width: 992px) and (max-width: 1199px) {
    .autosized .label { font-size: 18px; }

@media (min-width: 1200px) {
    .autosized .label { font-size: 20px; }

Here is how it could be used in the HTML:

<!-- any ancestor could be set to autosized -->
<div class="autosized">
            <span class="label label-primary">Label 1</span>

The Import cannot be resolved

Recent sdk-manager's download does not contain android-support-v7-appcompat.jar But the following dir contains aar file C:\Users\madan\android-sdks\extras\android\m2repository\com\ android\support\appcompat-v7\24.2.1\appcompat-v7-24.2.1.aar This file can be imported by right-click project, import, select general, select archieve and finally select aar file. Even this does not solve the problem. Later remove 'import android.R' and add 'import*;' Follow this tutorial for other details:

Datatable select method ORDER BY clause

You can use the below simple method of sorting:

datatable.DefaultView.Sort = "Col2 ASC,Col3 ASC,Col4 ASC";

By the above method, you will be able to sort N number of columns.

SMTP error 554

SMTP error 554 is one of the more vague error codes, but is typically caused by the receiving server seeing something in the From or To headers that it doesn't like. This can be caused by a spam trap identifying your machine as a relay, or as a machine not trusted to send mail from your domain.

We ran into this problem recently when adding a new server to our array, and we fixed it by making sure that we had the correct reverse DNS lookup set up.

Add data dynamically to an Array

$array[] = 'Hi';

pushes on top of the array.

$array['Hi'] = 'FooBar';

sets a specific index.

Angular 2: How to write a for loop, not a foreach loop

You can instantiate an empty array with a given number of entries if you pass an int to the Array constructor and then iterate over it via ngFor.

In your component code :

export class ForLoop {
  fakeArray = new Array(12);

In your template :

  <li *ngFor="let a of fakeArray; let index = index">Something {{ index }}</li>

The index properties give you the iteration number.

Live version

Load HTML File Contents to Div [without the use of iframes]

I'd suggest getting into one of the JS libraries out there. They ensure compatibility so you can get up and running really fast. jQuery and DOJO are both really great. To do what you're trying to do in jQuery, for example, it would go something like this:

<script type="text/javascript" language="JavaScript">
    url: "x.html", 
    context: document.body,
    success: function(response) {

What's the difference between disabled="disabled" and readonly="readonly" for HTML form input fields?

A readonly element is just not editable, but gets sent when the according form submits. A disabled element isn't editable and isn't sent on submit. Another difference is that readonly elements can be focused (and getting focused when "tabbing" through a form) while disabled elements can't.

Read more about this in this great article or the definition by w3c. To quote the important part:

Key Differences

The Disabled attribute

  • Values for disabled form elements are not passed to the processor method. The W3C calls this a successful element.(This works similar to form check boxes that are not checked.)
  • Some browsers may override or provide default styling for disabled form elements. (Gray out or emboss text) Internet Explorer 5.5 is particularly nasty about this.
  • Disabled form elements do not receive focus.
  • Disabled form elements are skipped in tabbing navigation.

The Read Only Attribute

  • Not all form elements have a readonly attribute. Most notable, the <SELECT> , <OPTION> , and <BUTTON> elements do not have readonly attributes (although they both have disabled attributes)
  • Browsers provide no default overridden visual feedback that the form element is read only. (This can be a problem… see below.)
  • Form elements with the readonly attribute set will get passed to the form processor.
  • Read only form elements can receive the focus
  • Read only form elements are included in tabbed navigation.

How to embed an autoplaying YouTube video in an iframe?

Nowadays I include a new attribute "allow" on iframe tag, for example:

allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture"

The final code is:

<iframe src="[VIDEO-CODE]?autoplay=1" 
frameborder="0" style="width: 100%; height: 100%;"
allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture"></iframe>

Execute jQuery function after another function completes

You can use below code

$.when( Typer() ).done(function() {

Get next element in foreach loop

You could probably use while loop instead of foreach:

while ($current = current($array) )
    $next = next($array);
    if (false !== $next && $next == $current)
        //do something with $current

sendKeys() in Selenium web driver

For python selenium,

Importing the library,

from selenium.webdriver.common.keys import Keys

Use this code to press any key you want,


You can find all the key names by searching this selenium.webdriver.common.keys.

Change EditText hint color when using TextInputLayout

Define android:textColorHint in your application theme:

<style name="AppTheme" parent="Theme.AppCompat.NoActionBar">
    <item name="colorPrimary">@color/primary</item>
    <item name="colorPrimaryDark">@color/primary_dark</item>
    <item name="colorAccent">@color/accent</item>

    <item name="android:textColorHint">@color/secondary_text</item>


Which loop is faster, while or for?

They should be equal. The for loop you wrote is doing exactly the same thing that the while loop is doing: setting $i=0, printing $i, and incrementing $i at the end of the loop.

nvm keeps "forgetting" node in new terminal session

$ nvm alias default {NODE_VERSION}

when we use the above command, only update the node version but the npm still uses the old version.

Here is another solution for update the both node and npm, in my case i want to use node 8.9.4 and i have used the below command.

$ nvm use default 8.9.4

And the command returns the output.

Now using node v8.9.4 (npm v5.6.0)

docker cannot start on windows

You need the admin privilege to run the service

I had the similar issue. The problem goes away when I run command prompt ( run as an administrator" , and type " docker version".

C:\WINDOWS\system32>docker version

Client: Docker Engine - Community Version: 19.03.8 API version: 1.40 Go version: go1.12.17 Git commit: afacb8b Built: Wed Mar 11 01:23:10 2020 OS/Arch: windows/amd64 Experimental: false

Server: Docker Engine - Community Engine: Version: 19.03.8 API version: 1.40 (minimum version 1.12) Go version: go1.12.17 Git commit: afacb8b Built: Wed Mar 11 01:29:16 2020 OS/Arch: linux/amd64 Experimental: false containerd: Version: v1.2.13 GitCommit: 7ad184331fa3e55e52b890ea95e65ba581ae3429 runc: Version: 1.0.0-rc10 GitCommit: dc9208a3303feef5b3839f4323d9beb36df0a9dd docker-init: Version: 0.18.0 GitCommit: fec3683

How to convert a time string to seconds?

For Python 2.7:

>>> import datetime
>>> import time
>>> x = time.strptime('00:01:00,000'.split(',')[0],'%H:%M:%S')
>>> datetime.timedelta(hours=x.tm_hour,minutes=x.tm_min,seconds=x.tm_sec).total_seconds()

Error "library not found for" after putting application in AdMob

Sometimes you just remove the reference of the library and add reference again.

Apart from adding the Google Mobile Ads SDK and other libraries again from scratch, I would recommend you checking the Library Search Paths. There are instances when you copy or duplicate a target, Xcode decides that it needs to escape any double quotes " with a '\'. Make sure you remove all the \’s - it should look like this -

enter image description here

I was able to duplicate the error, by doing prefixing my path with multiple '\'.

Replace String in all files in Eclipse

Depending on the file type you are focused on, Ctrl+H will open up different types of search screens.

A more consistent hotkey would be using the Alt method: Tap Alt, then A, then F.

Efficient Order of Operations:

  1. Ctrl+C the text you want to do the replacing (if available)
  2. Highlight the text you want to be replaced
  3. Tap ALT, then A, then F. Brings you to File Search. The selection from (2) will auto-fill the search box
  4. In the “File name patterns” input box, type in “.java” for replacing all Java files or type in "" to replace in all files
  5. Click “Replace…”
  6. Ctrl+V (Paste). Or type in the value you want to do the replacing
  7. Enter

You can find more details in my blog post:

How to generate a git patch for a specific commit?

Say you have commit id 2 after commit 1 you would be able to run:

git diff 2 1 > mypatch.diff

where 2 and 1 are SHA hashes.

MySQL DAYOFWEEK() - my week begins with monday

Use WEEKDAY() instead of DAYOFWEEK(), it begins on Monday.

If you need to start at index 1, use or WEEKDAY() + 1.

RecyclerView expand/collapse items

I am surprised that there's no concise answer yet, although such an expand/collapse animation is very easy to achieve with just 2 lines of code:

(recycler.itemAnimator as SimpleItemAnimator).supportsChangeAnimations = false // called once

together with

notifyItemChanged(position) // in adapter, whenever a child view in item's recycler gets hidden/shown

So for me, the explanations in the link below were really useful:

What version of javac built my jar?

Developers and administrators running Bash may find these convenience functions helpful:

jar_jdk_version() {
  [[ -n "$1" && -x "`command -v javap`" ]] && javap -classpath "$1" -verbose $(jar -tf "$1" | grep '.class' | head -n1 | sed -e 's/\.class$//') | grep 'major version' | sed -e 's/[^0-9]\{1,\}//'

print_jar_jdk_version() {
  local version
  version=$(jar_jdk_version "$1")
  case $version in 49) version=1.5;; 50) version=1.6;; 51) version=1.7;; 52) version=1.8;; esac
  [[ -n "$version" ]] && echo "`basename "$1"` contains classes compiled with JDK version $version."

You can paste them in for one-time usage or add them to ~/.bash_aliases or ~/.bashrc. The results look something like:

$ jar_jdk_version poi-ooxml-3.5-FINAL.jar


$ print_jar_jdk_version poi-ooxml-3.5-FINAL.jar
poi-ooxml-3.5-FINAL.jar contains classes compiled with JDK version 1.5.

EDIT As jackrabbit points out, you can't 100% rely on the manifest to tell you anything useful. If it was, then you could pull it out in your favorite UNIX shell with unzip:

$ unzip -pa poi-ooxml-3.5-FINAL.jar META-INF/MANIFEST.MF
Manifest-Version: 1.0
Ant-Version: Apache Ant 1.7.1
Created-By: 11.3-b02 (Sun Microsystems Inc.)
Built-By: yegor
Specification-Title: Apache POI
Specification-Version: 3.5-FINAL-20090928
Specification-Vendor: Apache
Implementation-Title: Apache POI
Implementation-Version: 3.5-FINAL-20090928
Implementation-Vendor: Apache

This .jar doesn't have anything useful in the manifest about the contained classes.

How to save/restore serializable object to/from file?

I just wrote a blog post on saving an object's data to Binary, XML, or Json. You are correct that you must decorate your classes with the [Serializable] attribute, but only if you are using Binary serialization. You may prefer to use XML or Json serialization. Here are the functions to do it in the various formats. See my blog post for more details.


/// <summary>
/// Writes the given object instance to a binary file.
/// <para>Object type (and all child types) must be decorated with the [Serializable] attribute.</para>
/// <para>To prevent a variable from being serialized, decorate it with the [NonSerialized] attribute; cannot be applied to properties.</para>
/// </summary>
/// <typeparam name="T">The type of object being written to the binary file.</typeparam>
/// <param name="filePath">The file path to write the object instance to.</param>
/// <param name="objectToWrite">The object instance to write to the binary file.</param>
/// <param name="append">If false the file will be overwritten if it already exists. If true the contents will be appended to the file.</param>
public static void WriteToBinaryFile<T>(string filePath, T objectToWrite, bool append = false)
    using (Stream stream = File.Open(filePath, append ? FileMode.Append : FileMode.Create))
        var binaryFormatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
        binaryFormatter.Serialize(stream, objectToWrite);

/// <summary>
/// Reads an object instance from a binary file.
/// </summary>
/// <typeparam name="T">The type of object to read from the binary file.</typeparam>
/// <param name="filePath">The file path to read the object instance from.</param>
/// <returns>Returns a new instance of the object read from the binary file.</returns>
public static T ReadFromBinaryFile<T>(string filePath)
    using (Stream stream = File.Open(filePath, FileMode.Open))
        var binaryFormatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
        return (T)binaryFormatter.Deserialize(stream);


Requires the System.Xml assembly to be included in your project.

/// <summary>
/// Writes the given object instance to an XML file.
/// <para>Only Public properties and variables will be written to the file. These can be any type though, even other classes.</para>
/// <para>If there are public properties/variables that you do not want written to the file, decorate them with the [XmlIgnore] attribute.</para>
/// <para>Object type must have a parameterless constructor.</para>
/// </summary>
/// <typeparam name="T">The type of object being written to the file.</typeparam>
/// <param name="filePath">The file path to write the object instance to.</param>
/// <param name="objectToWrite">The object instance to write to the file.</param>
/// <param name="append">If false the file will be overwritten if it already exists. If true the contents will be appended to the file.</param>
public static void WriteToXmlFile<T>(string filePath, T objectToWrite, bool append = false) where T : new()
    TextWriter writer = null;
        var serializer = new XmlSerializer(typeof(T));
        writer = new StreamWriter(filePath, append);
        serializer.Serialize(writer, objectToWrite);
        if (writer != null)

/// <summary>
/// Reads an object instance from an XML file.
/// <para>Object type must have a parameterless constructor.</para>
/// </summary>
/// <typeparam name="T">The type of object to read from the file.</typeparam>
/// <param name="filePath">The file path to read the object instance from.</param>
/// <returns>Returns a new instance of the object read from the XML file.</returns>
public static T ReadFromXmlFile<T>(string filePath) where T : new()
    TextReader reader = null;
        var serializer = new XmlSerializer(typeof(T));
        reader = new StreamReader(filePath);
        return (T)serializer.Deserialize(reader);
        if (reader != null)


You must include a reference to Newtonsoft.Json assembly, which can be obtained from the Json.NET NuGet Package.

/// <summary>
/// Writes the given object instance to a Json file.
/// <para>Object type must have a parameterless constructor.</para>
/// <para>Only Public properties and variables will be written to the file. These can be any type though, even other classes.</para>
/// <para>If there are public properties/variables that you do not want written to the file, decorate them with the [JsonIgnore] attribute.</para>
/// </summary>
/// <typeparam name="T">The type of object being written to the file.</typeparam>
/// <param name="filePath">The file path to write the object instance to.</param>
/// <param name="objectToWrite">The object instance to write to the file.</param>
/// <param name="append">If false the file will be overwritten if it already exists. If true the contents will be appended to the file.</param>
public static void WriteToJsonFile<T>(string filePath, T objectToWrite, bool append = false) where T : new()
    TextWriter writer = null;
        var contentsToWriteToFile = JsonConvert.SerializeObject(objectToWrite);
        writer = new StreamWriter(filePath, append);
        if (writer != null)

/// <summary>
/// Reads an object instance from an Json file.
/// <para>Object type must have a parameterless constructor.</para>
/// </summary>
/// <typeparam name="T">The type of object to read from the file.</typeparam>
/// <param name="filePath">The file path to read the object instance from.</param>
/// <returns>Returns a new instance of the object read from the Json file.</returns>
public static T ReadFromJsonFile<T>(string filePath) where T : new()
    TextReader reader = null;
        reader = new StreamReader(filePath);
        var fileContents = reader.ReadToEnd();
        return JsonConvert.DeserializeObject<T>(fileContents);
        if (reader != null)


// Write the contents of the variable someClass to a file.
WriteToBinaryFile<SomeClass>("C:\someClass.txt", object1);

// Read the file contents back into a variable.
SomeClass object1= ReadFromBinaryFile<SomeClass>("C:\someClass.txt");

Postgresql : Connection refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections

The error you quote has nothing to do with pg_hba.conf; it's failing to connect, not failing to authorize the connection.

Do what the error message says:

Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections

You haven't shown the command that produces the error. Assuming you're connecting on localhost port 5432 (the defaults for a standard PostgreSQL install), then either:

  • PostgreSQL isn't running

  • PostgreSQL isn't listening for TCP/IP connections (listen_addresses in postgresql.conf)

  • PostgreSQL is only listening on IPv4 ( or and you're connecting on IPv6 (::1) or vice versa. This seems to be an issue on some older Mac OS X versions that have weird IPv6 socket behaviour, and on some older Windows versions.

  • PostgreSQL is listening on a different port to the one you're connecting on

  • (unlikely) there's an iptables rule blocking loopback connections

(If you are not connecting on localhost, it may also be a network firewall that's blocking TCP/IP connections, but I'm guessing you're using the defaults since you didn't say).

So ... check those:

  • ps -f -u postgres should list postgres processes

  • sudo lsof -n -u postgres |grep LISTEN or sudo netstat -ltnp | grep postgres should show the TCP/IP addresses and ports PostgreSQL is listening on

BTW, I think you must be on an old version. On my 9.3 install, the error is rather more detailed:

$ psql -h localhost -p 12345
psql: could not connect to server: Connection refused
        Is the server running on host "localhost" (::1) and accepting
        TCP/IP connections on port 12345?

How to set border's thickness in percentages?

You can use em for percentage instead of pixels,


border:10PX dotted #c1a9ff; /* In Pixels */
border:0.75em dotted #c1a9ff; /* Exact same as above in Percentage */

Which sort algorithm works best on mostly sorted data?

Bubble sort is definitely the winner The next one on the radar would be insertion sort.

java.lang.ClassNotFoundException: org.springframework.boot.SpringApplication Maven

The answer to the above question is "none of the above". When you download new STS it won't support the old Spring Boot parent version. Just update parent version with latest comes with STS it will work.

    <relativePath/> <!-- lookup parent from repository -->

If you have problem getting the latest, just create a new Spring Starter Project. Go to File->New->Spring Start Project and create a demo project you will get the latest parent version, change your version with that all will work. I do this every time I change STS.

String Padding in C

#include <string.h>

void padLeft(int length, char pad, char* inStr,char* outStr) {
    int minLength = length * sizeof(char);
    if (minLength < sizeof(outStr)) {

    int padLen = length - strlen(inStr);
    padLen = padLen < 0 ? 0 : padLen;

    memset(outStr, 0, sizeof(outStr));
    memset(outStr, pad,padLen);
    memcpy(outStr+padLen, inStr, minLength - padLen);

Get Path from another app (WhatsApp)

You can try this it will help for you.You can't get path from WhatsApp directly.If you need an file path first copy file and send new file path. Using the code below

 public static String getFilePathFromURI(Context context, Uri contentUri) {
    String fileName = getFileName(contentUri);
    if (!TextUtils.isEmpty(fileName)) {
        File copyFile = new File(TEMP_DIR_PATH  + fileName+".jpg");
        copy(context, contentUri, copyFile);
        return copyFile.getAbsolutePath();
    return null;

public static String getFileName(Uri uri) {
    if (uri == null) return null;
    String fileName = null;
    String path = uri.getPath();
    int cut = path.lastIndexOf('/');
    if (cut != -1) {
        fileName = path.substring(cut + 1);
    return fileName;

public static void copy(Context context, Uri srcUri, File dstFile) {
    try {
        InputStream inputStream = context.getContentResolver().openInputStream(srcUri);
        if (inputStream == null) return;
        OutputStream outputStream = new FileOutputStream(dstFile);
        IOUtils.copy(inputStream, outputStream);
    } catch (IOException e) {
    } catch (Exception e) {

Then IOUtils class is like below

public class IOUtils {

private static final int BUFFER_SIZE = 1024 * 2;

private IOUtils() {
    // Utility class.

public static int copy(InputStream input, OutputStream output) throws Exception, IOException {
    byte[] buffer = new byte[BUFFER_SIZE];

    BufferedInputStream in = new BufferedInputStream(input, BUFFER_SIZE);
    BufferedOutputStream out = new BufferedOutputStream(output, BUFFER_SIZE);
    int count = 0, n = 0;
    try {
        while ((n =, 0, BUFFER_SIZE)) != -1) {
            out.write(buffer, 0, n);
            count += n;
    } finally {
        try {
        } catch (IOException e) {
            Log.e(e.getMessage(), e.toString());
        try {
        } catch (IOException e) {
            Log.e(e.getMessage(), e.toString());
    return count;


How to instantiate, initialize and populate an array in TypeScript?

An other solution:

interface bar {
    length: number;

bars = [{
  length: 1
} as bar];

How to ssh from within a bash script?

If you want to continue to use passwords and not use key exchange then you can accomplish this with 'expect' like so:

#!/usr/bin/expect -f
spawn ssh user@hostname
expect "password:"
sleep 1
send "<your password>\r"

Deleting rows with Python in a CSV file

You should have if row[2] != "0". Otherwise it's not checking to see if the string value is equal to 0.

Check if space is in a string

# The following would be a very simple solution.

string = input("Enter your string :")
noofspacesinstring = 0
for counter in string:
    if counter == " ":
       noofspacesinstring += 1
if noofspacesinstring == 0:
   message = "Your string is a single word" 
   message = "Your string is not a single word"

Mockito matcher and array of primitives

What works for me was org.mockito.ArgumentMatchers.isA

for example:


that works fine.

the implementation difference of each other is:

public static <T> T any(Class<T> type) {
    reportMatcher(new VarArgAware(type, "<any " + type.getCanonicalName() + ">"));
    return Primitives.defaultValue(type);

public static <T> T isA(Class<T> type) {
    reportMatcher(new InstanceOf(type));
    return Primitives.defaultValue(type);

Node - how to run app.js?

Node is complaining because there is no function called define, which your code tries to call on its very first line.

define comes from AMD, which is not used in standard node development.

It is possible that the developer you got your project from used some kind of trickery to use AMD in node. You should ask this person what special steps are necessary to run the code.

Chart.js v2 - hiding grid lines

I found a solution that works for hiding the grid lines in a Line chart.

Set the gridLines color to be the same as the div's background color.

var options = {
    scales: {
        xAxes: [{
            gridLines: {
                color: "rgba(0, 0, 0, 0)",
        yAxes: [{
            gridLines: {
                color: "rgba(0, 0, 0, 0)",

or use

var options = {
    scales: {
        xAxes: [{
            gridLines: {
        yAxes: [{
            gridLines: {

How can I generate a list of consecutive numbers?

In Python 3, you can use the builtin range function like this

>>> list(range(9))
[0, 1, 2, 3, 4, 5, 6, 7, 8]

Note 1: Python 3.x's range function, returns a range object. If you want a list you need to explicitly convert that to a list, with the list function like I have shown in the answer.

Note 2: We pass number 9 to range function because, range function will generate numbers till the given number but not including the number. So, we give the actual number + 1.

Note 3: There is a small difference in functionality of range in Python 2 and 3. You can read more about that in this answer.

How many concurrent AJAX (XmlHttpRequest) requests are allowed in popular browsers?

With IE6 / IE7 one can tweak the number of concurrent requests in the registry. Here's how to set it to four each.

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings]

Java synchronized block vs. Collections.synchronizedMap

Check out Google Collections' Multimap, e.g. page 28 of this presentation.

If you can't use that library for some reason, consider using ConcurrentHashMap instead of SynchronizedHashMap; it has a nifty putIfAbsent(K,V) method with which you can atomically add the element list if it's not already there. Also, consider using CopyOnWriteArrayList for the map values if your usage patterns warrant doing so.

How do I copy directories recursively with gulp?

The following works without flattening the folder structure:


The '**/*' is the important part. That expression is a glob which is a powerful file selection tool. For example, for copying only .js files use: 'input/folder/**/*.js'

What's the difference between the 'ref' and 'out' keywords?

To illustrate the many excellent explanations, I developed the following console app:

using System;
using System.Collections.Generic;

namespace CSharpDemos
  class Program
    static void Main(string[] args)
      List<string> StringList = new List<string> { "Hello" };
      List<string> StringListRef = new List<string> { "Hallo" };

      Console.WriteLine(StringList[0] + StringList[1]);

      HalloWelt(ref StringListRef);
      Console.WriteLine(StringListRef[0] + StringListRef[1]);

      CiaoMondo(out List<string> StringListOut);
      Console.WriteLine(StringListOut[0] + StringListOut[1]);

    static void AppendWorld(List<string> LiStri)
      LiStri.Add(" World!");
      LiStri = new List<string> { "¡Hola", " Mundo!" };
      Console.WriteLine(LiStri[0] + LiStri[1]);

    static void HalloWelt(ref List<string> LiStriRef)
     { LiStriRef = new List<string> { LiStriRef[0], " Welt!" }; }

    static void CiaoMondo(out List<string> LiStriOut)
     { LiStriOut = new List<string> { "Ciao", " Mondo!" }; }
¡Hola Mundo!
Hello World!
Hallo Welt!
Ciao Mondo!
  • AppendWorld: A copy of StringList named LiStri is passed. At the start of the method, this copy references the original list and therefore can be used to modify this list. Later LiStri references another List<string> object inside the method which doesn't affect the original list.

  • HalloWelt: LiStriRef is an alias of the already initialized ListStringRef. The passed List<string> object is used to initialize a new one, therefore ref was necessary.

  • CiaoMondo: LiStriOut is an alias of ListStringOut and must be initialized.

So, if a method just modifies the object referenced by the passed variable, the compiler will not let you use out and you should not use ref because it would confuse not the compiler but the reader of the code. If the method will make the passed argument reference another object, use ref for an already initialized object and out for methods that must initialize a new object for the passed argument. Besides that, ref and out behave the same.

IPython Notebook save location

To add to Victor's answer, I was able to change the save directory on Windows using...

c.NotebookApp.notebook_dir = 'C:\\Users\\User\\Folder'

HTML: How to limit file upload to be only images?

Because <input type="file" id="fileId" accept="image/*"> can't guarantee that someone will choose an image, you need some validation like this:

                alert('You can\'t upload this type of file.');

What's the difference between SHA and AES encryption?

SHA doesn't require anything but an input to be applied, while AES requires at least 3 things - what you're encrypting/decrypting, an encryption key, and the initialization vector.

How do I delete a Git branch locally and remotely?

Now you can do it with the GitHub Desktop application.

After launching the application

  1. Click on the project containing the branch
  2. Switch to the branch you would like to delete

    Switching branch

  3. From the "Branch" menu, select, "Unpublish...", to have the branch deleted from the GitHub servers.

    Unpublish branch

  4. From the "Branch" menu, select, 'Delete "branch_name"...', to have the branch deleted off of your local machine (AKA the machine you are currently working on)

    Delete local branch

Passing data to a bootstrap modal

I think you can make this work using jQuery's .on event handler.

Here's a fiddle you can test; just make sure to expand the HTML frame in the fiddle as much as possible so you can view the modal.


<p>Link 1</p>
<a data-toggle="modal" data-id="ISBN564541" title="Add this item" class="open-AddBookDialog btn btn-primary" href="#addBookDialog">test</a>


<p>Link 2</p>
<a data-toggle="modal" data-id="ISBN-001122" title="Add this item" class="open-AddBookDialog btn btn-primary" href="#addBookDialog">test</a>

<div class="modal hide" id="addBookDialog">
 <div class="modal-header">
    <button class="close" data-dismiss="modal">×</button>
    <h3>Modal header</h3>
    <div class="modal-body">
        <p>some content</p>
        <input type="text" name="bookId" id="bookId" value=""/>


$(document).on("click", ".open-AddBookDialog", function () {
     var myBookId = $(this).data('id');
     $(".modal-body #bookId").val( myBookId );
     // As pointed out in comments, 
     // it is unnecessary to have to manually call the modal.
     // $('#addBookDialog').modal('show');

Pandas - Compute z-score for all columns

To calculate a z-score for an entire column quickly, do as follows:

from scipy.stats import zscore
import pandas as pd

df = pd.DataFrame({'num_1': [1,2,3,4,5,6,7,8,9,3,4,6,5,7,3,2,9]})
df['num_1_zscore'] = zscore(df['num_1'])


nodejs module.js:340 error: cannot find module

Hi fellow Phonegap/Cordova/Ionic developers,

  I solved this issue by doing the following

  1. C: drive -> Users -> "username" eg. john -> AppData -> Roaming

  2. Inside the "Roaming" folder you need to delete both "npm" and "npm-cache" 

  3. Now build your project, and it should work

Happy coding!!!

How to check for file lock?

What I ended up doing is:

internal void LoadExternalData() {
    FileStream file;

    if (TryOpenRead("filepath/filename", 5, out file)) {
        using (file)
        using (StreamReader reader = new StreamReader(file)) {
         // do something 

internal bool TryOpenRead(string path, int timeout, out FileStream file) {
    bool isLocked = true;
    bool condition = true;

    do {
        try {
            file = File.OpenRead(path);
            return true;
        catch (IOException e) {
            var errorCode = Marshal.GetHRForException(e) & ((1 << 16) - 1);
            isLocked = errorCode == 32 || errorCode == 33;
            condition = (isLocked && timeout > 0);

            if (condition) {
                // we only wait if the file is locked. If the exception is of any other type, there's no point on keep trying. just return false and null;
                new System.Threading.ManualResetEvent(false).WaitOne(1000);
    while (condition);

    file = null;
    return false;

Set Colorbar Range in matplotlib

Use the CLIM function (equivalent to CAXIS function in MATLAB):

plt.pcolor(X, Y, v, cmap=cm)
plt.clim(-4,4)  # identical to caxis([-4,4]) in MATLAB

Split a string by another string in C#

There is an overload of Split that takes strings.

"THExxQUICKxxBROWNxxFOX".Split(new [] { "xx" }, StringSplitOptions.None);

You can use either of these StringSplitOptions

  • None - The return value includes array elements that contain an empty string
  • RemoveEmptyEntries - The return value does not include array elements that contain an empty string

So if the string is "THExxQUICKxxxxBROWNxxFOX", StringSplitOptions.None will return an empty entry in the array for the "xxxx" part while StringSplitOptions.RemoveEmptyEntries will not.

how do you insert null values into sql server

If you're using SSMS (or old school Enterprise Manager) to edit the table directly, press CTRL+0 to add a null.

How do I upload a file with the JS fetch API?

The problem for me was that I was using a response.blob() to populate the form data. Apparently you can't do that at least with react native so I ended up using

data.append('fileData', {
  uri : pickerResponse.uri,
  type: pickerResponse.type,
  name: pickerResponse.fileName

Fetch seems to recognize that format and send the file where the uri is pointing.

delete all from table

You can use the below query to remove all the rows from the table, also you should keep it in mind that it will reset the Identity too.


JavaScript - Get Browser Height

Try using jquery:

window_size = $(window).height();

Counting the number of True Booleans in a Python List

Just for completeness' sake (sum is usually preferable), I wanted to mention that we can also use filter to get the truthy values. In the usual case, filter accepts a function as the first argument, but if you pass it None, it will filter for all "truthy" values. This feature is somewhat surprising, but is well documented and works in both Python 2 and 3.

The difference between the versions, is that in Python 2 filter returns a list, so we can use len:

>>> bool_list = [True, True, False, False, False, True]
>>> filter(None, bool_list)
[True, True, True]
>>> len(filter(None, bool_list))

But in Python 3, filter returns an iterator, so we can't use len, and if we want to avoid using sum (for any reason) we need to resort to converting the iterator to a list (which makes this much less pretty):

>>> bool_list = [True, True, False, False, False, True]
>>> filter(None, bool_list)
<builtins.filter at 0x7f64feba5710>
>>> list(filter(None, bool_list))
[True, True, True]
>>> len(list(filter(None, bool_list)))


See (search the page for "BEGIN RSA PRIVATE KEY") (archive link for posterity, just in case).

BEGIN RSA PRIVATE KEY is PKCS#1 and is just an RSA key. It is essentially just the key object from PKCS#8, but without the version or algorithm identifier in front. BEGIN PRIVATE KEY is PKCS#8 and indicates that the key type is included in the key data itself. From the link:

The unencrypted PKCS#8 encoded data starts and ends with the tags:


Within the base64 encoded data the following DER structure is present:

PrivateKeyInfo ::= SEQUENCE {
  version         Version,
  algorithm       AlgorithmIdentifier,
  PrivateKey      BIT STRING

AlgorithmIdentifier ::= SEQUENCE {
  algorithm       OBJECT IDENTIFIER,
  parameters      ANY DEFINED BY algorithm OPTIONAL

So for an RSA private key, the OID is 1.2.840.113549.1.1.1 and there is a RSAPrivateKey as the PrivateKey key data bitstring.

As opposed to BEGIN RSA PRIVATE KEY, which always specifies an RSA key and therefore doesn't include a key type OID. BEGIN RSA PRIVATE KEY is PKCS#1:

RSA Private Key file (PKCS#1)

The RSA private key PEM file is specific for RSA keys.

It starts and ends with the tags:


Within the base64 encoded data the following DER structure is present:

RSAPrivateKey ::= SEQUENCE {
  version           Version,
  modulus           INTEGER,  -- n
  publicExponent    INTEGER,  -- e
  privateExponent   INTEGER,  -- d
  prime1            INTEGER,  -- p
  prime2            INTEGER,  -- q
  exponent1         INTEGER,  -- d mod (p-1)
  exponent2         INTEGER,  -- d mod (q-1)
  coefficient       INTEGER,  -- (inverse of q) mod p
  otherPrimeInfos   OtherPrimeInfos OPTIONAL

Error 'LINK : fatal error LNK1123: failure during conversion to COFF: file invalid or corrupt' after installing Visual Studio 2012 Release Preview

To summarize:


Project Properties 
   -> Configuration Properties 
       -> Linker (General) 
          -> Enable Incremental Linking -> "No (/INCREMENTAL:NO)"

if step1 not work, do Step2

Project Properties 
   -> Configuration Properties 
       -> Manifest Tool (Input and Output) 
          -> Enable Incremental Linking -> "No"

if step2 not work, do Step3 Copy file one of:

  1. C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin\cvtres.exe
  2. C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\bin\cvtres.exe
  3. C:\Program Files (x86)\Microsoft Visual Studio 13.0\VC\bin\cvtres.exe

    Then, replace to C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin\cvtres.exe With me, do 3 step it work

How to determine the installed webpack version

Version Installed:

Using webpack CLI: (--version, -v Show version number [boolean])

webpack --version


webpack -v

Using npm list command:

npm list webpack

Results in name@version-range:

<projectName>@<projectVersion> /path/to/project
+-- webpack@<version-range>

Using yarn list command:

yarn list webpack

How to do it programmatically?

Webpack 2 introduced Configuration Types.

Instead of exporting a configuration object, you may return a function which accepts an environment as argument. When running webpack, you may specify build environment keys via --env, such as --env.production or --env.platform=web.

We will use a build environment key called --env.version.

webpack --env.version $(webpack --version)


webpack --env.version $(webpack -v)

For this to work we will need to do two things:

Change our webpack.config.js file and use DefinePlugin.

The DefinePlugin allows you to create global constants which can be configured at compile time.

-module.exports = {
+module.exports = function(env) {
+  return {
    plugins: [
      new webpack.DefinePlugin({
+        WEBPACK_VERSION: JSON.stringify(env.version) //<version-range>
+  };

Now we can access the global constant like so:


Latest version available:

Using npm view command will return the latest version available on the registry:

npm view [<@scope>/]<name>[@<version>] [<field>[.<subfield>]...]

For webpack use:

npm view webpack version

add commas to a number in jQuery

Number(10000).toLocaleString('en');  // "10,000"

Html/PHP - Form - Input as array

HTML: Use names as

<input name="levels[level][]">
<input name="levels[build_time][]">


$array = filter_input_array(INPUT_POST);
$newArray = array();
foreach (array_keys($array) as $fieldKey) {
    foreach ($array[$fieldKey] as $key=>$value) {
        $newArray[$key][$fieldKey] = $value;

$newArray will hold data as you want

Array ( 
  [0] => Array ( [level] => 1 [build_time] => 123 ) 
  [1] => Array ( [level] => 2 [build_time] => 456 )

Multiple submit buttons on HTML form – designate one button as default

I'm resurrecting this because I was researching a non-JavaScript way to do this. I wasn't into the key handlers, and the CSS positioning stuff was causing tab ordering to break since CSS repositioning doesn't change tab order.

My solution is based on the response at

The solution source is below. tabindex is used to correct tab behaviour of the hidden button, as well as aria-hidden to avoid having the button read out by screen readers / identified by assistive devices.

<form method="post" action="">
  <button type="submit" name="useraction" value="2nd" class="default-button-handler" aria-hidden="true" tabindex="-1"></button>
  <div class="form-group">
    <label for="test-input">Focus into this input: </label>
    <input type="text" id="test-input" class="form-control" name="test-input" placeholder="Focus in here and press enter / go" />

1st button in DOM 2nd button in DOM 3rd button in DOM

Essential CSS for this solution:

.default-button-handler {
  width: 0;
  height: 0;
  padding: 0;
  border: 0;
  margin: 0;

HTML to PDF with Node.js

Phantom.js is an headless webkit server and it will load any web page and render it in memory, although you might not be able to see it, there is a Screen Capture feature, in which you can export the current view as PNG, PDF, JPEG and GIF. Have a look at this example from phantom.js documentation

Is it possible to decrypt SHA1

SHA1 is a one way hash. So you can not really revert it.

That's why applications use it to store the hash of the password and not the password itself.

Like every hash function SHA-1 maps a large input set (the keys) to a smaller target set (the hash values). Thus collisions can occur. This means that two values of the input set map to the same hash value.

Obviously the collision probability increases when the target set is getting smaller. But vice versa this also means that the collision probability decreases when the target set is getting larger and SHA-1's target set is 160 bit.

Jeff Preshing, wrote a very good blog about Hash Collision Probabilities that can help you to decide which hash algorithm to use. Thanks Jeff.

In his blog he shows a table that tells us the probability of collisions for a given input set.

Hash Collision Probabilities Table

As you can see the probability of a 32-bit hash is 1 in 2 if you have 77163 input values.

A simple java program will show us what his table shows:

public class Main {

    public static void main(String[] args) {
        char[] inputValue = new char[10];

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

        int collisionCount = 0;

        for (int i = 0; i < 77163; i++) {
            String asString = nextValue(inputValue);
            int hashCode = asString.hashCode();
            String collisionString = hashValues.put(hashCode, asString);
            if (collisionString != null) {
                System.out.println("Collision: " + asString + " <-> " + collisionString);

        System.out.println("Collision count: " + collisionCount);

    private static String nextValue(char[] inputValue) {
        nextValue(inputValue, 0);

        int endIndex = 0;
        for (int i = 0; i < inputValue.length; i++) {
            if (inputValue[i] == 0) {
                endIndex = i;

        return new String(inputValue, 0, endIndex);

    private static void nextValue(char[] inputValue, int index) {
        boolean increaseNextIndex = inputValue[index] == 'z';

        if (inputValue[index] == 0 || increaseNextIndex) {
            inputValue[index] = 'A';
        } else {
            inputValue[index] += 1;

        if (increaseNextIndex) {
            nextValue(inputValue, index + 1);



My output end with:

Collision: RvV <-> SWV
Collision: SvV <-> TWV
Collision: TvV <-> UWV
Collision: UvV <-> VWV
Collision: VvV <-> WWV
Collision: WvV <-> XWV
Collision count: 35135

It produced 35135 collsions and that's the nearly the half of 77163. And if I ran the program with 30084 input values the collision count is 13606. This is not exactly 1 in 10, but it is only a probability and the example program is not perfect, because it only uses the ascii chars between A and z.

Let's take the last reported collision and check


My output is



If you have a SHA-1 value and you want to get the input value back you can try a brute force attack. This means that you have to generate all possible input values, hash them and compare them with the SHA-1 you have. But that will consume a lot of time and computing power. Some people created so called rainbow tables for some input sets. But these do only exist for some small input sets.

And remember that many input values map to a single target hash value. So even if you would know all mappings (which is impossible, because the input set is unbounded) you still can't say which input value it was.

Find what 2 numbers add to something and multiply to something

Come on guys, there is no need to loop, just use simple math to solve this equation system:

a*b = i;

a+b = j;

a = j/b;

a = i-b;

j/b = i-b; so:

b + j/b + i = 0

b^2 + i*b + j = 0

From here, its a quadratic equation, and it's trivial to find b (just implement the quadratic equation formula) and from there get the value for a.


There you go:

function finder($add,$product)

 $inside_root = $add*$add - 4*$product;

 if($inside_root >=0)

     $b = ($add + sqrt($inside_root))/2;
     $a = $add - $b;

     echo "$a+$b = $add and $a*$b=$product\n";

   echo "No real solution\n";

Real live action:

jQuery autocomplete with callback ajax json

    $( "#search_product" ).autocomplete({
                  $.post("<?= base_url('ecommerce/autocomplete') ?>",{'name':$( "#search_product" ).val()}).done(function(data, status){


PHP code :

public function autocomplete(){
    foreach($result as $row){
    echo json_encode($names);

When to use MyISAM and InnoDB?

Use MyISAM for very unimportant data or if you really need those minimal performance advantages. The read performance is not better in every case for MyISAM.

I would personally never use MyISAM at all anymore. Choose InnoDB and throw a bit more hardware if you need more performance. Another idea is to look at database systems with more features like PostgreSQL if applicable.

EDIT: For the read-performance, this link shows that innoDB often is actually not slower than MyISAM:

Eliminate space before \begin{itemize}

The "proper" LaTeX ways to do it is to use a package which allows you to specify the spacing you want. There are several such package, and these two pages link to lists of them...

Getting assembly name

I use the Assembly to set the form's title as such:

private String BuildFormTitle()
    String AppName = System.Reflection.Assembly.GetEntryAssembly().GetName().Name;
    String FormTitle = String.Format("{0} {1} ({2})", 
    return FormTitle;

How to execute a .bat file from a C# windows form app?

Here is what you are looking for:

Service hangs up at WaitForExit after calling batch file

It's about a question as to why a service can't execute a file, but it shows all the code necessary to do so.

Get selected item value from Bootstrap DropDown with specific ID

$('#demolist li').on('click', function(){

Inheritance with base class constructor with parameters

I could be wrong, but I believe since you are inheriting from foo, you have to call a base constructor. Since you explicitly defined the foo constructor to require (int, int) now you need to pass that up the chain.

public bar(int a, int b) : base(a, b)
     c = a * b;

This will initialize foo's variables first and then you can use them in bar. Also, to avoid confusion I would recommend not naming parameters the exact same as the instance variables. Try p_a or something instead, so you won't accidentally be handling the wrong variable.

Rotating a point about another point (2D)

I struggled while working MS OCR Read API which returns back angle of rotation in range (-180, 180]. So I have to do an extra step of converting negative angles to positive. I hope someone struggling with point rotation with negative or positive angles can use the following.

def rotate(origin, point, angle):
    Rotate a point counter-clockwise by a given angle around a given origin.
    # Convert negative angles to positive
    angle = normalise_angle(angle)

    # Convert to radians
    angle = math.radians(angle)

    # Convert to radians
    ox, oy = origin
    px, py = point
    # Move point 'p' to origin (0,0)
    _px = px - ox
    _py = py - oy
    # Rotate the point 'p' 
    qx = (math.cos(angle) * _px) - (math.sin(angle) * _py)
    qy = (math.sin(angle) * _px) + (math.cos(angle) * _py)
    # Move point 'p' back to origin (ox, oy)
    qx = ox + qx
    qy = oy + qy
    return [qx, qy]

def normalise_angle(angle):
    """ If angle is negative then convert it to positive. """
    if (angle != 0) & (abs(angle) == (angle * -1)):
        angle = 360 + angle
    return angle is being requested by various other libraries

In my case, this solves the issue:

implementation ''

Automapper missing type map configuration or unsupported mapping - Error

Upgrade Automapper to version 6.2.2. It helped me

Open Facebook Page in Facebook App (if installed) on Android

I already have answered here and it's working for me, please refer this link

    String socailLink="";
    Intent intent = new Intent(Intent.ACTION_VIEW);
    String facebookUrl = Utils.getFacebookUrl(getActivity(), socailLink);
    if (facebookUrl == null || facebookUrl.length() == 0) {
        Log.d("facebook Url", " is coming as " + facebookUrl);

please refer link to get rest part.

Hash string in c#

I don't really understand the full scope of your question, but if all you need is a hash of the string, then it's very easy to get that.

Just use the GetHashCode method.

Like this:

string hash = username.GetHashCode();

Passing data between different controller action methods

I prefer to use this instead of TempData

public class Home1Controller : Controller 
    public ActionResult CheckBox(string date)
        return RedirectToAction("ActionName", "Home2", new { Date =date });

and another controller Action is

public class Home2Controller : Controller 
    Public ActionResult ActionName(string Date)
       // do whatever with Date
       return View();

it is too late but i hope to be helpful for any one in the future

How the single threaded non blocking IO model works in Node.js

The function c.query() has two argument

c.query("Fetch Data", "Post-Processing of Data")

The operation "Fetch Data" in this case is a DB-Query, now this may be handled by Node.js by spawning off a worker thread and giving it this task of performing the DB-Query. (Remember Node.js can create thread internally). This enables the function to return instantaneously without any delay

The second argument "Post-Processing of Data" is a callback function, the node framework registers this callback and is called by the event loop.

Thus the statement c.query (paramenter1, parameter2) will return instantaneously, enabling node to cater for another request.

P.S: I have just started to understand node, actually I wanted to write this as comment to @Philip but since didn't have enough reputation points so wrote it as an answer.

Left join only selected columns in R with the merge() function

You can do this by subsetting the data you pass into your merge:

merge(x = DF1, y = DF2[ , c("Client", "LO")], by = "Client", all.x=TRUE)

Or you can simply delete the column after your current merge :)

Skipping every other element after the first

# Initialize variables
new_list = []
i = 0
# Iterate through the list
for i in range(len(elements)):
    # Does this element belong in the resulting list?
    if i%2==0:
        # Add this element to the resulting list
    # Increment i
    i +=2

return new_list

What's the difference between OpenID and OAuth?

OpenID proves who you are.

OAuth grants access to the features provided by the authorizing party.

How to change font size in html?

If you want to do this without adding classes...

p:first-child {
    font-size: 16px;

p:last-child {
    font-size: 12px;


p:nth-child(1) {
    font-size: 16px;

p:nth-child(2) {
    font-size: 12px;

Compiling dynamic HTML strings from database

Found in a google discussion group. Works for me.

var $injector = angular.injector(['ng', 'myApp']);
$injector.invoke(function($rootScope, $compile) {

Is Android using NTP to sync time?

I have a Samsung Galaxy Tab 2 7.0 with Android 4.1.1. Apparently it does NOT sync to ntp. I loaded an app that says my tablet is 20 seconds off of ntp, but it can't set it unless I root the device.

How to write to a file without overwriting current contents?

Instead of "w" use "a" (append) mode with open function:

with open("games.txt", "a") as text_file:

How to build a RESTful API?

That is pretty much the same as created a normal website.

Normal pattern for a php website is:

  1. The user enter a url
  2. The server get the url, parse it and execute a action
  3. In this action, you get/generate every information you need for the page
  4. You create the html/php page with the info from the action
  5. The server generate a fully html page and send it back to the user

With a api, you just add a new step between 3 and 4. After 3, create a array with all information you need. Encode this array in json and exit or return this value.

$info = array("info_1" => 1; "info_2" => "info_2" ... "info_n" => array(1,2,3));

That all for the api. For the client side, you can call the api by the url. If the api work only with get call, I think it's possible to do a simply (To check, I normally use curl).

$info = file_get_contents(url);
$info = json_decode($info);

But it's more common to use the curl library to perform get and post call. You can ask me if you need help with curl.

Once the get the info from the api, you can do the 4 & 5 steps.

Look the php doc for json function and file_get_contents.

curl :


No, wait, I don't get it. "php API page" what do you mean by that ?

The api is only the creation/recuperation of your project. You NEVER send directly the html result (if you're making a website) throw a api. You call the api with the url, the api return information, you use this information to create the final result.

ex: you want to write a html page who say hello xxx. But to get the name of the user, you have to get the info from the api.

So let's say your api have a function who have user_id as argument and return the name of this user (let's say getUserNameById(user_id)), and you call this function only on a url like your/api/ulr/getUser/id.

Function getUserNameById(user_id)
  $userName = // call in db to get the user
  exit(json_encode($userName)); // maybe return work as well.

From the client side you do

    $username = file_get_contents(your/api/url/getUser/15); // You should normally use curl, but it simpler for the example
// So this function to this specifique url will call the api, and trigger the getUserNameById(user_id), whom give you the user name.
    <p>hello <?php echo $username ?> </p>

So the client never access directly the databases, that the api's role.

Is that clearer ?

Difference between del, remove, and pop on lists

Many best explanations are here but I will try my best to simplify more.

Among all these methods, remove & pop are postfix while delete is prefix.

remove(): It used to remove first occurrence of element

remove(i) => first occurrence of i value

>>> a = [0, 2, 3, 2, 1, 4, 6, 5, 7]
>>> a.remove(2)   # where i = 2
>>> a
[0, 3, 2, 1, 4, 6, 5, 7]

pop(): It used to remove element if:


pop() => from end of list

[0, 3, 2, 1, 4, 6, 5]


pop(index) => of index

[0, 3, 1, 4, 6, 5]

WARNING: Dangerous Method Ahead

delete(): Its a prefix method.

Keep an eye on two different syntax for same method: [] and (). It possesses power to:

1.Delete index

del a[index] => used to delete index and its associated value just like pop.

>>>del a[1]
[0, 1, 4, 6, 5]

2.Delete values in range [index 1:index N]

del a[0:3] => multiple values in range

>>>del a[0:3]
[6, 5]

3.Last but not list, to delete whole list in one shot

del (a) => as said above.

>>>del (a)

Hope this clarifies the confusion if any.

mysql query order by multiple items

SELECT some_cols
FROM prefix_users
WHERE (some conditions)
ORDER BY pic_set DESC, last_activity;

How to convert CLOB to VARCHAR2 inside oracle pl/sql

Converting VARCHAR2 to CLOB

In PL/SQL a CLOB can be converted to a VARCHAR2 with a simple assignment, SUBSTR, and other methods. A simple assignment will only work if the CLOB is less then or equal to the size of the VARCHAR2. The limit is 32767 in PL/SQL and 4000 in SQL (although 12c allows 32767 in SQL).

For example, this code converts a small CLOB through a simple assignment and then coverts the beginning of a larger CLOB.

    v_small_clob clob := lpad('0', 1000, '0');
    v_large_clob clob := lpad('0', 32767, '0') || lpad('0', 32767, '0');
    v_varchar2   varchar2(32767);
    v_varchar2 := v_small_clob;
    v_varchar2 := substr(v_large_clob, 1, 32767);


The above code does not convert the value to a LONG. It merely looks that way because of limitations with PL/SQL debuggers and strings over 999 characters long.

For example, in PL/SQL Developer, open a Test window and add and debug the above code. Right-click on v_varchar2 and select "Add variable to Watches". Step through the code and the value will be set to "(Long Value)". There is a ... next to the text but it does not display the contents. PLSQL Developer Long Value


I suspect the real problem here is with C# but I don't know how enough about C# to debug the problem.

What is a Y-combinator?

A Y-combinator is a "functional" (a function that operates on other functions) that enables recursion, when you can't refer to the function from within itself. In computer-science theory, it generalizes recursion, abstracting its implementation, and thereby separating it from the actual work of the function in question. The benefit of not needing a compile-time name for the recursive function is sort of a bonus. =)

This is applicable in languages that support lambda functions. The expression-based nature of lambdas usually means that they cannot refer to themselves by name. And working around this by way of declaring the variable, refering to it, then assigning the lambda to it, to complete the self-reference loop, is brittle. The lambda variable can be copied, and the original variable re-assigned, which breaks the self-reference.

Y-combinators are cumbersome to implement, and often to use, in static-typed languages (which procedural languages often are), because usually typing restrictions require the number of arguments for the function in question to be known at compile time. This means that a y-combinator must be written for any argument count that one needs to use.

Below is an example of how the usage and working of a Y-Combinator, in C#.

Using a Y-combinator involves an "unusual" way of constructing a recursive function. First you must write your function as a piece of code that calls a pre-existing function, rather than itself:

// Factorial, if func does the same thing as this bit of code...
x == 0 ? 1: x * func(x - 1);

Then you turn that into a function that takes a function to call, and returns a function that does so. This is called a functional, because it takes one function, and performs an operation with it that results in another function.

// A function that creates a factorial, but only if you pass in
// a function that does what the inner function is doing.
Func<Func<Double, Double>, Func<Double, Double>> fact =
  (recurs) =>
    (x) =>
      x == 0 ? 1 : x * recurs(x - 1);

Now you have a function that takes a function, and returns another function that sort of looks like a factorial, but instead of calling itself, it calls the argument passed into the outer function. How do you make this the factorial? Pass the inner function to itself. The Y-Combinator does that, by being a function with a permanent name, which can introduce the recursion.

// One-argument Y-Combinator.
public static Func<T, TResult> Y<T, TResult>(Func<Func<T, TResult>, Func<T, TResult>> F)
    t =>  // A function that...
      F(  // Calls the factorial creator, passing in...
        Y(F)  // The result of this same Y-combinator function call...
              // (Here is where the recursion is introduced.)
      (t); // And passes the argument into the work function.

Rather than the factorial calling itself, what happens is that the factorial calls the factorial generator (returned by the recursive call to Y-Combinator). And depending on the current value of t the function returned from the generator will either call the generator again, with t - 1, or just return 1, terminating the recursion.

It's complicated and cryptic, but it all shakes out at run-time, and the key to its working is "deferred execution", and the breaking up of the recursion to span two functions. The inner F is passed as an argument, to be called in the next iteration, only if necessary.

Java - creating a new thread

If you want more Thread to be created, in above case you have to repeat the code inside run method or at least repeat calling some method inside.

Try this, which will help you to call as many times you needed. It will be helpful when you need to execute your run more then once and from many place.

class A extends Thread {
    public void run() {
             //Code you want to get executed seperately then main thread.       

Main class

A obj1 = new A();

A obj2 = new A();

No Main class found in NetBeans

You need to add }} to the end of your code.

How to install gdb (debugger) in Mac OSX El Capitan?

Just spent a good few days trying to get this to work on High Sierra 10.13.1. The gdb 8.1 version from homebrew would not work no matter what I tried. Ended up installing gdb 8.0.1 via macports and this miraculously worked (after jumping through all of the other necessary hoops related to codesigning etc).

One additional issue is that in Eclipse you will get extraneous single quotes around all of your program arguments which can be worked around by providing the arguments inside .gdbinit instead.


Yes, it is. You can write :

INSERT INTO courses (name, location, gid) 
SELECT name, location, 'whatever you want' 
FROM courses 
WHERE cid = $ci

or you can get values from another join of the select ...

php create object without class

you can always use new stdClass(). Example code:

   $object = new stdClass();
   $object->property = 'Here we go';


   object(stdClass)#2 (1) {
      string(10) "Here we go"

Also as of PHP 5.4 you can get same output with:

$object = (object) ['property' => 'Here we go'];

How To Add An "a href" Link To A "div"?

try to implement with javascript this:

<div id="mydiv" onclick="myhref('');" >some stuff </div>
<script type="text/javascript">
    function myhref(web){
      window.location.href = web;}

Why is document.body null in my javascript?

document.body is not yet available when your code runs.

What you can do instead:

var docBody=document.getElementsByTagName("body")[0];

Best Practices for securing a REST API / web service

There are no standards for REST other than HTTP. There are established REST services out there. I suggest you take a peek at them and get a feel for how they work.

For example, we borrowed a lot of ideas from Amazon's S3 REST service when developing our own. But we opted not to use the more advanced security model based on request signatures. The simpler approach is HTTP Basic auth over SSL. You have to decide what works best in your situation.

Also, I highly recommend the book RESTful Web Services from O'reilly. It explains the core concepts and does provide some best practices. You can generally take the model they provide and map it to your own application.

Declare a Range relative to the Active Cell with VBA

Like this:

Dim rng as Range
Set rng = ActiveCell.Resize(numRows, numCols)

then read the contents of that range to an array:

Dim arr As Variant
arr = rng.Value
'arr is now a two-dimensional array of size (numRows, numCols)

or, select the range (I don't think that's what you really want, but you ask for this in the question).


In Bootstrap 3,How to change the distance between rows in vertical?

There's a simply way of doing it. You define for all the rows, except the first one, the following class with properties:

   position: relative;
   top: -20px;

Then you apply the class to all non-first rows and adjust the negative top value to fit your desired row space. It's easy and works way better. :) Hope it helped.

Can I call methods in constructor in Java?

Better design would be

public static YourObject getMyObject(File configFile){
    //process and create an object configure it and return it

AngularJS: How to run additional code after AngularJS has rendered a template?

This post is old, but I change your code to:

scope.$watch("assignments", function (value) {//I change here
  var val = value || null;            
  if (val)
    element.dataTable({"bDestroy": true});

see jsfiddle.

I hope it helps you

Column "invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause"

Put in other words, this error is telling you that SQL Server does not know which B to select from the group.

Either you want to select one specific value (e.g. the MIN, SUM, or AVG) in which case you would use the appropriate aggregate function, or you want to select every value as a new row (i.e. including B in the GROUP BY field list).

Consider the following data:

ID  A   B
1   1  13
1   1  79
1   2  13
1   2  13
1   2  42

The query


would return:

A  T1
1  2
2  3

which is all well and good.

However consider the following (illegal) query, which would produce this error:


And its returned data set illustrating the problem:

A  T1  B
1  2   13? 79? Both 13 and 79 as separate rows? (13+79=92)? ...?
2  3   13? 42? ...?

However, the following two queries make this clear, and will not cause the error:

  1. Using an aggregate

    FROM T2

    would return:

    A  T1  B
    1  2   92
    2  3   68
  2. Adding the column to the GROUP BY list

    FROM T2

    would return:

    A  T1  B
    1  1   13
    1  1   79
    2  2   13
    2  1   42

How to create a DataTable in C# and how to add rows?

The easiest way is to create a DtaTable as of now

DataTable table = new DataTable
    Columns = {
        "Name", // typeof(string) is implied
        {"Marks", typeof(int)}
    TableName = "MarksTable" //optional
table.Rows.Add("ravi", 500);

Material UI and Grid system

Below is made by purely MUI Grid system,

MUI - Grid Layout

With the code below,

// MuiGrid.js

import React from "react";
import { makeStyles } from "@material-ui/core/styles";
import Paper from "@material-ui/core/Paper";
import Grid from "@material-ui/core/Grid";

const useStyles = makeStyles(theme => ({
  root: {
    flexGrow: 1
  paper: {
    padding: theme.spacing(2),
    textAlign: "center",
    color: theme.palette.text.secondary,
    backgroundColor: "#b5b5b5",
    margin: "10px"

export default function FullWidthGrid() {
  const classes = useStyles();

  return (
    <div className={classes.root}>
      <Grid container spacing={0}>
        <Grid item xs={12}>
          <Paper className={classes.paper}>xs=12</Paper>
        <Grid item xs={12} sm={6}>
          <Paper className={classes.paper}>xs=12 sm=6</Paper>
        <Grid item xs={12} sm={6}>
          <Paper className={classes.paper}>xs=12 sm=6</Paper>
        <Grid item xs={6} sm={3}>
          <Paper className={classes.paper}>xs=6 sm=3</Paper>
        <Grid item xs={6} sm={3}>
          <Paper className={classes.paper}>xs=6 sm=3</Paper>
        <Grid item xs={6} sm={3}>
          <Paper className={classes.paper}>xs=6 sm=3</Paper>
        <Grid item xs={6} sm={3}>
          <Paper className={classes.paper}>xs=6 sm=3</Paper>

↓ CodeSandbox ↓

Edit MUI-Grid system

How to test if JSON object is empty in Java

I would do the following to check for an empty object

obj.similar(new JSONObject())

Can I get div's background-image url?

Using just one call to replace (regex version): var bgUrl = $('#element-id').css('background-image').replace(/url\(("|')(.+)("|')\)/gi, '$2');

DataGridView - Focus a specific cell

Just Simple Paste And Pass Gridcolor() any where You want.

Private Sub Gridcolor()
    With Me.GridListAll
        .SelectionMode = DataGridViewSelectionMode.FullRowSelect
        .MultiSelect = False
        '.DefaultCellStyle.SelectionBackColor = Color.MediumOrchid
    End With
End Sub

How to initialize struct?

Your struct can have methods and properties... why not try

public struct MyStruct { 
    public string s;
    public int length { return s.Length; }

Correction @Guffa's answer shows that it is possible... more info here:

Python idiom to return first item or None

Frankly speaking, I do not think there is a better idiom: your is clear and terse - no need for anything "better". Maybe, but this is really a matter of taste, you could change if len(list) > 0: with if list: - an empty list will always evaluate to False.

On a related note, Python is not Perl (no pun intended!), you do not have to get the coolest code possible.
Actually, the worst code I have seen in Python, was also very cool :-) and completely unmaintainable.

By the way, most of the solution I have seen here do not take into consideration when list[0] evaluates to False (e.g. empty string, or zero) - in this case, they all return None and not the correct element.

Javascript get object key name

Assuming that you have access to Prototype, this could work. I wrote this code for myself just a few minutes ago; I only needed a single key at a time, so this isn't time efficient for big lists of key:value pairs or for spitting out multiple key names.

function key(int) {
    var j = -1;
    for(var i in this) {
        if(j==int) {
            return i;
        } else {
Object.prototype.key = key;

This is numbered to work the same way that arrays do, to save headaches. In the case of your code:

buttons.key(0) // Should result in "button1"

Convert Select Columns in Pandas Dataframe to Numpy Array

The best way for converting to Numpy Array is using '.to_numpy(self, dtype=None, copy=False)'. It is new in version 0.24.0.Refrence

You can also use '.array'.Refrence

Pandas .as_matrix deprecated since version 0.23.0.

Generate Row Serial Numbers in SQL Query

I found one solution for MYSQL its easy to add new column for SrNo or kind of tepropery auto increment column by following this query:

SELECT @ab:=@ab+1 as SrNo, tablename.* FROM tablename, (SELECT @ab:= 0)
AS ab

How to implement a read only property

C# 6.0 adds readonly auto properties

public object MyProperty { get; }

So when you don't need to support older compilers you can have a truly readonly property with code that's just as concise as a readonly field.

I think it doesn't make much difference if you are only interested in source compatibility.
Using a property is better for binary compatibility since you can replace it by a property which has a setter without breaking compiled code depending on your library.

You are following the convention. In cases like this where the differences between the two possibilities are relatively minor following the convention is better. One case where it might come back to bite you is reflection based code. It might only accept properties and not fields, for example a property editor/viewer.

Changing from field to property will probably break a lot of serializers. And AFAIK XmlSerializer does only serialize public properties and not public fields.

Using an Autoproperty
Another common Variation is using an autoproperty with a private setter. While this is short and a property it doesn't enforce the readonlyness. So I prefer the other ones.

Readonly field is selfdocumenting
There is one advantage of the field though:
It makes it clear at a glance at the public interface that it's actually immutable (barring reflection). Whereas in case of a property you can only see that you cannot change it, so you'd have to refer to the documentation or implementation.

But to be honest I use the first one quite often in application code since I'm lazy. In libraries I'm typically more thorough and follow the convention.

Storing images in SQL Server?

Another option was released in 2012 called File tables:

Use SQL Server Management Studio to connect remotely to an SQL Server Express instance hosted on an Azure Virtual Machine

I too struggled with something similar. My guess is your actual problem is connecting to a SQL Express instance running on a different machine. The steps to do this can be summarized as follows:

  1. Ensure SQL Express is configured for SQL Authentication as well as Windows Authentication (the default). You do this via SQL Server Management Studio (SSMS) Server Properties/Security
  2. In SSMS create a new login called "sqlUser", say, with a suitable password, "sql", say. Ensure this new login is set for SQL Authentication, not Windows Authentication. SSMS Server Security/Logins/Properties/General. Also ensure "Enforce password policy" is unchecked
  3. Under Properties/Server Roles ensure this new user has the "sysadmin" role
  4. In SQL Server Configuration Manager SSCM (search for SQLServerManagerxx.msc file in Windows\SysWOW64 if you can't find SSCM) under SQL Server Network Configuration/Protocols for SQLExpress make sure TCP/IP is enabled. You can disable Named Pipes if you want
  5. Right-click protocol TCP/IP and on the IPAddresses tab, ensure every one of the IP addresses is set to Enabled Yes, and TCP Port 1433 (this is the default port for SQL Server)
  6. In Windows Firewall (WF.msc) create two new Inbound Rules - one for SQL Server and another for SQL Browser Service. For SQL Server you need to open TCP Port 1433 (if you are using the default port for SQL Server) and very importantly for the SQL Browser Service you need to open UDP Port 1434. Name these two rules suitably in your firewall
  7. Stop and restart the SQL Server Service using either SSCM or the Services.msc snap-in
  8. In the Services.msc snap-in make sure SQL Browser Service Startup Type is Automatic and then start this service

At this point you should be able to connect remotely, using SQL Authentication, user "sqlUser" password "sql" to the SQL Express instance configured as above. A final tip and easy way to check this out is to create an empty text file with the .UDL extension, say "Test.UDL" on your desktop. Double-clicking to edit this file invokes the Microsoft Data Link Properties dialog with which you can quickly test your remote SQL connection

How do I get a value of a <span> using jQuery?

In javascript wouldn't you use document.getElementById('item1').innertext?

How do I build an import library (.lib) AND a DLL in Visual C++?

By selecting 'Class Library' you were accidentally telling it to make a .Net Library using the CLI (managed) extenstion of C++.

Instead, create a Win32 project, and in the Application Settings on the next page, choose 'DLL'.

You can also make an MFC DLL or ATL DLL from those library choices if you want to go that route, but it sounds like you don't.

How to set selected item of Spinner by value, not by position?

Use following line to select using value:


Seconds CountDown Timer

Use Timer for this

   private System.Windows.Forms.Timer timer1; 
   private int counter = 60;
   private void btnStart_Click_1(object sender, EventArgs e)
        timer1 = new System.Windows.Forms.Timer();
        timer1.Tick += new EventHandler(timer1_Tick);
        timer1.Interval = 1000; // 1 second
        lblCountDown.Text = counter.ToString();

    private void timer1_Tick(object sender, EventArgs e)
        if (counter == 0)
        lblCountDown.Text = counter.ToString();

Convert integers to strings to create output filenames at run time

you can write to a unit, but you can also write to a string

program foo
    character(len=1024) :: filename

    write (filename, "(A5,I2)") "hello", 10

    print *, trim(filename)
end program

Please note (this is the second trick I was talking about) that you can also build a format string programmatically.

program foo

    character(len=1024) :: filename
    character(len=1024) :: format_string
    integer :: i

    do i=1, 10
        if (i < 10) then
            format_string = "(A5,I1)"
            format_string = "(A5,I2)"

        write (filename,format_string) "hello", i
        print *, trim(filename)

end program

Can we have multiple "WITH AS" in single sql - Oracle SQL

You can do this as:

WITH abc AS( select
             FROM ...)
, XYZ AS(select
         From abc ....) /*This one uses "abc" multiple times*/
  From XYZ....   /*using abc, XYZ multiple times*/

How do you get a string from a MemoryStream?

Only use method Convert.ToBase64String


What does href expression <a href="javascript:;"></a> do?

Old thread but thought I'd just add that the reason developers use this construct is not to create a dead link, but because javascript URLs for some reason do not pass references to the active html element correctly.

e.g. handler_function( works as onClick but not as a javascript URL.

Thus it's a choice between writing pedantically standards-compliant code that involves you in having to manually adjust the call for each hyperlink, or slightly non-standard code which can be written once and used everywhere.

How do I upgrade to Python 3.6 with conda?

Anaconda has not updated python internally to 3.6.

a) Method 1

  1. If you wanted to update you will type conda update python
  2. To update anaconda type conda update anaconda
  3. If you want to upgrade between major python version like 3.5 to 3.6, you'll have to do

    conda install python=$pythonversion$

b) Method 2 - Create a new environment (Better Method)

conda create --name py36 python=3.6

c) To get the absolute latest python(3.6.5 at time of writing)

conda create --name py365 python=3.6.5 --channel conda-forge

You can see all this from here

Also, refer to this for force upgrading

EDIT: Anaconda now has a Python 3.6 version here

Ajax passing data to php script

Try sending the data like this:

var data = {};
data.album = this.title;

Then you can access it like


Notice not a 'GET'

What causes a SIGSEGV

using an invalid/null pointer? Overrunning the bounds of an array? Kindof hard to be specific without any sample code.

Essentially, you are attempting to access memory that doesn't belong to your program, so the OS kills it.

Determine the line of code that causes a segmentation fault?

All of the above answers are correct and recommended; this answer is intended only as a last-resort if none of the aforementioned approaches can be used.

If all else fails, you can always recompile your program with various temporary debug-print statements (e.g. fprintf(stderr, "CHECKPOINT REACHED @ %s:%i\n", __FILE__, __LINE__);) sprinkled throughout what you believe to be the relevant parts of your code. Then run the program, and observe what the was last debug-print printed just before the crash occurred -- you know your program got that far, so the crash must have happened after that point. Add or remove debug-prints, recompile, and run the test again, until you have narrowed it down to a single line of code. At that point you can fix the bug and remove all of the temporary debug-prints.

It's quite tedious, but it has the advantage of working just about anywhere -- the only times it might not is if you don't have access to stdout or stderr for some reason, or if the bug you are trying to fix is a race-condition whose behavior changes when the timing of the program changes (since the debug-prints will slow down the program and change its timing)

How to set base url for rest in spring boot?

With Spring Boot 1.2+ (<2.0) all it takes is a single property in

ref link :

For 2.x, use


HttpRequest maximum allowable size in tomcat?

The full answer

1. The default (fresh install of tomcat)

When you download tomcat from their official website (of today that's tomcat version 9.0.26), all the apps you installed to tomcat can handle HTTP requests of unlimited size, given that the apps themselves do not have any limits on request size.

However, when you try to upload an app in tomcat's manager app, that app has a default war file limit of 50MB. If you're trying to install Jenkins for example which is 77 MB as ot today, it will fail.

2. Configure tomcat's per port http request size limit

Tomcat itself has size limit for each port, and this is defined in conf\server.xml. This is controlled by maxPostSize attribute of each Connector(port). If this attribute does not exist, which it is by default, there is no limit on the request size.

To add a limit to a specific port, set a byte size for the attribute. For example, the below config for the default 8080 port limits request size to 200 MB. This means that all the apps installed under port 8080 now has the size limit of 200MB

<Connector port="8080" protocol="HTTP/1.1"
           maxPostSize="209715200" />

3. Configure app level size limit

After passing the port level size limit, you can still configure app level limit. This also means that app level limit should be less than port level limit. The limit can be done through annotation within each servlet, or in the web.xml file. Again, if this is not set at all, there is no limit on request size.

To set limit through java annotation

@MultipartConfig( fileSizeThreshold = 0, maxFileSize = 209715200, maxRequestSize = 209715200)
public class FileUploadServlet extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response) {
        // ...

To set limit through web.xml


4. Appendix - If you see file upload size error when trying to install app through Tomcat's Manager app

Tomcat's Manager app (by default localhost:8080/manager) is nothing but a default web app. By default that app has a web.xml configuration of request limit of 50MB. To install (upload) app with size greater than 50MB through this manager app, you have to change the limit. Open the manager app's web.xml file from webapps\manager\WEB-INF\web.xml and follow the above guide to change the size limit and finally restart tomcat.

Angular ReactiveForms: Producing an array of checkbox values?

I was able to accomplish this using a FormArray of FormGroups. The FormGroup consists of two controls. One for the data and one to store the checked boolean.


options: options[] = [{id: 1, text: option1}, {id: 2, text: option2}];{
  options: this.fb.array([])

populateFormArray() {    
  this.options.forEach(option => {                       
    let checked = ***is checked logic here***;            
    this.checkboxGroup.get('options').push(this.createOptionGroup(option, checked))

createOptionGroup(option: Option, checked: boolean) {
    option: this.fb.control(option),
    checked: this.fb.control(checked)


This allows you to loop through the options and bind to the corresponding checked control.

<form [formGroup]="checkboxGroup">
  <div formArrayName="options" *ngFor="let option of options; index as i">   
    <div [formGroupName]="i">
      <input type="checkbox" formControlName="checked" />
      {{ option.text }}


The form returns data in the form {option: Option, checked: boolean}[].

You can get a list of checked options using the below code

 this.checkboxGroup.get('options').value.filter(el => el.checked).map(el => el.option);

How to know what the 'errno' means?

I have the following function in my .bashrc file - it looks up the errno value from the header files (can be either /usr/include/errno.h, /usr/include/linux/errno.h, etc., etc.)

It works if header files are installed on the machine;-)

Usually the header file have an error + next comes the explanation in the comment; something of the following:

./asm-generic/errno-base.h:#define EAGAIN 11 /* Try again */

function errno()
    local arg=$1

    if [[ "x$arg" == "x-h" ]]; then
        cat <<EOF
        Usage: errno <num>
        Prints text that describes errno error number
        pushd /usr/include
        find . -name "errno*.h" | xargs grep   "[[:space:]]${arg}[[:space:]]"

How to do select from where x is equal to multiple values?

You can try using parentheses around the OR expressions to make sure your query is interpreted correctly, or more concisely, use IN:

SELECT ads.*, location.county 
FROM ads
LEFT JOIN location ON location.county = ads.county_id
WHERE ads.published = 1 
AND ads.type = 13
AND ads.county_id IN (2,5,7,9)

Using module 'subprocess' with timeout

Was just trying to write something simpler.


from subprocess import Popen, PIPE
import datetime
import time 

popen = Popen(["/bin/sleep", "10"]);
pid =
sttime = time.time();
waittime =  3

print "Start time %s"%(sttime)

while True:
    rcode = popen.returncode
    now = time.time();
    if [ rcode is None ]  and  [ now > (sttime + waittime) ] :
        print "Killing it now"

'method' object is not subscriptable. Don't know what's wrong

You need to use parentheses: myList.insert([1, 2, 3]). When you leave out the parentheses, python thinks you are trying to access myList.insert at position 1, 2, 3, because that's what brackets are used for when they are right next to a variable.

Integrating MySQL with Python in Windows

I found a location were one person had successfully built mysql for python2.6, sharing the link, might see a warning while import MySQLdb which is fine and that won’t hurt anything,

C:\Python26\lib\site-packages\ DeprecationWarning: the sets module is deprecated from sets import ImmutableSet

Converting XML to JSON using Python?

There is a method to transport XML-based markup as JSON which allows it to be losslessly converted back to its original form. See

It's a kind of XSLT of JSON. I hope you find it helpful

How to encode the plus (+) symbol in a URL

Just to add this to the list:

Uri.EscapeUriString("Hi there+Hello there") // Hi%20there+Hello%20there
Uri.EscapeDataString("Hi there+Hello there") // Hi%20there%2BHello%20there


Usually you want to use EscapeDataString which does it right.

setting y-axis limit in matplotlib

This should work. Your code works for me, like for Tamás and Manoj Govindan. It looks like you could try to update Matplotlib. If you can't update Matplotlib (for instance if you have insufficient administrative rights), maybe using a different backend with matplotlib.use() could help.

How to query first 10 rows and next time query other 10 rows from table

Ok. So I think you just need to implement Pagination.

$perPage = 10;

$pageNo = $_GET['page'];

Now find total rows in database.

$totalRows = Get By applying sql query;

$pages = ceil($totalRows/$perPage);    

$offset = ($pageNo - 1) * $perPage + 1

$sql = "SELECT * FROM msgtable WHERE cdate='18/07/2012' LIMIT ".$offset." ,".$perPage

What do multiple arrow functions mean in javascript?

That is a curried function

First, examine this function with two parameters …

const add = (x, y) => x + y
add(2, 3) //=> 5

Here it is again in curried form …

const add = x => y => x + y

Here is the same1 code without arrow functions …

const add = function (x) {
  return function (y) {
    return x + y

Focus on return

It might help to visualize it another way. We know that arrow functions work like this – let's pay particular attention to the return value.

const f = someParam => returnValue

So our add function returns a function – we can use parentheses for added clarity. The bolded text is the return value of our function add

const add = x => (y => x + y)

In other words add of some number returns a function

add(2) // returns (y => 2 + y)

Calling curried functions

So in order to use our curried function, we have to call it a bit differently …

add(2)(3)  // returns 5

This is because the first (outer) function call returns a second (inner) function. Only after we call the second function do we actually get the result. This is more evident if we separate the calls on two lines …

const add2 = add(2) // returns function(y) { return 2 + y }
add2(3)             // returns 5

Applying our new understanding to your code

related: ”What’s the difference between binding, partial application, and currying?”

OK, now that we understand how that works, let's look at your code

handleChange = field => e => {
  /// Do something here

We'll start by representing it without using arrow functions …

handleChange = function(field) {
  return function(e) {
    // Do something here
    // return ...

However, because arrow functions lexically bind this, it would actually look more like this …

handleChange = function(field) {
  return function(e) {
    // Do something here
    // return ...

Maybe now we can see what this is doing more clearly. The handleChange function is creating a function for a specified field. This is a handy React technique because you're required to setup your own listeners on each input in order to update your applications state. By using the handleChange function, we can eliminate all the duplicated code that would result in setting up change listeners for each field. Cool!

1 Here I did not have to lexically bind this because the original add function does not use any context, so it is not important to preserve it in this case.

Even more arrows

More than two arrow functions can be sequenced, if necessary -

const three = a => b => c =>
  a + b + c

const four = a => b => c => d =>
  a + b + c + d

three (1) (2) (3) // 6

four (1) (2) (3) (4) // 10

Curried functions are capable of surprising things. Below we see $ defined as a curried function with two parameters, yet at the call site, it appears as though we can supply any number of arguments. Currying is the abstraction of arity -

const $ = x => k =>_x000D_
  $ (k (x))_x000D_
const add = x => y =>_x000D_
  x + y_x000D_
const mult = x => y =>_x000D_
  x * y_x000D_
$ (1)           // 1_x000D_
  (add (2))     // + 2 = 3_x000D_
  (mult (6))    // * 6 = 18_x000D_
  (console.log) // 18_x000D_
$ (7)            // 7_x000D_
  (add (1))      // + 1 = 8_x000D_
  (mult (8))     // * 8 = 64_x000D_
  (mult (2))     // * 2 = 128_x000D_
  (mult (2))     // * 2 = 256_x000D_
  (console.log)  // 256

Partial application

Partial application is a related concept. It allows us to partially apply functions, similar to currying, except the function does not have to be defined in curried form -

const partial = (f, ...a) => (...b) =>
  f (...a, ...b)

const add3 = (x, y, z) =>
  x + y + z

partial (add3) (1, 2, 3)   // 6

partial (add3, 1) (2, 3)   // 6

partial (add3, 1, 2) (3)   // 6

partial (add3, 1, 2, 3) () // 6

partial (add3, 1, 1, 1, 1) (1, 1, 1, 1, 1) // 3

Here's a working demo of partial you can play with in your own browser -

const partial = (f, ...a) => (...b) =>_x000D_
  f (...a, ...b)_x000D_
const preventDefault = (f, event) =>_x000D_
  ( event .preventDefault ()_x000D_
  , f (event)_x000D_
const logKeypress = event =>_x000D_
  console .log (event.which)_x000D_
  .querySelector ('input[name=foo]')_x000D_
  .addEventListener ('keydown', partial (preventDefault, logKeypress))
<input name="foo" placeholder="type here to see ascii codes" size="50">

How to import an existing directory into Eclipse?

The thing that works best for me when that happens is :

  1. Create a new eclipse project(JAVA)

  2. Take your source file (contents of the src folder!!!) and drag from finder and drop into the src folder in eclipse IDE

  3. Make sure you add your external jars and stuff and tada you're done!!

When does socket.recv(recv_size) return?

Yes, your conclusion is correct. socket.recv is a blocking call.

socket.recv(1024) will read at most 1024 bytes, blocking if no data is waiting to be read. If you don't read all data, an other call to socket.recv won't block.

socket.recv will also end with an empty string if the connection is closed or there is an error.

If you want a non-blocking socket, you can use the select module (a bit more complicated than just using sockets) or you can use socket.setblocking.

I had issues with socket.setblocking in the past, but feel free to try it if you want.

Removing "bullets" from unordered list <ul>

Have you tried setting

li {list-style-type: none;}

According to Need an unordered list without any bullets, you need to add this style to the li elements.

Identifying country by IP address

It's not that easy. IP adresses are not assigned to countries as such, but to companies and organizations.

But maybe this can help you out:

Why does a base64 encoded string have an = sign at the end

The equals sign (=) is used as padding in certain forms of base64 encoding. The Wikipedia article on base64 has all the details.

How to select unique records by SQL

It depends on which rown you want to return for each unique item. Your data seems to indicate the minimum data value so in this instance for SQL Server.

SELECT item, min(data)
FROM  table

Android Get Current timestamp?

The solution is :

Long tsLong = System.currentTimeMillis()/1000;
String ts = tsLong.toString();

Create a folder inside documents folder in iOS apps

This works fine for me,

NSFileManager *fm = [NSFileManager defaultManager];
NSArray *appSupportDir = [fm URLsForDirectory:NSDocumentsDirectory inDomains:NSUserDomainMask];
NSURL* dirPath = [[appSupportDir objectAtIndex:0] URLByAppendingPathComponent:@"YourFolderName"];

NSError*    theError = nil; //error setting
if (![fm createDirectoryAtURL:dirPath withIntermediateDirectories:YES
                           attributes:nil error:&theError])
   NSLog(@"not created");

How to achieve function overloading in C?

I hope the below code will help you to understand function overloading

#include <stdio.h>

int fun(int a, ...);
int main(int argc, char *argv[]){
   return 0;
int fun(int a, ...){
  va_list vl;

      printf("\n%s",va_arg(vl,char *));