Programs & Examples On #Treetop

Treetop is a Ruby parser generator for PEG grammars.

Bundler::GemNotFound: Could not find rake-10.3.2 in any of the sources

bundle install --path vendor/cache

generally fixes it as that is the more common problem. Basically, your bundler path configuration is messed up. See their documentation (first paragraph) for where to find those configurations and change them manually if needed.

Failed to build gem native extension — Rails install

The suggested answer only works for certain versions of ruby. Some commenters suggest using ruby-dev; that didn't work for me either.

sudo apt-get install ruby-all-dev

worked for me.

incompatible character encodings: ASCII-8BIT and UTF-8

I have a suspicion that you either copy/pasted a part of your Haml template into the file, or you're working with a non-Unicode/non-UTF-8 friendly editor.

See if you can recreate that file from the scratch in a UTF-8 friendly editor. There are plenty for any platform and see whether this fixes your problem. Start by erasing the line with #content and retyping it manually.

Struct inheritance in C++

Yes, struct is exactly like class except the default accessibility is public for struct (while it's private for class).

How do I use MySQL through XAMPP?

if(!@mysql_connect('', 'root', '*your default password*'))
    echo "mysql not connected ".mysql_error();

echo 'great work';

if no error then you will get greatwork as output.

Try it saved my life XD XD

What is the purpose of the "final" keyword in C++11 for functions?

Final keyword in C++ when added to a function, prevents it from being overridden by a base class. Also when added to a class prevents inheritance of any type. Consider the following example which shows use of final specifier. This program fails in compilation.

#include <iostream>
using namespace std;

class Base
  virtual void myfun() final
    cout << "myfun() in Base";
class Derived : public Base
  void myfun()
    cout << "myfun() in Derived\n";

int main()
  Derived d;
  Base &b = d;
  return 0;


#include <iostream>
class Base final

class Derived : public Base

int main()
  Derived d;
  return 0;

ReactJS - Call One Component Method From Another Component

Well, actually, React is not suitable for calling child methods from the parent. Some frameworks, like Cycle.js, allow easily access data both from parent and child, and react to it.

Also, there is a good chance you don't really need it. Consider calling it into existing component, it is much more independent solution. But sometimes you still need it, and then you have few choices:

  • Pass method down, if it is a child (the easiest one, and it is one of the passed properties)
  • add events library; in React ecosystem Flux approach is the most known, with Redux library. You separate all events into separated state and actions, and dispatch them from components
  • if you need to use function from the child in a parent component, you can wrap in a third component, and clone parent with augmented props.

UPD: if you need to share some functionality which doesn't involve any state (like static functions in OOP), then there is no need to contain it inside components. Just declare it separately and invoke when need:

let counter = 0;
function handleInstantiate() {

constructor(props) {

MongoDB: Is it possible to make a case-insensitive query?

For searching a variable and escaping it:

const escapeStringRegexp = require('escape-string-regexp')
const name = 'foo'
db.stuff.find({name: new RegExp('^' + escapeStringRegexp(name) + '$', 'i')})   

Escaping the variable protects the query against attacks with '.*' or other regex.


How to get the insert ID in JDBC?

Connection cn = DriverManager.getConnection("Host","user","pass");
Statement st = cn.createStatement("Ur Requet Sql");
int ret  = st.execute();

How do I specify new lines on Python, when writing on files?

You can either write in the new lines separately or within a single string, which is easier.

Example 1


line1 = "hello how are you"
line2 = "I am testing the new line escape sequence"
line3 = "this seems to work"

You can write the '\n' separately:



hello how are you
I am testing the new line escape sequence
this seems to work

Example 2


As others have pointed out in the previous answers, place the \n at the relevant points in your string:

line = "hello how are you\nI am testing the new line escape sequence\nthis seems to work"



hello how are you
I am testing the new line escape sequence
this seems to work

How to highlight a selected row in ngRepeat?

Each row has an ID. All you have to do is to send this ID to the function setSelected(), store it (in $scope.idSelectedVote for instance), and then check for each row if the selected ID is the same as the current one. Here is a solution (see the documentation for ngClass, if needed):

$scope.idSelectedVote = null;
$scope.setSelected = function (idSelectedVote) {
   $scope.idSelectedVote = idSelectedVote;
<ul ng-repeat="vote in votes" ng-click="setSelected(" ng-class="{selected: === idSelectedVote}">


Placing/Overlapping(z-index) a view above another view in android

There is a way to use LinearLayout. Just set the marginTop of your previous element to the corresponding negative value, and make sure the element you want on top is after the element you want below in your XML.

<linearLayout android:orientation="horizontal" ... >

Git asks for username every time I push

(Only For Mac OS)

for Windows and Linux please refer to Github's documentation link mentioned below.

From Github Documentation: Documentation Link

Caching your GitHub password in Git

  • You need Git 1.7.10 or newer to use the osxkeychain credential helper.

    to check your Git version: git --version

  • to find out osxkeychain helper is already installed:

    git credential-osxkeychain

    if you get following response then you have it already installed and ready to use on your mac:

    > Usage: git credential-osxkeychain <get|store|erase>

    if you don't get a response as shown above then you can install it running following command:

    git credential-osxkeychain

  • to tell git to globally use osxkeychain for git credentials:

    git config --global credential.helper osxkeychain

    It will prompt once before it saves credentials to the keychain.

Adding default parameter value with type hint in Python

If you're using typing (introduced in Python 3.5) you can use typing.Optional, where Optional[X] is equivalent to Union[X, None]. It is used to signal that the explicit value of None is allowed . From typing.Optional:

def foo(arg: Optional[int] = None) -> None:

How to cat <<EOF >> a file containing code?

Or, using your EOF markers, you need to quote the initial marker so expansion won't be done:

cat <<'EOF' >>
curr=`cat /sys/class/backlight/intel_backlight/actual_brightness`
if [ $curr -lt 4477 ]; then
   echo $curr  > /sys/class/backlight/intel_backlight/brightness;


SSIS Connection not found in package

This seems to also happen when you use the new SSIS 2012 "Shared Connection Manager" concept where the connection managers are not defined within your package but the Visual Studio project and just get referenced in the package. Executing it via SQL Agent or DTEXEC yields the same error message.

I haven't found a solution for that yet but would love to get some feedback if anybody experienced it before.

Git keeps asking me for my ssh key passphrase

For Windows or Linux users, a possible solution is described on GitHub Docs, which I report below for your convenience.

You can run ssh-agent automatically when you open bash or Git shell. Copy the following lines and paste them into your ~/.profile or ~/.bashrc file:


agent_load_env () { test -f "$env" && . "$env" >| /dev/null ; }

agent_start () {
    (umask 077; ssh-agent >| "$env")
    . "$env" >| /dev/null ; }


# agent_run_state: 0=agent running w/ key; 1=agent w/o key; 2= agent not running
agent_run_state=$(ssh-add -l >| /dev/null 2>&1; echo $?)

if [ ! "$SSH_AUTH_SOCK" ] || [ $agent_run_state = 2 ]; then
elif [ "$SSH_AUTH_SOCK" ] && [ $agent_run_state = 1 ]; then

unset env

If your private key is not stored in one of the default locations (like ~/.ssh/id_rsa), you'll need to tell your SSH authentication agent where to find it. To add your key to ssh-agent, type ssh-add ~/path/to/my_key.

Now, when you first run Git Bash, you are prompted for your passphrase. The ssh-agent process will continue to run until you log out, shut down your computer, or kill the process.

How to replace multiple strings in a file using PowerShell

With version 3 of PowerShell you can chain the replace calls together:

 (Get-Content $sourceFile) | ForEach-Object {
    $_.replace('something1', 'something1').replace('somethingElse1', 'somethingElse2')
 } | Set-Content $destinationFile

Where is `%p` useful with printf?

At least on one system that is not very uncommon, they do not print the same:

~/src> uname -m
~/src> gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
[some output snipped]
gcc version 4.1.2 (Gentoo 4.1.2)
~/src> gcc -o printfptr printfptr.c
~/src> ./printfptr

Notice how the pointer version adds a 0x prefix, for instance. Always use %p since it knows about the size of pointers, and how to best represent them as text.

Use Invoke-WebRequest with a username and password for basic authentication on the GitHub API

If someone would need a one liner:

iwr -Uri '' -Headers @{ Authorization = "Basic "+ [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes("user:pass")) }

Best way to log POST data in Apache?

Use Apache's mod_dumpio. Be careful for obvious reasons.

Note that mod_dumpio stops logging binary payloads at the first null character. For example a multipart/form-data upload of a gzip'd file will probably only show the first few bytes with mod_dumpio.

Also note that Apache might not mention this module in httpd.conf even when it's present in the /modules folder. Just manually adding LoadModule will work fine. is being requested by various other libraries

Resolved here: Me too faced the same problem when trying to add crashlytics in firebase. Please update the latest version of dependencies for and ....... It will automatically resolved the issues

Does HTML5 <video> playback support the .avi format?

Short answer: No. Use WebM or Ogg instead.

This article covers just about everything you need to know about the <video> element, including which browsers support which container formats and codecs.

Caused by: Cannot recover key

In order to not have the Cannot recover key exception, I had to apply the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files to the installation of Java that was running my application. Version 8 of those files can be found here or the latest version should be listed on this page. The download includes a file that explains how to apply the policy files.

Since JDK 8u151 it isn't necessary to add policy files. Instead the JCE jurisdiction policy files are controlled by a Security property called crypto.policy. Setting that to unlimited with allow unlimited cryptography to be used by the JDK. As the release notes linked to above state, it can be set by Security.setProperty() or via the file. The file could also be appended to by adding to the command to start the program as detailed here.

Since JDK 8u161 unlimited cryptography is enabled by default.

How to Get JSON Array Within JSON Object?

JSONObject jsonObject =new JSONObject(jsonStr);
JSONArray jsonArray = jsonObject.getJSONArray("data");
for(int i=0;i<jsonArray.length;i++){
    JSONObject json = jsonArray.getJSONObject(i);
    String id = json.getString("id");
    String name=json.getString("name");
    JSONArray ingArray = json.getJSONArray("Ingredients") // here you are going   to get ingredients
    for(int j=0;j<ingArray.length;j++){
        JSONObject ingredObject= ingArray.getJSONObject(j);
        String ingName = ingredObject.getString("name");//so you are going to get   ingredient name
        Log.e("name",ingName); // you will get 

How to send email to multiple recipients with addresses stored in Excel?

Both answers are correct. If you user .TO -method then the semicolumn is OK - but not for the addrecipients-method. There you need to split, e.g. :

                Dim Splitter() As String
                Splitter = Split(AddrMail, ";")
                For Each Dest In Splitter
                    .Recipients.Add (Trim(Dest))

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

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

Another way,

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

Can't create handler inside thread which has not called Looper.prepare()

Try running you asyntask from the UI thread. I faced this issue when I wasn't doing the same!

Convert Mongoose docs to json

You can use res.json() to jsonify any object. lean() will remove all the empty fields in the mongoose query.

UserModel.find().lean().exec(function (err, users) { return res.json(users); }

run main class of Maven project

Although maven exec does the trick here, I found it pretty poor for a real test. While waiting for maven shell, and hoping this could help others, I finally came out to this repo mvnexec

Clone it, and symlink the script somewhere in your path. I use ~/bin/mvnexec, as I have ~/bin in my path. I think mvnexec is a good name for the script, but is up to you to change the symlink...

Launch it from the root of your project, where you can see src and target dirs.

The script search for classes with main method, offering a select to choose one (Example with mavenized JMeld project)

$ mvnexec 
 1) org.jmeld.ui.JMeldComponent
 2) org.jmeld.ui.text.FileDocument
 3) org.jmeld.JMeld
 4) org.jmeld.util.UIDefaultsPrint
 5) org.jmeld.util.PrintProperties
 6) org.jmeld.util.file.DirectoryDiff
 7) org.jmeld.util.file.VersionControlDiff
17) org.jmeld.Main

If one is selected (typing number), you are prompt for arguments (you can avoid with mvnexec -P)

By default it compiles project every run. but you can avoid that using mvnexec -B

It allows to search only in test classes -M or --no-main, or only in main classes -T or --no-test. also has a filter by name option -f <whatever>

Hope this could save you some time, for me it does.

How to display with n decimal places in Matlab

You can convert a number to a string with n decimal places using the SPRINTF command:

>> x = 1.23;
>> sprintf('%0.6f', x)

ans =


>> x = 1.23456789;
>> sprintf('%0.6f', x)

ans =


How to get difference between two dates in Year/Month/Week/Day?

Based on Joaquim's answer, but fixing the calculation when end date month is less than start date month, and adding code to handle end date before start date:

        public static class GeneralHelper
          public static int GetYears(DateTime startDate, DateTime endDate)
                if (endDate < startDate)
                    return -GetYears(endDate, startDate);

                int years = (endDate.Year - startDate.Year);

                if (endDate.Year == startDate.Year)
                    return years;

                if (endDate.Month < startDate.Month)
                    return years - 1;

                if (endDate.Month == startDate.Month && endDate.Day < startDate.Day)
                    return years - 1;

                return years;

            public static int GetMonths(DateTime startDate, DateTime endDate)
                if (startDate > endDate)
                    return -GetMonths(endDate, startDate);

                int months = 12 * GetYears(startDate, endDate);

                if (endDate.Month > startDate.Month)
                    months = months + endDate.Month - startDate.Month;
                    months = 12 - startDate.Month + endDate.Month;

                if (endDate.Day < startDate.Day)
                    months = months - 1;

                return months;
    public class GeneralHelperTest
            public void GetYearsTest()
                Assert.AreEqual(0, GeneralHelper.GetYears(new DateTime(2000, 5, 5), new DateTime(2000, 12, 31)));
                Assert.AreEqual(0, GeneralHelper.GetYears(new DateTime(2000, 5, 5), new DateTime(2001, 4, 4)));
                Assert.AreEqual(0, GeneralHelper.GetYears(new DateTime(2000, 5, 5), new DateTime(2001, 5, 4)));
                Assert.AreEqual(1, GeneralHelper.GetYears(new DateTime(2000, 5, 5), new DateTime(2001, 5, 5)));
                Assert.AreEqual(1, GeneralHelper.GetYears(new DateTime(2000, 5, 5), new DateTime(2001, 12, 31)));

                Assert.AreEqual(0, GeneralHelper.GetYears(new DateTime(2000, 12, 31), new DateTime(2000, 5, 5)));
                Assert.AreEqual(0, GeneralHelper.GetYears(new DateTime(2001, 4, 4), new DateTime(2000, 5, 5)));
                Assert.AreEqual(0, GeneralHelper.GetYears(new DateTime(2001, 5, 4), new DateTime(2000, 5, 5)));
                Assert.AreEqual(-1, GeneralHelper.GetYears(new DateTime(2001, 5, 5), new DateTime(2000, 5, 5)));
                Assert.AreEqual(-1, GeneralHelper.GetYears(new DateTime(2001, 12, 31), new DateTime(2000, 5, 5)));

            public void GetMonthsTest()
                Assert.AreEqual(0, GeneralHelper.GetMonths(new DateTime(2000, 5, 5), new DateTime(2000, 6, 4)));
                Assert.AreEqual(1, GeneralHelper.GetMonths(new DateTime(2000, 5, 5), new DateTime(2000, 6, 5)));
                Assert.AreEqual(1, GeneralHelper.GetMonths(new DateTime(2000, 5, 5), new DateTime(2000, 6, 6)));
                Assert.AreEqual(11, GeneralHelper.GetMonths(new DateTime(2000, 5, 5), new DateTime(2001, 5, 4)));
                Assert.AreEqual(12, GeneralHelper.GetMonths(new DateTime(2000, 5, 5), new DateTime(2001, 5, 5)));
                Assert.AreEqual(13, GeneralHelper.GetMonths(new DateTime(2000, 5, 5), new DateTime(2001, 6, 6)));

                Assert.AreEqual(0, GeneralHelper.GetMonths(new DateTime(2000, 6, 4), new DateTime(2000, 5, 5)));
                Assert.AreEqual(-1, GeneralHelper.GetMonths(new DateTime(2000, 6, 5), new DateTime(2000, 5, 5)));
                Assert.AreEqual(-1, GeneralHelper.GetMonths(new DateTime(2000, 6, 6), new DateTime(2000, 5, 5)));
                Assert.AreEqual(-11, GeneralHelper.GetMonths(new DateTime(2001, 5, 4), new DateTime(2000, 5, 5)));
                Assert.AreEqual(-12, GeneralHelper.GetMonths(new DateTime(2001, 5, 5), new DateTime(2000, 5, 5)));
                Assert.AreEqual(-13, GeneralHelper.GetMonths(new DateTime(2001, 6, 6), new DateTime(2000, 5, 5)));

EDIT No that still doesn't work. It fails this test:

Assert.AreEqual(24, GeneralHelper.GetMonths(new DateTime(2000, 5, 5), new DateTime(2003, 5, 5)));

Expected:<24>. Actual:<12>

How to install popper.js with Bootstrap 4?

Try doing this:

npm install bootstrap jquery popper.js --save

See this page for more information: how-to-include-bootstrap-in-your-project-with-webpack

Numpy where function multiple conditions

This should work:

dists[((dists >= r) & (dists <= r+dr))]

The most elegant way~~

Database, Table and Column Naming Conventions?

Here's a link that offers a few choices. I was searching for a simple spec I could follow rather than having to rely on a partially defined one.

Get user profile picture by Id

Use url as: in src of img tag. type may be small,large.

How to build a query string for a URL in C#?

    public static string ToQueryString(this Dictionary<string, string> source)
        return String.Join("&", source.Select(kvp => String.Format("{0}={1}", HttpUtility.UrlEncode(kvp.Key), HttpUtility.UrlEncode(kvp.Value))).ToArray());

    public static string ToQueryString(this NameValueCollection source)
        return String.Join("&", source.Cast<string>().Select(key => String.Format("{0}={1}", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(source[key]))).ToArray());

"Could not load type [Namespace].Global" causing me grief

Old post but I go this error when trying to convert from website project to web application project.

Follow the instructions on this Link. I still got the global.asax error but all I did was delete it and re-add it back by right clicking on the project in visual studio and selecting add new item. Add the global.asax file and it worked.

Query an XDocument for elements by name at any depth

This my variant of the solution based on LINQ and the Descendants method of the XDocument class

using System;
using System.Linq;
using System.Xml.Linq;

class Test
    static void Main()
        XDocument xml = XDocument.Parse(@"
          <child id='1'/>
          <child id='2'>
            <subChild id='3'>
                <extChild id='5' />
                <extChild id='6' />
            <subChild id='4'>
                <extChild id='7' />

        xml.Descendants().Where(p => p.Name.LocalName == "extChild")
                         .ForEach(e => Console.WriteLine(e));



For more details on the Desendants method take a look here.

Adding a color background and border radius to a Layout

You don't need the separate fill item. In fact, it's invalid. You just have to add a solid block to the shape. The subsequent stroke draws on top of the solid:


    <corners android:radius="5dp" />
    <solid android:color="@android:color/white" />
        android:color="@color/bggrey" />

You also don't need the layer-list if you only have one shape.

typecast string to integer - Postgres

Common issue

Naively type casting any string into an integer like so

SELECT ''::integer

Often results to the famous error:

Query failed: ERROR: invalid input syntax for integer: ""


PostgreSQL has no pre-defined function for safely type casting any string into an integer.


Create a user-defined function inspired by PHP's intval() function.

CREATE FUNCTION intval(character varying) RETURNS integer AS $$

    WHEN length(btrim(regexp_replace($1, '[^0-9]', '','g')))>0 THEN btrim(regexp_replace($1, '[^0-9]', '','g'))::integer
    ELSE 0
END AS intval;



/* Example 1 */
SELECT intval('9000');
-- output: 9000

/* Example 2 */
SELECT intval('9gag');
-- output: 9

/* Example 3 */
SELECT intval('the quick brown fox jumps over the lazy dog');
-- output: 0

How to load image files with webpack file-loader

Install file loader first:

$ npm install file-loader --save-dev

And add this rule in webpack.config.js

                test: /\.(png|jpg|gif)$/,
                use: [{
                    loader: 'file-loader',
                    options: {}

google map API zoom range

Available Zoom Levels

Zoom level 0 is the most zoomed out zoom level available and each integer step in zoom level halves the X and Y extents of the view and doubles the linear resolution.

Google Maps was built on a 256x256 pixel tile system where zoom level 0 was a 256x256 pixel image of the whole earth. A 256x256 tile for zoom level 1 enlarges a 128x128 pixel region from zoom level 0.

As correctly stated by bkaid, the available zoom range depends on where you are looking and the kind of map you are using:

  • Road maps - seem to go up to zoom level 22 everywhere
  • Hybrid and satellite maps - the max available zoom levels depend on location. Here are some examples:
  • Remote regions of Antarctica: 13
  • Gobi Desert: 17
  • Much of the U.S. and Europe: 21
  • "Deep zoom" locations: 22-23 (see bkaid's link)

Note that these values are for the Google Static Maps API which seems to give one more zoom level than the Javascript API. It appears that the extra zoom level available for Static Maps is just an upsampled version of the max-resolution image from the Javascript API.

Map Scale at Various Zoom Levels

Google Maps uses a Mercator projection so the scale varies substantially with latitude. A formula for calculating the correct scale based on latitude is:

meters_per_pixel = 156543.03392 * Math.cos( * Math.PI / 180) / Math.pow(2, zoom)

Formula is from Chris Broadfoot's comment.

Google Maps basics

Zoom Level - zoom

0 - 19

0 lowest zoom (whole world)

19 highest zoom (individual buildings, if available) Retrieve current zoom level using mapObject.getZoom()

What you're looking for are the scales for each zoom level. Use these:

20 : 1128.497220
19 : 2256.994440
18 : 4513.988880
17 : 9027.977761
16 : 18055.955520
15 : 36111.911040
14 : 72223.822090
13 : 144447.644200
12 : 288895.288400
11 : 577790.576700
10 : 1155581.153000
9  : 2311162.307000
8  : 4622324.614000
7  : 9244649.227000
6  : 18489298.450000
5  : 36978596.910000
4  : 73957193.820000
3  : 147914387.600000
2  : 295828775.300000
1  : 591657550.500000

Converting ISO 8601-compliant String to java.util.Date

After I searched a lot to convert ISO8601 to date I suddenly found a java class that is and this was part of So you can use it to convert dates.

ISO8601Utils.parse("2010-01-01T12:00:00Z" , ParsePosition(0))

and you can simply use this kotlin extension function

fun String.getDateFromString() : Date? = ISO8601Utils.parse(this , 

How to add click event to a iframe with JQuery

It works only if the frame contains page from the same domain (does not violate same-origin policy)

See this:

var iframe = $('#your_iframe').contents();

   console.log('work fine');

Is there any standard for JSON API response format?

Following is the json format instagram is using

    "meta": {
         "error_type": "OAuthException",
         "code": 400,
         "error_message": "..."
    "data": {
    "pagination": {
         "next_url": "...",
         "next_max_id": "13872296"

Should I check in folder "node_modules" to Git when creating a Node.js app on Heroku?

I believe that npm install should not run in a production environment. There are several things that can go wrong - npm outage, download of newer dependencies (shrinkwrap seems to have solved this) are two of them.

On the other hand, folder node_modules should not be committed to Git. Apart from their big size, commits including them can become distracting.

The best solutions would be this: npm install should run in a CI environment that is similar to the production environment. All tests will run and a zipped release file will be created that will include all dependencies.

How to fix: Error device not found with ADB.exe

Just wanted to provide a simple answer here. I am just messing with an old Android device for the first time doing these root and unlock procedures. I received an error like this one when an adb push "..." "/sdcard/" command failed, and the key was that my device was in the bootloader screen. Booting to recovery then allowed me copy over the file(s), and I presume the normal OS would as well.

How can I print the contents of a hash in Perl?

I append one space for every element of the hash to see it well:

print map {$_ . " "} %h, "\n";

Spring Boot, Spring Data JPA with multiple DataSources

here is my solution. base on spring-boot.1.2.5.RELEASE.

first.datasource.validation-query=select 1

second.datasource.validation-query=select 1

public class DataSourceConfig {
    public DataSource firstDataSource() {
        DataSource ds =  DataSourceBuilder.create().build();
        return ds;

    public DataSource secondDataSource() {
        DataSource ds =  DataSourceBuilder.create().build();
        return ds;

Dynamically changing font size of UILabel

Single line:

factLabel.numberOfLines = 1;
factLabel.minimumFontSize = 8;
factLabel.adjustsFontSizeToFitWidth = YES;

The above code will adjust your text's font size down to (for example) 8 trying to fit your text within the label. numberOfLines = 1 is mandatory.

Multiple lines:

For numberOfLines > 1 there is a method to figure out the size of final text through NSString's sizeWithFont:... UIKit addition methods, for example:

CGSize lLabelSize = [yourText sizeWithFont:factLabel.font

After that you can just resize your label using resulting lLabelSize, for example (assuming that you will change only label's height):

factLabel.frame = CGRectMake(factLabel.frame.origin.x, factLabel.frame.origin.y, factLabel.frame.size.width, lLabelSize.height);


Single line:

Starting with iOS6, minimumFontSize has been deprecated. The line

factLabel.minimumFontSize = 8.;

can be changed to:

factLabel.minimumScaleFactor = 8./factLabel.font.pointSize;


Multiple lines:

Starting with iOS7, sizeWithFont becomes deprecated. Multiline case is reduced to:

factLabel.numberOfLines = 0;
factLabel.lineBreakMode = NSLineBreakByWordWrapping;
CGSize maximumLabelSize = CGSizeMake(factLabel.frame.size.width, CGFLOAT_MAX);
CGSize expectSize = [factLabel sizeThatFits:maximumLabelSize];
factLabel.frame = CGRectMake(factLabel.frame.origin.x, factLabel.frame.origin.y, expectSize.width, expectSize.height);

iOS 13 (Swift 5):

label.adjustsFontSizeToFitWidth = true
label.minimumScaleFactor = 0.5

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

I just encountered this on Windows 10 and the latest NodeJS (14.15.1). In my case our admins have our profiles and true "home" folder remotely mount onto our work machine(s). Npm wanted to put its cache over on the remote server and that has worked until this release.

I was unaware that npm has a .npmrc file available. I added one to my actual machine's C:\Users\my-id folder and it contains:


I also added these paths to my PATH environment variable.

I went to the APPDATA folder on my work machine and the remote "home" server and deleted all the npm related Roaming folders. I deleted the node_modules folder in my project.

I closed all open windows and reopened them. I brought up a command prompt in my project dir and re inited npm and reinstalled the modules I wanted.

After that everything is rolling along.

if else in a list comprehension

Make a list from items in an iterable

It seems best to first generalize all the possible forms rather than giving specific answers to questions. Otherwise, the reader won't know how the answer was determined. Here are a few generalized forms I thought up before I got a headache trying to decide if a final else' clause could be used in the last form.

[expression1(item)                                        for item in iterable]

[expression1(item) if conditional1                        for item in iterable]

[expression1(item) if conditional1 else expression2(item) for item in iterable]

[expression1(item) if conditional1 else expression2(item) for item in iterable if conditional2]

The value of item doesn't need to be used in any of the conditional clauses. A conditional3 can be used as a switch to either add or not add a value to the output list.

For example, to create a new list that eliminates empty strings or whitespace strings from the original list of strings:

newlist = [s for s in firstlist if s.strip()]

Sending JWT token in the headers with Postman

If you wish to use postman the right way is to use the headers as such

key: Authorization

value: jwt {token}

as simple as that.

What do all of Scala's symbolic operators mean?

I consider a modern IDE to be critical for understanding large scala projects. Since these operators are also methods, in intellij idea I just control-click or control-b into the definitions.

You can control-click right into a cons operator (::) and end up at the scala javadoc saying "Adds an element at the beginning of this list." In user-defined operators, this becomes even more critical, since they could be defined in hard-to-find implicits... your IDE knows where the implicit was defined.

jQuery Ajax error handling, show custom exception messages

If making a call to, this will return the error message title:

I didn't write all of formatErrorMessage myself but i find it very useful.

function formatErrorMessage(jqXHR, exception) {

    if (jqXHR.status === 0) {
        return ('Not connected.\nPlease verify your network connection.');
    } else if (jqXHR.status == 404) {
        return ('The requested page not found. [404]');
    } else if (jqXHR.status == 500) {
        return ('Internal Server Error [500].');
    } else if (exception === 'parsererror') {
        return ('Requested JSON parse failed.');
    } else if (exception === 'timeout') {
        return ('Time out error.');
    } else if (exception === 'abort') {
        return ('Ajax request aborted.');
    } else {
        return ('Uncaught Error.\n' + jqXHR.responseText);

var jqxhr = $.post(addresshere, function() {
.done(function() { alert("second success"); })
.fail(function(xhr, err) { 

    var responseTitle= $(xhr.responseText).filter('title').get(0);
    alert($(responseTitle).text() + "\n" + formatErrorMessage(xhr, err) ); 

Using Spring RestTemplate in generic method with generic parameter

Actually, you can do this, but with additional code.

There is Guava equivalent of ParameterizedTypeReference and it's called TypeToken.

Guava's class is much more powerful then Spring's equivalent. You can compose the TypeTokens as you wish. For example:

static <K, V> TypeToken<Map<K, V>> mapToken(TypeToken<K> keyToken, TypeToken<V> valueToken) {
  return new TypeToken<Map<K, V>>() {}
    .where(new TypeParameter<K>() {}, keyToken)
    .where(new TypeParameter<V>() {}, valueToken);

If you call mapToken(TypeToken.of(String.class), TypeToken.of(BigInteger.class)); you will create TypeToken<Map<String, BigInteger>>!

The only disadvantage here is that many Spring APIs require ParameterizedTypeReference and not TypeToken. But we can create ParameterizedTypeReference implementation which is adapter to TypeToken itself.

import org.springframework.core.ParameterizedTypeReference;

import java.lang.reflect.Type;

public class ParameterizedTypeReferenceBuilder {

    public static <T> ParameterizedTypeReference<T> fromTypeToken(TypeToken<T> typeToken) {
        return new TypeTokenParameterizedTypeReference<>(typeToken);

    private static class TypeTokenParameterizedTypeReference<T> extends ParameterizedTypeReference<T> {

        private final Type type;

        private TypeTokenParameterizedTypeReference(TypeToken<T> typeToken) {
            this.type = typeToken.getType();

        public Type getType() {
            return type;

        public boolean equals(Object obj) {
            return (this == obj || (obj instanceof ParameterizedTypeReference &&
                    this.type.equals(((ParameterizedTypeReference<?>) obj).getType())));

        public int hashCode() {
            return this.type.hashCode();

        public String toString() {
            return "ParameterizedTypeReference<" + this.type + ">";



Then you can use it like this:

public <T> ResponseWrapper<T> makeRequest(URI uri, Class<T> clazz) {
   ParameterizedTypeReference<ResponseWrapper<T>> responseTypeRef =
               new TypeToken<ResponseWrapper<T>>() {}
                   .where(new TypeParameter<T>() {}, clazz));
   ResponseEntity<ResponseWrapper<T>> response =
    return response;

And call it like:

ResponseWrapper<MyClass> result = makeRequest(uri, MyClass.class);

And the response body will be correctly deserialized as ResponseWrapper<MyClass>!

You can even use more complex types if you rewrite your generic request method (or overload it) like this:

public <T> ResponseWrapper<T> makeRequest(URI uri, TypeToken<T> resultTypeToken) {
   ParameterizedTypeReference<ResponseWrapper<T>> responseTypeRef =
               new TypeToken<ResponseWrapper<T>>() {}
                   .where(new TypeParameter<T>() {}, resultTypeToken));
   ResponseEntity<ResponseWrapper<T>> response =
    return response;

This way T can be complex type, like List<MyClass>.

And call it like:

ResponseWrapper<List<MyClass>> result = makeRequest(uri, new TypeToken<List<MyClass>>() {});

How do I bind Twitter Bootstrap tooltips to dynamically created elements?

Rather than search it in full Body. One could just use dynamic title option already available in such scenarios I think:

  title: function(){
    return $(this).attr('title');

regular expression for finding 'href' value of a <a> link

Thanks everyone (specially @plalx)

I find it quite overkill enforce the validity of the href attribute with such a complex and cryptic pattern while a simple expression such as
would suffice to capture all URLs. If you want to make sure they contain at least a query string, you could just use

My final regex string:

First use one of this:
st = @"((www\.|https?|ftp|gopher|telnet|file|notes|ms-help):((//)|(\\\\))+ \w\d:#@%/;$()~_?\+-=\\\.&]*)";
st = @"<a href[^>]*>(.*?)</a>";
st = @"((([A-Za-z]{3,9}:(?:\/\/)?)(?:[-;:&=\+\$,\w]+@)?[A-Za-z0-9.-]+|(?:www.|[-;:&=\+\$,\w]+@)[A-Za-z0-9.-]+)((?:\/[\+~%\/.\w-_]*)?\??(?:[-\+=&;%@.\w_]*)#?(?:[\w]*))?)";
st = @"((?:(?:https?|ftp|gopher|telnet|file|notes|ms-help):(?://|\\\\)(?:www\.)?|www\.)[\w\d:#@%/;$()~_?\+,\-=\\.&]+)";
st = @"(?:(?:https?|ftp|gopher|telnet|file|notes|ms-help):(?://|\\\\)(?:www\.)?|www\.)";
st = @"(((https?|ftp|gopher|telnet|file|notes|ms-help):((//)|(\\\\))+)|(www\.)[\w\d:#@%/;$()~_?\+-=\\\.&]*)";
st = @"href=[""'](?<url>(http|https)://[^/]*?\.(com|org|net|gov))(/.*)?[""']";
st = @"(<a.*?>.*?</a>)";
st = @"(?:hrefs*=)(?:[s""']*)(?!#|mailto|location.|javascript|.*css|.*this.)(?.*?)(?:[s>""'])";
st = @"http://([\\w+?\\.\\w+])+([a-zA-Z0-9\\~\\!\\@\\#\\$\\%\\^\\&amp;\\*\\(\\)_\\-\\=\\+\\\\\\/\\?\\.\\:\\;\\'\\,]*)?";
st = @"http(s)?://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?";
st = @"(http|https)://([a-zA-Z0-9\\~\\!\\@\\#\\$\\%\\^\\&amp;\\*\\(\\)_\\-\\=\\+\\\\\\/\\?\\.\\:\\;\\'\\,]*)?";
st = @"((http|ftp|https):\/\/[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&amp;:/~\+#]*[\w\-\@?^=%&amp;/~\+#])?)";
st = @"http://([\\w+?\\.\\w+])+([a-zA-Z0-9\\~\\!\\@\\#\\$\\%\\^\\&amp;\\*\\(\\)_\\-\\=\\+\\\\\\/\\?\\.\\:\\;\\'\\,]*)?";
st = @"http(s?)\:\/\/[0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*(:(0-9)*)*(\/?)([a-zA-Z0-9\-\.\?\,\'\/\\\+&amp;%\$#_]*)?$";
st = @"(?<Protocol>\w+):\/\/(?<Domain>[\w.]+\/?)\S*";

my choice is


Second Use this:

st = "(.*)?(.*)=(.*)";

Problem Solved. Thanks every one :)

Grant execute permission for a user on all stored procedures in database?

Without over-complicating the problem, to grant the EXECUTE on chosen database:

GRANT EXEC TO [User_Name];

In Python, how do I split a string and keep the separators?

>>> re.split('(\W)', 'foo/bar spam\neggs')
['foo', '/', 'bar', ' ', 'spam', '\n', 'eggs']

MySQL stored procedure return value


  • DELIMITER at the beginning and end of the SP.
  • DROP PROCEDURE IF EXISTS validar_egreso; at the beginning
  • When calling the SP, use @variableName.

This works for me. (I modified some part of your script so ANYONE can run it with out having your tables).

DROP PROCEDURE IF EXISTS `validar_egreso`;


CREATE DEFINER='root'@'localhost' PROCEDURE `validar_egreso` (
    IN codigo_producto VARCHAR(100),
    IN cantidad INT,
    OUT valido INT(11)

    DECLARE resta INT;
    SET resta = 0;

    SELECT (codigo_producto - cantidad) INTO resta;

    IF(resta > 1) THEN
       SET valido = 1;
       SET valido = -1;
    END IF;

    SELECT valido;
END $$


-- execute the stored procedure
CALL validar_egreso(4, 1, @val);

-- display the result
select @val;

Attach event to dynamic elements in javascript

I have created a small library to help with this: Library source on GitHub

<script src="dynamicListener.min.js"></script>
// Any `li` or element with class `.myClass` will trigger the callback, 
// even elements created dynamically after the event listener was created.
addDynamicEventListener(document.body, 'click', '.myClass, li', function (e) {

The functionality is similar to jQuery.on().

The library uses the Element.matches() method to test the target element against the given selector. When an event is triggered the callback is only called if the target element matches the selector given.

clear javascript console in Google Chrome

Chrome Console Clear button

If you want to just clear the console when debugging, you can simply click the "ban-circle" ? button to clear console.log.

Alternatively just press "Ctrl+L" to clear the console using your keyboard.

How to format date in angularjs

After looking at all the above solutions, the following was the quickest solution for me. If you are using angular-material:

 <md-datepicker ng-model="member.reg_date" md-placeholder="Enter date"></md-datepicker>

To set the format:

app.config(function($mdDateLocaleProvider) {
    $mdDateLocaleProvider.formatDate = function(date) {
        // Requires Moment.js OR enter your own formatting code here....
        return moment(date).format('DD-MM-YYYY');

Edit: You also need to set the parseDate for typing in a date (from this answer Change format of md-datepicker in Angular Material)

$mdDateLocaleProvider.parseDate = function(dateString) {
    var m = moment(dateString, 'DD/MM/YYYY', true);
    return m.isValid() ? m.toDate() : new Date(NaN);

How to handle notification when app in background in Firebase

I figured out the scenarios,

When app is in foreground, onMessageReceived() method is called from the FirebaseService.So the pendingIntent defined in the service class will be called.

And when app is in background, first activity is called.

Now, if you use a splash activity, then must keep in mind the splashactivity will be called, else if there is no splashActivity, then whatever the first activity is, will be called.

Then you need to check getIntent() of the firstActivity to see if it has any bundle .if everything is alright you will see bundle is there with values filled in. If the value in data tag sent from server looks like this,

"data": {
    "user_name": "arefin sajib",
    "value": "user name notification"

Then in the first activity, you will see, there is a valid intent( getIntent() is not null) , valid bundle and inside bundle , there will the whole JSON mentioned above with data as key.

For this scenario, code for extraction of value will look like this,

            Bundle bundle = getIntent().getExtras();
            if (bundle != null) {
                try {
                   JSONObject object = new JSONObject(bundle.getStringExtra("data"));
String user_name = object.optString("user_name");

                } catch (JSONException e) {


passing form data to another HTML page

Using pure JavaScript.It's very easy using local storage.
The first page form:

function getData()
    //gettting the values
    var email = document.getElementById("email").value;
    var password= document.getElementById("password").value; 
    var telephone= document.getElementById("telephone").value; 
    var mobile= document.getElementById("mobile").value; 
    //saving the values in local storage
    localStorage.setItem("txtValue", email);
    localStorage.setItem("txtValue1", password);
    localStorage.setItem("txtValue2", mobile);
    localStorage.setItem("txtValue3", telephone);   
    font-size: 25px;
    color: rgb(16, 8, 46);
    font-weight: bolder;

   <fieldset style="width: fit-content; margin: 0 auto; font-size: 30px;">
        <form action="action.html">
        <legend>Sign Up Form</legend>
        <label>Email:<br />
        <input type="text" name="email" id="email"/></label><br />
        <label>Password<br />
        <input type="text" name="password" id="password"/></label><br>
        <label>Mobile:<br />
        <input type="text" name="mobile" id="mobile"/></label><br />
        <label>Telephone:<br />
        <input type="text" name="telephone" id="telephone"/></label><br> 
        <input type="submit" value="Submit" onclick="getData()">

This is the second page:

//displaying the value from local storage to another page by their respective Ids
 <div style=" font-size: 30px;  color: rgb(32, 7, 63); text-align: center;">
    <div style="font-size: 40px; color: red; margin: 0 auto;">
        Here's Your data
    The Email is equal to: <span id="data"> Email</span><br> 
    The Password is equal to <span id="data1"> Password</span><br>
    The Mobile is equal to <span id="data2"> Mobile</span><br>
    The Telephone is equal to <span id="data3"> Telephone</span><br>

Important Note:

Please don't forget to give name "action.html" to the second html file to work the code properly. I can't use multiple pages in a snippet, that's why its not working here try in the browser in your editor where it will surely work.

Multiple IF AND statements excel

With your ANDs you shouldn't have a FALSE value -2, until right at the end, e.g. with just 2 ANDs

=IF(AND(E2="In Play",F2="Closed"),3,IF(AND(E2="In Play",F2=" Suspended"),3,-2))

although it might be better with a combination of nested IFs and ANDs - try like this for the full formula:[Edited - thanks David]

=IF(E2="In Play",IF(F2="Closed",3,IF(F2="Suspended",2,IF(F2="Null",1))),IF(AND(E2="Pre-play",F2="Null"),-1,IF(AND(E2="Completed",F2="Closed"),2,IF(AND(E2="Pre-play",F2="Null"),3,-2))))

To avoid a long formula like the above you could create a table with all E2 possibilities in a column like K2:K5 and all F2 possibilities in a row like L1:N1 then fill in the required results in L2:N5 and use this formula


Getting Checkbox Value in ASP.NET MVC 4

This has been a major pain and feels like it should be simpler. Here's my setup and solution.

I'm using the following HTML helper:

@Html.CheckBoxFor(model => model.ActiveFlag)

Then, in the controller, I am checking the form collection and processing accordingly:

bool activeFlag = collection["ActiveFlag"] == "false" ? false : true;
[modelObject].ActiveFlag = activeFlag;

setTimeout / clearTimeout problems

You need to declare timer outside the function. Otherwise, you get a brand new variable on each function invocation.

var timer;
function endAndStartTimer() {
  //var millisecBeforeRedirect = 10000; 
  timer = window.setTimeout(function(){alert('Hello!');},10000); 

How do I convert an array object to a string in PowerShell?

1> $a = "This", "Is", "a", "cat"

2> [system.String]::Join(" ", $a)

Line two performs the operation and outputs to host, but does not modify $a:

3> $a = [system.String]::Join(" ", $a)

4> $a

This Is a cat

5> $a.Count


Android: How do bluetooth UUIDs work?

It usually represents some common service (protocol) that bluetooth device supports.

When creating your own rfcomm server (with listenUsingRfcommWithServiceRecord), you should specify your own UUID so that the clients connecting to it could identify it; it is one of the reasons why createRfcommSocketToServiceRecord requires an UUID parameter.

Otherwise, some common services have the same UUID, just find one you need and use it.

See here

Return string Input with parse.string

You don't need to parse the string, it's defined as a string already.

Just do:

    private static String getStringInput (String prompt) {
     String input = EZJ.getUserInput(prompt);
     return input;

Set UILabel line spacing

This guy created a class to get line-height (without using CoreText, as MTLabel library) :

How to disable/enable a button with a checkbox if checked

Here is a clean way to disable and enable submit button:

<input type="submit" name="sendNewSms" class="inputButton" id="sendNewSms" value=" Send " />
<input type="checkbox" id="disableBtn" />

var submit = document.getElementById('sendNewSms'),
    checkbox = document.getElementById('disableBtn'),
    disableSubmit = function(e) {
        submit.disabled = this.checked

checkbox.addEventListener('change', disableSubmit);

Here is a fiddle of it in action:

"id cannot be resolved or is not a field" error?

I also had this error when I was working in a Java class once. My problem was simply that my xml file, with the references in it, was not saved. If you have both the xml file and java class open in tabs, check to make sure the xml file name in the tab doesn't have a * by it.

Hope this helps.

Parsing CSV files in C#, with header

Let a library handle all the nitty-gritty details for you! :-)

Check out FileHelpers and stay DRY - Don't Repeat Yourself - no need to re-invent the wheel a gazillionth time....

You basically just need to define that shape of your data - the fields in your individual line in the CSV - by means of a public class (and so well-thought out attributes like default values, replacements for NULL values and so forth), point the FileHelpers engine at a file, and bingo - you get back all the entries from that file. One simple operation - great performance!

Getting "The remote certificate is invalid according to the validation procedure" when SMTP server has a valid certificate

Old post but as you said "why is it not using the correct certificate" I would like to offer an way to find out which SSL certificate is used for SMTP (see here) which required openssl:

openssl s_client -connect -starttls smtp

This will outline the used SSL certificate for the SMTP service. Based on what you see here you can replace the wrong certificate (like you already did) with a correct one (or trust the certificate manually).

delete all from table

There is a mySQL bug report from 2004 that still seems to have some validity. It seems that in 4.x, this was fastest:

DROP table_name
CREATE TABLE table_name

TRUNCATE table_name was DELETE FROM internally back then, providing no performance gain.

This seems to have changed, but only in 5.0.3 and younger. From the bug report:

[11 Jan 2005 16:10] Marko Mäkelä

I've now implemented fast TRUNCATE TABLE, which will hopefully be included in MySQL 5.0.3.

Increase max_execution_time in PHP?

For increasing execution time and file size, you need to mention below values in your .htaccess file. It will work.

php_value upload_max_filesize 80M
php_value post_max_size 80M
php_value max_input_time 18000
php_value max_execution_time 18000

Using different Web.config in development and production environment

You could also make it a post-build step. Setup a new configuration which is "Deploy" in addition to Debug and Release, and then have the post-build step copy over the correct web.config.

We use automated builds for all of our projects, and with those the build script updates the web.config file to point to the correct location. But that won't help you if you are doing everything from VS.

Delete all rows in table

Truncate table is faster than delete * from XXX. Delete is slow because it works one row at a time. There are a few situations where truncate doesn't work, which you can read about on MSDN.

find filenames NOT ending in specific extensions on Unix?

Linux/OS X:

Starting from the current directory, recursively find all files ending in .dll or .exe

find . -type f | grep -P "\.dll$|\.exe$"

Starting from the current directory, recursively find all files that DON'T end in .dll or .exe

find . -type f | grep -vP "\.dll$|\.exe$"


(1) The P option in grep indicates that we are using the Perl style to write our regular expressions to be used in conjunction with the grep command. For the purpose of excecuting the grep command in conjunction with regular expressions, I find that the Perl style is the most powerful style around.

(2) The v option in grep instructs the shell to exclude any file that satisfies the regular expression

(3) The $ character at the end of say ".dll$" is a delimiter control character that tells the shell that the filename string ends with ".dll"

cmake - find_library - custom library location

There is no way to automatically set CMAKE_PREFIX_PATH in a way you want. I see following ways to solve this problem:

  1. Put all libraries files in the same dir. That is, include/ would contain headers for all libs, lib/ - binaries, etc. FYI, this is common layout for most UNIX-like systems.

  2. Set global environment variable CMAKE_PREFIX_PATH to D:/develop/cmake/libs/libA;D:/develop/cmake/libs/libB;.... When you run CMake, it would aautomatically pick up this env var and populate it's own CMAKE_PREFIX_PATH.

  3. Write a wrapper .bat script, which would call cmake command with -D CMAKE_PREFIX_PATH=... argument.

How can I start InternetExplorerDriver using Selenium WebDriver

package Browser;

import org.openqa.selenium.WebDriver; import;

public class Hello {

public static void main(String[] args) {

    // setting IEdriver property
            "paste the path of the IEDriverserver.exe");

    WebDriver driver = new InternetExplorerDriver();

    // launching the google home screen


} //Hope this will work

Best practice for partial updates in a RESTful service

RFC 7396: JSON Merge Patch (published four years after the question was posted) describes the best practices for a PATCH in terms of the format and processing rules.

In a nutshell, you submit an HTTP PATCH to a target resource with the application/merge-patch+json MIME media type and a body representing only the parts that you want to be changed/added/removed and then follow the below processing rules.


  • If the provided merge patch contains members that do not appear within the target, those members are added.

  • If the target does contain the member, the value is replaced.

  • Null values in the merge patch are given special meaning to indicate the removal of existing values in the target.

Example test cases that illustrate the rules above (as seen in the appendix of that RFC):

 ORIGINAL         PATCH           RESULT
{"a":"b"}       {"a":"c"}       {"a":"c"}

{"a":"b"}       {"b":"c"}       {"a":"b",
{"a":"b"}       {"a":null}      {}

{"a":"b",       {"a":null}      {"b":"c"}

{"a":["b"]}     {"a":"c"}       {"a":"c"}

{"a":"c"}       {"a":["b"]}     {"a":["b"]}

{"a": {         {"a": {         {"a": {
  "b": "c"}       "b": "d",       "b": "d"
}                 "c": null}      }
                }               }

{"a": [         {"a": [1]}      {"a": [1]}

["a","b"]       ["c","d"]       ["c","d"]

{"a":"b"}       ["c"]           ["c"]

{"a":"foo"}     null            null

{"a":"foo"}     "bar"           "bar"

{"e":null}      {"a":1}         {"e":null,

[1,2]           {"a":"b",       {"a":"b"}

{}              {"a":            {"a":
                 {"bb":           {"bb":
                  {"ccc":          {}}}

Difference between if () { } and if () : endif;

At our company, the preferred way for handling HTML is:

<? if($condition) { ?>
   HTML content here
<? } else { ?>
   Other HTML content here
<? } ?>

In the end, it really is a matter of choosing one and sticking with it.

Creating a UIImage from a UIColor to use as a background image for UIButton

Are you using ARC? The problem here is that you don't have a reference to the UIColor object that you're trying to apply; the CGColor is backed by that UIColor, but ARC will deallocate the UIColor before you have a chance to use the CGColor.

The clearest solution is to have a local variable pointing to your UIColor with the objc_precise_lifetime attribute.

You can read more about this exact case on this article about UIColor and short ARC lifetimes or get more details about the objc_precise_lifetime attribute.

Define preprocessor macro through CMake?

For a long time, CMake had the add_definitions command for this purpose. However, recently the command has been superseded by a more fine grained approach (separate commands for compile definitions, include directories, and compiler options).

An example using the new add_compile_definitions:



add_compile_definitions(OPENCV_VERSION=${OpenCV_VERSION} WITH_OPENCV2)

The good part about this is that it circumvents the shabby trickery CMake has in place for add_definitions. CMake is such a shabby system, but they are finally finding some sanity.

Find more explanation on which commands to use for compiler flags here:

Likewise, you can do this per-target as explained in Jim Hunziker's answer.

How to change the Jupyter start-up folder

If your goal is to permanently change the start-up location. You can do so by changing the shortcut for the notebook. Assuming you are on Windows 10

  1. Press start and find Jupter Notebook in the Anaconda Folder
  2. Right click -> More -> Open File location
  3. Right click the Jupyter Notebook short cute -> Properties
  4. Now in target: you will see something at the end that looks like: "%USERPROFILE%/". Replace the contents of %USERPROFILE%/ with your desired DIRECTORY. e.g. "D:\GoogleDrive"

Good Luck

An URL to a Windows shared folder

If you are allowed to go further then javascript/html facilities - I would use the apache web server to represent your directory listing via http.

If this solution is appropriate. these are the steps:

  1. download apache hhtp server from one of the mirrors

  2. unzip/install (if msi) it to the directory e.g C:\opt\Apache (the instruction is for windows)

  3. map the network forlder as a local drive on windows (\server\folder to let's say drive H:)

  4. open conf/httpd.conf file

  5. make sure the next line is present and not commented

    LoadModule autoindex_module modules/

  6. Add directory configuration

<Directory "H:/path">

Options +Indexes

AllowOverride None

Order allow,deny

Allow from all

</Directory> 7. Start the web server and make sure the directory listingof the remote folder is available by http. hit localhost/path 8. use a frame inside your web page to access the listing

What is missed: 1. you mignt need more fancy configuration for the host name, refer to Apache Web Server docs. Register the host name in DNS server

  1. the mapping to the network drive might not work, i did not check. As a posible resolution - host your web server on the same machine as smb server.

CSS filter: make color image with transparency white

You can use

filter: brightness(0) invert(1);

html {_x000D_
  background: red;_x000D_
p {_x000D_
  float: left;_x000D_
  max-width: 50%;_x000D_
  text-align: center;_x000D_
img {_x000D_
  display: block;_x000D_
  max-width: 100%;_x000D_
.filter {_x000D_
  -webkit-filter: brightness(0) invert(1);_x000D_
  filter: brightness(0) invert(1);_x000D_
  <img src="" />_x000D_
  <img src="" class="filter" />_x000D_

First, brightness(0) makes all image black, except transparent parts, which remain transparent.

Then, invert(1) makes the black parts white.

Is it safe to store a JWT in localStorage with ReactJS?

It is not safe if you use CDN's:

Malicious JavaScript can be embedded on the page, and Web Storage is compromised. These types of XSS attacks can get everyone’s Web Storage that visits your site, without their knowledge. This is probably why a bunch of organizations advise not to store anything of value or trust any information in web storage. This includes session identifiers and tokens.

via stormpath

Any script you require from the outside could potentially be compromised and could grab any JWTS from your client's storage and send personal data back to the attacker's server.

jQuery prevent change for select

if anybody still interested, this solved the problem, using jQuery 3.3.1


    jQuery(v).data('lastSelected', jQuery(v).find('option:selected').val());
    jQuery(v).on('change', function(){

    if(!confirm('Are you sure?'))
        var self = jQuery(this);
        jQuery(this).find('option').each(function(key, value){
           if(parseInt(jQuery(value).val()) === parseInt('lastSelected')))
               jQuery(this).prop('selected', 'selected');
    jQuery(v).data('lastSelected', jQuery(v).find('option:selected').val());    


JavaScript check if variable exists (is defined/initialized)

In the particular situation outlined in the question,

typeof window.console === "undefined"

is identical to

window.console === undefined

I prefer the latter since it's shorter.

Please note that we look up for console only in global scope (which is a window object in all browsers). In this particular situation it's desirable. We don't want console defined elsewhere.

@BrianKelley in his great answer explains technical details. I've only added lacking conclusion and digested it into something easier to read.

Password Strength Meter

Update: created a js fiddle here to see it live:

I went through tons of google searches and didn't find anything satisfying. i like how passpack have done it so essentially reverse-engineered their approach, here we go:

function scorePassword(pass) {
    var score = 0;
    if (!pass)
        return score;

    // award every unique letter until 5 repetitions
    var letters = new Object();
    for (var i=0; i<pass.length; i++) {
        letters[pass[i]] = (letters[pass[i]] || 0) + 1;
        score += 5.0 / letters[pass[i]];

    // bonus points for mixing it up
    var variations = {
        digits: /\d/.test(pass),
        lower: /[a-z]/.test(pass),
        upper: /[A-Z]/.test(pass),
        nonWords: /\W/.test(pass),

    var variationCount = 0;
    for (var check in variations) {
        variationCount += (variations[check] == true) ? 1 : 0;
    score += (variationCount - 1) * 10;

    return parseInt(score);

Good passwords start to score around 60 or so, here's function to translate that in words:

function checkPassStrength(pass) {
    var score = scorePassword(pass);
    if (score > 80)
        return "strong";
    if (score > 60)
        return "good";
    if (score >= 30)
        return "weak";

    return "";

you might want to tune this a bit but i found it working for me nicely

How to insert a file in MySQL database?

The BLOB datatype is best for storing files.

Changing ViewPager to enable infinite page scrolling

For infinite scrolling with days it's important you have the good fragment in the pager therefore I wrote my answer on this on page (Viewpager in Android to switch between days endlessly)

It's working very well! Above answers did not work for me as I wanted it to work.

Importing xsd into wsdl

import vs. include

The primary purpose of an import is to import a namespace. A more common use of the XSD import statement is to import a namespace which appears in another file. You might be gathering the namespace information from the file, but don't forget that it's the namespace that you're importing, not the file (don't confuse an import statement with an include statement).

Another area of confusion is how to specify the location or path of the included .xsd file: An XSD import statement has an optional attribute named schemaLocation but it is not necessary if the namespace of the import statement is at the same location (in the same file) as the import statement itself.

When you do chose to use an external .xsd file for your WSDL, the schemaLocation attribute becomes necessary. Be very sure that the namespace you use in the import statement is the same as the targetNamespace of the schema you are importing. That is, all 3 occurrences must be identical:


xs:import namespace="urn:listing3" schemaLocation="listing3.xsd"/>


<xsd:schema targetNamespace="urn:listing3"

Another approach to letting know the WSDL about the XSD is through Maven's pom.xml:


You can read more on this in this great IBM article. It has typos such as xsd:import instead of xs:import but otherwise it's fine.

Add querystring parameters to link_to

The API docs on link_to show some examples of adding querystrings to both named and oldstyle routes. Is this what you want?

link_to can also produce links with anchors or query strings:

link_to "Comment wall", profile_path(@profile, :anchor => "wall")
#=> <a href="/profiles/1#wall">Comment wall</a>

link_to "Ruby on Rails search", :controller => "searches", :query => "ruby on rails"
#=> <a href="/searches?query=ruby+on+rails">Ruby on Rails search</a>

link_to "Nonsense search", searches_path(:foo => "bar", :baz => "quux")
#=> <a href="/searches?foo=bar&amp;baz=quux">Nonsense search</a>

How to Identify Microsoft Edge browser via CSS?

For Internet Explorer 

@media all and (-ms-high-contrast: none) {
            background: rgba(0, 0, 0, 0.16)

For Edge
@supports (-ms-ime-align:auto) {
            background: rgba(0, 0, 0, 0.16);

bodyParser is deprecated express 4

It means that using the bodyParser() constructor has been deprecated, as of 2014-06-19.

app.use(bodyParser()); //Now deprecated

You now need to call the methods separately



And so on.

If you're still getting a warning with urlencoded you need to use

  extended: true

The extended config object key now needs to be explicitly passed, since it now has no default value.

If you are using Express >= 4.16.0, body parser has been re-added under the methods express.json() and express.urlencoded().

Android video streaming example

I had the same problem but finally I found the way.

Here is the walk through:

1- Install VLC on your computer (SERVER) and go to Media->Streaming (Ctrl+S)

2- Select a file to stream or if you want to stream your webcam or... click on "Capture Device" tab and do the configuration and finally click on "Stream" button.

3- Here you should do the streaming server configuration, just go to "Option" tab and paste the following command:


NOTE: Replace YOURCOMPUTER_SERVER_IP_ADDR with your computer IP address or any server which is running VLC...

NOTE: You can see, the video codec is MP4V which is supported by android.

4- go to eclipse and create a new project for media playbak. create a VideoView object and in the OnCreate() function write some code like this:

mVideoView = (VideoView) findViewById(;

mVideoView.setMediaController(new MediaController(this));

5- run the apk on the device (not simulator, i did not check it) and wait for the playback to be started. please consider the buffering process will take about 10 seconds...

Question: Anybody know how to reduce buffering time and play video almost live ?

How to set a dropdownlist item as selected in ASP.NET?

This is a very nice and clean example:(check this great tutorial for a full explanation link)

public static IEnumerable<SelectListItem> ToSelectListItems(
              this IEnumerable<Album> albums, int selectedId)
        albums.OrderBy(album => album.Name)
              .Select(album => 
                  new SelectListItem
                    Selected = (album.ID == selectedId),
                    Text = album.Name,
                    Value = album.ID.ToString()

In this MSDN link you can read de DropDownList method documentation.

Hope it helps.

MySQL pivot table query with dynamic columns

The only way in MySQL to do this dynamically is with Prepared statements. Here is a good article about them:

Dynamic pivot tables (transform rows to columns)

Your code would look like this:

SET @sql = NULL;
      'MAX(IF(pa.fieldname = ''',
      ''', pa.fieldvalue, NULL)) AS ',
  ) INTO @sql
FROM product_additional;

                    , p.description, ', @sql, ' 
                   FROM product p
                   LEFT JOIN product_additional AS pa 
                    ON =
                   GROUP BY');

PREPARE stmt FROM @sql;

See Demo

NOTE: GROUP_CONCAT function has a limit of 1024 characters. See parameter group_concat_max_len

Error handling in getJSON calls

This is quite an old thread, but it does come up in Google search, so I thought I would add a jQuery 3 answer using promises. This snippet also shows:

  • You no longer need to switch to $.ajax to pass in your bearer token
  • Uses .then() to make sure you can process synchronously any outcome (I was coming across this problem .always() callback firing too soon - although I'm not sure that was 100% true)
  • I'm using .always() to simply show the outcome whether positive or negative
  • In the .always() function I'm updating two targets with the HTTP Status code and message body

The code snippet is:

         url: "",
         headers: { "Authorization": "Bearer " + user.access_token}
    }).then().always(   function (data, textStatus) {

How to convert a Java String to an ASCII byte array?

There is only one character wrong in the code you tried:

Charset characterSet = Charset.forName("US-ASCII");
String string = "Wazzup";
byte[] bytes = String.getBytes(characterSet);

Notice the upper case "String". This tries to invoke a static method on the string class, which does not exist. Instead you need to invoke the method on your string instance:

byte[] bytes = string.getBytes(characterSet);

entity object cannot be referenced by multiple instances of IEntityChangeTracker. while adding related objects to entity in Entity Framework 4.1

Alternatively to injection and even worse Singleton, you can call Detach method before Add.

EntityFramework 6: ((IObjectContextAdapter)cs).ObjectContext.Detach(city1);

EntityFramework 4: cs.Detach(city1);

There is yet another way, in case you don't need first DBContext object. Just wrap it with using keyword:

Payroll.Entities.City city1;
using (CityService cs = new CityService())
  city1 = cs.SelectCity(Convert.ToInt64(cmbCity.SelectedItem.Value));

Is it possible to have a default parameter for a mysql stored procedure?

No, this is not supported in MySQL stored routine syntax.

Feel free to submit a feature request at

Gradle project refresh failed after Android Studio update

This might be too late to answer. But this may help someone.

In my case there was problem of JDK path.

I just set proper JDK path for Android Studio 2.1

File -> Project Structure -> From Left Side Panel "SDK Location" -> JDK Location -> Click to select JDK Path

How to remove entity with ManyToMany relationship in JPA (and corresponding join table rows)?

For what its worth, I am using EclipseLink 2.3.2.v20111125-r10461 and if I have a @ManyToMany unidirectional relationship I observe the problem that you describe. However, if I change it to be a bi-directional @ManyToMany relationship I am able to delete an entity from the non-owning side and the JOIN table is updated appropriately. This is all without the use of any cascade attributes.

Javascript - Replace html using innerHTML

You are replacing the starting tag and then putting that back in innerHTML, so the code will be invalid. Make all the replacements before you put the code back in the element:

var html = strMessage1.innerHTML;
html = html.replace( /aaaaaa./g,'<a href=\"');
html = html.replace( /.bbbbbb/g,'/world\">Helloworld</a>');
strMessage1.innerHTML = html;

Reading an Excel file in python using pandas

You just need to feed the path to your file to pd.read_excel

import pandas as pd

file_path = "./my_excel.xlsx"
data_frame = pd.read_excel(file_path)

Checkout the documentation to explore parameters like skiprows to ignore rows when loading the excel

Format decimal for percentage values?

If you have a good reason to set aside culture-dependent formatting and get explicit control over whether or not there's a space between the value and the "%", and whether the "%" is leading or trailing, you can use NumberFormatInfo's PercentPositivePattern and PercentNegativePattern properties.

For example, to get a decimal value with a trailing "%" and no space between the value and the "%":

myValue.ToString("P2", new NumberFormatInfo { PercentPositivePattern = 1, PercentNegativePattern = 1 });

More complete example:

using System.Globalization; 


decimal myValue = -0.123m;
NumberFormatInfo percentageFormat = new NumberFormatInfo { PercentPositivePattern = 1, PercentNegativePattern = 1 };
string formattedValue = myValue.ToString("P2", percentageFormat); // "-12.30%" (in en-us)

Include PHP file into HTML file

You'll have to configure the server to interpret .html files as .php files. This configuration is different depending on the server software. This will also add an extra step to the server and will slow down response on all your pages and is probably not ideal.

How to replace a whole line with sed?

If you would like to use awk then this would work too

awk -F= '{$2="xxx";print}' OFS="\=" filename

How do I get a substring of a string in Python?

Just for completeness as nobody else has mentioned it. The third parameter to an array slice is a step. So reversing a string is as simple as:


Or selecting alternate characters would be:

"H-e-l-l-o- -W-o-r-l-d"[::2] # outputs "Hello World"

The ability to step forwards and backwards through the string maintains consistency with being able to array slice from the start or end.

Android Support Design TabLayout: Gravity Center and Mode Scrollable

add this line in your actiity when you adding tabs in tablayout


When do I use super()?

You call super() to specifically run a constructor of your superclass. Given that a class can have multiple constructors, you can either call a specific constructor using super() or super(param,param) oder you can let Java handle that and call the standard constructor. Remember that classes that follow a class hierarchy follow the "is-a" relationship.

Understanding repr( ) function in Python

>>> x = 'foo'
>>> x

So the name x is attached to 'foo' string. When you call for example repr(x) the interpreter puts 'foo' instead of x and then calls repr('foo').

>>> repr(x)
>>> x.__repr__()

repr actually calls a magic method __repr__ of x, which gives the string containing the representation of the value 'foo' assigned to x. So it returns 'foo' inside the string "" resulting in "'foo'". The idea of repr is to give a string which contains a series of symbols which we can type in the interpreter and get the same value which was sent as an argument to repr.

>>> eval("'foo'")

When we call eval("'foo'"), it's the same as we type 'foo' in the interpreter. It's as we directly type the contents of the outer string "" in the interpreter.

>>> eval('foo')

Traceback (most recent call last):
  File "<pyshell#5>", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'foo' is not defined

If we call eval('foo'), it's the same as we type foo in the interpreter. But there is no foo variable available and an exception is raised.

>>> str(x)
>>> x.__str__()

str is just the string representation of the object (remember, x variable refers to 'foo'), so this function returns string.

>>> str(5)

String representation of integer 5 is '5'.

>>> str('foo')

And string representation of string 'foo' is the same string 'foo'.

The service cannot be started, either because it is disabled or because it has no enabled devices associated with it

Try to open Services Window, by writing services.msc into Start->Run and hit Enter.

When window appears, then find SQL Browser service, right click and choose Properties, and then in dropdown list choose Automatic, or Manual, whatever you want, and click OK. Eventually, if not started immediately, you can again press right click on this service and click Start.

PHP - Debugging Curl

You can enable the CURLOPT_VERBOSE option and log that information to a (temporary) CURLOPT_STDERR:

// CURLOPT_VERBOSE: TRUE to output verbose information. Writes output to STDERR, 
// or the file specified using CURLOPT_STDERR.
curl_setopt($handle, CURLOPT_VERBOSE, true);

$verbose = fopen('php://temp', 'w+');
curl_setopt($handle, CURLOPT_STDERR, $verbose);

You can then read it after curl has done the request:

$result = curl_exec($handle);
if ($result === FALSE) {
    printf("cUrl error (#%d): %s<br>\n", curl_errno($handle),

$verboseLog = stream_get_contents($verbose);

echo "Verbose information:\n<pre>", htmlspecialchars($verboseLog), "</pre>\n";

(I originally answered similar but more extended in a related question.)

More information like metrics about the last request is available via curl_getinfo. This information can be useful for debugging curl requests, too. A usage example, I would normally wrap that into a function:

$version = curl_version();
$metrics = <<<EOD
URL....: $url
Code...: $http_code ($redirect_count redirect(s) in $redirect_time secs)
Content: $content_type Size: $download_content_length (Own: $size_download) Filetime: $filetime
Time...: $total_time Start @ $starttransfer_time (DNS: $namelookup_time Connect: $connect_time Request: $pretransfer_time)
Speed..: Down: $speed_download (avg.) Up: $speed_upload (avg.)
Curl...: v{$version['version']}

jQuery: load txt file and insert into div

The .load("file.txt") is much easier. Which works but even if testing, you won't get results from a localdrive, you'll need an actual http server. The invisible error is an XMLHttpRequest error.

Find and replace string values in list

In case you're wondering about the performance of the different approaches, here are some timings:

In [1]: words = [str(i) for i in range(10000)]

In [2]: %timeit replaced = [w.replace('1', '<1>') for w in words]
100 loops, best of 3: 2.98 ms per loop

In [3]: %timeit replaced = map(lambda x: str.replace(x, '1', '<1>'), words)
100 loops, best of 3: 5.09 ms per loop

In [4]: %timeit replaced = map(lambda x: x.replace('1', '<1>'), words)
100 loops, best of 3: 4.39 ms per loop

In [5]: import re

In [6]: r = re.compile('1')

In [7]: %timeit replaced = [r.sub('<1>', w) for w in words]
100 loops, best of 3: 6.15 ms per loop

as you can see for such simple patterns the accepted list comprehension is the fastest, but look at the following:

In [8]: %timeit replaced = [w.replace('1', '<1>').replace('324', '<324>').replace('567', '<567>') for w in words]
100 loops, best of 3: 8.25 ms per loop

In [9]: r = re.compile('(1|324|567)')

In [10]: %timeit replaced = [r.sub('<\1>', w) for w in words]
100 loops, best of 3: 7.87 ms per loop

This shows that for more complicated substitutions a pre-compiled reg-exp (as in 9-10) can be (much) faster. It really depends on your problem and the shortest part of the reg-exp.

Postgres could not connect to server

For us, we had to define localhost in the psql command like the following:

psql -h localhost -U postgres

Not sure why the -h doesn't default to localhost...

MySql ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

Just to confirm: You are sure you are running MySQL 5.7, and not MySQL 5.6 or earlier version. And the plugin column contains "mysql_native_password". (Before MySQL 5.7, the password hash was stored in a column named password. Starting in MySQL 5.7, the password column is removed, and the password has is stored in the authentication_string column.) And you've also verified the contents of authentication string matches the return from PASSWORD('mysecret'). Also, is there a reason we are using DML against the mysql.user table instead of using the SET PASSWORD FOR syntax? – spencer7593

So Basically Just make sure that the Plugin Column contains "mysql_native_password".

Not my work but I read comments and noticed that this was stated as the answer but was not posted as a possible answer yet.

How do I enable saving of filled-in fields on a PDF form?

Open your PDF in Google Chrome. Edit the PDF as you want. Hit ctrl + p. Save as PDF to your desktop.

Convert LocalDateTime to LocalDateTime in UTC


Looking at the answers and the question, it seems the question has been modified significantly. So to answer the current question:

Convert LocalDateTime to LocalDateTime in UTC.


LocalDateTime does not store any information about the time-zone, it just basically holds the values of year, month, day, hour, minute, second, and smaller units. So an important question is: What is the timezone of the original LocalDateTime? It might as well be UTC already, therefore no conversion has to be made.

System Default Timezone

Considering that you asked the question anyway, you probably meant that the original time is in your system-default timezone and you want to convert it to UTC. Because usually a LocalDateTime object is created by using which returns the current time in the system-default timezone. In this case, the conversion would be the following:

LocalDateTime convertToUtc(LocalDateTime time) {
    return time.atZone(ZoneId.systemDefault()).withZoneSameInstant(ZoneOffset.UTC).toLocalDateTime();

An example of the conversion process:

2019-02-25 11:39 // [time] original LocalDateTime without a timezone
2019-02-25 11:39 GMT+1 // [atZone] converted to ZonedDateTime (system timezone is Madrid)
2019-02-25 10:39 GMT // [withZoneSameInstant] converted to UTC, still as ZonedDateTime
2019-02-25 10:39 // [toLocalDateTime] losing the timezone information

Explicit Timezone

In any other case, when you explicitly specify the timezone of the time to convert, the conversion would be the following:

LocalDateTime convertToUtc(LocalDateTime time, ZoneId zone) {
    return time.atZone(zone).withZoneSameInstant(ZoneOffset.UTC).toLocalDateTime();

An example of the conversion process:

2019-02-25 11:39 // [time] original LocalDateTime without a timezone
2019-02-25 11:39 GMT+2 // [atZone] converted to ZonedDateTime (zone is Europe/Tallinn)
2019-02-25 09:39 GMT // [withZoneSameInstant] converted to UTC, still as ZonedDateTime
2019-02-25 09:39 // [toLocalDateTime] losing the timezone information

The atZone() Method

The result of the atZone() method depends on the time passed as its argument, because it considers all the rules of the timezone, including Daylight Saving Time (DST). In the examples, the time was 25th February, in Europe this means winter time (no DST).

If we were to use a different date, let's say 25th August from last year, the result would be different, considering DST:

2018-08-25 11:39 // [time] original LocalDateTime without a timezone
2018-08-25 11:39 GMT+3 // [atZone] converted to ZonedDateTime (zone is Europe/Tallinn)
2018-08-25 08:39 GMT // [withZoneSameInstant] converted to UTC, still as ZonedDateTime
2018-08-25 08:39 // [toLocalDateTime] losing the timezone information

The GMT time does not change. Therefore the offsets in the other timezones are adjusted. In this example, the summer time of Estonia is GMT+3, and winter time GMT+2.

Also, if you specify a time within the transition of changing clocks back one hour. E.g. October 28th, 2018 03:30 for Estonia, this can mean two different times:

2018-10-28 03:30 GMT+3 // summer time [UTC 2018-10-28 00:30]
2018-10-28 04:00 GMT+3 // clocks are turned back 1 hour [UTC 2018-10-28 01:00]
2018-10-28 03:00 GMT+2 // same as above [UTC 2018-10-28 01:00]
2018-10-28 03:30 GMT+2 // winter time [UTC 2018-10-28 01:30]

Without specifying the offset manually (GMT+2 or GMT+3), the time 03:30 for the timezone Europe/Tallinn can mean two different UTC times, and two different offsets.


As you can see, the end result depends on the timezone of the time passed as an argument. Because the timezone cannot be extracted from the LocalDateTime object, you have to know yourself which timezone it is coming from in order to convert it to UTC.

LINQ to SQL Left Outer Join

Not quite - since each "left" row in a left-outer-join will match 0-n "right" rows (in the second table), where-as yours matches only 0-1. To do a left outer join, you need SelectMany and DefaultIfEmpty, for example:

var query = from c in db.Customers
            join o in db.Orders
               on c.CustomerID equals o.CustomerID into sr
            from x in sr.DefaultIfEmpty()
            select new {
               CustomerID = c.CustomerID, ContactName = c.ContactName,
               OrderID = x == null ? -1 : x.OrderID };   

(or via the extension methods)

Python: most idiomatic way to convert None to empty string?

def xstr(s):
    return s if s else ''

s = "%s%s" % (xstr(a), xstr(b))

Difference between variable declaration syntaxes in Javascript (including global variables)?

Yes, there are a couple of differences, though in practical terms they're not usually big ones.

There's a fourth way, and as of ES2015 (ES6) there's two more. I've added the fourth way at the end, but inserted the ES2015 ways after #1 (you'll see why), so we have:

var a = 0;     // 1
let a = 0;     // 1.1 (new with ES2015)
const a = 0;   // 1.2 (new with ES2015)
a = 0;         // 2
window.a = 0;  // 3
this.a = 0;    // 4

Those statements explained

#1 var a = 0;

This creates a global variable which is also a property of the global object, which we access as window on browsers (or via this a global scope, in non-strict code). Unlike some other properties, the property cannot be removed via delete.

In specification terms, it creates an identifier binding on the object Environment Record for the global environment. That makes it a property of the global object because the global object is where identifier bindings for the global environment's object Environment Record are held. This is why the property is non-deletable: It's not just a simple property, it's an identifier binding.

The binding (variable) is defined before the first line of code runs (see "When var happens" below).

Note that on IE8 and earlier, the property created on window is not enumerable (doesn't show up in statements). In IE9, Chrome, Firefox, and Opera, it's enumerable.

#1.1 let a = 0;

This creates a global variable which is not a property of the global object. This is a new thing as of ES2015.

In specification terms, it creates an identifier binding on the declarative Environment Record for the global environment rather than the object Environment Record. The global environment is unique in having a split Environment Record, one for all the old stuff that goes on the global object (the object Environment Record) and another for all the new stuff (let, const, and the functions created by class) that don't go on the global object.

The binding is created before any step-by-step code in its enclosing block is executed (in this case, before any global code runs), but it's not accessible in any way until the step-by-step execution reaches the let statement. Once execution reaches the let statement, the variable is accessible. (See "When let and const happen" below.)

#1.2 const a = 0;

Creates a global constant, which is not a property of the global object.

const is exactly like let except that you must provide an initializer (the = value part), and you cannot change the value of the constant once it's created. Under the covers, it's exactly like let but with a flag on the identifier binding saying its value cannot be changed. Using const does three things for you:

  1. Makes it a parse-time error if you try to assign to the constant.
  2. Documents its unchanging nature for other programmers.
  3. Lets the JavaScript engine optimize on the basis that it won't change.

#2 a = 0;

This creates a property on the global object implicitly. As it's a normal property, you can delete it. I'd recommend not doing this, it can be unclear to anyone reading your code later. If you use ES5's strict mode, doing this (assigning to a non-existent variable) is an error. It's one of several reasons to use strict mode.

And interestingly, again on IE8 and earlier, the property created not enumerable (doesn't show up in statements). That's odd, particularly given #3 below.

#3 window.a = 0;

This creates a property on the global object explicitly, using the window global that refers to the global object (on browsers; some non-browser environments have an equivalent global variable, such as global on NodeJS). As it's a normal property, you can delete it.

This property is enumerable, on IE8 and earlier, and on every other browser I've tried.

#4 this.a = 0;

Exactly like #3, except we're referencing the global object through this instead of the global window. This won't work in strict mode, though, because in strict mode global code, this doesn't have a reference to the global object (it has the value undefined instead).

Deleting properties

What do I mean by "deleting" or "removing" a? Exactly that: Removing the property (entirely) via the delete keyword:

window.a = 0;
display("'a' in window? " + ('a' in window)); // displays "true"
delete window.a;
display("'a' in window? " + ('a' in window)); // displays "false"

delete completely removes a property from an object. You can't do that with properties added to window indirectly via var, the delete is either silently ignored or throws an exception (depending on the JavaScript implementation and whether you're in strict mode).

Warning: IE8 again (and presumably earlier, and IE9-IE11 in the broken "compatibility" mode): It won't let you delete properties of the window object, even when you should be allowed to. Worse, it throws an exception when you try (try this experiment in IE8 and in other browsers). So when deleting from the window object, you have to be defensive:

try {
    delete window.prop;
catch (e) {
    window.prop = undefined;

That tries to delete the property, and if an exception is thrown it does the next best thing and sets the property to undefined.

This only applies to the window object, and only (as far as I know) to IE8 and earlier (or IE9-IE11 in the broken "compatibility" mode). Other browsers are fine with deleting window properties, subject to the rules above.

When var happens

The variables defined via the var statement are created before any step-by-step code in the execution context is run, and so the property exists well before the var statement.

This can be confusing, so let's take a look:

display("foo in window? " + ('foo' in window)); // displays "true"
display(" = " +;          // displays "undefined"
display("bar in window? " + ('bar' in window)); // displays "false"
display(" = " +;          // displays "undefined"
var foo = "f";
bar = "b";
display("foo in window? " + ('foo' in window)); // displays "true"
display(" = " +;          // displays "f"
display("bar in window? " + ('bar' in window)); // displays "true"
display(" = " +;          // displays "b"

Live example:

display("foo in window? " + ('foo' in window)); // displays "true"_x000D_
display(" = " +;          // displays "undefined"_x000D_
display("bar in window? " + ('bar' in window)); // displays "false"_x000D_
display(" = " +;          // displays "undefined"_x000D_
var foo = "f";_x000D_
bar = "b";_x000D_
display("foo in window? " + ('foo' in window)); // displays "true"_x000D_
display(" = " +;          // displays "f"_x000D_
display("bar in window? " + ('bar' in window)); // displays "true"_x000D_
display(" = " +;          // displays "b"_x000D_
function display(msg) {_x000D_
  var p = document.createElement('p');_x000D_
  p.innerHTML = msg;_x000D_

As you can see, the symbol foo is defined before the first line, but the symbol bar isn't. Where the var foo = "f"; statement is, there are really two things: defining the symbol, which happens before the first line of code is run; and doing an assignment to that symbol, which happens where the line is in the step-by-step flow. This is known as "var hoisting" because the var foo part is moved ("hoisted") to the top of the scope, but the foo = "f" part is left in its original location. (See Poor misunderstood var on my anemic little blog.)

When let and const happen

let and const are different from var in a couple of ways. The way that's relevant to the question is that although the binding they define is created before any step-by-step code runs, it's not accessible until the let or const statement is reached.

So while this runs:

display(a);    // undefined
var a = 0;
display(a);    // 0

This throws an error:

display(a);    // ReferenceError: a is not defined
let a = 0;

The other two ways that let and const differ from var, which aren't really relevant to the question, are:

  1. var always applies to the entire execution context (throughout global code, or throughout function code in the function where it appears), but let and const apply only within the block where they appear. That is, var has function (or global) scope, but let and const have block scope.

  2. Repeating var a in the same context is harmless, but if you have let a (or const a), having another let a or a const a or a var a is a syntax error.

Here's an example demonstrating that let and const take effect immediately in their block before any code within that block runs, but aren't accessible until the let or const statement:

var a = 0;
if (true)
  console.log(a); // ReferenceError: a is not defined
  let a = 1;

Note that the second console.log fails, instead of accessing the a from outside the block.

Off-topic: Avoid cluttering the global object (window)

The window object gets very, very cluttered with properties. Whenever possible, strongly recommend not adding to the mess. Instead, wrap up your symbols in a little package and export at most one symbol to the window object. (I frequently don't export any symbols to the window object.) You can use a function to contain all of your code in order to contain your symbols, and that function can be anonymous if you like:

(function() {
    var a = 0; // `a` is NOT a property of `window` now

    function foo() {
        alert(a);   // Alerts "0", because `foo` can access `a`

In that example, we define a function and have it executed right away (the () at the end).

A function used in this way is frequently called a scoping function. Functions defined within the scoping function can access variables defined in the scoping function because they're closures over that data (see: Closures are not complicated on my anemic little blog).

How To Accept a File POST

I used Mike Wasson's answer before I updated all the NuGets in my webapi mvc4 project. Once I did, I had to re-write the file upload action:

    public Task<HttpResponseMessage> Upload(int id)
        HttpRequestMessage request = this.Request;
        if (!request.Content.IsMimeMultipartContent())
            throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.UnsupportedMediaType));

        string root = System.Web.HttpContext.Current.Server.MapPath("~/App_Data/uploads");
        var provider = new MultipartFormDataStreamProvider(root);

        var task = request.Content.ReadAsMultipartAsync(provider).
            ContinueWith<HttpResponseMessage>(o =>
                FileInfo finfo = new FileInfo(provider.FileData.First().LocalFileName);

                string guid = Guid.NewGuid().ToString();

                File.Move(finfo.FullName, Path.Combine(root, guid + "_" + provider.FileData.First().Headers.ContentDisposition.FileName.Replace("\"", "")));

                return new HttpResponseMessage()
                    Content = new StringContent("File uploaded.")
        return task;

Apparently BodyPartFileNames is no longer available within the MultipartFormDataStreamProvider.

Html helper for <input type="file" />

Improved version of Paulius Zaliaduonis' answer:

In order to make the validation work properly I had to change the Model to:

public class ViewModel
      public HttpPostedFileBase File { get; set; }

        [Required(ErrorMessage="A header image is required"), FileExtensions(ErrorMessage = "Please upload an image file.")]
        public string FileName
                if (File != null)
                    return File.FileName;
                    return String.Empty;

and the view to:

@using (Html.BeginForm("Action", "Controller", FormMethod.Post, new 
                                       { enctype = "multipart/form-data" }))
    @Html.TextBoxFor(m => m.File, new { type = "file" })
    @Html.ValidationMessageFor(m => m.FileName)

This is required because what @Serj Sagan wrote about FileExtension attribute working only with strings.

Copy a variable's value into another

I found using JSON works but watch our for circular references

var newInstance = JSON.parse(JSON.stringify(firstInstance));

php_network_getaddresses: getaddrinfo failed: Name or service not known

in simple word your site has been blocked to access network. may be you have automated some script and it caused your whole website to be blocked. the better way to resolve this is contact that site and tell your issue. if issue is genuine they may consider unblocking

Submit a form using jQuery

I recommend a generic solution so you don't have to add the code for every form. Use the jquery form plugin ( and add this code.

$('form.ajax_submit').submit(function() {
            //validation and other stuff
        return false; 


Error Installing Homebrew - Brew Command Not Found

nano ~/.profile

add these lines:

export PATH="$HOME/.linuxbrew/bin:$PATH"
export MANPATH="$HOME/.linuxbrew/share/man:$MANPATH"
export INFOPATH="$HOME/.linuxbrew/share/info:$INFOPATH"

save the file:

Ctrl + X then Y then Enter

then render the changes:

source ~/.profile

Stop Excel from automatically converting certain text values to dates

In my case, "Sept8" in a csv file generated using R was converted into "8-Sept" by Excel 2013. The problem was solved by using write.xlsx2() function in the xlsx package to generate the output file in xlsx format, which can be loaded by Excel without unwanted conversion. So, if you are given a csv file, you can try loading it into R and converting it into xlsx using the write.xlsx2() function.

How can I check file size in Python?

#Get file size , print it , process it...
#Os.stat will provide the file size in (.st_size) property. 
#The file size will be shown in bytes.

import os

print('size:' + fsize.st_size.__str__())

#check if the file size is less than 10 MB

if fsize.st_size < 10000000:
    process it ....

How to make Regular expression into non-greedy?

The non-greedy regex modifiers are like their greedy counter-parts but with a ? immediately following them:

*  - zero or more
*? - zero or more (non-greedy)
+  - one or more
+? - one or more (non-greedy)
?  - zero or one
?? - zero or one (non-greedy)

How to destroy a JavaScript object?

You can't delete objects, they are removed when there are no more references to them. You can delete references with delete.

However, if you have created circular references in your objects you may have to de-couple some things.

MySQL Install: ERROR: Failed to build gem native extension

A number of people found this post helpful.

Also, I needed to do first type this:

yum install mysql-devel

and then:

gem install mysql 

For some people you may need to type:

gem install mysql -- --with-mysql-config=/usr/local/mysql/mysql_config

What is the difference between Visual Studio Express 2013 for Windows and Visual Studio Express 2013 for Windows Desktop?

More importantly, the 2013 versions of Visual Studio Express have all the languages that comes with the commercial versions. You can use the Windows desktop versions not only to program using Windows Forms, it is possible to write those windowed applications with any language that comes with the software, may it be C++ using the windows.h header if you want to actually learn how to create windows applications from scratch, or use Windows form to create windows in C# or visual Basic.

In the past, you had to download one version for each language or type of content. Or just download an all-in-one that still installed separate versions of the software for different languages. Now with 2013 you get all the languages needed in each content oriented version of the 2013 express.

You pick what matters the most to you.

Besides, it might be a good way to learn using notepad and the command line to write and compile, but I find that a bit tedious to use. While using an IDE might be overwhelming at first, you start small, learning how to create a project, write code, compile your code. They have gone way over their heads to ease up your day when you take it for the first time.

Dynamic classname inside ngClass in angular 2

  <div *ngFor="let celeb of singers">
  <p [ngClass]="{
    'text-success' === 'USA',
    'text-secondary' === 'Canada',
    'text-danger' === 'Puorto Rico',
    'text-info' === 'India'
  }">{{ celeb.artist }} ({{ }})

System.Data.OracleClient requires Oracle client software version 8.1.7

Update 1: It is possible for different users to have different path. But its not the likely problem here. There is more chance that the user that the iwam user doesn't have permission to the oracle client directory.

Update 0: Its suppose to work. Check for environment variable ( That are needed to find the oracle client and tnsnames.ora ). Also, Maybe you have a 32/64 bit issues. Also, consider using the Oracle Data Provider for .NET ( search for

How to access component methods from “outside” in ReactJS?

As of React 16.3 React.createRef can be used, (use ref.current to access)

var ref = React.createRef()

var parent = (
    <Child ref={ref} />
    <button onClick={e=>console.log(ref.current)}

React.renderComponent(parent, document.body)

Add vertical whitespace using Twitter Bootstrap?

My trick. Not elegant, but it works:


HTML 5: Is it <br>, <br/>, or <br />?

According to the spec the expected form is <br> for HTML 5 but a closing slash is permitted.

Can you write virtual functions / methods in Java?

In Java, all public (non-private) variables & functions are Virtual by default. Moreover variables & functions using keyword final are not virtual.

How to use If Statement in Where Clause in SQL?

You have to use CASE Statement/Expression

Select * from Customer
WHERE  (I.IsClose=@ISClose OR @ISClose is NULL)  
    (C.FirstName like '%'+@ClientName+'%' or @ClientName is NULL )    
     CASE @Value
         WHEN 2 THEN (CASE I.RecurringCharge WHEN @Total or @Total is NULL) 
         WHEN 3 THEN (CASE WHEN I.RecurringCharge like 
                               '%'+cast(@Total as varchar(50))+'%' 
                     or @Total is NULL )

Multiple commands in an alias for bash

Aliases are meant for aliasing command names. Anything beyond that should be done with functions.

alias ll='ls -l' # The ll command is an alias for ls -l

Aliases are names that are still associated with the original name. ll is just a slightly specific kind of ls.

d() {
    if exists colordiff; then
        colordiff -ur "$@"
    elif exists diff; then
        diff -ur "$@"
    elif exists comm; then
        comm -3 "$1" "$2"
    fi | less

A function is a new command that has internal logic. It isn't simply a rename of another command. It does internal operations.

Technically, aliases in the Bash shell language are so limited in capabilities that they are extremely ill suited for anything that involves more than a single command. Use them for making a small mutation of a single command, nothing more.

Since the intention is to create a new command that performs an operation which internally will resolve in other commands, the only correct answer is to use a function here:

lock() {
    gnome-screensaver-command --lock

Usage of aliases in a scenario like this runs into a lot of issues. Contrary to functions, which are executed as commands, aliases are expanded into the current command, which will lead to very unexpected issues when combining this alias "command" with other commands. They also don't work in scripts.

How to cast an object in Objective-C

Casting for inclusion is just as important as casting for exclusion for a C++ programmer. Type casting is not the same as with RTTI in the sense that you can cast an object to any type and the resulting pointer will not be nil.

Create two blank lines in Markdown

For an empty line in Markdown, escape a space (\ ), and then add a new line.




Remember: escape a space and escape a new line. That way is Markdown compliant and should compile properly in any compiler. You may have to select the example text to see how it is set up.

How to write to error log file in PHP

If you don't want to change anything in your php.ini file, according to PHP documentation, you can do this.

error_log("Error message\n", 3, "/mypath/php.log");

The first parameter is the string to be sent to the log. The second parameter 3 means expect a file destination. The third parameter is the log file path.

How do I choose grid and block dimensions for CUDA kernels?

There are two parts to that answer (I wrote it). One part is easy to quantify, the other is more empirical.

Hardware Constraints:

This is the easy to quantify part. Appendix F of the current CUDA programming guide lists a number of hard limits which limit how many threads per block a kernel launch can have. If you exceed any of these, your kernel will never run. They can be roughly summarized as:

  1. Each block cannot have more than 512/1024 threads in total (Compute Capability 1.x or 2.x and later respectively)
  2. The maximum dimensions of each block are limited to [512,512,64]/[1024,1024,64] (Compute 1.x/2.x or later)
  3. Each block cannot consume more than 8k/16k/32k/64k/32k/64k/32k/64k/32k/64k registers total (Compute 1.0,1.1/1.2,1.3/2.x-/3.0/3.2/3.5-5.2/5.3/6-6.1/6.2/7.0)
  4. Each block cannot consume more than 16kb/48kb/96kb of shared memory (Compute 1.x/2.x-6.2/7.0)

If you stay within those limits, any kernel you can successfully compile will launch without error.

Performance Tuning:

This is the empirical part. The number of threads per block you choose within the hardware constraints outlined above can and does effect the performance of code running on the hardware. How each code behaves will be different and the only real way to quantify it is by careful benchmarking and profiling. But again, very roughly summarized:

  1. The number of threads per block should be a round multiple of the warp size, which is 32 on all current hardware.
  2. Each streaming multiprocessor unit on the GPU must have enough active warps to sufficiently hide all of the different memory and instruction pipeline latency of the architecture and achieve maximum throughput. The orthodox approach here is to try achieving optimal hardware occupancy (what Roger Dahl's answer is referring to).

The second point is a huge topic which I doubt anyone is going to try and cover it in a single StackOverflow answer. There are people writing PhD theses around the quantitative analysis of aspects of the problem (see this presentation by Vasily Volkov from UC Berkley and this paper by Henry Wong from the University of Toronto for examples of how complex the question really is).

At the entry level, you should mostly be aware that the block size you choose (within the range of legal block sizes defined by the constraints above) can and does have a impact on how fast your code will run, but it depends on the hardware you have and the code you are running. By benchmarking, you will probably find that most non-trivial code has a "sweet spot" in the 128-512 threads per block range, but it will require some analysis on your part to find where that is. The good news is that because you are working in multiples of the warp size, the search space is very finite and the best configuration for a given piece of code relatively easy to find.

ctypes - Beginner

Firstly: The >>> code you see in python examples is a way to indicate that it is Python code. It's used to separate Python code from output. Like this:

>>> 4+5

Here we see that the line that starts with >>> is the Python code, and 9 is what it results in. This is exactly how it looks if you start a Python interpreter, which is why it's done like that.

You never enter the >>> part into a .py file.

That takes care of your syntax error.

Secondly, ctypes is just one of several ways of wrapping Python libraries. Other ways are SWIG, which will look at your Python library and generate a Python C extension module that exposes the C API. Another way is to use Cython.

They all have benefits and drawbacks.

SWIG will only expose your C API to Python. That means you don't get any objects or anything, you'll have to make a separate Python file doing that. It is however common to have a module called say "wowza" and a SWIG module called "_wowza" that is the wrapper around the C API. This is a nice and easy way of doing things.

Cython generates a C-Extension file. It has the benefit that all of the Python code you write is made into C, so the objects you write are also in C, which can be a performance improvement. But you'll have to learn how it interfaces with C so it's a little bit extra work to learn how to use it.

ctypes have the benefit that there is no C-code to compile, so it's very nice to use for wrapping standard libraries written by someone else, and already exists in binary versions for Windows and OS X.

Extract Month and Year From Date in R

Use substring?

d = "2004-02-06"

HTML/CSS: Making two floating divs the same height

By using css property --> display:table-cell

div {_x000D_
    border: 1px solid #000;_x000D_
    margin: 5px;_x000D_
    padding: 4px;_x000D_
 width:25% ;position:relative;_x000D_
 border-spacing:5px 5px}
    This is my div one This is my div one This is my div one_x000D_
    This is my div two This is my div two This is my div two This is my div two This is my div two This is my div two_x000D_
    This is my div 3 This is my div 3 This is my div 3 This is my div 3 This is my div 3 This is my div 3 This is my div 3 This is my div 3 This is my div 3 This is my div 3 This is my div 3 This is my div 3_x000D_

How can I disable a specific LI element inside a UL?

Using JQuery :


In :

<ul class="lul">
    <li class="one">a</li>
    <li class="two">b</li>
    <li class="three">c</li>

On document ready.

What is JAVA_HOME? How does the JVM find the javac path stored in JAVA_HOME?

JAVA_HOME and JRE_HOME are not used by Java itself. Some third-party programs (for example Apache Tomcat) expect one of these environment variables to be set to the installation directory of the JDK or JRE. If you are not using software that requires them, you do not need to set JAVA_HOME and JRE_HOME. PATH is an environment variable used by the operating system (Windows, Mac OS X, Linux) where it will look for native executable programs to run. You should add the bin subdirectory of your JDK installation directory to the PATH, so that you can use the javac and java commands and other JDK tools in a command prompt window. Courtesy: coderanch

How do I explicitly specify a Model's table-name mapping in Rails?

class Countries < ActiveRecord::Base
    self.table_name = "cc"

In Rails 3.x this is the way to specify the table name.

How to set JAVA_HOME environment variable on Mac OS X 10.9?

Since I'm using openjdk managed with sdkman, I added

sudo ln -sfn /path/to/my/installed/jdk/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk

Adding this to your system lets java_home recognize your installed version of Java even when its not installed via standard packages

How to create empty constructor for data class in Kotlin Android

From the documentation

NOTE: On the JVM, if all of the parameters of the primary constructor have default values, the compiler will generate an additional parameterless constructor which will use the default values. This makes it easier to use Kotlin with libraries such as Jackson or JPA that create class instances through parameterless constructors.

ViewPager PagerAdapter not updating the View

This is a horrible problem and I'm happy to present an excellent solution; simple, efficient, and effective !

See below, the code shows using a flag to indicate when to return POSITION_NONE

public class ViewPagerAdapter extends PagerAdapter
    // Members
    private boolean mForceReinstantiateItem = false;

    // This is used to overcome terrible bug that Google isn't fixing
    // We know that getItemPosition() is called right after notifyDataSetChanged()
    // Therefore, the fix is to return POSITION_NONE right after the notifyDataSetChanged() was called - but only once
    public int getItemPosition(Object object)
        if (mForceReinstantiateItem)
            mForceReinstantiateItem = false;
            return POSITION_NONE;
            return super.getItemPosition(object);

    public void setData(ArrayList<DisplayContent> newContent)
        mDisplayContent = newContent;
        mForceReinstantiateItem = true;


Are lists thread-safe?

Here's a comprehensive yet non-exhaustive list of examples of list operations and whether or not they are thread safe. Hoping to get an answer regarding the obj in a_list language construct here.

Printing reverse of any String without using any predefined function?

String x = "stack overflow";
String reversed = "";
for(int i = x.length()-1 ; i>=0; i--){
    reversed = reversed+ x.charAt(i);
System.out.println("reversed string is : "+ reversed);

What is the use of "assert"?

Watch out for the parentheses. As has been pointed out above, in Python 3, assert is still a statement, so by analogy with print(..), one may extrapolate the same to assert(..) or raise(..) but you shouldn't.

This is important because:

assert(2 + 2 == 5, "Houston we've got a problem")

won't work, unlike

assert 2 + 2 == 5, "Houston we've got a problem"

The reason the first one will not work is that bool( (False, "Houston we've got a problem") ) evaluates to True.

In the statement assert(False), these are just redundant parentheses around False, which evaluate to their contents. But with assert(False,) the parentheses are now a tuple, and a non-empty tuple evaluates to True in a boolean context.

Spring data jpa- No bean named 'entityManagerFactory' is defined; Injection of autowired dependencies failed

Spring Data JPA by default looks for an EntityManagerFactory named entityManagerFactory. Check out this part of the Javadoc of EnableJpaRepositories or Table 2.1 of the Spring Data JPA documentation.

That means that you either have to rename your emf bean to entityManagerFactory or change your Spring configuration to:

<jpa:repositories base-package="your.package" entity-manager-factory-ref="emf" /> 

(if you are using XML)


@EnableJpaRepositories(basePackages="your.package", entityManagerFactoryRef="emf")

(if you are using Java Config)

List<object>.RemoveAll - How to create an appropriate Predicate

I wanted to address something none of the answers have so far:

From what I've read so far, it appears that I can use Vehicles.RemoveAll() to delete an item with a particular VehicleID. As an[sic] supplementary question, is a Generic list the best repository for these objects?

Assuming VehicleID is unique as the name suggests, a list is a terribly inefficient way to store them when you get a lot of vehicles, as removal(and other methods like Find) is still O(n). Have a look at a HashSet<Vehicle> instead, it has O(1) removal(and other methods) using:

int GetHashCode(Vehicle vehicle){return vehicle.VehicleID;}
int Equals(Vehicle v1, Vehicle v2){return v1.VehicleID == v2.VehicleID;}

Removing all vehicles with a specific EnquiryID still requires iterating over all elements this way, so you could consider a GetHashCode that returns the EnquiryID instead, depending on which operation you do more often. This has the downside of a lot of collisions if a lot of Vehicles share the same EnquiryID though.

In this case, a better alternative is to make a Dictionary<int, List<Vehicle>> that maps EnquiryIDs to Vehicles and keep that up to date when adding/removing vehicles. Removing these vehicles from a HashSet is then an O(m) operation, where m is the number of vehicles with a specific EnquiryID.

Make outer div be automatically the same height as its floating content

You may want to try self-closing floats, as detailed on

So perhaps try either overflow: auto (usually works), or overflow: hidden, as alex said.

Excel Define a range based on a cell value

Based on answer by @Cici I give here a more generic solution:


In Italian version of Excel:


Where B1-C2 cells hold these values:

  • A, 1
  • A, 5

You can change these valuese to change the final range at wish.

Splitting the formula in parts:

  • CONCATENATE(B1,C1) - result is A1
  • INDIRECT(CONCATENATE(B1,C1)) - result is reference to A1



results in


I'll write down here a couple of SEO keywords for Italian users:

  • come creare dinamicamente l'indirizzo di un intervallo in excel
  • formula per definire un intervallo di celle in excel.

Con la formula indicata qui sopra basta scrivere nelle caselle da B1 a C2 gli estremi dell'intervallo per vedelo cambiare dentro la formula stessa.

RSpec: how to test if a method was called?

it "should call 'bar' with appropriate arguments" do
  expect(subject).to receive(:bar).with("an argument I want")

Using HeapDumpOnOutOfMemoryError parameter for heap dump for JBoss

I found it hard to decipher what is meant by "working directory of the VM". In my example, I was using the Java Service Wrapper program to execute a jar - the dump files were created in the directory where I had placed the wrapper program, e.g. c:\myapp\bin. The reason I discovered this is because the files can be quite large and they filled up the hard drive before I discovered their location.

How to find out if an item is present in a std::vector?

You can try this code:

#include <algorithm>
#include <vector>

// You can use class, struct or primitive data type for Item
struct Item {
    //Some fields
typedef std::vector<Item> ItemVector;
typedef ItemVector::iterator ItemIterator;
ItemVector vtItem;
//... (init data for vtItem)
Item itemToFind;

ItemIterator itemItr;
itemItr = std::find(vtItem.begin(), vtItem.end(), itemToFind);
if (itemItr != vtItem.end()) {
    // Item found
    // doThis()
else {
    // Item not found
    // doThat()

Convert String to Integer in XSLT 1.0

XSLT 1.0 does not have an integer data type, only double. You can use number() to convert a string to a number.

How can I parse a local JSON file from assets folder into a ListView?

With Kotlin have this extension function to read the file return as string.

fun AssetManager.readAssetsFile(fileName : String): String = open(fileName).bufferedReader().use{it.readText()}

Parse the output string using any JSON parser.

What does this GCC error "... relocation truncated to fit..." mean?

Often, this error means your program is too large, and often it's too large because it contains one or more very large data objects. For example,

char large_array[1ul << 31];
int other_global;
int main(void) { return other_global; }

will produce a "relocation truncated to fit" error on x86-64/Linux, if compiled in the default mode and without optimization. (If you turn on optimization, it could, at least theoretically, figure out that large_array is unused and/or that other_global is never written, and thus generate code that doesn't trigger the problem.)

What's going on is that, by default, GCC uses its "small code model" on this architecture, in which all of the program's code and statically allocated data must fit into the lowest 2GB of the address space. (The precise upper limit is something like 2GB - 2MB, because the very lowest 2MB of any program's address space is permanently unusable. If you are compiling a shared library or position-independent executable, all of the code and data must still fit into two gigabytes, but they're not nailed to the bottom of the address space anymore.) large_array consumes all of that space by itself, so other_global is assigned an address above the limit, and the code generated for main cannot reach it. You get a cryptic error from the linker, rather than a helpful "large_array is too large" error from the compiler, because in more complex cases the compiler can't know that other_global will be out of reach, so it doesn't even try for the simple cases.

Most of the time, the correct response to getting this error is to refactor your program so that it doesn't need gigantic static arrays and/or gigabytes of machine code. However, if you really have to have them for some reason, you can use the "medium" or "large" code models to lift the limits, at the price of somewhat less efficient code generation. These code models are x86-64-specific; something similar exists for most other architectures, but the exact set of "models" and the associated limits will vary. (On a 32-bit architecture, for instance, you might have a "small" model in which the total amount of code and data was limited to something like 224 bytes.)

Jackson - Deserialize using generic class

public class Data<T> extends JsonDeserializer implements ContextualDeserializer {
    private Class<T> cls;
    public JsonDeserializer createContextual(DeserializationContext ctx, BeanProperty prop) throws JsonMappingException {
        cls = (Class<T>) ctx.getContextualType().getRawClass();
        return this;

not finding android sdk (Unity)

Unity 5.6.1 / 2017.1 fixes the Android SDK Tools 25.3.1+ compatibility issue. This is noted in Unity bug tracker under issue 888859 and their 5.6.1 release notes.

How to round the corners of a button

Swift 4 Update

I also tried many options still i wasn't able to get my UIButton round cornered. I added the corner radius code inside the viewDidLayoutSubviews() Solved My issue.

func viewDidLayoutSubviews() {
        anyButton.layer.cornerRadius = anyButton.frame.height / 2

Also we can adjust the cornerRadius as follows

func viewDidLayoutSubviews() {
        anyButton.layer.cornerRadius = 10 //Any suitable number as you prefer can be applied 

How to upgrade PowerShell version from 2.0 to 3.0

Just run this in a console.

@powershell -NoProfile -ExecutionPolicy unrestricted -Command "iex ((new-object net.webclient).DownloadString(''))" && SET PATH=%PATH%;%systemdrive%\chocolatey\bin
cinst powershell

It installs the latest version using a Chocolatey repository.

Originally I was using command cinst powershell 3.0.20121027, but it looks like it later stopped working. Since this question is related to PowerShell 3.0 this was the right way. At this moment (June 26, 2014) cinst powershell refers to version 3.0 of PowerShell, and that may change in future.

See the Chocolatey PowerShell package page for details on what version will be installed.

SQLite add Primary Key

You can do it like this:

CREATE TABLE mytable (
field1 text,
field2 text,
field3 integer,
PRIMARY KEY (field1, field2)

Could not create the Java virtual machine

Set the JVM memory:

export _JAVA_OPTIONS=-Xmx512M

Make XmlHttpRequest POST using JSON

If you use JSON properly, you can have nested object without any issue :

var xmlhttp = new XMLHttpRequest();   // new HttpRequest instance 
var theUrl = "/json-handler";"POST", theUrl);
xmlhttp.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
xmlhttp.send(JSON.stringify({ "email": "[email protected]", "response": { "name": "Tester" } }));

How can I add a variable to console.log?

You can use the backslash to include both the story and the players name in one line.

var name=prompt("what is your name?"); console.log("story"\name\"story");

NLS_NUMERIC_CHARACTERS setting for decimal

You can see your current session settings by querying nls_session_parameters:

select value
from nls_session_parameters
where parameter = 'NLS_NUMERIC_CHARACTERS';


That may differ from the database defaults, which you can see in nls_database_parameters.

In this session your query errors:

select to_number('100,12') from dual;

Error report -
SQL Error: ORA-01722: invalid number
01722. 00000 -  "invalid number"

I could alter my session, either directly with alter session or by ensuring my client is configured in a way that leads to the setting the string needs (it may be inherited from a operating system or Java locale, for example):

alter session set NLS_NUMERIC_CHARACTERS = ',.';
select to_number('100,12') from dual;


In SQL Developer you can set your preferred value in Tool->Preferences->Database->NLS.

But I can also override that session setting as part of the query, with the optional third nlsparam parameter to to_number(); though that makes the optional second fmt parameter necessary as well, so you'd need to be able pick a suitable format:

alter session set NLS_NUMERIC_CHARACTERS = '.,';
select to_number('100,12', '99999D99', 'NLS_NUMERIC_CHARACTERS='',.''')
from dual;


By default the result is still displayed with my session settings, so the decimal separator is still a period.

Remove certain characters from a string

You can use Replace function as;

REPLACE ('Your String with cityname here', 'cityname', 'xyz')
'Your String with xyz here'

If you apply this to a table column where stringColumnName, cityName both are columns of YourTable

SELECT REPLACE(stringColumnName, cityName, '')
FROM YourTable

Or if you want to remove 'cityName' string from out put of a column then

SELECT REPLACE(stringColumnName, 'cityName', '')
FROM yourTable

EDIT: Since you have given more details now, REPLACE function is not the best method to sort your problem. Following is another way of doing it. Also @MartinSmith has given a good answer. Now you have the choice to select again.

SELECT RIGHT (O.Ort, LEN(O.Ort) - LEN(C.CityName)-1) As WithoutCityName
FROM   tblOrtsteileGeo O
       JOIN dbo.Cities C
         ON =
WHERE  O.GKZ = '06440004'

Converting a PDF to PNG

To convert pdf to image files use following commands:

For PNG gs -sDEVICE=png16m -dTextAlphaBits=4 -r300 -o a.png a.pdf

For JPG gs -sDEVICE=jpeg -dTextAlphaBits=4 -r300 -o a.jpg a.pdf

If you have multiple pages add to name %03d gs -o a%03d.jpg a.pdf

What each option means:

  • sDEVICE={jpeg,pngalpha,png16m...} - filetype
  • -o - output file (%stdout to stdout)
  • -dTextAlphaBits=4 - font antialiasing.
  • -r300 - 300 dpi

How to pass a datetime parameter?

By looking at your code, I assume you do not have a concern about the 'Time' of the DateTime object. If so, you can pass the date, month and the year as integer parameters. Please see the following code. This is a working example from my current project.

The advantage is; this method helps me to avoid DateTime format issues and culture incompatibilities.

    /// <summary>
    /// Get Arrivals Report Seven Day Forecast
    /// </summary>
    /// <param name="day"></param>
    /// <param name="month"></param>
    /// <param name="year"></param>
    /// <returns></returns>
    public async Task<ActionResult<List<ArrivalsReportSevenDayForecastModel>>> GetArrivalsReportSevenDayForecast(int day, int month, int year)
        DateTime selectedDate = new DateTime(year, month, day);
        IList<ArrivalsReportSevenDayForecastModel> arrivingStudents = await _applicationService.Value.GetArrivalsReportSevenDayForecast(selectedDate);
        return Ok(arrivingStudents);

If you are keen to see the front-end as well, feel free to read the code below. Unfortunately, that is written in Angular. This is how I normally pass a DateTime as a query parameter in Angular GET requests.

public getArrivalsReportSevenDayForecast(selectedDate1 : Date): Observable<ArrivalsReportSevenDayForecastModel[]> {
const params = new HttpParams();
const day = selectedDate1.getDate();
const month = selectedDate1.getMonth() + 1
const year = selectedDate1.getFullYear();

const data = this.svcHttp.get<ArrivalsReportSevenDayForecastModel[]>(this.routePrefix +
  `/arrivalreportsevendayforecast/${day}/${month}/${year}`, { params: params }).pipe(
  map<ArrivalsReportSevenDayForecastModel[], ArrivalsReportSevenDayForecastModel[]>(arrivingList => {
    // do mapping here if needed       
    return arrivingList;
  catchError((err) => this.svcError.handleError(err)));

return data;

sudo: docker-compose: command not found

Or, just add your binary path into the PATH. At the end of the bashrc:

export PATH=$PATH:/home/user/.local/bin/

save the file and run:

source .bashrc

and the command will work.

Is there a JavaScript function that can pad a string to get to a determined length?

A faster method

If you are doing this repeatedly, for example to pad values in an array, and performance is a factor, the following approach can give you nearly a 100x advantage in speed (jsPerf) over other solution that are currently discussed on the inter webs. The basic idea is that you are providing the pad function with a fully padded empty string to use as a buffer. The pad function just appends to string to be added to this pre-padded string (one string concat) and then slices or trims the result to the desired length.

function pad(pad, str, padLeft) {
  if (typeof str === 'undefined') 
    return pad;
  if (padLeft) {
    return (pad + str).slice(-pad.length);
  } else {
    return (str + pad).substring(0, pad.length);

For example, to zero pad a number to a length of 10 digits,


To pad a string with whitespace, so the entire string is 255 characters,

var padding = Array(256).join(' '), // make a string of 255 spaces

Performance Test

See the jsPerf test here.

And this is faster than ES6 string.repeat by 2x as well, as shown by the revised JsPerf here

Please note that jsPerf is no longer online

Please note that the jsPerf site that we originally used to benchmark the various methods is no longer online. Unfortunately, this means we can't get to those test results. Sad but true.

Python subprocess.Popen "OSError: [Errno 12] Cannot allocate memory"

swap may not be the red herring previously suggested. How big is the python process in question just before the ENOMEM?

Under kernel 2.6, /proc/sys/vm/swappiness controls how aggressively the kernel will turn to swap, and overcommit* files how much and how precisely the kernel may apportion memory with a wink and a nod. Like your facebook relationship status, it's complicated.

...but swap is actually available on demand (according to the web host)...

but not according to the output of your free(1) command, which shows no swap space recognized by your server instance. Now, your web host may certainly know much more than I about this topic, but virtual RHEL/CentOS systems I've used have reported swap available to the guest OS.

Adapting Red Hat KB Article 15252:

A Red Hat Enterprise Linux 5 system will run just fine with no swap space at all as long as the sum of anonymous memory and system V shared memory is less than about 3/4 the amount of RAM. .... Systems with 4GB of ram or less [are recommended to have] a minimum of 2GB of swap space.

Compare your /proc/sys/vm settings to a plain CentOS 5.3 installation. Add a swap file. Ratchet down swappiness and see if you live any longer.

How to add images in select list?

You already have several answers that suggest using JavaScript/jQuery. I am going to add an alternative that only uses HTML and CSS without any JS.

The basic idea is to use a set of radio buttons and labels (that will activate/deactivate the radio buttons), and with CSS control that only the label associated to the selected radio button will be displayed. If you want to allow selecting multiple values, you could achieve it by using checkboxes instead of radio buttons.

Here is an example. The code may be a bit messier (specially compared to the other solutions):

.select-sim {_x000D_
  border:1px solid #ccc;_x000D_
.select-sim::after {_x000D_
  transform:translate(0, -50%);_x000D_
.select-sim:hover::after {_x000D_
.select-sim:hover {_x000D_
.select-sim:hover .options .option label {_x000D_
.select-sim:hover .options {_x000D_
  border:1px solid #ccc;_x000D_
.select-sim .options .option {_x000D_
.select-sim:hover .options .option {_x000D_
.select-sim .options .option img {_x000D_
.select-sim .options .option label {_x000D_
.select-sim .options .option input {_x000D_
  /* fix specific for Firefox */_x000D_
  position: absolute;_x000D_
  left: -10000px;_x000D_
.select-sim .options .option input:checked + label {_x000D_
.select-sim:hover .options .option input + label {_x000D_
.select-sim:hover .options .option input:checked + label {_x000D_
<div class="select-sim" id="select-color">_x000D_
  <div class="options">_x000D_
    <div class="option">_x000D_
      <input type="radio" name="color" value="" id="color-" checked />_x000D_
      <label for="color-">_x000D_
        <img src="" alt="" /> Select an option_x000D_
    <div class="option">_x000D_
      <input type="radio" name="color" value="red" id="color-red" />_x000D_
      <label for="color-red">_x000D_
        <img src="" alt="" /> Red_x000D_
    <div class="option">_x000D_
      <input type="radio" name="color" value="green" id="color-green" />_x000D_
      <label for="color-green">_x000D_
        <img src="" alt="" /> Green_x000D_
    <div class="option">_x000D_
      <input type="radio" name="color" value="blue" id="color-blue" />_x000D_
      <label for="color-blue">_x000D_
        <img src="" alt="" /> Blue_x000D_
    <div class="option">_x000D_
      <input type="radio" name="color" value="yellow" id="color-yellow" />_x000D_
      <label for="color-yellow">_x000D_
        <img src="" alt="" /> Yellow_x000D_
    <div class="option">_x000D_
      <input type="radio" name="color" value="pink" id="color-pink" />_x000D_
      <label for="color-pink">_x000D_
        <img src="" alt="" /> Pink_x000D_
    <div class="option">_x000D_
      <input type="radio" name="color" value="turquoise" id="color-turquoise" />_x000D_
      <label for="color-turquoise">_x000D_
        <img src="" alt="" /> Turquoise_x000D_

CSS: auto height on containing div, 100% height on background div inside containing div

In 2018 a lot of browsers support the Flexbox and Grid which are very powerful CSS display modes that overshine classical methods such as Faux Columns or Tabular Displays (which are treated later in this answer).

In order to implement this with the Grid, it is enough to specify display: grid and grid-template-columns on the container. The grid-template-columns depends on the number of columns you have, in this example I will use 3 columns, hence the property will look: grid-template-columns: auto auto auto, which basically means that each of the columns will have auto width.

Full working example with Grid:

html, body {_x000D_
    padding: 0;_x000D_
    margin: 0;_x000D_
.grid-container {_x000D_
    display: grid;_x000D_
    grid-template-columns: auto auto auto;_x000D_
    width: 100%;_x000D_
.grid-item {_x000D_
    padding: 20px;_x000D_
.a {_x000D_
    background-color: DarkTurquoise;_x000D_
.b {_x000D_
    background-color: LightSalmon;_x000D_
.c {_x000D_
    background-color: LightSteelBlue;_x000D_
<!DOCTYPE html>_x000D_
    <title>Three Columns with Grid</title>_x000D_
    <link rel="stylesheet" type="text/css" href="style.css">_x000D_
    <div class="grid-container">_x000D_
        <div class="grid-item a">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas id sapien auctor, faucibus felis et, commodo magna. Sed eu molestie nibh, ac tincidunt turpis. Pellentesque accumsan nunc non arcu tincidunt auctor eget ut magna. In vel est egestas, ultricies dui a, gravida diam. Vivamus tempor facilisis lectus nec porta.</p>_x000D_
        <div class="grid-item b">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas id sapien auctor, faucibus felis et, commodo magna. Sed eu molestie nibh, ac tincidunt turpis. Pellentesque accumsan nunc non arcu tincidunt auctor eget ut magna. In vel est egestas, ultricies dui a, gravida diam. Vivamus tempor facilisis lectus nec porta. Donec commodo elit mattis, bibendum turpis eu, malesuada nunc. Vestibulum sit amet dui tincidunt, mattis nisl et, tincidunt eros. Vivamus eu ultrices sapien. Integer leo arcu, lobortis sed tellus in, euismod ultricies massa. Mauris gravida quis ligula nec dignissim. Proin elementum mattis fringilla. Donec id malesuada orci, eu aliquam ipsum. Vestibulum fermentum elementum egestas. Quisque sit amet tempor mi.</p>_x000D_
        <div class="grid-item c">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas id sapien auctor, faucibus felis et, commodo magna. Sed eu molestie nibh, ac tincidunt turpis.</p>_x000D_

Another way would be to use the Flexbox by specifying display: flex on the container of the columns, and giving the columns a relevant width. In the example that I will be using, which is with 3 columns, you basically need to split 100% in 3, so it's 33.3333% (close enough, who cares about 0.00003333... which isn't visible anyway).

Full working example using Flexbox:

html, body {_x000D_
    padding: 0;_x000D_
    margin: 0;_x000D_
.flex-container {_x000D_
    display: flex;_x000D_
    width: 100%;_x000D_
.flex-column {_x000D_
    padding: 20px;_x000D_
    width: 33.3333%;_x000D_
.a {_x000D_
    background-color: DarkTurquoise;_x000D_
.b {_x000D_
    background-color: LightSalmon;_x000D_
.c {_x000D_
    background-color: LightSteelBlue;_x000D_
<!DOCTYPE html>_x000D_
    <title>Three Columns with Flexbox</title>_x000D_
    <link rel="stylesheet" type="text/css" href="style.css">_x000D_
    <div class="flex-container">_x000D_
        <div class="flex-column a">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas id sapien auctor, faucibus felis et, commodo magna. Sed eu molestie nibh, ac tincidunt turpis. Pellentesque accumsan nunc non arcu tincidunt auctor eget ut magna. In vel est egestas, ultricies dui a, gravida diam. Vivamus tempor facilisis lectus nec porta.</p>_x000D_
        <div class="flex-column b">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas id sapien auctor, faucibus felis et, commodo magna. Sed eu molestie nibh, ac tincidunt turpis. Pellentesque accumsan nunc non arcu tincidunt auctor eget ut magna. In vel est egestas, ultricies dui a, gravida diam. Vivamus tempor facilisis lectus nec porta. Donec commodo elit mattis, bibendum turpis eu, malesuada nunc. Vestibulum sit amet dui tincidunt, mattis nisl et, tincidunt eros. Vivamus eu ultrices sapien. Integer leo arcu, lobortis sed tellus in, euismod ultricies massa. Mauris gravida quis ligula nec dignissim. Proin elementum mattis fringilla. Donec id malesuada orci, eu aliquam ipsum. Vestibulum fermentum elementum egestas. Quisque sit amet tempor mi.</p>_x000D_
        <div class="flex-column c">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas id sapien auctor, faucibus felis et, commodo magna. Sed eu molestie nibh, ac tincidunt turpis.</p>_x000D_

The Flexbox and Grid are supported by all major browsers since 2017/2018, fact also confirmed by Can I use grid, Can I use flex.

There are also a number of classical solutions, used before the age of Flexbox and Grid, like OneTrueLayout Technique, Faux Columns Technique, CSS Tabular Display Technique and there is also a Layering Technique.

I do not recommend using these methods for they have a hackish nature and are not so elegant in my opinion, but it is good to know them for academic reasons.

A solution for equally height-ed columns is the CSS Tabular Display Technique that means to use the display:table feature. It works for Firefox 2+, Safari 3+, Opera 9+ and IE8.

The code for the CSS Tabular Display:

#container {_x000D_
  display: table;_x000D_
  background-color: #CCC;_x000D_
  margin: 0 auto;_x000D_
.row {_x000D_
  display: table-row;_x000D_
.col {_x000D_
  display: table-cell;_x000D_
#col1 {_x000D_
  background-color: #0CC;_x000D_
  width: 200px;_x000D_
#col2 {_x000D_
  background-color: #9F9;_x000D_
  width: 300px;_x000D_
#col3 {_x000D_
  background-color: #699;_x000D_
  width: 200px;_x000D_
<div id="container">_x000D_
  <div id="rowWraper" class="row">_x000D_
    <div id="col1" class="col">_x000D_
      Column 1<br />Lorem ipsum<br />ipsum lorem_x000D_
    <div id="col2" class="col">_x000D_
      Column 2<br />Eco cologna duo est!_x000D_
    <div id="col3" class="col">_x000D_
      Column 3_x000D_

Even if there is a problem with the auto-expanding of the width of the table-cell it can be resolved easy by inserting another div withing the table-cell and giving it a fixed width. Anyway, the over-expanding of the width happens in the case of using extremely long words (which I doubt anyone would use a, let's say, 600px long word) or some div's who's width is greater than the table-cell's width.

The Faux Column Technique is the most popular classical solution to this problem, but it has some drawbacks such as, you have to resize the background tiled image if you want to resize the columns and it is also not an elegant solution.

The OneTrueLayout Technique consists of creating a padding-bottom of an extreme big height and cut it out by bringing the real border position to the "normal logical position" by applying a negative margin-bottom of the same huge value and hiding the extent created by the padding with overflow: hidden applied to the content wraper. A simplified example would be:

Working example:

.wraper {_x000D_
    overflow: hidden; /* This is important */_x000D_
.floatLeft {_x000D_
    float: left;_x000D_
.block {_x000D_
    padding-left: 20px;_x000D_
    padding-right: 20px;_x000D_
    padding-bottom: 30000px; /* This is important */_x000D_
    margin-bottom: -30000px; /* This is important */_x000D_
    width: 33.3333%;_x000D_
    box-sizing: border-box; /* This is so that the padding right and left does not affect the width */_x000D_
.a {_x000D_
    background-color: DarkTurquoise;_x000D_
.b {_x000D_
    background-color: LightSalmon;_x000D_
.c {_x000D_
    background-color: LightSteelBlue;_x000D_
    <div class="wraper">_x000D_
        <div class="block floatLeft a">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras malesuada ipsum pretium tellus condimentum aliquam. Donec eget tempor mi, a consequat enim. Mauris a massa id nisl sagittis iaculis.</p>_x000D_
        <div class="block floatLeft b">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras malesuada ipsum pretium tellus condimentum aliquam. Donec eget tempor mi, a consequat enim. Mauris a massa id nisl sagittis iaculis. Duis mattis diam vitae tellus ornare, nec vehicula elit luctus. In auctor urna ac ante bibendum, a gravida nunc hendrerit. Praesent sed pellentesque lorem. Nam neque ante, egestas ut felis vel, faucibus tincidunt risus. Maecenas egestas diam massa, id rutrum metus lobortis non. Sed quis tellus sed nulla efficitur pharetra. Fusce semper sapien neque. Donec egestas dolor magna, ut efficitur purus porttitor at. Mauris cursus, leo ac porta consectetur, eros quam aliquet erat, condimentum luctus sapien tellus vel ante. Vivamus vestibulum id lacus vel tristique.</p>_x000D_
        <div class="block floatLeft c">_x000D_
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras malesuada ipsum pretium tellus condimentum aliquam. Donec eget tempor mi, a consequat enim. Mauris a massa id nisl sagittis iaculis. Duis mattis diam vitae tellus ornare, nec vehicula elit luctus. In auctor urna ac ante bibendum, a gravida nunc hendrerit.</p>_x000D_

The Layering Technique must be a very neat solution that involves absolute positioning of div's withing a main relative positioned wrapper div. It basically consists of a number of child divs and the main div. The main div has imperatively position: relative to it's css attribute collection. The children of this div are all imperatively position:absolute. The children must have top and bottom set to 0 and left-right dimensions set to accommodate the columns with each another. For example if we have two columns, one of width 100px and the other one of 200px, considering that we want the 100px in the left side and the 200px in the right side, the left column must have {left: 0; right: 200px} and the right column {left: 100px; right: 0;}

In my opinion the unimplemented 100% height within an automated height container is a major drawback and the W3C should consider revising this attribute (which since 2018 is solvable with Flexbox and Grid).

Other resources: link1, link2, link3, link4, link5 (important)

How do you merge two Git repositories?

If you're trying to simply glue two repositories together, submodules and subtree merges are the wrong tool to use because they don't preserve all of the file history (as people have noted on other answers). See this answer here for the simple and correct way to do this.

Error:Unknown host You may need to adjust the proxy settings in Gradle

If you are using WAMP/XAMP server turn it off. This resolved my problem.

jQuery .val() vs .attr("value")

PS: This is not an answer but just a supplement to the above answers.

Just for the future reference, I have included a good example that might help us to clear our doubt:

Try the following. In this example I shall create a file selector which can be used to select a file and then I shall try to retrieve the name of the file that I selected: The HTML code is below:

        <form action="#" method="post">
            <input id ="myfile" type="file"/>
        <script type="text/javascript" src="jquery.js"> </script>
        <script type="text/javascript" src="code.js"> </script>

The code.js file contains the following jQuery code. Try to use both of the jQuery code snippets one by one and see the output.

jQuery code with attr('value'):


jQuery code with val():



The output of jQuery code with attr('value') will be 'undefined'. The output of jQuery code with val() will the file name that you selected.

Explanation: Now you may understand easily what the top answers wanted to convey. The output of jQuery code with attr('value') will be 'undefined' because initially there was no file selected so the value is undefined. It is better to use val() because it gets the current value.

In order to see why the undefined value is returned try this code in your HTML and you'll see that now the attr.('value') returns 'test' always, because the value is 'test' and previously it was undefined.

<input id ="myfile" type="file" value='test'/>

I hope it was useful to you.

How to use font-awesome icons from node-modules

With expressjs, public it:

app.use('/stylesheets/fontawesome', express.static(__dirname + '/node_modules/@fortawesome/fontawesome-free/'));

And you can see it at:

Detect end of ScrollView

I went through the solutions on the internet. Mostly solutions didn't work in the project I'm working on. Following solutions work fine for me.

Using onScrollChangeListener (works on API 23):

   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        scrollView.setOnScrollChangeListener(new View.OnScrollChangeListener() {
            public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {

                int bottom =   (scrollView.getChildAt(scrollView.getChildCount() - 1)).getHeight()-scrollView.getHeight()-scrollY;

                    //top detected
                    //bottom detected

using scrollChangeListener on TreeObserver

 scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
        public void onScrollChanged() {
            int bottom =   (scrollView.getChildAt(scrollView.getChildCount() - 1)).getHeight()-scrollView.getHeight()-scrollView.getScrollY();

                //top detected
            if(bottom==0) {
                //bottom detected

Hope this solution helps :)

Makefile ifeq logical or

Here more flexible variant: it uses external shell, but allows to check for arbitrary conditions:

ifeq ($(shell test ".$(GCC_MINOR)" = .4  -o  \
                   ".$(GCC_MINOR)" = .5  -o  \
                   ".$(TODAY)"     = .Friday  &&  printf "true"), true)
    CFLAGS += -fno-strict-overflow

How do I send an HTML email?

If you are using Google app engine/Java, then use the following...

MimeMessage msg = new MimeMessage(session);
msg.setFrom(new InternetAddress(SENDER_EMAIL_ADDRESS, "Admin"));
                 new InternetAddress(toAddress, "user");


Multipart mp = new MimeMultipart();
MimeBodyPart htmlPart = new MimeBodyPart();
htmlPart.setContent(message, "text/html");