Programs & Examples On #Assembly name

gdb fails with "Unable to find Mach task port for process-id" error

The problem is that you are not logged in as a root user (which you don't want). You need to create a certificate for gdb to be allowed access. Follow this tutorial and you should be good to go...

If all else fails, just use: sudo gdb executableFileName

How can I see the entire HTTP request that's being sent by my Python application?

A simple method: enable logging in recent versions of Requests (1.x and higher.)

Requests uses the http.client and logging module configuration to control logging verbosity, as described here.


Code excerpted from the linked documentation:

import requests
import logging

# These two lines enable debugging at httplib level (requests->urllib3->http.client)
# You will see the REQUEST, including HEADERS and DATA, and RESPONSE with HEADERS but without DATA.
# The only thing missing will be the response.body which is not logged.
    import http.client as http_client
except ImportError:
    # Python 2
    import httplib as http_client
http_client.HTTPConnection.debuglevel = 1

# You must initialize logging, otherwise you'll not see debug output.
requests_log = logging.getLogger("requests.packages.urllib3")
requests_log.propagate = True


Example Output

$ python 
INFO:requests.packages.urllib3.connectionpool:Starting new HTTPS connection (1):
send: 'GET /headers HTTP/1.1\r\nHost:\r\nAccept-Encoding: gzip, deflate, compress\r\nAccept: */*\r\nUser-Agent: python-requests/1.2.0 CPython/2.7.3 Linux/3.2.0-48-generic\r\n\r\n'
reply: 'HTTP/1.1 200 OK\r\n'
header: Content-Type: application/json
header: Date: Sat, 29 Jun 2013 11:19:34 GMT
header: Server: gunicorn/0.17.4
header: Content-Length: 226
header: Connection: keep-alive
DEBUG:requests.packages.urllib3.connectionpool:"GET /headers HTTP/1.1" 200 226

iOS 7's blurred overlay effect using CSS?

This is sort of possible with FireFox now thanks to the element style attribute.

This experimental attribute lets you use any HTML content as a background image. So, to create the background you need three overlays:

  1. Simple overlay with a solid background (to hide the real overlay content).
  2. Overlay with a -moz-element background that sets the content. Note that FX doesn't support the filter: blur() attribute, so we need to us an SVG.
  3. Overlay with non blurred content.

So, put together:

SVG blur filter (works in FX, other browsers could use filter:blur()):

    <filter id="svgBlur">
      <feGaussianBlur stdDeviation="10"/>

CSS blur style:

    filter         : url(#svgBlur); 
    opacity: .4;
    background: -moz-element(#content);
    background-repeat: no-repeat;

Finally 3 layers:

<div class="header" style="background-color: #fff">&nbsp;</div>
<div class="header behind-blur">&nbsp;</div>
<div class="header">
    Header Text, content blurs behind

Then to move this around just set the background-position (sample in jQuery but you could use anything):

    'background-position': '-' + left + 'px -' + top + 'px'

Here it is as a JS Fiddle, FX only.

Find methods calls in Eclipse project

Select mymethod() and press ctrl+alt+h.

To see some detailed Information about any method you can use this by selecting that particular Object or method and right click. you can see the "OpenCallHierarchy" (Ctrl+Alt+H). Like that many tools are there to make your work Easier like "Quick Outline" (Ctrl+O) to view the Datatypes and methods declared in a particular .java file.

To know more about this, refer this eclipse Reference

How to get the row number from a datatable?

ArrayList check = new ArrayList();            

for (int i = 0; i < oDS.Tables[0].Rows.Count; i++)
    int iValue = Convert.ToInt32(oDS.Tables[0].Rows[i][3].ToString());


How to use forEach in vueJs?

You can also use .map() as:

var list=[];, key) {

How to create User/Database in script for Docker Postgres

By using docker-compose:

Assuming that you have following directory layout:


File: docker-compose.yml

version: "3.3"
      context: ./Docker
      dockerfile: db.Dockerfile
      - ./var/pgdata:/var/lib/postgresql/data
      - "5432:5432"

File: Docker/init.sql




File: Docker/db.Dockerfile

FROM postgres:11.5-alpine
COPY init.sql /docker-entrypoint-initdb.d/

Composing and starting services:

docker-compose -f docker-compose.yml up --no-start
docker-compose -f docker-compose.yml start

JavaScript: Create and save file

Tried this in the console, and it works.

var aFileParts = ['<a id="a"><b id="b">hey!</b></a>'];
var oMyBlob = new Blob(aFileParts, {type : 'text/html'}); // the blob;

Split List into Sublists with LINQ

Old code, but this is what I've been using:

    public static IEnumerable<List<T>> InSetsOf<T>(this IEnumerable<T> source, int max)
        var toReturn = new List<T>(max);
        foreach (var item in source)
            if (toReturn.Count == max)
                yield return toReturn;
                toReturn = new List<T>(max);
        if (toReturn.Any())
            yield return toReturn;

from list of integers, get number closest to a given value

Iterate over the list and compare the current closest number with abs(currentNumber - myNumber):

def takeClosest(myList, myNumber):
    closest = myList[0]
    for i in range(1, len(myList)):
        if abs(i - myNumber) < closest:
            closest = i
    return closest

How to change folder with git bash?

The command is:

cd  /c/project/

Use the pwd command to see which path you are currently in, handy when you did a right-click "Git Bash here..."

submit the form using ajax

What about

  type: 'POST',
  url: $("form").attr("action"),
  data: $("form").serialize(), 
  //or your custom data either as object {foo: "bar", ...} or foo=bar&...
  success: function(response) { ... },

How can I avoid getting this MySQL error Incorrect column specifier for column COLUMN NAME?

To use AUTO_INCREMENT you need to deifne column as INT or floating-point types, not CHAR.

AUTO_INCREMENT use only unsigned value, so it's good to use UNSIGNED as well;

CREATE TABLE discussion_topics (

     topic_id INT NOT NULL unsigned AUTO_INCREMENT,
     project_id char(36) NOT NULL,
     topic_subject VARCHAR(255) NOT NULL,
     topic_content TEXT default NULL,
     date_created DATETIME NOT NULL,
     date_last_post DATETIME NOT NULL,
     created_by_user_id char(36) NOT NULL,
     last_post_user_id char(36) NOT NULL,
     posts_count char(36) default NULL,
     PRIMARY KEY (topic_id) 

How do I launch the Android emulator from the command line?

I wrote this simple shell script using Zenity that lets you pick which avd you want to run. If you don't have ANDROID_HOME defined, you can just replace that with the full path to emulator. This would be easy to do with select instead of Zenity also, but I opted for Zenity since I'm running it from the xfce-application menu (though a .desktop-file).


opt=$(zenity --title="Choose AVD" --text="Choose which emulator to start" --list \
                   --column="Devices" --separator="\n" `$ANDROID_HOME/emulator/emulator -list-avds`);

$ANDROID_HOME/emulator/emulator -avd $opt

Factorial in numpy and scipy

enter image description here

after running different aforementioned functions for factorial, by different people, turns out that math.factorial is the fastest to calculate the factorial.

find running times for different functions in the attached image

Difference between "and" and && in Ruby?

and has lower precedence, mostly we use it as a control-flow modifier such as if:

next if widget = widgets.pop


widget = widgets.pop and next

For or:

raise "Not ready!" unless ready_to_rock?


ready_to_rock? or raise "Not ready!"

I prefer to use if but not and, because if is more intelligible, so I just ignore and and or.

Refer to "Using “and” and “or” in Ruby" for more information.

How do I return multiple values from a function in C?

I don't know what your string is, but I'm going to assume that it manages its own memory.

You have two solutions:

1: Return a struct which contains all the types you need.

struct Tuple {
    int a;
    string b;

struct Tuple getPair() {
    Tuple r = { 1, getString() };
    return r;

void foo() {
    struct Tuple t = getPair();

2: Use pointers to pass out values.

void getPair(int* a, string* b) {
    // Check that these are not pointing to NULL
    *a = 1;
    *b = getString();

void foo() {
    int a, b;
    getPair(&a, &b);

Which one you choose to use depends largely on personal preference as to whatever semantics you like more.

CertPathValidatorException : Trust anchor for certificate path not found - Retrofit Android

DISCLAIMER: this answer is from Jul 2015 and uses Retrofit and OkHttp from that time.
Check this link for more info on Retrofit v2 and this one for the current OkHttp methods.

Okay, I got it working using Android Developers guide.

Just as OP, I'm trying to use Retrofit and OkHttp to connect to a self-signed SSL-enabled server.

Here's the code that got things working (I've removed the try/catch blocks):

public static RestAdapter createAdapter(Context context) {
  // loading CAs from an InputStream
  CertificateFactory cf = CertificateFactory.getInstance("X.509");
  InputStream cert = context.getResources().openRawResource(R.raw.my_cert);
  Certificate ca;
  try {
    ca = cf.generateCertificate(cert);
  } finally { cert.close(); }

  // creating a KeyStore containing our trusted CAs
  String keyStoreType = KeyStore.getDefaultType();
  KeyStore keyStore = KeyStore.getInstance(keyStoreType);
  keyStore.load(null, null);
  keyStore.setCertificateEntry("ca", ca);

  // creating a TrustManager that trusts the CAs in our KeyStore
  String tmfAlgorithm = TrustManagerFactory.getDefaultAlgorithm();
  TrustManagerFactory tmf = TrustManagerFactory.getInstance(tmfAlgorithm);

  // creating an SSLSocketFactory that uses our TrustManager
  SSLContext sslContext = SSLContext.getInstance("TLS");
  sslContext.init(null, tmf.getTrustManagers(), null);

  // creating an OkHttpClient that uses our SSLSocketFactory
  OkHttpClient okHttpClient = new OkHttpClient();

  // creating a RestAdapter that uses this custom client
  return new RestAdapter.Builder()
              .setClient(new OkClient(okHttpClient))

To help in debugging, I also added .setLogLevel(RestAdapter.LogLevel.FULL) to my RestAdapter creation commands and I could see it connecting and getting the response from the server.

All it took was my original .crt file saved in main/res/raw. The .crt file, aka the certificate, is one of the two files created when you create a certificate using openssl. Generally, it is a .crt or .cert file, while the other is a .key file.

Afaik, the .crt file is your public key and the .key file is your private key.

As I can see, you already have a .cert file, which is the same, so try to use it.

PS: For those that read it in the future and only have a .pem file, according to this answer, you only need this to convert one to the other:

openssl x509 -outform der -in your-cert.pem -out your-cert.crt

PS²: For those that don't have any file at all, you can use the following command (bash) to extract the public key (aka certificate) from any server:

echo -n | openssl s_client -connect | \
  sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > ~/my_cert.crt

Just replace the and the port (if it is not standard HTTPS) and choose a valid path for your output file to be created.

Is background-color:none valid CSS?

CSS Level 3 specifies the unset property value. From MDN:

The unset CSS keyword is the combination of the initial and inherit keywords. Like these two other CSS-wide keywords, it can be applied to any CSS property, including the CSS shorthand all. This keyword resets the property to its inherited value if it inherits from its parent or to its initial value if not. In other words, it behaves like the inherit keyword in the first case and like the initial keyword in the second case.

Unfortunately this value is currently not supported in all browsers, including IE, Safari and Opera. I suggest using transparent for the time being.

How can I extract a predetermined range of lines from a text file on Unix?

I was looking for an answer to this but I had to end up writing my own code which worked. None of the answers above were satisfactory. Consider you have very large file and have certain line numbers that you want to print out but the numbers are not in order. You can do the following:

My relatively large file for letter in {a..k} ; do echo $letter; done | cat -n > myfile.txt

 1  a
 2  b
 3  c
 4  d
 5  e
 6  f
 7  g
 8  h
 9  i
10  j
11  k

Specific line numbers I want: shuf -i 1-11 -n 4 > line_numbers_I_want.txt


To print these line numbers, do the following. awk '{system("head myfile.txt -n " $0 " | tail -n 1")}' line_numbers_I_want.txt

What the above does is to head the n line then take the last line using tail

If you want your line numbers in order, sort ( is -n numeric sort) first then get the lines.

cat line_numbers_I_want.txt | sort -n | awk '{system("head myfile.txt -n " $0 " | tail -n 1")}'

 4  d
 9  i
10  j
11  k

Replacing objects in array

I am only submitting this answer because people expressed concerns over browsers and maintaining the order of objects. I recognize that it is not the most efficient way to accomplish the goal.

Having said this, I broke the problem down into two functions for readability.

// The following function is used for each itertion in the function updateObjectsInArr
const newObjInInitialArr = function(initialArr, newObject) {
  let id =;
  let newArr = [];
  for (let i = 0; i < initialArr.length; i++) {
    if (id === initialArr[i].id) {
    } else {
  return newArr;

const updateObjectsInArr = function(initialArr, newArr) {
    let finalUpdatedArr = initialArr;  
    for (let i = 0; i < newArr.length; i++) {
      finalUpdatedArr = newObjInInitialArr(finalUpdatedArr, newArr[i]);

    return finalUpdatedArr

const revisedArr = updateObjectsInArr(arr1, arr2);


Setting up enviromental variables in Windows 10 to use java and javac

Adding Environment Variable simplified with screenshot. Check the below URL and you should be able to do without any trouble.

How to see local history changes in Visual Studio Code?

I built an extension called Checkpoints, an alternative to Local History. Checkpoints has support for viewing history for all files (that has checkpoints) in the tree view, not just the currently active file. There are some other minor differences aswell, but overall they are pretty similar.

Mocking a function to raise an Exception to test an except block

Your mock is raising the exception just fine, but the error.resp.status value is missing. Rather than use return_value, just tell Mock that status is an attribute:

barMock.side_effect = HttpError(mock.Mock(status=404), 'not found')

Additional keyword arguments to Mock() are set as attributes on the resulting object.

I put your foo and bar definitions in a my_tests module, added in the HttpError class so I could use it too, and your test then can be ran to success:

>>> from my_tests import foo, HttpError
>>> import mock
>>> with mock.patch('') as barMock:
...     barMock.side_effect = HttpError(mock.Mock(status=404), 'not found')
...     result =
404 - 
>>> result is None

You can even see the print '404 - %s' % error.message line run, but I think you wanted to use error.content there instead; that's the attribute HttpError() sets from the second argument, at any rate.

How do I print the full value of a long string in gdb?

As long as your program's in a sane state, you can also call (void)puts(your_string) to print it to stdout. Same principle applies to all functions available to the debugger, actually.

Find the day of a week

df = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02")) 
df$day <- weekdays(as.Date(df$date))
##         date       day
## 1 2012-02-01 Wednesday
## 2 2012-02-01 Wednesday
## 3 2012-02-02  Thursday

Edit: Just to show another way...

The wday component of a POSIXlt object is the numeric weekday (0-6 starting on Sunday).

## [1] 3 3 4

which you could use to subset a character vector of weekday names

c("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", 
    "Friday", "Saturday")[as.POSIXlt(df$date)$wday + 1]
## [1] "Wednesday" "Wednesday" "Thursday" 

How to prevent scientific notation in R?

To set the use of scientific notation in your entire R session, you can use the scipen option. From the documentation (?options):

‘scipen’: integer.  A penalty to be applied when deciding to print
          numeric values in fixed or exponential notation.  Positive
          values bias towards fixed and negative towards scientific
          notation: fixed notation will be preferred unless it is more
          than ‘scipen’ digits wider.

So in essence this value determines how likely it is that scientific notation will be triggered. So to prevent scientific notation, simply use a large positive value like 999:


Regular expression to extract URL from an HTML link

this should work, although there might be more elegant ways.

import re
url='<a href="" target="_blank"></a>'
r = re.compile('(?<=href=").*?(?=")')

Set color of TextView span in Android

Below works perfectly for me

    tvPrivacyPolicy = (TextView) findViewById(;
    String originalText = (String)tvPrivacyPolicy.getText();
    int startPosition = 15;
    int endPosition = 31;

    SpannableString spannableStr = new SpannableString(originalText);
    UnderlineSpan underlineSpan = new UnderlineSpan();
    spannableStr.setSpan(underlineSpan, startPosition, endPosition, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

    ForegroundColorSpan backgroundColorSpan = new ForegroundColorSpan(Color.BLUE);
    spannableStr.setSpan(backgroundColorSpan, startPosition, endPosition, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

    StyleSpan styleSpanItalic  = new StyleSpan(Typeface.BOLD);

    spannableStr.setSpan(styleSpanItalic, startPosition, endPosition, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);


Output for above code

enter image description here

How to create an object property from a variable value in JavaScript?

You could just use this:

function createObject(propName, propValue){
    this[propName] = propValue;
var myObj1 = new createObject('string1','string2');

Anything you pass as the first parameter will be the property name, and the second parameter is the property value.

Selecting Multiple Values from a Dropdown List in Google Spreadsheet

If the answers must be constrained to Google Sheets, this answer works but it has limitations and is clumsy enough UX that it may be hard to get others to adopt. In trying to solve this problem I've found that, for many applications, Airtable solves this by allowing for multi-select columns and the UX is worlds better.

How do I get the dialer to open with phone number displayed?

As @ashishduh mentioned above, using android:autoLink="phone is also a good solution. But this option comes with one drawback, it doesn't work with all phone number lengths. For instance, a phone number of 11 numbers won't work with this option. The solution is to prefix your phone numbers with the country code.


08034448845 won't work

but +2348034448845 will

What does @media screen and (max-width: 1024px) mean in CSS?

It means if the screen size is 1024 then only apply below CSS rules.

How to send multiple data fields via Ajax?

Try this:

$(document).ready(function() {
  $("#btnSubmit").click(function() {
    var status = $("#activitymessage").val();
    var name = "Ronny";
      type: "POST",
      url: "ajax/activity_save.php",
      data: {'status': status, 'name': name},
        success: function(msg) {...

Setting Curl's Timeout in PHP

You can't run the request from a browser, it will timeout waiting for the server running the CURL request to respond. The browser is probably timing out in 1-2 minutes, the default network timeout.

You need to run it from the command line/terminal.

How do I get started with Node.js

First, learn the core concepts of Node.js:

Then, you're going to want to see what the community has to offer:

The gold standard for Node.js package management is NPM.

Finally, you're going to want to know what some of the more popular packages are for various tasks:

Useful Tools for Every Project:

  • Underscore contains just about every core utility method you want.
  • Lo-Dash is a clone of Underscore that aims to be faster, more customizable, and has quite a few functions that underscore doesn't have. Certain versions of it can be used as drop-in replacements of underscore.
  • TypeScript makes JavaScript considerably more bearable, while also keeping you out of trouble!
  • JSHint is a code-checking tool that'll save you loads of time finding stupid errors. Find a plugin for your text editor that will automatically run it on your code.

Unit Testing:

  • Mocha is a popular test framework.
  • Vows is a fantastic take on asynchronous testing, albeit somewhat stale.
  • Expresso is a more traditional unit testing framework.
  • node-unit is another relatively traditional unit testing framework.
  • AVA is a new test runner with Babel built-in and runs tests concurrently.

Web Frameworks:

  • Express.js is by far the most popular framework.
  • Koa is a new web framework designed by the team behind Express.js, which aims to be a smaller, more expressive, and more robust foundation for web applications and APIs.
  • sails.js the most popular MVC framework for Node.js, and is based on express. It is designed to emulate the familiar MVC pattern of frameworks like Ruby on Rails, but with support for the requirements of modern apps: data-driven APIs with a scalable, service-oriented architecture.
  • Meteor bundles together jQuery, Handlebars, Node.js, WebSocket, MongoDB, and DDP and promotes convention over configuration without being a Ruby on Rails clone.
  • Tower (deprecated) is an abstraction of a top of Express.js that aims to be a Ruby on Rails clone.
  • Geddy is another take on web frameworks.
  • RailwayJS is a Ruby on Rails inspired MVC web framework.
  • Sleek.js is a simple web framework, built upon Express.js.
  • Hapi is a configuration-centric framework with built-in support for input validation, caching, authentication, etc.
  • Trails is a modern web application framework. It builds on the pedigree of Rails and Grails to accelerate development by adhering to a straightforward, convention-based, API-driven design philosophy.

  • Danf is a full-stack OOP framework providing many features in order to produce a scalable, maintainable, testable and performant applications and allowing to code the same way on both the server (Node.js) and client (browser) sides.

  • Derbyjs is a reactive full-stack JavaScript framework. They are using patterns like reactive programming and isomorphic JavaScript for a long time.

  • is a powerful Node.js framework for creating APIs and easily connecting to backend data sources. It has an Angular.js SDK and provides SDKs for iOS and Android.

Web Framework Tools:


  • Connect is the Rack or WSGI of the Node.js world.
  • Request is a very popular HTTP request library.
  • is handy for building WebSocket servers.

Command Line Interaction:

  • minimist just command line argument parsing.
  • Yargs is a powerful library for parsing command-line arguments.
  • Commander.js is a complete solution for building single-use command-line applications.
  • Vorpal.js is a framework for building mature, immersive command-line applications.
  • Chalk makes your CLI output pretty.

Code Generators:

  • Yeoman Scaffolding tool from the command-line.
  • Skaffolder Code generator with visual and command-line interface. It generates a customizable CRUD application starting from the database schema or an OpenAPI 3.0 YAML file.

Work with streams:

How to access route, post, get etc. parameters in Zend Framework 2

If You have no access to plugin for instance outside of controller You can get params from servicelocator like this

//from POST
$foo = $this->serviceLocator->get('request')->getPost('foo'); 
//from GET
$foo = $this->serviceLocator->get('request')->getQuery()->foo;
//from route
$foo = $this->serviceLocator->get('application')->getMvcEvent()->getRouteMatch()->getParam('foo');

Identifier is undefined

Are you missing a function declaration?

void ac_search(uint num_patterns, uint pattern_length, const char *patterns, 
               uint num_records, uint record_length, const char *records, int *matches, Node* trie);

Add it just before your implementation of ac_benchmark_search.

How do I fetch only one branch of a remote Git repository?

My workarounds:

git fetch --depth=1
git checkout <branch_name>

if you don't have a local clone:

git clone --depth 1 -b <branch_name> <repo_url>

Should you use rgba(0, 0, 0, 0) or rgba(255, 255, 255, 0) for transparency in CSS?

There are two ways of storing a color with alpha. The first is exactly as you see it, with each component as-is. The second is to use pre-multiplied alpha, where the color values are multiplied by the alpha after converting it to the range 0.0-1.0; this is done to make compositing easier. Ordinarily you shouldn't notice or care which way is implemented by any particular engine, but there are corner cases where you might, for example if you tried to increase the opacity of the color. If you use rgba(0, 0, 0, 0) you are less likely to to see a difference between the two approaches.

Selenium wait until document is ready

Are you using Angular? If you are it is possible that the webdriver doesn't recognize that the async calls have finished.

I recommend looking at Paul Hammants ngWebDriver. The method waitForAngularRequestsToFinish() could come in handy.

React Native absolute positioning horizontal centre

create a full-width View with alignItems: "center" then insert desired children inside.

import React from "react";
import {View} from "react-native";

export default class AbsoluteComponent extends React.Component {
     <View style={{position: "absolute", left: 0, right: 0, alignItems: "center"}}>

you can add properties like bottom: 30 for bottom aligned component.

Key Value Pair List

Using one of the subsets method in this question

var list = new List<KeyValuePair<string, int>>() { 
    new KeyValuePair<string, int>("A", 1),
    new KeyValuePair<string, int>("B", 0),
    new KeyValuePair<string, int>("C", 0),
    new KeyValuePair<string, int>("D", 2),
    new KeyValuePair<string, int>("E", 8),

int input = 11;
var items = SubSets(list).FirstOrDefault(x => x.Sum(y => y.Value)==input);


a full console application:

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

namespace ConsoleApplication1
    class Program
        static void Main(string[] args)
            var list = new List<KeyValuePair<string, int>>() { 
                new KeyValuePair<string, int>("A", 1),
                new KeyValuePair<string, int>("B", 2),
                new KeyValuePair<string, int>("C", 3),
                new KeyValuePair<string, int>("D", 4),
                new KeyValuePair<string, int>("E", 5),
                new KeyValuePair<string, int>("F", 6),

            int input = 12;
            var alternatives = list.SubSets().Where(x => x.Sum(y => y.Value) == input);

            foreach (var res in alternatives)
                Console.WriteLine(String.Join(",", res.Select(x => x.Key)));

    public static class Extenions
        public static IEnumerable<IEnumerable<T>> SubSets<T>(this IEnumerable<T> enumerable)
            List<T> list = enumerable.ToList();
            ulong upper = (ulong)1 << list.Count;

            for (ulong i = 0; i < upper; i++)
                List<T> l = new List<T>(list.Count);
                for (int j = 0; j < sizeof(ulong) * 8; j++)
                    if (((ulong)1 << j) >= upper) break;

                    if (((i >> j) & 1) == 1)

                yield return l;

SQL Server Regular expressions in T-SQL

If anybody is interested in using regex with CLR here is a solution. The function below (C# .net 4.5) returns a 1 if the pattern is matched and a 0 if the pattern is not matched. I use it to tag lines in sub queries. The SQLfunction attribute tells sql server that this method is the actual UDF that SQL server will use. Save the file as a dll in a place where you can access it from management studio.

// default using statements above
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.Text.RegularExpressions;

namespace CLR_Functions
    public class myFunctions
        public static SqlInt16 RegexContain(SqlString text, SqlString pattern)
            SqlInt16 returnVal = 0;
                string myText = text.ToString();
                string myPattern = pattern.ToString();
                MatchCollection mc = Regex.Matches(myText, myPattern);
                if (mc.Count > 0)
                    returnVal = 1;
                returnVal = 0;

            return returnVal;

In management studio import the dll file via programability -- assemblies -- new assembly

Then run this query:

CREATE FUNCTION RegexContain(@text NVARCHAR(50), @pattern NVARCHAR(50))
RETURNS smallint 
EXTERNAL NAME CLR_Functions.[CLR_Functions.myFunctions].RegexContain

Then you should have complete access to the function via the database you stored the assembly in.

Then use in queries like so:

        dbo.RegexContain(Researcher, '[\p{L}\s]+') as 'is null values'
    FROM [DailyOps].[dbo].[DailyLog]
) AS a
WHERE a.[is null values] = 0

How to fix height of TR?

Your table width is 90% which is relative to it's container.

If you squeeze the page, you are probably squeezing the table width as well. The width of the cells reduce too and the browser compensate by increasing the height.

To have the height untouched, you have to make sure the widths of the cells can hold the intented content. Fixing the table width is probably something you want to try. Or perhaps play around with the min-width of the table.

Is there a way to create xxhdpi, xhdpi, hdpi, mdpi and ldpi drawables from a large scale image?

I use a tool called Android Icon Set in the Eclipse for standard icons like Launcher, ActionBar, Tab icons and notification icons. You can launch it from File --> New --> Other.. --> Android --> Android Icon Set. The best part is that you can choose any file from your computer and it will automatically place all the images of standard sizes into your project directory.

enter image description here

How to quickly form groups (quartiles, deciles, etc) by ordering column(s) in a data frame

I'll add the data.table version for anyone else Googling it (i.e., @BondedDust's solution translated to data.table and pared down a tad):

temp[ , quartile := cut(value,
                        breaks = quantile(value, probs = 0:4/4),
                        labels = 1:4, right = FALSE)]

Which is much better (cleaner, faster) than what I had been doing:

temp[ , quartile := 
        as.factor(ifelse(value < quantile(value, .25), 1,
                         ifelse(value < quantile(value, .5), 2,
                                ifelse(value < quantile(value, .75), 3, 4))]

Note, however, that this approach requires the quantiles to be distinct, e.g. it will fail on rep(0:1, c(100, 1)); what to do in this case is open ended so I leave it up to you.

how to calculate binary search complexity

Here a more mathematical way of seeing it, though not really complicated. IMO much clearer as informal ones:

The question is, how many times can you divide N by 2 until you have 1? This is essentially saying, do a binary search (half the elements) until you found it. In a formula this would be this:

1 = N / 2x

multiply by 2x:

2x = N

now do the log2:

log2(2x)    = log2 N
x * log2(2) = log2 N
x * 1         = log2 N

this means you can divide log N times until you have everything divided. Which means you have to divide log N ("do the binary search step") until you found your element.

You should not use <Link> outside a <Router>

Write router in place of Main in render (last line in the code). Like this ReactDOM.render(router, document.getElementById('root'));

HTML: Select multiple as dropdown

It's quite unpractical to make multiple select with size 1. think about it. I made a fiddle here:

<select name="test" multiple>

Try to explore other options such as using checkboxes to achieve your goal.

Can't Load URL: The domain of this URL isn't included in the app's domains

I had the same problem, and it came from a wrong client_id / Facebook App ID.

Did you switch your Facebook app to "public" or "online ? When you do so, Facebook creates a new app with a new App ID.

You can compare the "client_id" parameter value in the url with the one in your Facebook dashboard.

Also Make sure your app is public. Click on + Add product Now go to products => Facebook Login Now do the following:

Valid OAuth redirect URIs :

Select row on click react-table

I am not familiar with, react-table, so I do not know it has direct support for selecting and deselecting (it would be nice if it had).

If it does not, with the piece of code you already have you can install the onCLick handler. Now instead of trying to attach style directly to row, you can modify state, by for instance adding selected: true to row data. That would trigger rerender. Now you only have to override how are rows with selected === true rendered. Something along lines of:

// Any Tr element will be green if its (row.age > 20) 
  getTrProps={(state, rowInfo, column) => {
    return {
      style: {
        background: rowInfo.row.selected ? 'green' : 'red'

How to access Spring MVC model object in javascript file?

I recently faced the same need. So I tried Aurand's way but it seems the code is missing ${}. So the code inside SomeJsp.jsp <head></head>is:

  var model=[];

Note that you can't asssign using var model = ${model} as it will assign a java object reference. So to access this in external JS:

$(document).ready(function() {

Moment.js get day name from date

With moment you can parse the date string you have:

var dt = moment(, "YYYY-MM-DD HH:mm:ss")

That's for UTC, you'll have to convert the time zone from that point if you so desire.

Then you can get the day of the week:


Create a 3D matrix

If you want to define a 3D matrix containing all zeros, you write

A = zeros(8,4,20);

All ones uses ones, all NaN's uses NaN, all false uses false instead of zeros.

If you have an existing 2D matrix, you can assign an element in the "3rd dimension" and the matrix is augmented to contain the new element. All other new matrix elements that have to be added to do that are set to zero.

For example

B = magic(3); %# creates a 3x3 magic square
B(2,1,2) = 1; %# and you have a 3x3x2 array

Create sequence of repeated values, in sequence?

You missed the each= argument to rep():

R> n <- 3
R> rep(1:5, each=n)
 [1] 1 1 1 2 2 2 3 3 3 4 4 4 5 5 5

so your example can be done with a simple

R> rep(1:8, each=20)

iOS: set font size of UILabel Programmatically

Swift 3.0 / Swift 4.2 / Swift 5.0

labelName.font = labelName.font.withSize(15)

What processes are using which ports on unix?

Which process uses port in unix;

1. netstat -Aan | grep port

root> netstat -Aan | grep 3872

output> f1000e000bb5c3b8 tcp 0 0 *.3872 . LISTEN

2. rmsock f1000e000bb5c3b8 tcpcb

output> The socket 0xf1000e000bb5c008 is being held by proccess 13959354 (java).

3. ps -ef | grep 13959354

NPM clean modules

You can just delete the node_module directory

rm -rf node_modules/

Calling a method inside another method in same class

It is not recursion, it is overloading. The two add methods (the one in your snippet, and the one "provided" by ArrayList that you are extending) are not the same method, cause they are declared with different parameters.

how to put focus on TextBox when the form load?

You can use either; or the TabIndex in textbox setting. TabIndex=0 focoused first.

UPDATE with CASE and IN - Oracle

"The list are variables/paramaters that is pre-defined as comma separated lists". Do you mean that your query is actually

UPDATE tab1   SET budgpost_gr1=     
CASE  WHEN (budgpost in ('1001,1012,50055'))  THEN 'BP_GR_A'   
      WHEN (budgpost in ('5,10,98,0'))  THEN 'BP_GR_B'  
      WHEN (budgpost in ('11,876,7976,67465'))     
      ELSE 'Missing' END`

If so, you need a function to take a string and parse it into a list of numbers.

create type tab_num is table of number;

create or replace function f_str_to_nums (i_str in varchar2) return tab_num is
  v_tab_num tab_num := tab_num();
  v_start   number := 1;
  v_end     number;
  v_delim   VARCHAR2(1) := ',';
  v_cnt     number(1) := 1;
  v_end := instr(i_str||v_delim,v_delim,1, v_start);
  WHILE v_end > 0 LOOP
    v_cnt := v_cnt + 1;
    v_tab_num(v_tab_num.count) := 
    v_start := v_end + 1;
    v_end := instr(i_str||v_delim,v_delim,v_start);
  RETURN v_tab_num;

Then you can use the function like so:

select column_id, 
   case when column_id in 
     (select column_value from table(f_str_to_nums('1,2,3,4'))) then 'red' 
   else 'blue' end
from  user_tab_columns
where table_name = 'EMP'

Get day of week using NSDate

Swift 3 Date extension

extension Date {
    var weekdayOrdinal: Int {
        return Calendar.current.component(.weekday, from: self)

Using UPDATE in stored procedure with optional parameters

    @Firstname nvarchar(200)


    UPDATE tbl_Students1
    SET Firstname=@Firstname 

    WHERE Studentid=3

exec LN 'Thanvi'

All ASP.NET Web API controllers return 404

I have been working on a problem similar to this and it took me ages to find the problem. It is not the solution for this particular post, but hopefully adding this will save someone some time trying to find the issue when they are searching for why they might be getting a 404 error for their controller.

Basically, I had spelt "Controller" wrong at the end of my class name. Simple as that!

JavaScript seconds to time string with format hh:mm:ss

You can manage to do this without any external JS library with the help of JS Date method like following:

var date = new Date(0);_x000D_
date.setSeconds(45); // specify value for SECONDS here_x000D_
var timeString = date.toISOString().substr(11, 8);_x000D_

How to remove a directory from git repository?

A combination of the 2 answers worked for me

git rm -r one-of-the-directories
git commit . -m "Remove duplicated directory"
git push

if it still shows some warning, remove the files manually

git filter-branch --tree-filter 'rm -rf path/to/your/file' HEAD
git push

Android ADT error, dx.jar was not loaded from the SDK folder

Updating Android SDK platform-tools with the Android SDK Manager and restarting Eclipse did it for me

Maven: How to change path to target directory from command line?

You should use profiles.


And start maven with your profile

mvn compile -PotherOutputDir

If you really want to define your directory from the command line you could do something like this (NOT recommended at all) :



And compile like this :

mvn compile -DbuildDirectory=test

That's because you can't change the target directory by using

How to replace text in a column of a Pandas dataframe?

If you only need to replace characters in one specific column, somehow regex=True and in place=True all failed, I think this way will work:

data["column_name"] = data["column_name"].apply(lambda x: x.replace("characters_need_to_replace", "new_characters"))

lambda is more like a function that works like a for loop in this scenario. x here represents every one of the entries in the current column.

The only thing you need to do is to change the "column_name", "characters_need_to_replace" and "new_characters".

How to concatenate properties from multiple JavaScript objects

Why should the function be restricted to 3 arguments? Also, check for hasOwnProperty.

function Collect() {
    var o={};
    for(var i=0;i<arguments.length;i++) {
      var arg=arguments[i];
      if(typeof arg != "object") continue;
      for(var p in arg) {
        if(arg.hasOwnProperty(p)) o[p] = arg[p];
    return o;

Import CSV into SQL Server (including automatic table creation)

You can create a temp table variable and insert the data into it, then insert the data into your actual table by selecting it from the temp table.

 declare @TableVar table 
    firstCol varchar(50) NOT NULL,
    secondCol varchar(50) NOT NULL


INSERT INTO dbo.ExistingTable
SELECT firstCol,
FROM @TableVar


Setting Windows PATH for Postgres tools

Set path For PostgreSQL in Windows:

  1. Searching for env will show Edit environment variables for your account
  2. Select Environment Variables
  3. From the System Variables box select PATH
  4. Click New (to add new path)

Change the PATH variable to include the bin directory of your PostgreSQL installation.
then add new path their....[for example]

C:\Program Files\PostgreSQL\12\bin

After that click OK

Open CMD/Command Prompt. Type this to open psql

psql -U username database_name

For Example psql -U postgres test

Now, you will be prompted to give Password for the User. (It will be hidden as a security measure).

Then you are good to go.

Mysql: Select all data between two dates

its very easy to handle this situation

You can use BETWEEN CLAUSE in combination with date_sub( now( ) , INTERVAL 30 DAY ) AND NOW( )

    sc_cust_design.design_id as id,
    sc_cust_design.publish = 1 
    AND **`datein`BETWEEN date_sub( now( ) , INTERVAL 30 DAY ) AND NOW( )**

Happy Coding :)

Is there an upside down caret character?

An upside-down circumflex is called a caron, or a hácek.

It has an HTML entity in the TADS Latin-2 extension to HTML: &caron; and looks like this: ˇ which unfortunately doesn't display in the same size/proportion as the ^ caret.

Or you can use the unicode U+30C.

SQL UPDATE with sub-query that references the same table in MySQL

UPDATE user_account 
SET (student_education_facility_id) = ( 
    SELECT teacher.education_facility_id
    FROM user_account teacher
    WHERE teacher.user_account_id = teacher_id
    AND teacher.user_type = 'ROLE_TEACHER'
WHERE user_type = 'ROLE_STUDENT'

Above are the sample update query...

You can write sub query with update SQL statement, you don't need to give alias name for that table. give alias name to sub query table. I tried and it's working fine for me....

How can I make a UITextField move up when the keyboard is present - on starting to edit?

This piece of code will calculate how much need to move up based on the keyboard height and how deep the text field as gone. Remember to add delegate and inherit UITextFieldDelegate at your header.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
    [_tbxUsername resignFirstResponder];
    [_tbxPassword resignFirstResponder];

- (void)textFieldDidBeginEditing:(UITextField *) textField
    [self animateTextField:textField up:YES];

- (void)textFieldDidEndEditing:(UITextField *) textField
    [self animateTextField:textField up:NO];

- (void) animateTextField: (UITextField*) textField up: (BOOL) up
    int animatedDistance;
    int moveUpValue = textField.frame.origin.y+ textField.frame.size.height;
    UIInterfaceOrientation orientation =
    [[UIApplication sharedApplication] statusBarOrientation];
    if (orientation == UIInterfaceOrientationPortrait ||
        orientation == UIInterfaceOrientationPortraitUpsideDown)

        animatedDistance = 236-(460-moveUpValue-5);
        animatedDistance = 182-(320-moveUpValue-5);

        const int movementDistance = animatedDistance;
        const float movementDuration = 0.3f;
        int movement = (up ? -movementDistance : movementDistance);
        [UIView beginAnimations: nil context: nil];
        [UIView setAnimationBeginsFromCurrentState: YES];
        [UIView setAnimationDuration: movementDuration];
        self.view.frame = CGRectOffset(self.view.frame, 0, movement);
        [UIView commitAnimations];

Delegate to add at ViewDidLoad

_tbxUsername.delegate = self;
_tbxPassword.delegate = self;

Android Studio build fails with "Task '' not found in root project 'MyProject'."

Yet another solution to the same problem:

This happened to me every time I imported an eclipse project into studio using the wizard (studio version 1.3.2).

What I found, quite by chance, was that quitting out of Android studio and then restarting studio again made the problem go away.

Frustrating, but hope this helps someone...

How to get the real and total length of char * (char array)?

There are only two ways:

  • If the memory pointer to by your char * represents a C string (that is, it contains characters that have a 0-byte to mark its end), you can use strlen(a).

  • Otherwise, you need to store the length somewhere. Actually, the pointer only points to one char. But we can treat it as if it points to the first element of an array. Since the "length" of that array isn't known you need to store that information somewhere.

Android REST client, Sample?

EDIT 2 (October 2017):

It is 2017. Just use Retrofit. There is almost no reason to use anything else.


The original answer is more than a year and a half old at the time of this edit. Although the concepts presented in original answer still hold, as other answers point out, there are now libraries out there that make this task easier for you. More importantly, some of these libraries handle device configuration changes for you.

The original answer is retained below for reference. But please also take the time to examine some of the Rest client libraries for Android to see if they fit your use cases. The following is a list of some of the libraries I've evaluated. It is by no means intended to be an exhaustive list.

Original Answer:

Presenting my approach to having REST clients on Android. I do not claim it is the best though :) Also, note that this is what I came up with in response to my requirement. You might need to have more layers/add more complexity if your use case demands it. For example, I do not have local storage at all; because my app can tolerate loss of a few REST responses.

My approach uses just AsyncTasks under the covers. In my case, I "call" these Tasks from my Activity instance; but to fully account for cases like screen rotation, you might choose to call them from a Service or such.

I consciously chose my REST client itself to be an API. This means, that the app which uses my REST client need not even be aware of the actual REST URL's and the data format used.

The client would have 2 layers:

  1. Top layer: The purpose of this layer is to provide methods which mirror the functionality of the REST API. For example, you could have one Java method corresponding to every URL in your REST API (or even two - one for GETs and one for POSTs).
    This is the entry point into the REST client API. This is the layer the app would use normally. It could be a singleton, but not necessarily.
    The response of the REST call is parsed by this layer into a POJO and returned to the app.

  2. This is the lower level AsyncTask layer, which uses HTTP client methods to actually go out and make that REST call.

In addition, I chose to use a Callback mechanism to communicate the result of the AsyncTasks back to the app.

Enough of text. Let's see some code now. Lets take a hypothetical REST API URL -

The top layer might look like this:

 * Entry point into the API.
public class HypotheticalApi{   
    public static HypotheticalApi getInstance(){
        //Choose an appropriate creation strategy.
     * Request a User Profile from the REST server.
     * @param userName The user name for which the profile is to be requested.
     * @param callback Callback to execute when the profile is available.
    public void getUserProfile(String userName, final GetResponseCallback callback){
        String restUrl = Utils.constructRestUrlForProfile(userName);
        new GetTask(restUrl, new RestTaskCallback (){
            public void onTaskComplete(String response){
                Profile profile = Utils.parseResponseAsProfile(response);
     * Submit a user profile to the server.
     * @param profile The profile to submit
     * @param callback The callback to execute when submission status is available.
    public void postUserProfile(Profile profile, final PostCallback callback){
        String restUrl = Utils.constructRestUrlForProfile(profile);
        String requestBody = Utils.serializeProfileAsString(profile);
        new PostTask(restUrl, requestBody, new RestTaskCallback(){
            public void onTaskComplete(String response){

 * Class definition for a callback to be invoked when the response data for the
 * GET call is available.
public abstract class GetResponseCallback{
     * Called when the response data for the REST call is ready. <br/>
     * This method is guaranteed to execute on the UI thread.
     * @param profile The {@code Profile} that was received from the server.
    abstract void onDataReceived(Profile profile);
     * Additional methods like onPreGet() or onFailure() can be added with default implementations.
     * This is why this has been made and abstract class rather than Interface.

 * Class definition for a callback to be invoked when the response for the data 
 * submission is available.
public abstract class PostCallback{
     * Called when a POST success response is received. <br/>
     * This method is guaranteed to execute on the UI thread.
    public abstract void onPostSuccess();


Note that the app doesn't use the JSON or XML (or whatever other format) returned by the REST API directly. Instead, the app only sees the bean Profile.

Then, the lower layer (AsyncTask layer) might look like this:

 * An AsyncTask implementation for performing GETs on the Hypothetical REST APIs.
public class GetTask extends AsyncTask<String, String, String>{
    private String mRestUrl;
    private RestTaskCallback mCallback;
     * Creates a new instance of GetTask with the specified URL and callback.
     * @param restUrl The URL for the REST API.
     * @param callback The callback to be invoked when the HTTP request
     *            completes.
    public GetTask(String restUrl, RestTaskCallback callback){
        this.mRestUrl = restUrl;
        this.mCallback = callback;
    protected String doInBackground(String... params) {
        String response = null;
        //Use HTTP Client APIs to make the call.
        //Return the HTTP Response body here.
        return response;
    protected void onPostExecute(String result) {

     * An AsyncTask implementation for performing POSTs on the Hypothetical REST APIs.
    public class PostTask extends AsyncTask<String, String, String>{
        private String mRestUrl;
        private RestTaskCallback mCallback;
        private String mRequestBody;
         * Creates a new instance of PostTask with the specified URL, callback, and
         * request body.
         * @param restUrl The URL for the REST API.
         * @param callback The callback to be invoked when the HTTP request
         *            completes.
         * @param requestBody The body of the POST request.
        public PostTask(String restUrl, String requestBody, RestTaskCallback callback){
            this.mRestUrl = restUrl;
            this.mRequestBody = requestBody;
            this.mCallback = callback;
        protected String doInBackground(String... arg0) {
            //Use HTTP client API's to do the POST
            //Return response.
        protected void onPostExecute(String result) {
     * Class definition for a callback to be invoked when the HTTP request
     * representing the REST API Call completes.
    public abstract class RestTaskCallback{
         * Called when the HTTP request completes.
         * @param result The result of the HTTP request.
        public abstract void onTaskComplete(String result);

Here's how an app might use the API (in an Activity or Service):

HypotheticalApi myApi = HypotheticalApi.getInstance();
        myApi.getUserProfile("techie.curious", new GetResponseCallback() {

            void onDataReceived(Profile profile) {
                //Use the profile to display it on screen, etc.
        Profile newProfile = new Profile();
        myApi.postUserProfile(newProfile, new PostCallback() {
            public void onPostSuccess() {
                //Display Success

I hope the comments are sufficient to explain the design; but I'd be glad to provide more info.

Any way to limit border length?

for horizontal lines you can use hr tag:

hr { width: 90%; }

but its not possible to limit border height. only element height.

Validation failed for one or more entities. See 'EntityValidationErrors' property for more details

Just throwing my two cents in...

Within my dbConfiguration.cs, I like to wrap my context.SaveChanges() method into a try/catch and produce an output text file that allows me to read the Error(s) clearly, and this code also timestamps them - handy if you run into more than one error at different times!

        catch (DbEntityValidationException e)
            //Create empty list to capture Validation error(s)
            var outputLines = new List<string>();

            foreach (var eve in e.EntityValidationErrors)
                    $"{DateTime.Now}: Entity of type \"{eve.Entry.Entity.GetType().Name}\" in state \"{eve.Entry.State}\" has the following validation errors:");
                outputLines.AddRange(eve.ValidationErrors.Select(ve =>
                    $"- Property: \"{ve.PropertyName}\", Error: \"{ve.ErrorMessage}\""));
            //Write to external file
            File.AppendAllLines(@"c:\temp\dbErrors.txt", outputLines);

How to find numbers from a string?

Based on @brettdj's answer using a VBScript regex ojbect with two modifications:

  • The function handles variants and returns a variant. That is, to take care of a null case; and
  • Uses explicit object creation, with a reference to the "Microsoft VBScript Regular Expressions 5.5" library
Function GetDigitsInVariant(inputVariant As Variant) As Variant
  ' Returns:
  '     Only the digits found in a varaint.
  ' Examples:
  '     GetDigitsInVariant(Null) => Null
  '     GetDigitsInVariant("") => ""
  '     GetDigitsInVariant(2021-/05-May/-18, Tue) => 20210518
  '     GetDigitsInVariant(2021-05-18) => 20210518
  ' Notes:
  '     If the inputVariant is null, null will be returned.
  '     If the inputVariant is "", "" will be returned.
  ' Usage:
  '     VBA IDE Menu > Tools > References ...
  '       > "Microsoft VBScript Regular Expressions 5.5" > [OK]

  ' With an explicit object reference to RegExp we can get intellisense
  ' and review the object heirarchy with the object browser
  ' (VBA IDE Menu > View > Object Browser).
  Dim regex As VBScript_RegExp_55.RegExp
  Set regex = New VBScript_RegExp_55.RegExp
  Dim result As Variant
  result = Null
  If IsNull(inputVariant) Then
    result = Null
    With regex
      .Global = True
      .Pattern = "[^\d]+"
      result = .Replace(inputVariant, vbNullString)
    End With
  End If
  GetDigitsInVariant = result
End Function


Private Sub TestGetDigitsInVariant()
  Dim dateVariants As Variant
  dateVariants = Array(Null, "", "2021-/05-May/-18, Tue", _
          "2021-05-18", "18/05/2021", "3434 ..,sdf,sfd 444")
  Dim dateVariant As Variant
  For Each dateVariant In dateVariants
    Debug.Print dateVariant & ": ", , GetDigitsInVariant(dateVariant)
  Next dateVariant
End Sub

Matrix Transpose in Python

The problem with your original code was that you initialized transpose[t] at every element, rather than just once per row:

def matrixTranspose(anArray):
    transposed = [None]*len(anArray[0])
    for t in range(len(anArray)):
        transposed[t] = [None]*len(anArray)
        for tt in range(len(anArray[t])):
            transposed[t][tt] = anArray[tt][t]
    print transposed

This works, though there are more Pythonic ways to accomplish the same things, including @J.F.'s zip application.

How to have PHP display errors? (I've added ini_set and error_reporting, but just gives 500 on errors)

I have had this problem when using PHP5.4 and Plesk 11.5

Somehow, the error reporting and display error settings in the Plesk domain configuration page were completely overriding any local settings in .htaccess or the PHP scripts. I have not found a way to prevent this happening, so use the Plesk settings to turn error reporting on and off.

You may have settings in your php.ini that prevents the local site from overriding these settings, perhaps enforced by the control panel used on your server.

Delete all documents from index/type without deleting type

Starting from Elasticsearch 2.x delete is not anymore allowed, since documents remain in the index causing index corruption.

How to hide column of DataGridView when using custom DataSource?

If you want to use the BrowsableAttribute, then you can look for it at runtime on the model and hide the column accordingly:

private void Form_Load(object sender, EventArgs e)
    //add this line after your DataGridView initialization

private void HideColumns<T>(DataGridView dvg)
    var type = typeof(T);
    foreach (var column in dvg.Columns.Cast<DataGridViewColumn>())
        column.Visible = IsBrowsable(type.GetProperty(column.Name));

private bool IsBrowsable(PropertyInfo propertyInfo)
    var attribute = propertyInfo.GetCustomAttributes(true).FirstOrDefault(att => att.GetType() == typeof(BrowsableAttribute));
    return attribute == null || (attribute as BrowsableAttribute).Browsable;

When should I use a struct rather than a class in C#?

Struct can be used to improve garbage collection performance. While you usually don't have to worry about GC performance, there are scenarios where it can be a killer. Like large caches in low latency applications. See this post for an example:

Uploading a file in Rails

Sept 2018

For anyone checking this question recently, Rails 5.2+ now has ActiveStorage by default & I highly recommend checking it out.

Since it is part of the core Rails 5.2+ now, it is very well integrated & has excellent capabilities out of the box (still all other well-known gems like Carrierwave, Shrine, paperclip,... are great but this one offers very good features that we can consider for any new Rails project)

Paperclip team deprecated the gem in favor of the Rails ActiveStorage.

Here is the github page for the ActiveStorage & plenty of resources are available everywhere

Also I found this video to be very helpful to understand the features of Activestorage

xsl: how to split strings?

I. Plain XSLT 1.0 solution:

This transformation:

<xsl:stylesheet version="1.0"
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="text()" name="split">
  <xsl:param name="pText" select="."/>
  <xsl:if test="string-length($pText)">
   <xsl:if test="not($pText=.)">
    <br />
   <xsl:value-of select=
   <xsl:call-template name="split">
    <xsl:with-param name="pText" select=
     "substring-after($pText, ';')"/>

when applied on this XML document:

<t>123 Elm Street;PO Box 222;c/o James Jones</t>

produces the wanted, corrected result:

123 Elm Street<br />PO Box 222<br />c/o James Jones

II. FXSL 1 (for XSLT 1.0):

Here we just use the FXSL template str-map (and do not have to write recursive template for the 999th time):

<xsl:stylesheet version="1.0" 
exclude-result-prefixes="xsl f testmap"
   <xsl:import href="str-dvc-map.xsl"/>


   <xsl:output omit-xml-declaration="yes" indent="yes"/>

   <xsl:template match="/">
     <xsl:variable name="vTestMap" select="document('')/*/testmap:*[1]"/>
     <xsl:call-template name="str-map">
       <xsl:with-param name="pFun" select="$vTestMap"/>
       <xsl:with-param name="pStr" select=
       "'123 Elm Street;PO Box 222;c/o James Jones'"/>

    <xsl:template name="replace" mode="f:FXSL"
         match="*[namespace-uri() = 'testmap']">
      <xsl:param name="arg1"/>

       <xsl:when test="not($arg1=';')">
        <xsl:value-of select="$arg1"/>
       <xsl:otherwise><br /></xsl:otherwise>

when this transformation is applied on any XML document (not used), the same, wanted correct result is produced:

123 Elm Street<br/>PO Box 222<br/>c/o James Jones

III. Using XSLT 2.0

<xsl:stylesheet version="2.0"
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="text()">
  <xsl:for-each select="tokenize(.,';')">
   <xsl:sequence select="."/>
   <xsl:if test="not(position() eq last())"><br /></xsl:if>

when this transformation is applied on this XML document:

<t>123 Elm Street;PO Box 222;c/o James Jones</t>

the wanted, correct result is produced:

123 Elm Street<br />PO Box 222<br />c/o James Jones

How to call a stored procedure from Java and JPA

The following works for me:

Query query = em.createNativeQuery("BEGIN VALIDACIONES_QPAI.RECALC_COMP_ASSEMBLY('X','X','X',0); END;");

How to filter input type="file" dialog by specific file type?

This will give the correct (custom) filter when the file dialog is showing:

<input type="file" accept=".jpg, .png, .jpeg, .gif, .bmp, .tif, .tiff|image/*">

How to detect when a UIScrollView has finished scrolling

There is a method of UIScrollViewDelegate which can be used to detect (or better to say 'predict') when scrolling has really finished:

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>)

of UIScrollViewDelegate which can be used to detect (or better to say 'predict') when scrolling has really finished.

In my case I used it with horizontal scrolling as following (in Swift 3):

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    perform(#selector(self.actionOnFinishedScrolling), with: nil, afterDelay: Double(velocity.x))
func actionOnFinishedScrolling() {
    print("scrolling is finished")
    // do what you need

How to increment variable under DOS?

I've found my own solution.

Download FreeDOS from here:

Then using my Counter.exe file (which basically generates a Counter.txt file and increments the number inside every time it's being called), I can assign the value of the number to a variable using:

Set /P Variable =< Counter.txt

Then, I can check if it has run 250 cycles by doing:

if %variable%==250 echo PASS

BTW, I still can't use Set /A since FreeDOS doesn't support this command, but at least it supports the Set /P command.

Build the full path filename in Python

This works fine:

os.path.join(dir_name, base_filename + "." + filename_suffix)

Keep in mind that os.path.join() exists only because different operating systems use different path separator characters. It smooths over that difference so cross-platform code doesn't have to be cluttered with special cases for each OS. There is no need to do this for file name "extensions" (see footnote) because they are always connected to the rest of the name with a dot character, on every OS.

If using a function anyway makes you feel better (and you like needlessly complicating your code), you can do this:

os.path.join(dir_name, '.'.join((base_filename, filename_suffix)))

If you prefer to keep your code clean, simply include the dot in the suffix:

suffix = '.pdf'
os.path.join(dir_name, base_filename + suffix)

That approach also happens to be compatible with the suffix conventions in pathlib, which was introduced in python 3.4 after this question was asked. New code that doesn't require backward compatibility can do this:

suffix = '.pdf'
pathlib.PurePath(dir_name, base_filename + suffix)

You might prefer the shorter Path instead of PurePath if you're only handling paths for the local OS.

Warning: Do not use pathlib's with_suffix() for this purpose. That method will corrupt base_filename if it ever contains a dot.

Footnote: Outside of Micorsoft operating systems, there is no such thing as a file name "extension". Its presence on Windows comes from MS-DOS and FAT, which borrowed it from CP/M, which has been dead for decades. That dot-plus-three-letters that many of us are accustomed to seeing is just part of the file name on every other modern OS, where it has no built-in meaning.

sqlalchemy IS NOT NULL select

Starting in version 0.7.9 you can use the filter operator .isnot instead of comparing constraints, like this:


This method is only necessary if pep8 is a concern.

source: sqlalchemy documentation

Click a button with XPath containing partial id and title in Selenium IDE

Now that you have provided your HTML sample, we're able to see that your XPath is slightly wrong. While it's valid XPath, it's logically wrong.

You've got:

//*[contains(@id, 'ctl00_btnAircraftMapCell')]//*[contains(@title, 'Select Seat')]

Which translates into:

Get me all the elements that have an ID that contains ctl00_btnAircraftMapCell. Out of these elements, get any child elements that have a title that contains Select Seat.

What you actually want is:

//a[contains(@id, 'ctl00_btnAircraftMapCell') and contains(@title, 'Select Seat')]

Which translates into:

Get me all the anchor elements that have both: an id that contains ctl00_btnAircraftMapCell and a title that contains Select Seat.

Using numpy to build an array of all combinations of two arrays

you can use np.array(itertools.product(a, b))

Limiting Powershell Get-ChildItem by File Creation Date Range

Use Where-Object and test the $_.CreationTime:

Get-ChildItem 'PATH' -recurse -include @("*.tif*","*.jp2","*.pdf") | 
    Where-Object { $_.CreationTime -ge "03/01/2013" -and $_.CreationTime -le "03/31/2013" }

Header and footer in CodeIgniter

This question has been answered properly, but I would like to add my approach, it's not that different than what the others have mentioned.

I use different layouts pages to call different headers/footers, some call this layout, some call it template etc.

  1. Edit core/Loader.php and add your own function to load your layout, I called the function e.g.layout.

  2. Create your own template page and make it call header/footer for you, I called it default.php and put in a new directory e.g. view/layout/default.php

  3. Call your own view page from your controller as you would normally. But instead of calling $this-load->view use $this->load->layout, layout function will call the default.php and default.php will call your header and footer.

1) In core/Loader.php under view() function I duplicated it and added mine

   public function layout($view, $vars = array(), $return = FALSE)
       $vars["display_page"] = $view;//will be called from the layout page
       $layout               = isset($vars["layout"]) ? $vars["layout"] : "default";
       return $this->_ci_load(array('_ci_view' => "layouts/$layout", '_ci_vars' =>  $this->_ci_object_to_array($vars), '_ci_return' => $return));

2) Create layout folder and put default.php in it in view/layout/default.php

   $this->load->view('parts/header');//or wherever your header is
   $this->load->view('parts/footer');or wherever your footer is

3) From your controller, call your layout

 $this->load->layout('projects');// will use 'view/layout/default.php' layout which in return will call header and footer as well. 

To use another layout, include the new layout name in your $data array

 $data["layout"] = "full_width";
 $this->load->layout('projects', $data);// will use full_width.php layout

and of course you must have your new layout in the layout directory as in:


Unable to resolve host "<insert URL here>" No address associated with hostname

My bet is that you forgot to give your app the permission to use the internet. Try adding this to your android manifest:

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

Use of #pragma in C

#pragma is for compiler directives that are machine-specific or operating-system-specific, i.e. it tells the compiler to do something, set some option, take some action, override some default, etc. that may or may not apply to all machines and operating systems.

See msdn for more info.

Sound effects in JavaScript / HTML5


For game authoring, one of the best solutions is to use a library which solves the many problems we face when writing code for the web, such as howler.js. howler.js abstracts the great (but low-level) Web Audio API into an easy to use framework. It will attempt to fall back to HTML5 Audio Element if Web Audio API is unavailable.

var sound = new Howl({
  urls: ['sound.mp3', 'sound.ogg']
// it also provides calls for spatial/3d audio effects (most browsers)


Another great library is wad.js, which is especially useful for producing synth audio, such as music and effects. For example:

var saw = new Wad({source : 'sawtooth'}){
    volume  : 0.8,
    wait    : 0,     // Time in seconds between calling play() and actually triggering the note.
    loop    : false, // This overrides the value for loop on the constructor, if it was set. 
    pitch   : 'A4',  // A4 is 440 hertz.
    label   : 'A',   // A label that identifies this note.
    env     : {hold : 9001},
    panning : [1, -1, 10],
    filter  : {frequency : 900},
    delay   : {delayTime : .8}

Sound for Games

Another library similar to Wad.js is "Sound for Games", it has more focus on effects production, while providing a similar set of functionality through a relatively distinct (and perhaps more concise feeling) API:

function shootSound() {
    1046.5,           //frequency
    0,                //attack
    0.3,              //decay
    "sawtooth",       //waveform
    1,                //Volume
    -0.8,             //pan
    0,                //wait before playing
    1200,             //pitch bend amount
    false,            //reverse bend
    0,                //random pitch range
    25,               //dissonance
    [0.2, 0.2, 2000], //echo array: [delay, feedback, filter]
    undefined         //reverb array: [duration, decay, reverse?]


Each of these libraries are worth a look, whether you need to play back a single sound file, or perhaps create your own html-based music editor, effects generator, or video game.

How to hide scrollbar in Firefox?

I was able to hide the scrollbar but still be able to scroll with mouse wheel with this solution:

html {overflow: -moz-scrollbars-none;}

Download the plugin and include this function:

jQuery('html,body').bind('mousewheel', function(event) {
    var scrollTop = this.scrollTop;
    this.scrollTop = (scrollTop + ((event.deltaY * event.deltaFactor) * -1));
    //console.log(event.deltaY, event.deltaFactor, event.originalEvent.deltaMode, event.originalEvent.wheelDelta);

JavaScript .replace only replaces first Match

Try using a regex instead of a string for the first argument.

"this is a test".replace(/ /g,'%20') // #=> "this%20is%20a%20test"

How to execute a shell script in PHP?

Residuum did provide a correct answer to how you should get shell exec to find your script, but in regards to security, there are a couple of points.

I would imagine you don't want your shell script to be in your web root, as it would be visible to anyone with web access to your server.

I would recommend moving the shell script to outside of the webroot

      $tempFolder = '/tmp';
      $webRootFolder = '/var/www';
      $scriptName = '';
      $moveCommand = "mv $webRootFolder/$scriptName $tempFolder/$scriptName";
      $output = shell_exec($moveCommand);

In regards to the:

i added www-data ALL=(ALL) NOPASSWD:ALL to /etc/sudoers works

You can modify this to only cover the specific commands in your script which require sudo. Otherwise, if none of the commands in your sh script require sudo to execute, you don't need to do this at all anyway.

Try running the script as the apache user (use the su command to switch to the apache user) and if you are not prompted for sudo or given permission denied, etc, it'll be fine.


sudo su apache (or www-data)
cd /var/www
sh ./myscript

Also... what brought me here was that I wanted to run a multi line shell script using commands that are dynamically generated. I wanted all of my commands to run in the same shell, which won't happen using multiple calls to shell_exec(). The answer to that one is to do it like Jenkins - create your dynamically generated multi line of commands, put it in a variable, save it to a file in a temp folder, execute that file (using shell_exec in() php as Jenkins is Java), then do whatever you want with the output, and delete the temp file

... voila

Could not load file or assembly 'Newtonsoft.Json, Version=, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' or one of its dependencies

I solved this issue by removing all the NuGet packages from solution and reinstalling them. One of the NuGet Packages was dependent upon NewtonSoft and it was not showing in references

Python: Generate random number between x and y which is a multiple of 5

Create an integer random between e.g. 1-11 and multiply it by 5. Simple math.

import random
for x in range(20):
  print random.randint(1,11)*5,

produces e.g.

5 40 50 55 5 15 40 45 15 20 25 40 15 50 25 40 20 15 50 10

How to get base URL in Web API controller?

In .NET Core WebAPI (version 3.0 and above):

var requestUrl = $"{Request.Scheme}://{Request.Host.Value}/";


Maven error: Not authorized, ReasonPhrase:Unauthorized

You have an old password in the settings.xml. It is trying to connect to the repositories, but is not able to, since the password is not updated. Once you update and re-run the command, you should be good.

No 'Access-Control-Allow-Origin' header in Angular 2 app

Simply you can set in php file as

header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");

How to escape indicator characters (i.e. : or - ) in YAML

According to the YAML spec, neither the : nor the - should be a problem. : is only a key separator with a space after it, and - is only an array indicator at the start of a line with a space after it.

But if your YAML implementation has a problem with it, you potentially have lots of options:

- url: ''
- url: ""
- url:
- url: >-
- url: |-

There is explicitly no form of escaping possible in "plain style", however.

What svn command would list all the files modified on a branch?

You can use the following command:

svn status -q

According to svnbook:

With --quiet (-q), it prints only summary information about locally modified items.

WARNING: The output of this command only shows your modification. So I suggest to do a svn up to get latest version of the file and then use svn status -q to get the files you have modified.

What are the differences between git branch, fork, fetch, merge, rebase and clone?

Here is Oliver Steele's image of how it all fits together:

enter image description here

Change header text of columns in a GridView

I Think this Works:


python - checking odd/even numbers and changing outputs on number size

Sample Instruction Given an integer, n, performing the following conditional actions:

  • If n is odd, print Weird
  • If n is even and in the inclusive range of 2 to 5, print Not Weird
  • If n is even and in the inclusive range of 6 to 20, print Weird
  • If n is even and greater than 20, print Not Weird
import math
n = int(input())

if n % 2 ==1:
elif n % 2==0 and n in range(2,6):
    print("Not Weird")
elif n % 2 == 0 and n in range(6,21):
elif n % 2==0 and n>20:
    print("Not Weird")

Regular expression to match a word or its prefix

Square brackets are meant for character class, and you're actually trying to match any one of: s, |, s (again), e, a, s (again), o and n.

Use parentheses instead for grouping:


or non-capturing group:


Note: Non-capture groups tell the engine that it doesn't need to store the match, while the other one (capturing group does). For small stuff, either works, for 'heavy duty' stuff, you might want to see first if you need the match or not. If you don't, better use the non-capture group to allocate more memory for calculation instead of storing something you will never need to use.

How do I create a user account for basic authentication?

Right click on Computer and choose "Manage" (or go to Control Panel > Administrative Tools > Computer Management) and under "Local Users and Groups" you can add a new user. Then, give that user permission to read the directory where the site is hosted.

Note: After creating the user, be sure to edit the user and remove all roles.

What is the difference between background, backgroundTint, backgroundTintMode attributes in android layout xml?

I won't stress much on the difference as it is already covered, but notice the below:

  • android:backgroundTint android:backgroundTintMode are only available at API 21
  • If you have a widget that has a png/vector drawable background set by android:background, and you want to change its default color, then you can use android:backgroundTint to add a shade to it.


    android:background="@android:drawable/ic_dialog_email" />

enter image description here

    android:backgroundTint="@color/colorAccent" />

enter image description here

Another example

If you try to change the accent color of the FloatingActionButton using android:background you won't notice a change, that is because it's already utilizes app:srcCompat, so in order to do that you can use android:backgroundTint instead

ng-model for `<input type="file"/>` (with directive DEMO)

If you want something a little more elegant/integrated, you can use a decorator to extend the input directive with support for type=file. The main caveat to keep in mind is that this method will not work in IE9 since IE9 didn't implement the File API. Using JavaScript to upload binary data regardless of type via XHR is simply not possible natively in IE9 or earlier (use of ActiveXObject to access the local filesystem doesn't count as using ActiveX is just asking for security troubles).

This exact method also requires AngularJS 1.4.x or later, but you may be able to adapt this to use $provide.decorator rather than angular.Module.decorator - I wrote this gist to demonstrate how to do it while conforming to John Papa's AngularJS style guide:

(function() {
    'use strict';

    * @ngdoc input
    * @name input[file]
    * @description
    * Adds very basic support for ngModel to `input[type=file]` fields.
    * Requires AngularJS 1.4.x or later. Does not support Internet Explorer 9 - the browser's
    * implementation of `HTMLInputElement` must have a `files` property for file inputs.
    * @param {string} ngModel
    *  Assignable AngularJS expression to data-bind to. The data-bound object will be an instance
    *  of {@link `FileList`}.
    * @param {string=} name Property name of the form under which the control is published.
    * @param {string=} ngChange
    *  AngularJS expression to be executed when input changes due to user interaction with the
    *  input element.
        .decorator('inputDirective', myInputFileDecorator);

    myInputFileDecorator.$inject = ['$delegate', '$browser', '$sniffer', '$filter', '$parse'];
    function myInputFileDecorator($delegate, $browser, $sniffer, $filter, $parse) {
        var inputDirective = $delegate[0],
            preLink =; = function (scope, element, attr, ctrl) {
            if (ctrl[0]) {
                if (angular.lowercase(attr.type) === 'file') {
                        scope, element, attr, ctrl[0], $sniffer, $browser, $filter, $parse);
                } else {
                    preLink.apply(this, arguments);

        return $delegate;

    function fileInputType(scope, element, attr, ctrl, $sniffer, $browser, $filter, $parse) {
        element.on('change', function (ev) {
            if (angular.isDefined(element[0].files)) {
                ctrl.$setViewValue(element[0].files, ev && ev.type);

        ctrl.$isEmpty = function (value) {
            return !value || value.length === 0;

Why wasn't this done in the first place? AngularJS support is intended to reach only as far back as IE9. If you disagree with this decision and think they should have just put this in anyway, then jump the wagon to Angular 2+ because better modern support is literally why Angular 2 exists.

The issue is (as was mentioned before) that without the file api support doing this properly is unfeasible for the core given our baseline being IE9 and polyfilling this stuff is out of the question for core.

Additionally trying to handle this input in a way that is not cross-browser compatible only makes it harder for 3rd party solutions, which now have to fight/disable/workaround the core solution.


I'm going to close this just as we closed #1236. Angular 2 is being build to support modern browsers and with that file support will easily available.

URL to compose a message in Gmail (with full Gmail interface and specified to, bcc, subject, etc.)

For Chrome:

  1. Set your email manager to Gmail

gmail handler

  1. Write mailto: in the address bar and press enter.


  1. Edit search engines:

Edit search engines

Edit search engines

  1. Write mt and enter in address bar.

JavaScript/JQuery: $(window).resize how to fire AFTER the resize is completed?

If you have Underscore.js installed, you could:


Bootstrap - floating navbar button right

Create a separate ul.nav for just that list item and float that ul right.


When to use Common Table Expression (CTE)

There are two reasons I see to use cte's.

To use a calculated value in the where clause. This seems a little cleaner to me than a derived table.

Suppose there are two tables - Questions and Answers joined together by Questions.ID = Answers.Question_Id (and quiz id)

    Select Question_Text,
           (SELECT Count(*) FROM Answers A WHERE A.Question_ID = Q.ID) AS Number_Of_Answers
    FROM Questions Q
WHERE Number_Of_Answers > 0

Here's another example where I want to get a list of questions and answers. I want the Answers to be grouped with the questions in the results.

    SELECT [Quiz_ID] 
      ,[ID] AS Question_Id
      ,null AS Answer_Id
          ,null AS Answer
          ,1 AS Is_Question
    FROM [Questions]


    SELECT Q.[Quiz_ID]
      ,A.[ID] AS  Answer_Id
          ,0 AS Is_Question
        FROM [Answers] A INNER JOIN [Questions] Q ON Q.Quiz_ID = A.Quiz_ID AND Q.Id = A.Question_Id
    (CASE WHEN Answer IS NULL THEN Question_Text ELSE Answer END) as Name
FROM cte    
GROUP BY Quiz_Id, Question_Id, Answer_id, Question_Text, Answer, Is_Question 
order by Quiz_Id, Question_Id, Is_Question Desc, Name

add/remove active class for ul list with jquery?

you can use siblings and removeClass method

$('.nav-link li').click(function() {

Copy a variable's value into another

Most of the answers here are using built-in methods or using libraries/frameworks. This simple method should work fine:

function copy(x) {
    return JSON.parse( JSON.stringify(x) );

// Usage
var a = 'some';
var b = copy(a);
a += 'thing';

console.log(b); // "some"

var c = { x: 1 };
var d = copy(c);
c.x = 2;

console.log(d); // { x: 1 }

Rails 4 - passing variable to partial

ou are able to create local variables once you call the render function on a partial, therefore if you want to customize a partial you can for example render the partial _form.html.erb by:

<%= render 'form', button_label: "Create New Event", url: new_event_url %>
<%= render 'form', button_label: "Update Event", url: edit_event_url %>

this way you can access in the partial to the label for the button and the URL, those are different if you try to create or update a record. finally, for accessing to this local variables you have to put in your code local_assigns[:button_label] (local_assigns[:name_of_your_variable])

<%=form_for(@event, url: local_assigns[:url]) do |f|  %>
<%= render 'shared/error_messages_events' %>
<%= f.label :title ,"Title"%>
  <%= f.text_field :title, class: 'form-control'%>
  <%=f.label :date, "Date"%>
  <%=f.date_field :date, class: 'form-control'  %>
  <%=f.label :description, "Description"%>
  <%=f.text_area :description, class: 'form-control'  %>
  <%= f.submit local_assigns[:button_label], class:"btn btn-primary"%>

How to make my layout able to scroll down?

Just wrap all that inside a ScrollView:

<?xml version="1.0" encoding="utf-8"?>
    <!-- Here you put the rest of your current view-->

As David Hedlund said, ScrollView can contain just one item... so if you had something like this:

<?xml version="1.0" encoding="utf-8"?>
    <!-- bla bla bla-->

You must change it to:

<?xml version="1.0" encoding="utf-8"?>
        <!-- bla bla bla-->

Indent List in HTML and CSS

You can use [Adjacent sibling combinators] as described in the W3 CSS Selectors Recommendation1 So you can use a + sign (or even a ~ tilde) apply a padding to the nested ul tag, as you described in your question and you'll get the result you need. I also think what you want it to override the main css, locally. You can do this:

    li+ul {padding-left: 20px;}

This way the inner ul will be nested including the bullets of the li elements. I wish this was helpful! =)

AngularJS routing without the hash '#'



More info at $locationProvider
Using $location

Having both a Created and Last Updated timestamp columns in MySQL 4.0

My web host is stuck on version 5.1 of mysql so anyone like me that doesn't have the option of upgrading can follow these directions:

Handlebars/Mustache - Is there a built in way to loop through the properties of an object?

I was using old version 1.0.beta.6 of handlebars, i think somewhere during 1.1 - 1.3 this functionality was added, so updating to 1.3.0 solved the issue, here is the usage:


{{#each object}}
  Key {{@key}} : Value {{this}}

WaitAll vs WhenAll

As an example of the difference -- if you have a task the does something with the UI thread (e.g. a task that represents an animation in a Storyboard) if you Task.WaitAll() then the UI thread is blocked and the UI is never updated. if you use await Task.WhenAll() then the UI thread is not blocked, and the UI will be updated.

Import SQL file by command line in Windows 7

If you are running WampServer on your local machine, import means restoring the dump file that you have (in sql format)

Here are the steps

  1. Go to command line by going to Start -> Run and typing in cmd.
  2. Change the directory to Mysql bin directory. It will be like


  3. It would be better to keep the dump file in the above directory( we can delete, after restoration)

  4. Hope you have created the database (either through phpMyadmin or using command line)

  5. Then type the command mysql.exe -u root -p databasename < filename.sql

Please note the difference, it is 'mysql.exe' not 'mysql'

How can I convert radians to degrees with Python?

Python convert radians to degrees or degrees to radians:

What are Radians and what problem does it solve?:

Radians and degrees are two separate units of measure that help people express and communicate precise changes in direction. Wikipedia has some great intuition with their infographics on how one Radian is defined relative to degrees:

Conversion from radians to degrees

Python examples using libraries calculating degrees from radians:

>>> import math
>>> math.degrees(0)                       #0 radians == 0 degrees
>>> math.degrees(math.pi/2)               #pi/2 radians is 90 degrees
>>> math.degrees(math.pi)                 #pi radians is 180 degrees
>>> math.degrees(math.pi+(math.pi/2))     #pi+pi/2 radians is 270 degrees
>>> math.degrees(math.pi+math.pi)         #2*pi radians is 360 degrees

Python examples using libraries calculating radians from degrees:

>>> import math
>>> math.radians(0)           #0 degrees == 0 radians
>>> math.radians(90)          #90 degrees is pi/2 radians
>>> math.radians(180)         #180 degrees is pi radians
>>> math.radians(270)         #270 degrees is pi+(pi/2) radians
>>> math.radians(360)         #360 degrees is 2*pi radians


The mathematical notation:

Mathematical notation of degrees and radians

You can do degree/radian conversion without libraries:

If you roll your own degree/radian converter, you have to write your own code to handle edge cases.

Mistakes here are easy to make, and will hurt just like it hurt the developers of the 1999 mars orbiter who sunk $125m dollars crashing it into Mars because of non intuitive edge cases here.

Lets crash that orbiter and Roll our own Radians to Degrees:

Invalid radians as input return garbage output.

>>> 0 * 180.0 / math.pi                         #0 radians is 0 degrees
>>> (math.pi/2) * 180.0 / math.pi               #pi/2 radians is 90 degrees
>>> (math.pi) * 180.0 / math.pi                 #pi radians is 180 degrees
>>> (math.pi+(math.pi/2)) * 180.0 / math.pi     #pi+(pi/2) radians is 270 degrees
>>> (2 * math.pi) * 180.0 / math.pi             #2*pi radians is 360 degrees

Degrees to radians:

>>> 0 * math.pi / 180.0              #0 degrees in radians
>>> 90 * math.pi / 180.0             #90 degrees in radians
>>> 180 * math.pi / 180.0            #180 degrees in radians
>>> 270 * math.pi / 180.0            #270 degrees in radians
>>> 360 * math.pi / 180.0            #360 degrees in radians

Expressing multiple rotations with degrees and radians

Single rotation valid radian values are between 0 and 2*pi. Single rotation degree values are between 0 and 360. However if you want to express multiple rotations, valid radian and degree values are between 0 and infinity.

>>> import math
>>> math.radians(360)                 #one complete rotation
>>> math.radians(360+360)             #two rotations
>>> math.degrees(12.566370614359172)  #math.degrees and math.radians preserve the
720.0                                 #number of rotations

Collapsing multiple rotations:

You can collapse multiple degree/radian rotations into a single rotation by modding against the value of one rotation. For degrees you mod by 360, for radians you modulus by 2*pi.

>>> import math
>>> math.radians(720+90)        #2 whole rotations plus 90 is 14.14 radians
>>> math.radians((720+90)%360)  #14.1 radians brings you to 
1.5707963267948966              #the end point as 1.57 radians.

>>> math.degrees((2*math.pi)+(math.pi/2))            #one rotation plus a quarter 
450.0                                                #rotation is 450 degrees.
>>> math.degrees(((2*math.pi)+(math.pi/2))%(2*math.pi)) #one rotation plus a quarter
90.0                                                    #rotation brings you to 90.


Khan academy has some excellent content to solidify intuition around trigonometry and angular mathematics:

Merging arrays with the same keys

Try with array_merge_recursive

$A = array('a' => 1, 'b' => 2, 'c' => 3);
$B = array('c' => 4, 'd'=> 5);
$c = array_merge_recursive($A,$B);

echo "<pre>";
echo "</pre>";

will return

    [a] => 1
    [b] => 2
    [c] => Array
            [0] => 3
            [1] => 4

    [d] => 5

RestSharp JSON Parameter Posting

Hope this will help someone. It worked for me -

RestClient client = new RestClient("");
RestRequest request = new RestRequest("login", Method.POST);
request.AddHeader("Accept", "application/json");
var body = new
    Host = "host_environment",
    Username = "UserID",
    Password = "Password"

var response = client.Execute(request).Content;

Datatype for storing ip address in SQL Server

The technically correct way to store IPv4 is binary(4), since that is what it actually is (no, not even an INT32/INT(4), the numeric textual form that we all know and love ( being just the display conversion of its binary content).

If you do it this way, you will want functions to convert to and from the textual-display format:

Here's how to convert the textual display form to binary:


                + CAST( CAST( PARSENAME( @ip, 3 ) AS INTEGER) AS BINARY(1))
                + CAST( CAST( PARSENAME( @ip, 2 ) AS INTEGER) AS BINARY(1))
                + CAST( CAST( PARSENAME( @ip, 1 ) AS INTEGER) AS BINARY(1))

    RETURN @bin

And here's how to convert the binary back to the textual display form:

    DECLARE @str AS VARCHAR(15) 

    SELECT @str = CAST( CAST( SUBSTRING( @ip, 1, 1) AS INTEGER) AS VARCHAR(3) ) + '.'
                + CAST( CAST( SUBSTRING( @ip, 2, 1) AS INTEGER) AS VARCHAR(3) ) + '.'
                + CAST( CAST( SUBSTRING( @ip, 3, 1) AS INTEGER) AS VARCHAR(3) ) + '.'
                + CAST( CAST( SUBSTRING( @ip, 4, 1) AS INTEGER) AS VARCHAR(3) );

    RETURN @str

Here's a demo of how to use them:

SELECT dbo.fnBinaryIPv4('')
--should return 0xC04144C9

SELECT dbo.fnDisplayIPv4( 0xC04144C9 )
-- should return ''

Finally, when doing lookups and compares, always use the binary form if you want to be able to leverage your indexes.


I wanted to add that one way to address the inherent performance problems of scalar UDFs in SQL Server, but still retain the code-reuse of a function is to use an iTVF (inline table-valued function) instead. Here's how the first function above (string to binary) can be re-written as an iTVF:

               CAST( CAST( PARSENAME( @ip, 4 ) AS INTEGER) AS BINARY(1))
            +  CAST( CAST( PARSENAME( @ip, 3 ) AS INTEGER) AS BINARY(1))
            +  CAST( CAST( PARSENAME( @ip, 2 ) AS INTEGER) AS BINARY(1))
            +  CAST( CAST( PARSENAME( @ip, 1 ) AS INTEGER) AS BINARY(1))
                AS BINARY(4)) As bin

Here's it in the example:

SELECT bin FROM dbo.fnBinaryIPv4('')
--should return 0xC04144C9

And here's how you would use it in an INSERT

SELECT {other_column_values,...},
       (SELECT bin FROM dbo.itvfBinaryIPv4(''))

How to specify multiple return types using type-hints

From the documentation

class typing.Union

Union type; Union[X, Y] means either X or Y.

Hence the proper way to represent more than one return data type is

from typing import Union

def foo(client_id: str) -> Union[list,bool]

But do note that typing is not enforced. Python continues to remain a dynamically-typed language. The annotation syntax has been developed to help during the development of the code prior to being released into production. As PEP 484 states, "no type checking happens at runtime."

>>> def foo(a:str) -> list:
...     return("Works")
>>> foo(1)

As you can see I am passing a int value and returning a str. However the __annotations__ will be set to the respective values.

>>> foo.__annotations__ 
{'return': <class 'list'>, 'a': <class 'str'>}

Please Go through PEP 483 for more about Type hints. Also see What are Type hints in Python 3.5?

Kindly note that this is available only for Python 3.5 and upwards. This is mentioned clearly in PEP 484.

How do I compile a .cpp file on Linux?

You'll need to compile it using:

g++ inputfile.cpp -o outputbinary

The file you are referring has a missing #include <cstdlib> directive, if you also include that in your file, everything shall compile fine.

Video streaming over websockets using JavaScript

It's definitely conceivable but I am not sure we're there yet. In the meantime, I'd recommend using something like Silverlight with IIS Smooth Streaming. Silverlight is plugin-based, but it works on Windows/OSX/Linux. Some day the HTML5 <video> element will be the way to go, but that will lack support for a little while.

iPhone/iPad browser simulator?

There's no good substitute to testing on an actual device.

Real devices have higher display densities, meaning that pixels are smaller. If you don't test on a real device, you may not realise that your design includes text that is too small to read or buttons that are too small to tap.

You use real devices with your fingers, not a mouse. This means that the accuracy of your taps is much lower and what you are tapping is obscured by your finger. If you don't test on a real device, you may not realise you've introduced usability problems into your design.

Which method performs better: .Any() vs .Count() > 0?

If you are using the Entity Framework and have a huge table with many records Any() will be much faster. I remember one time I wanted to check to see if a table was empty and it had millions of rows. It took 20-30 seconds for Count() > 0 to complete. It was instant with Any().

Any() can be a performance enhancement because it may not have to iterate the collection to get the number of things. It just has to hit one of them. Or, for, say, LINQ-to-Entities, the generated SQL will be IF EXISTS(...) rather than SELECT COUNT ... or even SELECT * ....

What does the line "#!/bin/sh" mean in a UNIX shell script?

It's called a shebang, and tells the parent shell which interpreter should be used to execute the script.

#!/bin/sh <--------- bourne shell compatible script
#!/usr/bin/perl  <-- perl script
#!/usr/bin/php  <--- php script
#!/bin/false <------ do-nothing script, because false returns immediately anyways.

Most scripting languages tend to interpret a line starting with # as comment and will ignore the following !/usr/bin/whatever portion, which might otherwise cause a syntax error in the interpreted language.

How to add Certificate Authority file in CentOS 7

Maybe late to the party but in my case it was RHEL 6.8:

Copy certificate.crt issued by hosting to:



update-ca-trust force-enable (ignore not found warnings)
update-ca-trust extract

Hope it helps

How can I create persistent cookies in ASP.NET?

Here's how you can do that.

Writing the persistent cookie.

//create a cookie
HttpCookie myCookie = new HttpCookie("myCookie");

//Add key-values in the cookie

//set cookie expiry date-time. Made it to last for next 12 hours.
myCookie.Expires = DateTime.Now.AddHours(12);

//Most important, write the cookie to client.

Reading the persistent cookie.

//Assuming user comes back after several hours. several < 12.
//Read the cookie from Request.
HttpCookie myCookie = Request.Cookies["myCookie"];
if (myCookie == null)
    //No cookie found or cookie expired.
    //Handle the situation here, Redirect the user or simply return;

//ok - cookie is found.
//Gracefully check if the cookie has the key-value as expected.
if (!string.IsNullOrEmpty(myCookie.Values["userid"]))
    string userId = myCookie.Values["userid"].ToString();
    //Yes userId is found. Mission accomplished.

How to add data via $.ajax ( serialize() + extra data ) like this

Personally, I'd append the element to the form instead of hacking the serialized data, e.g.

moredata = 'your custom data here';

// do what you like with the input
$input = $('<input type="text" name="moredata"/>').val(morevalue);

// append to the form

// then..
data: $('#myForm').serialize()

That way, you don't have to worry about ? or &

How to fix a Div to top of page with CSS only

You can do something like this:

<head><title>My Glossary</title></head>
<body style="margin:0px;">
        <div id="top" style="position:fixed;background:white;width:100%;">
            <a href="#A">A</a> |
             <a href="#B">B</a> |
            <a href="#Z">Z</a>

        <div id="term-defs" style="padding-top:1em;">
               <span id="A"></span>
               <dd>This is the sound made by a fool</dd>
               <!-- and so on ... ->

It's the position:fixed that's most important, because it takes the top div from the normal page flow and fixes it at it's pre-determined position. It's also important to use the padding-top:1em because otherwise the term-defs div would start right under the top div. The background and width are there to cover the contents of the term-defs div as they scroll under the top div.

Hope this helps.

Extracting double-digit months and days from a Python date

Look at the types of those properties:

In [1]: import datetime

In [2]: d =

In [3]: type(d.month)
Out[3]: <type 'int'>

In [4]: type(
Out[4]: <type 'int'>

Both are integers. So there is no automatic way to do what you want. So in the narrow sense, the answer to your question is no.

If you want leading zeroes, you'll have to format them one way or another. For that you have several options:

In [5]: '{:02d}'.format(d.month)
Out[5]: '03'

In [6]: '%02d' % d.month
Out[6]: '03'

In [7]: d.strftime('%m')
Out[7]: '03'

In [8]: f'{d.month:02d}'
Out[8]: '03'

Sending JSON to PHP using ajax

To send javascript obj to php using json and ajax:


var dataPost = {
   "var": "foo"
var dataString = JSON.stringify(dataPost);

   url: 'server.php',
   data: {myData: dataString},
   type: 'POST',
   success: function(response) {

to use that object in php:

$obj = json_decode($_POST["myData"]);

echo $obj->var;

Hook up Raspberry Pi via Ethernet to laptop without router?

No router + no screen + regular Ethernet cable + RPI 2 + Raspbian Lite 2018-11-13 + Ubuntu 18.10

First we must enable the SSH server on the Pi, which is disabled by default for security.

If you already have a shell on the Pi through a non-SSH method such as screen + keyboard or UART (see below), just run:

sudo systemctl enable ssh
sudo service sshd start

as explained at: This persists across boots.

Otherwise, insert he SD card on your host, and create a magic empty file named ssh file in the boot/ partition.

On Ubuntu hosts, it gets mounted automatically and you can do just:

sudo touch /media/$USER/boot/ssh

which you can confirm with:


which contains:

mmcblk0     179:0    0  14.4G  0 disk
+-mmcblk0p1 179:1    0  43.9M  0 part /media/ciro/boot
+-mmcblk0p2 179:2    0  14.4G  0 part /media/ciro/rootfs

If you don't enable the SSHD daemon on the Pi then SSH connection will fail with:

ssh: connect to host port 22: Connection refused

when we try it later on.

After enabling the SSH server

Next, boot the Pi, and link an Ethernet cable from your laptop directly to the Pi:

enter image description here

On Ubuntu 17.04 to work around this bug as mentioned on this answer you first need:

sudo apt-get install dnsmasq-base

On the host, open the network manager:


And go:

  1. + sign (Add a new connection)
  2. Ethernet
  3. Create
  4. IPv4 Settings
  5. Method: Shared to other computers
  6. Set a good name for it
  7. Save

enter image description here

Find the IP of the Pi on host:

cat /var/lib/misc/dnsmasq.leases

outputs something like:

1532204957 b8:27:eb:0c:1f:69 raspberrypi 01:b8:27:eb:0c:1f:69 is the IP, then as usual:

ssh [email protected]

I also have the following in my .bashrc:

piip() ( cat /var/lib/misc/dnsmasq.leases | cut -d ' ' -f 3; )
pissh() ( sshpass -p raspberry ssh "pi@$(piip)"; )

From inside the Pi, notice that it can access the internet normally through your host's other interfaces:


For example on my laptop, the Pi takes up the Ethernet, but the host is also connected to the internet through WiFi.

The crossover cable is not required if the host network card supports Auto MDI-X. This is the case for most recent hardware, including for example the 2012 Lenovo T430 I tested with, which has an "Intel® 82579LM Gigabit Network Connection" which documents support for Auto MDI-X.

Now you can also:

UART serial USB converter

This is an alternative to SSH if you just want to get a shell on the Pi:

This does not use SSH or networking itself, but rather the older, simpler, more direct, more reliable, lower bandwidth, lower distance serial interface. The Pi won't have access to the Internet with this method.

Desktop computers still have a serial port which you can connect directly wire to wire with the Pi, but these are hidden in most laptops, and so we need to buy a cheap USB adapter. Here I've used: See also:

First plug the SD card on the host, and edit the config.txt file present in the first partition to add:


as explained at:

This first partition contains the bootloader, its configuration files and the (Linux / your) kernel, config.txt being one of them. The second partition contains the actual Linux root filesystem.

Now connect your computer to the Pi as:

enter image description here

You only need to attach 3 cables:

  • Ground to Ground
  • Tx on Pi to Rx on the USB to serial port
  • Rx on Pi to Tx on tye USB to serial port

This is also documented at:

Be careful not to link the Ground to the 5V, I've already burned 2 UART to USB chips and a RPI UART by doing that!

You don't need to connect the 5V to the 5V at all. I think you can power your Pi like that, but I've read that this is a bad idea, just use the usual USB power source.

Finally, plug the USB side of the connector to your host computer, and get a shell with:

sudo apt install screen
sudo usermod -a -G dialout $USER
screen /dev/ttyUSB0 115200

Exit with Ctrl-A \.

Here is a video by Adafruit showing it:

See also

Similar question on RPI SE:

Is there StartsWith or Contains in t sql with variables?

It seems like what you want is

In your example it would be (starts with):

set @isExpress = (CharIndex('Express Edition', @edition) = 1)

Or contains

set @isExpress = (CharIndex('Express Edition', @edition) >= 1)

Negative matching using grep (match lines that do not contain foo)

You can also use awk for these purposes, since it allows you to perform more complex checks in a clearer way:

Lines not containing foo:

awk '!/foo/'

Lines containing neither foo nor bar:

awk '!/foo/ && !/bar/'

Lines containing neither foo nor bar which contain either foo2 or bar2:

awk '!/foo/ && !/bar/ && (/foo2/ || /bar2/)'

And so on.

$(document).click() not working correctly on iPhone. jquery

Adding in the following code works.

The problem is iPhones dont raise click events. They raise "touch" events. Thanks very much apple. Why couldn't they just keep it standard like everyone else? Anyway thanks Nico for the tip.

Credit to:

$(document).ready(function () {
  $(document).click(function (e) {

function fire(e) { alert('hi'); }

function touchHandler(event)
    var touches = event.changedTouches,
        first = touches[0],
        type = "";

       case "touchstart": type = "mousedown"; break;
       case "touchmove":  type = "mousemove"; break;        
       case "touchend":   type = "mouseup"; break;
       default: return;

    //initMouseEvent(type, canBubble, cancelable, view, clickCount, 
    //           screenX, screenY, clientX, clientY, ctrlKey, 
    //           altKey, shiftKey, metaKey, button, relatedTarget);

    var simulatedEvent = document.createEvent("MouseEvent");
    simulatedEvent.initMouseEvent(type, true, true, window, 1, 
                          first.screenX, first.screenY, 
                          first.clientX, first.clientY, false, 
                          false, false, false, 0/*left*/, null);;

function init() 
    document.addEventListener("touchstart", touchHandler, true);
    document.addEventListener("touchmove", touchHandler, true);
    document.addEventListener("touchend", touchHandler, true);
    document.addEventListener("touchcancel", touchHandler, true);    

How to iterate through LinkedHashMap with lists as values

In Java 8:

Map<String, List<String>> test1 = new LinkedHashMap<String, List<String>>();
test1.forEach((key,value) -> {
    System.out.println(key + " -> " + value);

Use of symbols '@', '&', '=' and '>' in custom directive's scope binding: AngularJS

I had trouble binding a value with any of the symbols in AngularJS 1.6. I did not get any value at all, only undefined, even though I did it the exact same way as other bindings in the same file that did work.

Problem was: my variable name had an underscore.

This fails:

bindings: { import_nr: '='}

This works:

bindings: { importnr: '='}

(Not completely related to the original question, but that was one of the top search results when I looked, so hopefully this helps someone with the same problem.)

Python to open Chrome browser

You can call get() with the path to Chrome. Below is an example - replace chrome_path with the correct path for your platform.

import webbrowser

url = ''

# MacOS
chrome_path = 'open -a /Applications/Google\ %s'

# Windows
# chrome_path = 'C:/Program Files (x86)/Google/Chrome/Application/chrome.exe %s'

# Linux
# chrome_path = '/usr/bin/google-chrome %s'


versionCode vs versionName in Android Manifest

It is indeed based on versionCode and not on versionName. However, I noticed that changing the versionCode in AndroidManifest.xml wasn't enough with Android Studio - Gradle build system. I needed to change it in the build.gradle.

How to change the font size and color of x-axis and y-axis label in a scatterplot with plot function in R?

To track down the correct parameters you need to go first to ?plot.default, which refers you to ?par and ?axis:

plot(1, 1 ,xlab="x axis", ylab="y axis",  pch=19,
           col.lab="red", cex.lab=1.5,    #  for the xlab and ylab
           col="green")                   #  for the points

Raw_Input() Is Not Defined

For Python 3.x, use input(). For Python 2.x, use raw_input(). Don't forget you can add a prompt string in your input() call to create one less print statement. input("GUESS THAT NUMBER!").

JavaScript: get code to run every minute

Using setInterval:

setInterval(function() {
    // your code goes here...
}, 60 * 1000); // 60 * 1000 milsec

The function returns an id you can clear your interval with clearInterval:

var timerID = setInterval(function() {
    // your code goes here...
}, 60 * 1000); 

clearInterval(timerID); // The setInterval it cleared and doesn't run anymore.

A "sister" function is setTimeout/clearTimeout look them up.

If you want to run a function on page init and then 60 seconds after, 120 sec after, ...:

function fn60sec() {
    // runs every 60 sec and runs on init.
setInterval(fn60sec, 60*1000);

MVC - Set selected value of SelectList

I usually use this method

        public static SelectList SetSelectedValue(SelectList list, string value)
        if (value != null)
            var selected = list.Where(x => x.Value == value).First();
            selected.Selected = true;
            return list;
        return list;

How can I auto increment the C# assembly version via our CI platform (Hudson)?

As a continuation of MikeS's answer I wanted to add that VS + Visual Studio Visualization and Modeling SDK needs to be installed for this to work, and you need to modify the project file as well. Should also be mentioned I use Jenkins as build server running on a windows 2008 R2 server box with version module, where I get the BUILD_NUMBER.

My Text Template file looks like this

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ output extension=".cs" #>
var build = Environment.GetEnvironmentVariable("BUILD_NUMBER");
build = build == null ? "0" : int.Parse(build).ToString();
var revision = Environment.GetEnvironmentVariable("_BuildVersion");
revision = revision == null ? "" : revision;    
using System.Reflection;
[assembly: AssemblyVersion("<#=revision#>")]
[assembly: AssemblyFileVersion("<#=revision#>")]

I have the following in the Property Groups


after import of Microsoft.CSharp.targets, I have this (dependant of where you install VS

<Import Project="C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\TextTemplating\v10.0\Microsoft.TextTemplating.targets" />

On my build server I then have the following script to run the text transformation before the actual build, to get the last changeset number on TFS

set _Path="C:\Build_Source\foo"

pushd %_Path% 
"%ProgramFiles(x86)%\Microsoft Visual Studio 10.0\Common7\IDE\tf.exe" history . /r /noprompt /stopafter:1 /Version:W > bar
FOR /f "tokens=1" %%foo in ('findstr /R "^[0-9][0-9]*" bar') do set _BuildVersion=5.0.%BUILD_NUMBER%.%%foo
del bar

echo %_BuildVersion%
cd C:\Program Files (x86)\Jenkins\jobs\MyJob\workspace\MyProject
MSBuild MyProject.csproj /t:TransformAll 
<rest of bld script>

This way I can keep track of builds AND changesets, so if I haven't checked anything in since last build, the last digit should not change, however I might have made changes to the build process, hence the need for the second last number. Of course if you make multiple check-ins before a build you only get the last change reflected in the version. I guess you could concatenate of that is required.

I'm sure you can do something fancier and call TFS directly from within the tt Template, however this works for me.

I can then get my version at runtime like this

Assembly assembly = Assembly.GetExecutingAssembly();
FileVersionInfo fvi = FileVersionInfo.GetVersionInfo(assembly.Location);
return fvi.FileVersion;

What is uintptr_t data type

There are already many good answers to the part "what is uintptr_t data type". I will try to address the "what it can be used for?" part in this post.

Primarily for bitwise operations on pointers. Remember that in C++ one cannot perform bitwise operations on pointers. For reasons see Why can't you do bitwise operations on pointer in C, and is there a way around this?

Thus in order to do bitwise operations on pointers one would need to cast pointers to type unitpr_t and then perform bitwise operations.

Here is an example of a function that I just wrote to do bitwise exclusive or of 2 pointers to store in a XOR linked list so that we can traverse in both directions like a doubly linked list but without the penalty of storing 2 pointers in each node.

 template <typename T>
 T* xor_ptrs(T* t1, T* t2)
     return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(t1)^reinterpret_cast<uintptr_t>(t2));

How can I change the user on Git Bash?

If you want to change the user at git Bash .You just need to configure particular user and email(globally) at the git bash.

$ git config --global "abhi"
$ git config --global "[email protected]"

Note: No need to delete the user from Keychain .

Is there a library function for Root mean square error (RMSE) in python?

What is RMSE? Also known as MSE, RMD, or RMS. What problem does it solve?

If you understand RMSE: (Root mean squared error), MSE: (Mean Squared Error) RMD (Root mean squared deviation) and RMS: (Root Mean Squared), then asking for a library to calculate this for you is unnecessary over-engineering. All these metrics are a single line of python code at most 2 inches long. The three metrics rmse, mse, rmd, and rms are at their core conceptually identical.

RMSE answers the question: "How similar, on average, are the numbers in list1 to list2?". The two lists must be the same size. I want to "wash out the noise between any two given elements, wash out the size of the data collected, and get a single number feel for change over time".

Intuition and ELI5 for RMSE:

Imagine you are learning to throw darts at a dart board. Every day you practice for one hour. You want to figure out if you are getting better or getting worse. So every day you make 10 throws and measure the distance between the bullseye and where your dart hit.

You make a list of those numbers list1. Use the root mean squared error between the distances at day 1 and a list2 containing all zeros. Do the same on the 2nd and nth days. What you will get is a single number that hopefully decreases over time. When your RMSE number is zero, you hit bullseyes every time. If the rmse number goes up, you are getting worse.

Example in calculating root mean squared error in python:

import numpy as np
d = [0.000, 0.166, 0.333]   #ideal target distances, these can be all zeros.
p = [0.000, 0.254, 0.998]   #your performance goes here

print("d is: " + str(["%.8f" % elem for elem in d]))
print("p is: " + str(["%.8f" % elem for elem in p]))

def rmse(predictions, targets):
    return np.sqrt(((predictions - targets) ** 2).mean())

rmse_val = rmse(np.array(d), np.array(p))
print("rms error is: " + str(rmse_val))

Which prints:

d is: ['0.00000000', '0.16600000', '0.33300000']
p is: ['0.00000000', '0.25400000', '0.99800000']
rms error between lists d and p is: 0.387284994115

The mathematical notation:

root mean squared deviation explained

Glyph Legend: n is a whole positive integer representing the number of throws. i represents a whole positive integer counter that enumerates sum. d stands for the ideal distances, the list2 containing all zeros in above example. p stands for performance, the list1 in the above example. superscript 2 stands for numeric squared. di is the i'th index of d. pi is the i'th index of p.

The rmse done in small steps so it can be understood:

def rmse(predictions, targets):

    differences = predictions - targets                       #the DIFFERENCEs.

    differences_squared = differences ** 2                    #the SQUAREs of ^

    mean_of_differences_squared = differences_squared.mean()  #the MEAN of ^

    rmse_val = np.sqrt(mean_of_differences_squared)           #ROOT of ^

    return rmse_val                                           #get the ^

How does every step of RMSE work:

Subtracting one number from another gives you the distance between them.

8 - 5 = 3         #absolute distance between 8 and 5 is +3
-20 - 10 = -30    #absolute distance between -20 and 10 is +30

If you multiply any number times itself, the result is always positive because negative times negative is positive:

3*3     = 9   = positive
-30*-30 = 900 = positive

Add them all up, but wait, then an array with many elements would have a larger error than a small array, so average them by the number of elements.

But wait, we squared them all earlier to force them positive. Undo the damage with a square root!

That leaves you with a single number that represents, on average, the distance between every value of list1 to it's corresponding element value of list2.

If the RMSE value goes down over time we are happy because variance is decreasing.

RMSE isn't the most accurate line fitting strategy, total least squares is:

Root mean squared error measures the vertical distance between the point and the line, so if your data is shaped like a banana, flat near the bottom and steep near the top, then the RMSE will report greater distances to points high, but short distances to points low when in fact the distances are equivalent. This causes a skew where the line prefers to be closer to points high than low.

If this is a problem the total least squares method fixes this:

Gotchas that can break this RMSE function:

If there are nulls or infinity in either input list, then output rmse value is is going to not make sense. There are three strategies to deal with nulls / missing values / infinities in either list: Ignore that component, zero it out or add a best guess or a uniform random noise to all timesteps. Each remedy has its pros and cons depending on what your data means. In general ignoring any component with a missing value is preferred, but this biases the RMSE toward zero making you think performance has improved when it really hasn't. Adding random noise on a best guess could be preferred if there are lots of missing values.

In order to guarantee relative correctness of the RMSE output, you must eliminate all nulls/infinites from the input.

RMSE has zero tolerance for outlier data points which don't belong

Root mean squared error squares relies on all data being right and all are counted as equal. That means one stray point that's way out in left field is going to totally ruin the whole calculation. To handle outlier data points and dismiss their tremendous influence after a certain threshold, see Robust estimators that build in a threshold for dismissal of outliers.

Android Studio - Failed to notify project evaluation listener error

For me I had to specifically stop the gradlew and clear caches and this fixed my issues:

./gradlew --stop
// Delete all cache files in your project. With git: `git -xfd clean` 
// Delete global cache dir. On Mac it is located in `~/.gradle/caches

Found here:

What does operator "dot" (.) mean?

The dot itself is not an operator, .^ is.

The .^ is a pointwise¹ (i.e. element-wise) power, as .* is the pointwise product.

.^ Array power. A.^B is the matrix with elements A(i,j) to the B(i,j) power. The sizes of A and B must be the same or be compatible.


¹) Hence the dot.

Max length UITextField

Swift 5

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let MAX_LENGTH = 4
        let updatedString = (textField.text! as NSString).replacingCharacters(in: range, with: string)
        return updatedString.count <= MAX_LENGTH

Trim last 3 characters of a line WITHOUT using sed, or perl, etc

I can guarantee you that bash alone won't be any faster than sed for this task. Starting up external processes in bash is a generally bad idea but only if you do it a lot.

So, if you're starting a sed process for each line of your input, I'd be concerned. But you're not. You only need to start one sed which will do all the work for you.

You may however find that the following sed will be a bit faster than your version:

(whatever) | sed 's/...$//'

All this does is remove the last three characters on each line, rather than substituting the whole line with a shorter version of itself. Now maybe more modern RE engines can optimise your command but why take the risk.

To be honest, about the only way I can think of that would be faster would be to hand-craft your own C-based filter program. And the only reason that may be faster than sed is because you can take advantage of the extra knowledge you have on your processing needs (sed has to allow for generalised procession so may be slower because of that).

Don't forget the optimisation mantra: "Measure, don't guess!"

If you really want to do this one line at a time in bash (and I still maintain that it's a bad idea), you can use:

pax> line=123456789abc
pax> line2=${line%%???}
pax> echo ${line2}
pax> _

You may also want to investigate whether you actually need a speed improvement. If you process the lines as one big chunk, you'll see that sed is plenty fast. Type in the following:


echo This is a pretty chunky line with three bad characters at the end.XXX >qq1
for i in 4 16 64 256 1024 4096 16384 65536 ; do
    cat qq1 qq1 >qq2
    cat qq2 qq2 >qq1

head -20000l qq1 >qq2
wc -l qq2

time sed 's/...$//' qq2 >qq1
head -3l qq1

and run it. Here's the output on my (not very fast at all) R40 laptop:

pax> ./
20000 qq2
Sat Jul 24 13:09:15 WAST 2010

real    0m0.851s
user    0m0.781s
sys     0m0.050s
Sat Jul 24 13:09:16 WAST 2010
This is a pretty chunky line with three bad characters at the end.
This is a pretty chunky line with three bad characters at the end.
This is a pretty chunky line with three bad characters at the end.

That's 20,000 lines in under a second, pretty good for something that's only done every hour. not found, what is it exactly?

Monkey is right, according to the link given by monkey

Basically it's a way to map a combined/minified file back to an unbuilt state. When you build for production, along with minifying and combining your JavaScript files, you generate a source map which holds information about your original files. When you query a certain line and column number in your generated JavaScript you can do a lookup in the source map which returns the original location.

I am not sure if it is angular's fault that no map files were generated. But you can turn off source map files by unchecking this option in chrome console setting

enter image description here

reducing number of plot ticks

Alternatively, if you want to simply set the number of ticks while allowing matplotlib to position them (currently only with MaxNLocator), there is pyplot.locator_params,


You can specify specific axis in this method as mentioned below, default is both:

# To specify the number of ticks on both or any single axes
pyplot.locator_params(axis='y', nbins=6)
pyplot.locator_params(axis='x', nbins=10)

Why is this error, 'Sequence contains no elements', happening?

Check again. Use debugger if must. My guess is that for some item in userResponseDetails this query finds no elements:

.Where(y => y.ResponseId.Equals(item.ResponseId))

so you can't call


on it. Maybe try


if it solves the issue.

Do NOT return NULL value! This is purely so that you can see and diagnose where problem is. Handle these cases properly.

Spring MVC Controller redirect using URL parameters instead of in response

If you don't want the success message in the URL, then one option is to put it in the session (in the processForm method) and then check for it (and remove it) in the setupForm method.

Edited to add: if this is a pain to do manually, then you could write a subclass of RedirectView that adds a "message" attribute and wraps the process of inserting it into the session. Not sure, though, if there's an easy way to wrap getting the message back out of the session...

Honestly, I don't think there's an easy answer -- the nature of an HTTP redirect is that state isn't carried over; if you want to maintain state anyway, you're stuck with the various usual ways to maintain state in web applications: the session, a cookie, a querystring...

How to define unidirectional OneToMany relationship in JPA

My bible for JPA work is the Java Persistence wikibook. It has a section on unidirectional OneToMany which explains how to do this with a @JoinColumn annotation. In your case, i think you would want:

private Set<Text> text;

I've used a Set rather than a List, because the data itself is not ordered.

The above is using a defaulted referencedColumnName, unlike the example in the wikibook. If that doesn't work, try an explicit one:

@JoinColumn(name="TXTHEAD_CODE", referencedColumnName="DATREG_META_CODE")
private Set<Text> text;

Warning: mysqli_error() expects exactly 1 parameter, 0 given error


die (mysqli_error()); 


die('Error: ' . mysqli_error($myConnection));

in the query

$query = mysqli_query($myConnection, $sqlCommand) or die (mysqli_error()); 

How to create and add users to a group in Jenkins for authentication?

I installed the Role plugin under Jenkins-3.5, but it does not show the "Manage Roles" option under "Manage Jenkins", and when one follows the security install page from the wiki, all users are locked out instantly. I had to manually shutdown Jenkins on the server, restore the correct configuration settings (/me is happy to do proper backups) and restart Jenkins.

I didn't have high hopes, as that plugin was last updated in 2011

How to get bean using application context in spring boot

actually you want to get the object from the Spring engine, where the engine already maintaining the object of your required class at that starting of the spring application(Initialization of the Spring engine).Now the thing is you just have to get that object to a reference.

in a service class

private ApplicationContext context;

SomeClass sc = (SomeClass)context.getBean(SomeClass.class);

now in the reference of the sc you are having the object. Hope explained well. If any doubt please let me know.

Is there a reason for C#'s reuse of the variable in a foreach?

Having been bitten by this, I have a habit of including locally defined variables in the innermost scope which I use to transfer to any closure. In your example:

foreach (var s in strings)
    query = query.Where(i => i.Prop == s); // access to modified closure

I do:

foreach (var s in strings)
    string search = s;
    query = query.Where(i => i.Prop == search); // New definition ensures unique per iteration.

Once you have that habit, you can avoid it in the very rare case you actually intended to bind to the outer scopes. To be honest, I don't think I have ever done so.

Include another JSP file

At page translation time, the content of the file given in the include directive is ‘pasted’ as it is, in the place where the JSP include directive is used. Then the source JSP page is converted into a java servlet class. The included file can be a static resource or a JSP page. Generally, JSP include directive is used to include header banners and footers.

Syntax for include a jsp file:

<%@ include file="relative url">


<%@include file="page_name.jsp" %>

Sun JSTL taglib declaration fails with "Can not find the tag library descriptor"

I was getting the same problem onenter image description here Spring Tool Suite 3.2 and changed the version of jstl to 1.2 (from 1.1.2) manually when adding it to the dependency list, and the error got disappeared.

How can I disable all views inside the layout?

If you're interested in disabling views in a specific ViewGroup then you can use the interesting, perhaps slightly obscure duplicateParentState. A view state is a set of boolean attributes such as pressed, enabled, activated, and others. Just use this on each child you want to sync to parent ViewGroup:


Note that it duplicates the entire state and not just the enabled state. This may be what you want! Of course, this approach is best if you're loading layout XML.

Iterating through array - java

You should definitely encapsulate this logic into a method.

There is no benefit to repeating identical code multiple times.

Also, if you place the logic in a method and it changes, you only need to modify your code in one place.

Whether or not you want to use a 3rd party library is an entirely different decision.

Append to the end of a Char array in C++

If your arrays are character arrays(which seems to be the case), You need a strcat().
Your destination array should have enough space to accommodate the appended data though.

In C++, You are much better off using std::string and then you can use std::string::append()

When is it acceptable to call GC.Collect?

i am still pretty unsure about this. I am working since 7 years on an Application Server. Our bigger installations take use of 24 GB Ram. Its hightly Multithreaded, and ALL calls for GC.Collect() ran into really terrible performance issues.

Many third party Components used GC.Collect() when they thought it was clever to do this right now. So a simple bunch of Excel-Reports blocked the App Server for all threads several times a minute.

We had to refactor all the 3rd Party Components in order to remove the GC.Collect() calls, and all worked fine after doing this.

But i am running Servers on Win32 as well, and here i started to take heavy use of GC.Collect() after getting a OutOfMemoryException.

But i am also pretty unsure about this, because i often noticed, when i get a OOM on 32 Bit, and i retry to run the same Operation again, without calling GC.Collect(), it just worked fine.

One thing i wonder is the OOM Exception itself... If i would have written the .Net Framework, and i can't alloc a memory block, i would use GC.Collect(), defrag memory (??), try again, and if i still cant find a free memory block, then i would throw the OOM-Exception.

Or at least make this behavior as configurable option, due the drawbacks of the performance issue with GC.Collect.

Now i have lots of code like this in my app to "solve" the problem:

public static TResult ExecuteOOMAware<T1, T2, TResult>(Func<T1,T2 ,TResult> func, T1 a1, T2 a2)

    int oomCounter = 0;
    int maxOOMRetries = 10;
            return func(a1, a2);
        catch (OutOfMemoryException)
            if (maxOOMRetries > 10)
                Log.Info("OutOfMemory-Exception caught, Trying to fix. Counter: " + oomCounter.ToString());
                System.Threading.Thread.Sleep(TimeSpan.FromSeconds(oomCounter * 10));
    } while (oomCounter < maxOOMRetries);

    // never gets hitted.
    return default(TResult);

(Note that the Thread.Sleep() behavior is a really App apecific behavior, because we are running a ORM Caching Service, and the service takes some time to release all the cached objects, if RAM exceeds some predefined values. so it waits a few seconds the first time, and has increased waiting time each occurence of OOM.)

How to redirect the output of DBMS_OUTPUT.PUT_LINE to a file?

An old thread, but there is another alternative.

Since 9i you can use pipelined table function.

First, create a type as a table of varchar:

CREATE TYPE t_string_max IS TABLE OF VARCHAR2(32767);

Second, wrap your code in a pipelined function declaration:

CREATE FUNCTION fn_foo (bar VARCHAR2) -- your params
  RETURN t_string_max PIPELINED IS 
  -- your vars
  -- your code


Finally, call it like this:

SELECT * FROM TABLE(fn_foo('param'));

Hope it helps.

CSS get height of screen resolution

In order to get screen resolution you can also use . This link help you very much to resolve.

MVC web api: No 'Access-Control-Allow-Origin' header is present on the requested resource

I know that people will probably find this very obvious at first, but really think about this. This can often happen if you've done something wrong.

For instance, I've had this problem because I didn't add a host entry to my hosts file. The real problem was DNS resolution. Or I just got the base URL wrong.

Sometimes I get this error if the identity token came from one server, but I'm trying to use it on another.

Sometimes you'll get this error if you've got the resource wrong.

You might get this if you put the CORS middleware too late in the chain.

Rock, Paper, Scissors Game Java

I would recommend making Rock, Paper and Scissors objects. The objects would have the logic of both translating to/from Strings and also "knowing" what beats what. The Java enum is perfect for this.

public enum Type{


  public static Type parseType(String value){
     //if /else logic here to return either ROCK, PAPER or SCISSOR

     //if value is not either, you can return null

The parseType method can return null if the String is not a valid type. And you code can check if the value is null and if so, print "invalid try again" and loop back to re-read the Scanner.

Type person=null;

      System.out.println("Enter your play: "); 
      person= Type.parseType(;
      if(person ==null){
         System.out.println("invalid try again");

Furthermore, your type enum can determine what beats what by having each Type object know:

public enum Type{


    //each type will implement this method differently
    public abstract boolean beats(Type other);


each type will implement this method differently to see what beats what:


   public boolean beats(Type other){            
        return other ==  SCISSOR;



Then in your code

 Type person, computer;
   if (person.equals(computer)) 
   System.out.println("It's a tie!");
  }else if({
     System.out.println(person+ " beats " + computer + "You win!!"); 
     System.out.println(computer + " beats " + person+ "You lose!!");

Difference between 2 dates in seconds

$timeFirst  = strtotime('2011-05-12 18:20:20');
$timeSecond = strtotime('2011-05-13 18:20:20');
$differenceInSeconds = $timeSecond - $timeFirst;

You will then be able to use the seconds to find minutes, hours, days, etc.

how can select from drop down menu and call javascript function

<script type="text/javascript">
function report(func)

function daily()

function monthly()

python pip on Windows - command 'cl.exe' failed

Refer to this link:

Download the right whl package for you python version(if you have trouble knowing what version of python you have, just lunch the interpreter )

use pip to install the package, assuming that the file is in downloads folder and you have python 3.6 32 bit :

python -m pip install C:\Users\%USER%\Downloads\cytoolz-

this is not valid for just this package, but for any package that cannot compile under your own windows installation.

How do I call Objective-C code from Swift?

Using Objective-C Classes in Swift

If you have an existing class that you'd like to use, perform Step 2 and then skip to Step 5. (For some cases, I had to add an explicit #import <Foundation/Foundation.h to an older Objective-C File.)

Step 1: Add Objective-C Implementation -- .m

Add a .m file to your class, and name it CustomObject.m.

Step 2: Add Bridging Header

When adding your .m file, you'll likely be hit with a prompt that looks like this:

A macOS sheet-style dialog from Xcode asking if you would "like to configure an Objective-C bridging header"

Click Yes!

If you did not see the prompt, or accidentally deleted your bridging header, add a new .h file to your project and name it <#YourProjectName#>-Bridging-Header.h.

In some situations, particularly when working with Objective-C frameworks, you don't add an Objective-C class explicitly and Xcode can't find the linker. In this case, create your .h file named as mentioned above, then make sure you link its path in your target's project settings like so:

An animation demonstrating the above paragraph


It's best practice to link your project using the $(SRCROOT) macro so that if you move your project, or work on it with others using a remote repository, it will still work. $(SRCROOT) can be thought of as the directory that contains your .xcodeproj file. It might look like this:


Step 3: Add Objective-C Header -- .h

Add another .h file and name it CustomObject.h.

Step 4: Build your Objective-C Class

In CustomObject.h

#import <Foundation/Foundation.h>

@interface CustomObject : NSObject

@property (strong, nonatomic) id someProperty;

- (void) someMethod;


In CustomObject.m

#import "CustomObject.h"

@implementation CustomObject 

- (void) someMethod {
    NSLog(@"SomeMethod Ran");


Step 5: Add Class to Bridging-Header

In YourProject-Bridging-Header.h:

#import "CustomObject.h"

Step 6: Use your Object

In SomeSwiftFile.swift:

var instanceOfCustomObject = CustomObject()
instanceOfCustomObject.someProperty = "Hello World"

There is no need to import explicitly; that's what the bridging header is for.

Using Swift Classes in Objective-C

Step 1: Create New Swift Class

Add a .swift file to your project, and name it MySwiftObject.swift.

In MySwiftObject.swift:

import Foundation

class MySwiftObject : NSObject {

    var someProperty: AnyObject = "Some Initializer Val" as NSString

    init() {}

    func someFunction(someArg: Any) -> NSString {
        return "You sent me \(someArg)"

Step 2: Import Swift Files to ObjC Class

In SomeRandomClass.m:

#import "<#YourProjectName#>-Swift.h"

The file:<#YourProjectName#>-Swift.h should already be created automatically in your project, even if you can not see it.

Step 3: Use your class

MySwiftObject * myOb = [MySwiftObject new];
NSLog(@"MyOb.someProperty: %@", myOb.someProperty);
myOb.someProperty = @"Hello World";
NSLog(@"MyOb.someProperty: %@", myOb.someProperty);

NSString * retString = [myOb someFunctionWithSomeArg:@"Arg"];

NSLog(@"RetString: %@", retString);


  1. If Code Completion isn't behaving as you expect, try running a quick build with ??R to help Xcode find some of the Objective-C code from a Swift context and vice versa.

  2. If you add a .swift file to an older project and get the error dyld: Library not loaded: @rpath/libswift_stdlib_core.dylib, try completely restarting Xcode.

  3. While it was originally possible to use pure Swift classes (Not descendents of NSObject) which are visible to Objective-C by using the @objc prefix, this is no longer possible. Now, to be visible in Objective-C, the Swift object must either be a class conforming to NSObjectProtocol (easiest way to do this is to inherit from NSObject), or to be an enum marked @objc with a raw value of some integer type like Int. You may view the edit history for an example of Swift 1.x code using @objc without these restrictions.

Representing Directory & File Structure in Markdown Syntax

Under OSX, using reveal.js, I have got rendering issue if I just user tree and then copy/paste the output: strange symbols appear.

I have found 2 possible solutions.

1) Use charset ascii and simply copy/paste the output in the markdown file

tree -L 1 --charset=ascii

2) Use directly HTML and unicode in the markdown file

&#8866; docs
&#8866; e2e
&#8866; karma.conf.js
&#8866; node_modules
&#8866; package.json
&#8866; protractor.conf.js
&#8866; src
&#8866; tsconfig.json
&#8985; tslint.json

Hope it helps.

Web API Put Request generates an Http 405 Method Not Allowed error

Your client application and server application must be under same domain, for example :

client - localhost

server - localhost

and not :

client - localhost:21234

server - localhost

Objective-C: Calling selectors with multiple arguments

Your method signature is:

- (void) myTest:(NSString *)

withAString happens to be the parameter (the name is misleading, it looks like it is part of the selector's signature).

If you call the function in this manner:

[self performSelector:@selector(myTest:) withObject:myString];

It will work.

But, as the other posters have suggested, you may want to rename the method:

- (void)myTestWithAString:(NSString*)aString;

And call:

[self performSelector:@selector(myTestWithAString:) withObject:myString];

ReactJS lifecycle method inside a function Component

You can use react-pure-lifecycle to add lifecycle functions to functional components.


import React, { Component } from 'react';
import lifecycle from 'react-pure-lifecycle';

const methods = {
  componentDidMount(props) {
    console.log('I mounted! Here are my props: ', props);

const Channels = props => (

export default lifecycle(methods)(Channels);

Request exceeded the limit of 10 internal redirects due to probable configuration error

This error occurred to me when I was debugging the PHP header() function:

header('Location: /aaa/bbb/ccc'); // error

If I use a relative path it works:

header('Location: aaa/bbb/ccc'); // success, but not what I wanted

However when I use an absolute path like /aaa/bbb/ccc, it gives the exact error:

Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace.

It appears the header function redirects internally without going HTTP at all which is weird. After some tests and trials, I found the solution of adding exit after header():

header('Location: /aaa/bbb/ccc');

And it works properly.