Programs & Examples On #Infinite

An infinite structure or process is one which does not terminate. Infinite loops or structures may be bugs in certain contexts, but also may be desired behavior, particularly in server-processes or lazy languages.

Is it possible to set a number to NaN or infinity?

Yes, you can use numpy for that.

import numpy as np
a = arange(3,dtype=float)

a[0] = np.nan
a[1] = np.inf
a[2] = -np.inf

a # is now [nan,inf,-inf]

np.isnan(a[0]) # True
np.isinf(a[1]) # True
np.isinf(a[2]) # True

Bash: infinite sleep (infinite blocking)

What about sending a SIGSTOP to itself?

This should pause the process until SIGCONT is received. Which is in your case: never.

kill -STOP "$$";
# grace time for signal delivery
sleep 60;

How can I represent an infinite number in Python?

Since Python 3.5 you can use math.inf:

>>> import math
>>> math.inf

GridView VS GridLayout in Android Apps

A GridView is a ViewGroup that displays items in two-dimensional scrolling grid. The items in the grid come from the ListAdapter associated with this view.

This is what you'd want to use (keep using). Because a GridView gets its data from a ListAdapter, the only data loaded in memory will be the one displayed on screen. GridViews, much like ListViews reuse and recycle their views for better performance.

Whereas a GridLayout is a layout that places its children in a rectangular grid.

It was introduced in API level 14, and was recently backported in the Support Library. Its main purpose is to solve alignment and performance problems in other layouts. Check out this tutorial if you want to learn more about GridLayout.

Is nested function a good approach when required by only one function?

Generally, no, do not define functions inside functions.

Unless you have a really good reason. Which you don't.

Why not?

What is a really good reason to define functions inside functions?

When what you actually want is a dingdang closure.

Inserting a PDF file in LaTeX

Use the pdfpages package.


To include all the pages in the PDF file:


To include just the first page of a PDF:


Run texdoc pdfpages in a shell to see the complete manual for pdfpages.

Multiple inputs with same name through POST in php

Change the names of your inputs:

<input name="xyz[]" value="Lorem" />
<input name="xyz[]" value="ipsum"  />
<input name="xyz[]" value="dolor" />
<input name="xyz[]" value="sit" />
<input name="xyz[]" value="amet" />


$_POST['xyz'][0] == 'Lorem'
$_POST['xyz'][4] == 'amet'

If so, that would make my life ten times easier, as I could send an indefinite amount of information through a form and get it processed by the server simply by looping through the array of items with the name "xyz".

Note that this is probably the wrong solution. Obviously, it depends on the data you are sending.

Does Django scale?

The developer advocate for YouTube gave a talk about scaling Python at PyCon 2012, which is also relevant to scaling Django.

YouTube has more than a billion users, and YouTube is built on Python.

Select from where field not equal to Mysql Php

select * from table where fiels1 NOT LIKE 'x' AND field2 NOT LIKE 'y'

//this work in case insensitive manner

Shell script - remove first and last quote (") from a variable

My version

strip_quotes() {
    while [[ $# -gt 0 ]]; do
        local value=${!1}
        local len=${#value}
        [[ ${value:0:1} == \" && ${value:$len-1:1} == \" ]] && declare -g $1="${value:1:$len-2}"

The function accepts variable name(s) and strips quotes in place. It only strips a matching pair of leading and trailing quotes. It doesn't check if the trailing quote is escaped (preceded by \ which is not itself escaped).

In my experience, general-purpose string utility functions like this (I have a library of them) are most efficient when manipulating the strings directly, not using any pattern matching and especially not creating any sub-shells, or calling any external tools such as sed, awk or grep.

var1="\"test \\ \" end \""
echo before:
for i in var{1,2,3,4}; do
    echo $i="${!i}"
strip_quotes var{1,2,3,4}
echo after:
for i in var{1,2,3,4}; do
    echo $i="${!i}"

How to run the sftp command with a password from Bash script?

You can use a Python script with scp and os library to make a system call.

  1. ssh-keygen -t rsa -b 2048 (local machine)
  2. ssh-copy-id user@remote_server_address
  3. create a Python script like:
    import os
    cmd = 'scp user@remote_server_address:remote_file_path local_file_path'
  1. create a rule in crontab to automate your script
  2. done

Creating multiple objects with different names in a loop to store in an array list

You can use this code...

public class Main {

    public static void main(String args[]) {
        String[] names = {"First", "Second", "Third"};//You Can Add More Names
        double[] amount = {20.0, 30.0, 40.0};//You Can Add More Amount
        List<Customer> customers = new ArrayList<Customer>();
        int i = 0;
        while (i < names.length) {
            customers.add(new Customer(names[i], amount[i]));

Adding rows to tbody of a table using jQuery

Here is an appendTo version using the html dropdown you mentioned. It inserts another row on "change".

$('#dropdown').on( 'change', function(e) {

With an example for you to play with. Best of luck!

Changing column names of a data frame

My column names is as below

[1] "Class"    "Sex"      "Age"      "Survived" "Freq" 

I want to change column name of Class and Sex


Convert ASCII number to ASCII Character in C

If i is the int, then

char c = i;

makes it a char. You might want to add a check that the value is <128 if it comes from an untrusted source. This is best done with isascii from <ctype.h>, if available on your system (see @Steve Jessop's comment to this answer).

How can I get the order ID in WooCommerce?

$order = new WC_Order( $post_id ); 

If you

echo $order->id;

then you'll be returned the id of the post from which the order is made. As you've already got that, it's probably not what you want.

echo $order->get_order_number();

will return the id of the order (with a # in front of it). To get rid of the #,

echo trim( str_replace( '#', '', $order->get_order_number() ) );

as per the accepted answer.

How to get row data by clicking a button in a row in an ASP.NET gridview

 protected void btnS10_click(object sender, EventArgs e)
        foreach (GridViewRow row in Grd.Rows)
            CheckBox chk_Single = (CheckBox)row.FindControl("ChkSendOne");
            if (row.RowType == DataControlRowType.DataRow)
                string id = (row.Cells[0].FindControl("lblSNo") as Label).Text;
                if (Convert.ToInt32(id) <= 10)
                    chk_Single.Checked = true;
                    if (chk_Single.Checked == true)
                        lblSelectedRecord.InnerText = (Convert.ToInt32(lblSelectedRecord.InnerText) + 1).ToString();

What is the difference between active and passive FTP?

Active mode: -server initiates the connection.

Passive mode: -client initiates the connection.

How do you clear your Visual Studio cache on Windows Vista?

The accepted answer gave two locations:


C:\Documents and Settings\Administrator\Local Settings\Temp\VWDWebCache

and possibly here

C:\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft\WebsiteCache

Did you try those?

Edited to add

On my Windows Vista machine, it's located in


and in


From your additional information (regarding team edition) this comes from Clear Client TFS Cache:

Clear Client TFS Cache

Visual Studio and Team Explorer provide a caching mechanism which can get out of sync. If I have multiple instances of a single TFS which can be connected to from a single Visual Studio client, that client can become confused.

To solve it..

For Windows Vista delete contents of this folder

%LocalAppData%\Microsoft\Team Foundation\1.0\Cache

How do I check if an HTML element is empty using jQuery?

White space and line breaks are the main issues with using :empty selector. Careful, in CSS the :empty pseudo class behaves the same way. I like this method:

if ($someElement.children().length == 0){

How can I include a YAML file inside another?

Probably it was not supported when question was asked but you can import other YAML file into one:

imports: [/your_location_to_yaml_file/Util.area.yaml]

Though I don't have any online reference but this works for me.

What's the best UI for entering date of birth?

I would take a DatePicker. It's the only component that allows expert users to enter it manually and guides novices to enter a date very easy.

The calendar should not pop up if you enter via pressing tab, but clicking on a button. So no expert user is annoyed of it.

Remove folder and its contents from git/GitHub's history

I find that the --tree-filter option used in other answers can be very slow, especially on larger repositories with lots of commits.

Here is the method I use to completely remove a directory from the git history using the --index-filter option, which runs much quicker:

# Make a fresh clone of YOUR_REPO
git clone YOUR_REPO

# Create tracking branches of all branches
for remote in `git branch -r | grep -v /HEAD`; do git checkout --track $remote ; done

# Remove DIRECTORY_NAME from all commits, then remove the refs to the old commits
# (repeat these two commands for as many directories that you want to remove)
git filter-branch --index-filter 'git rm -rf --cached --ignore-unmatch DIRECTORY_NAME/' --prune-empty --tag-name-filter cat -- --all
git for-each-ref --format="%(refname)" refs/original/ | xargs -n 1 git update-ref -d

# Ensure all old refs are fully removed
rm -Rf .git/logs .git/refs/original

# Perform a garbage collection to remove commits with no refs
git gc --prune=all --aggressive

# Force push all branches to overwrite their history
# (use with caution!)
git push origin --all --force
git push origin --tags --force

You can check the size of the repository before and after the gc with:

git count-objects -vH

Force flex item to span full row width

When you want a flex item to occupy an entire row, set it to width: 100% or flex-basis: 100%, and enable wrap on the container.

The item now consumes all available space. Siblings are forced on to other rows.

.parent {
  display: flex;
  flex-wrap: wrap;

#range, #text {
  flex: 1;

.error {
  flex: 0 0 100%; /* flex-grow, flex-shrink, flex-basis */
  border: 1px dashed black;
<div class="parent">
  <input type="range" id="range">
  <input type="text" id="text">
  <label class="error">Error message (takes full width)</label>

More info: The initial value of the flex-wrap property is nowrap, which means that all items will line up in a row. MDN

Moving Average Pandas

A moving average can also be calculated and visualized directly in a line chart by using the following code:

Example using stock price data:

import as web
import matplotlib.pyplot as plt
import datetime'ggplot')

# Input variables
start = datetime.datetime(2016, 1, 01)
end = datetime.datetime(2018, 3, 29)
stock = 'WFC'

# Extrating data
df = web.DataReader(stock,'morningstar', start, end)
df = df['Close']

print df 

plt.plot(df['WFC'],label= 'Close')
plt.plot(df['WFC'].rolling(9).mean(),label= 'MA 9 days')
plt.plot(df['WFC'].rolling(21).mean(),label= 'MA 21 days')
plt.title('Wells Fargo\nClose and Moving Averages')

Tutorial on how to do this:

How can I filter a date of a DateTimeField in Django?

See the article Django Documentation

ur_data_model.objects.filter(ur_date_field__gte=datetime(2009, 8, 22), ur_date_field__lt=datetime(2009, 8, 23))

Getting all types in a namespace via reflection

You won't be able to get all types in a namespace, because a namespace can bridge multiple assemblies, but you can get all classes in an assembly and check to see if they belong to that namespace.

Assembly.GetTypes() works on the local assembly, or you can load an assembly first then call GetTypes() on it.

How to display data from database into textbox, and update it

Populate the text box values in the Page Init event as opposed to using the Postback.

protected void Page_Init(object sender, EventArgs e)

How does += (plus equal) work?

...and don't forget what happens when you mix types:

x = 127;
x += " hours "
// x is now a string: "127 hours "
x += 1 === 0;
// x is still a string: "127 hours false"

Javascript: open new page in same window

The second parameter of is a string representing the name of the target window.

Set it to: "_self".

<a href="javascript:q=(document.location.href);void(open(''+escape(q),'_self','resizable,location,menubar,toolbar,scrollbars,status'));">click here</a>

Sidenote: The following question gives an overview of an arguably better way to bind event handlers to HTML links.

What's the best way to replace links with js functions?

MySQL error - #1932 - Table 'phpmyadmin.pma user config' doesn't exist in engine

if someone is still facing this issue, for me it started to occur after I changed my mysql/data with mysql/backup earlier to solve another issue.

I tried a lot of methods, and finally found the solution was very simple! Just click on this icon(Reset session) after opening PhPMyAdmin(it was loading in my case) just below the logo of PhPMyAdmin. It fixed the issue in one-click!

For me, the error code was #1142

PhpMyAdmin Reset Session

PhpMyAdmin Reset Session

How to download an entire directory and subdirectories using wget?

You can use this in a shell:

wget -r -nH --cut-dirs=7 --reject="index.html*" \

The Parameters are:

-r recursively download

-nH (--no-host-directories) cuts out hostname 

--cut-dirs=X (cuts out X directories)

MVC Razor @foreach

The answer will not work when using the overload to indicate the template @Html.DisplayFor(x => x.Foos, "YourTemplateName) .

Seems to be designed that way, see this case. Also the exception the framework gives (about the type not been as expected) is quite misleading and fooled me on the first try (thanks @CodeCaster)

In this case you have to use @foreach

@foreach (var item in Model.Foos)
    @Html.DisplayFor(x => item, "FooTemplate")

Serializing an object as UTF-8 XML in .NET

I found this blog post which explains the problem very well, and defines a few different solutions:

(dead link removed)

I've settled for the idea that the best way to do it is to completely omit the XML declaration when in memory. It actually is UTF-16 at that point anyway, but the XML declaration doesn't seem meaningful until it has been written to a file with a particular encoding; and even then the declaration is not required. It doesn't seem to break deserialization, at least.

As @Jon Hanna mentions, this can be done with an XmlWriter created like this:

XmlWriter writer = XmlWriter.Create (output, new XmlWriterSettings() { OmitXmlDeclaration = true });

Update using LINQ to SQL

In the absence of more detailed info:

using(var dbContext = new dbDataContext())
    var data = dbContext.SomeTable.SingleOrDefault(row => == requiredId);
    if(data != null)
        data.SomeField = newValue;

Position Relative vs Absolute?

Marco Pellicciotta: The position of the element inside another element can be relative or absolute, about the element it's inside.

If you need to position the element in the browser window point of view it's best to use position:fixed

How to convert a ruby hash object to JSON?

You can also use JSON.generate:

require 'json'

JSON.generate({ foo: "bar" })
=> "{\"foo\":\"bar\"}"

Or its alias, JSON.unparse:

require 'json'

JSON.unparse({ foo: "bar" })
=> "{\"foo\":\"bar\"}"

How do I move a table into a schema in T-SQL

ALTER SCHEMA TargetSchema 
    TRANSFER SourceSchema.TableName;

If you want to move all tables into a new schema, you can use the undocumented (and to be deprecated at some point, but unlikely!) sp_MSforeachtable stored procedure:

exec sp_MSforeachtable "ALTER SCHEMA TargetSchema TRANSFER ?"


SQL 2008: How do I change db schema to dbo

Oracle PL/SQL - How to create a simple array variable?

Another solution is to use an Oracle Collection as a Hashmap:

-- create a type for your "Array" - it can be of any kind, record might be useful
  type hash_map is table of varchar2(1000) index by varchar2(30);
  my_hmap hash_map ;
-- i will be your iterator: it must be of the index's type
  i varchar2(30);
  my_hmap('a') := 'apple';
  my_hmap('b') := 'box';
  my_hmap('c') := 'crow';
-- then how you use it:

  dbms_output.put_line (my_hmap('c')) ;

-- or to loop on every element - it's a "collection"
  i := my_hmap.FIRST;

  while (i is not null)  loop     
    i := my_hmap.NEXT(i);
  end loop;


case statement in SQL, how to return multiple variables?

You can return multiple value inside a xml data type in "case" expression, then extract them, also "else" block is available

xmlcol.value('(value1)[1]', 'NVARCHAR(MAX)') AS value1,
xmlcol.value('(value2)[1]', 'NVARCHAR(MAX)') AS value2
WHEN <condition 1> THEN
CAST((SELECT a1 AS value1, b1 AS value2 FOR XML PATH('')) AS XML)
WHEN <condition 2> THEN
CAST((SELECT a2 AS value1, b2 AS value2 FOR XML PATH('')) AS XML)
CAST((SELECT a3 AS value1, b3 AS value2 FOR XML PATH('')) AS XML)
END AS xmlcol
FROM <table>) AS tmp

How to align flexbox columns left and right?

I came up with 4 methods to achieve the results. Here is demo

Method 1:

#a {
    margin-right: auto;

Method 2:

#a {
    flex-grow: 1;

Method 3:

#b {
    margin-left: auto;

Method 4:

#container {
    justify-content: space-between;

Visual Studio move project to a different folder

It's easy in VS2012; just use the change mapping feature:

  1. Create the folder where you want the solution to be moved to.
  2. Check-in all your project files (if you want to keep you changes), or rollback any checked out files.
  3. Close the solution.
  4. Open the Source Control Explorer.
  5. Right-click the solution, and select "Advanced -> Remove Mapping..."
  6. Change the "Local Folder" value to the one you created in step #1.
  7. Select "Change".
  8. Open the solution by double-clicking it in the source control explorer.

How to configure slf4j-simple

This is a sample which you can place on the classpath (uncomment the properties you wish to use):

# SLF4J's SimpleLogger configuration file
# Simple implementation of Logger that sends all enabled log messages, for all defined loggers, to System.err.

# Default logging detail level for all instances of SimpleLogger.
# Must be one of ("trace", "debug", "info", "warn", or "error").
# If not specified, defaults to "info".

# Logging detail level for a SimpleLogger instance named "xxxxx".
# Must be one of ("trace", "debug", "info", "warn", or "error").
# If not specified, the default logging detail level is used.

# Set to true if you want the current date and time to be included in output messages.
# Default is false, and will output the number of milliseconds elapsed since startup.

# The date and time format to be used in the output messages.
# The pattern describing the date and time format is the same that is used in java.text.SimpleDateFormat.
# If the format is not specified or is invalid, the default format is used.
# The default format is yyyy-MM-dd HH:mm:ss:SSS Z.
#org.slf4j.simpleLogger.dateTimeFormat=yyyy-MM-dd HH:mm:ss:SSS Z

# Set to true if you want to output the current thread name.
# Defaults to true.

# Set to true if you want the Logger instance name to be included in output messages.
# Defaults to true.

# Set to true if you want the last component of the name to be included in output messages.
# Defaults to false.

How to call a method defined in an AngularJS directive?

Maybe this is not the best choice, but you can do angular.element("#element").isolateScope() or $("#element").isolateScope() to access the scope and/or the controller of your directive.

Change background position with jQuery

rebellion's answer above won't actually work, because to CSS, 'background-position' is actually shorthand for 'background-position-x' and 'background-position-y' so the correct version of his code would be:

    $('#submenu li').hover(function(){
        $('#carousel').css('background-position-x', newValueX);
        $('#carousel').css('background-position-y', newValue);
    }, function(){
        $('#carousel').css('background-position-x', oldValueX);
        $('#carousel').css('background-position-y', oldValueY);

It took about 4 hours of banging my head against it to come to that aggravating realization.

How to increase the gap between text and underlining in CSS

I was able to Do it using the U (Underline Tag)

u {
    text-decoration: none;
    position: relative;
u:after {
    content: '';
    width: 100%;
    position: absolute;
    left: 0;
    bottom: 1px;
    border-width: 0 0 1px;
    border-style: solid;

<a href="" style="text-decoration:none">
    <div style="text-align: right; color: Red;">
        <u> Shop Now</u>

How do I properly force a Git push?

And if push --force doesn't work you can do push --delete. Look at 2nd line on this instance:

git reset --hard HEAD~3  # reset current branch to 3 commits ago
git push origin master --delete  # do a very very bad bad thing
git push origin master  # regular push

But beware...

Never ever go back on a public git history!

In other words:

  • Don't ever force push on a public repository.
  • Don't do this or anything that can break someone's pull.
  • Don't ever reset or rewrite history in a repo someone might have already pulled.

Of course there are exceptionally rare exceptions even to this rule, but in most cases it's not needed to do it and it will generate problems to everyone else.

Do a revert instead.

And always be careful with what you push to a public repo. Reverting:

git revert -n HEAD~3..HEAD  # prepare a new commit reverting last 3 commits
git commit -m "sorry - revert last 3 commits because I was not careful"
git push origin master  # regular push

In effect, both origin HEADs (from the revert and from the evil reset) will contain the same files.

edit to add updated info and more arguments around push --force

Consider pushing force with lease instead of push, but still prefer revert

Another problem push --force may bring is when someone push anything before you do, but after you've already fetched. If you push force your rebased version now you will replace work from others.

git push --force-with-lease introduced in the git 1.8.5 (thanks to @VonC comment on the question) tries to address this specific issue. Basically, it will bring an error and not push if the remote was modified since your latest fetch.

This is good if you're really sure a push --force is needed, but still want to prevent more problems. I'd go as far to say it should be the default push --force behaviour. But it's still far from being an excuse to force a push. People who fetched before your rebase will still have lots of troubles, which could be easily avoided if you had reverted instead.

And since we're talking about git --push instances...

Why would anyone want to force push?

@linquize brought a good push force example on the comments: sensitive data. You've wrongly leaked data that shouldn't be pushed. If you're fast enough, you can "fix"* it by forcing a push on top.

* The data will still be on the remote unless you also do a garbage collect, or clean it somehow. There is also the obvious potential for it to be spread by others who'd fetched it already, but you get the idea.

Drop all the tables, stored procedures, triggers, constraints and all the dependencies in one sql statement

To drop all tables:

exec sp_MSforeachtable 'DROP TABLE ?'

This will, of course, drop all constraints, triggers etc., everything but the stored procedures.

For the stored procedures I'm afraid you will need another stored procedure stored in master.

How to analyze disk usage of a Docker container

(this answer is not useful, but leaving it here since some of the comments may be)

docker images will show the 'virtual size', i.e. how much in total including all the lower layers. So some double-counting if you have containers that share the same base image.


How to hide reference counts in VS2013?


In VS 2015 Professional (and probably other versions). Go to Tools / Options / Environment / Fonts and Colours. In the "Show Settings For" drop-down, select "CodeLens" Choose the smallest font you can find e.g. Calibri 6. Change the foreground colour to your editor foreground colour (say "White") Click OK.

How to select the first element in the dropdown using jquery?

I'm answering because the previous answers have stopped working with the latest version of jQuery. I don't know when it stopped working, but the documentation says that .prop() has been the preferred method to get/set properties since jQuery 1.6.

This is how I got it to work (with jQuery 3.2.1):

$('select option:nth-child(1)').prop("selected", true);

I am using knockoutjs and the change bindings weren't firing with the above code, so I added .change() to the end.

Here's what I needed for my solution:

$('select option:nth-child(1)').prop("selected", true).change();

See .prop() notes in the documentation here:

Android: How do I get string from resources using its name?

getResources().getString(getResources().getIdentifier("propertyName", "string", getPackageName()))

How to get a list of installed android applications and pick one to run

If there are multiple launchers in a one package above code has a problem. Eg: on LG Optimus Facebook for LG, MySpace for LG, Twitter for LG contains in a one package name SNS and if you use above SNS will repeat. After hours of research I came with below code. Seems to work well.

private List<String> getInstalledComponentList()
            throws NameNotFoundException {
        final Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
        List<ResolveInfo> ril = getPackageManager().queryIntentActivities(mainIntent, 0);
        List<String> componentList = new ArrayList<String>();
        String name = null;

        for (ResolveInfo ri : ril) {
            if (ri.activityInfo != null) {
                Resources res = getPackageManager().getResourcesForApplication(ri.activityInfo.applicationInfo);
                if (ri.activityInfo.labelRes != 0) {
                    name = res.getString(ri.activityInfo.labelRes);
                } else {
                    name = ri.activityInfo.applicationInfo.loadLabel(
        return componentList;

libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

It could also be wrong Segue Identifier Name. Eg -

performSegueWithIdentifier("wrongSegueName", sender: self)

How can I debug a HTTP POST in Chrome?

You can use Canary version of Chrome to see request payload of POST requests.

Request payload

How do I add a simple onClick event handler to a canvas element?

I recommand the following article : Hit Region Detection For HTML5 Canvas And How To Listen To Click Events On Canvas Shapes which goes through various situations.

However, it does not cover the addHitRegion API, which must be the best way (using math functions and/or comparisons is quite error prone). This approach is detailed on developer.mozilla

Visual studio code CSS indentation and formatting

Beautify (Github) & Prettier (Github) are the best plugin for web development in Visual Studio Code.

How do I convert a datetime to date?

You use the method:

Obviously, the expression above can (and should IMHO :) be written as:

How to Configure SSL for Amazon S3 bucket

Custom domain SSL certs were just added today for $600/cert/month. Sign up for your invite below:

Update: SNI customer provided certs are now available for no additional charge. Much cheaper than $600/mo, and with XP nearly killed off, it should work well for most use cases.

@skalee AWS has a mechanism for achieving what the poster asks for, "implement SSL for an Amazon s3 bucket", it's called CloudFront. I'm reading "implement" as "use my SSL certs," not "just put an S on the HTTP URL which I'm sure the OP could have surmised.

Since CloudFront costs exactly the same as S3 ($0.12/GB), but has a ton of additional features around SSL AND allows you to add your own SNI cert at no additional cost, it's the obvious fix for "implementing SSL" on your domain.

Error: Configuration with name 'default' not found in Android Studio

If you want to use the same library folder for several projects, you can reference it in gradle to an external location like this:


include 'app', ':volley'
project(':volley').projectDir = new File('../libraries/volley')

in your app build.gradle

dependencies {
    compile project(':volley')

C# winforms combobox dynamic autocomplete

Here is my final solution. It works fine with a large amount of data. I use Timer to make sure the user want find current value. It looks like complex but it doesn't. Thanks to Max Lambertini for the idea.

        private bool _canUpdate = true; 

        private bool _needUpdate = false;       

        //If text has been changed then start timer
        //If the user doesn't change text while the timer runs then start search
        private void combobox1_TextChanged(object sender, EventArgs e)
            if (_needUpdate)
                if (_canUpdate)
                    _canUpdate = false;

        private void UpdateData()
            if (combobox1.Text.Length > 1)
                List<string> searchData = Search.GetData(combobox1.Text);

        //If an item was selected don't start new search
        private void combobox1_SelectedIndexChanged(object sender, EventArgs e)
            _needUpdate = false;

        //Update data only when the user (not program) change something
        private void combobox1_TextUpdate(object sender, EventArgs e)
            _needUpdate = true;

        //While timer is running don't start search
        //timer1.Interval = 1500;
        private void RestartTimer()
            _canUpdate = false;

        //Update data when timer stops
        private void timer1_Tick(object sender, EventArgs e)
            _canUpdate = true;

        //Update combobox with new data
        private void HandleTextChanged(List<string> dataSource)
            var text = combobox1.Text;

            if (dataSource.Count() > 0)
                combobox1.DataSource = dataSource;  

                var sText = combobox1.Items[0].ToString();
                combobox1.SelectionStart = text.Length;
                combobox1.SelectionLength = sText.Length - text.Length;
                combobox1.DroppedDown = true;

                combobox1.DroppedDown = false;
                combobox1.SelectionStart = text.Length;

This solution isn't very cool. So if someone has another solution please share it with me.

PHP convert XML to JSON

Optimizing Antonio Max answer:

$xmlfile = 'yourfile.xml';
$xmlparser = xml_parser_create();

// open a file and read data
$fp = fopen($xmlfile, 'r');
//9999999 is the length which fread stops to read.
$xmldata = fread($fp, 9999999);

// converting to XML
$xml = simplexml_load_string($xmldata, "SimpleXMLElement", LIBXML_NOCDATA);

// converting to JSON
$json = json_encode($xml);
$array = json_decode($json,TRUE);

How do I import a namespace in Razor View Page?

One issue that you must know is that when you import a namespace via web.config in Views folder, that namespace is imported JUST for views in that folder. Means if you want to import a namespace in an area views, you must also import that namespace, in that area's web.config file, located in area's Views folder;

VBA: How to display an error message just like the standard error message which has a "Debug" button?

First the good news. This code does what you want (please note the "line numbers")

Sub a()
 10:    On Error GoTo ErrorHandler
 20:    DivisionByZero = 1 / 0
 30:    Exit Sub
 41: If Err.Number <> 0 Then
 42:    Msg = "Error # " & Str(Err.Number) & " was generated by " _
         & Err.Source & Chr(13) & "Error Line: " & Erl & Chr(13) & Err.Description
 43:    MsgBox Msg, , "Error", Err.HelpFile, Err.HelpContext
 44:    End If
 50:    Resume Next
 60: End Sub

When it runs, the expected MsgBox is shown:

alt text

And now the bad news:
Line numbers are a residue of old versions of Basic. The programming environment usually took charge of inserting and updating them. In VBA and other "modern" versions, this functionality is lost.

However, Here there are several alternatives for "automatically" add line numbers, saving you the tedious task of typing them ... but all of them seem more or less cumbersome ... or commercial.


How do I test a private function or a class that has private methods, fields or inner classes?

PowerMock.Whitebox is the best option I have seen, but when I read its source code, it reads private fields with reflection, so I think I have my answer:

  • test private internal states(fields) with PowerMock, or just reflection without the overhead of introducing another independency
  • for private methods: actually, the upvote for this question itself, and the huge number of comments and answers, shows that it is a very concurrent and controversial topic where no definite answer could be given to suit every circumstance. I understand that only contract should be tested, but we also have coverage to consider. Actually, I doubt that only testing contracts will 100% make a class immune to errors. Private methods are those who process data in the class where it is defined and thus does not interest other classes, so we cannot simply expose to make it testable. I will try not to test them, but when you have to, just go for it and forget all the answers here. You know better your situation and restrictions than any other one in the Internet. When you have control over your code, use that. With consideration, but without over-thinking.

After some time, when I reconsider it, I still believe this is true, but I saw better approaches.

First of all, Powermock.Whitebox is still usable.

And, Mockito Whitebox has been hidden after v2(the latest version I can find with Whitebox is testImplementation 'org.mockito:mockito-core:1.10.19') and it has always been part of org.mockito.internal package, which is prone of breaking changes in the future(see this post). So now I tend not to use it.

In Gradle/Maven projects, if you define private methods or fields, there is no other ways then reflection to get access to them, so the first part stays true. But, if you change the visibility to "package private", the tests following the same structure in test package will have access to them. That is also another important reason why we are encouraged to create the same hierarchy in main and test package. So, when you have control over production code as well as tests, delete that private access modifier may be the best option for you because relatively it does not cause huge impact. And, that makes testing as well as private method spying possible.

private SomeService service; // with a package private method "doSomething()"

void shouldReturnTrueDoSomething() {
    assertThat(doSomething(input), is(true)); // package private method testing

void shouldReturnTrueWhenServiceThrowsException() {
    SomeService spy = Mockito.spy(service); // spying real object
    doThrow(new AppException()).when(spy).doSomething(input); // spy package private method


When it comes to internal fields, in Spring you have ReflectionUtils.setField().

At last, sometimes we can bypass the problem itself: if there is a coverage requirement to meet, maybe you can move these private methods into an inner static class and ignore this class in Jacoco. I just found some way to ignore inner class in Jacoco gradle tasks. another question

excel vba getting the row,cell value from selection.address

Dim f as Range

Set f=ActiveSheet.Cells.Find(...)

If Not f Is Nothing then
    msgbox "Row=" & f.Row & vbcrlf & "Column=" & f.Column
    msgbox "value not found!"
End If


We had the same problem on a CentOS7 machine. Disabling the VERIFYHOST VERIFYPEER did not solve the problem, we did not have the cURL error anymore but the response still was invalid. Doing a wget to the same link as the cURL was doing also resulted in a certificate error.

-> Our solution also was to reboot the VPS, this solved it and we were able to complete the request again.

For us this seemed to be a memory corruption problem. Rebooting the VPS reloaded the libary in the memory again and now it works. So if the above solution from @clover does not work try to reboot your machine.

Connect to mysql in a docker container from the host

For conversion,you can create ~/.my.cnf file in host:


Then next time just run mysql for mysql client to open connection.

Composer: file_put_contents(./composer.json): failed to open stream: Permission denied

This might be super edge case, but if you are using Travis CI and taking advantage of caching, you might want to clear all cache and retry.

Fixed my issue when I was going from sudo to non sudo builds.

HTML Input="file" Accept Attribute File Type (CSV)

Now you can use new html5 input validation attribute pattern=".+\.(xlsx|xls|csv)".

Getting Current time to display in Label.


total.Text = DateTime.Now.ToString()


Dim theDate As DateTime = System.DateTime.Now
total.Text = theDate.ToString()

You declare Start as an Integer, while you are trying to put a DateTime in it, which is not possible.

Getting XML Node text value with Java DOM

I'd print out the result of an2.getNodeName() as well for debugging purposes. My guess is that your tree crawling code isn't crawling to the nodes that you think it is. That suspicion is enhanced by the lack of checking for node names in your code.

Other than that, the javadoc for Node defines "getNodeValue()" to return null for Nodes of type Element. Therefore, you really should be using getTextContent(). I'm not sure why that wouldn't give you the text that you want.

Perhaps iterate the children of your tag node and see what types are there?

Tried this code and it works for me:

String xml = "<add job=\"351\">\n" +
             "    <tag>foobar</tag>\n" +
             "    <tag>foobar2</tag>\n" +
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
ByteArrayInputStream bis = new ByteArrayInputStream(xml.getBytes());
Document doc = db.parse(bis);
Node n = doc.getFirstChild();
NodeList nl = n.getChildNodes();
Node an,an2;

for (int i=0; i < nl.getLength(); i++) {
    an = nl.item(i);
    if(an.getNodeType()==Node.ELEMENT_NODE) {
        NodeList nl2 = an.getChildNodes();

        for(int i2=0; i2<nl2.getLength(); i2++) {
            an2 = nl2.item(i2);
            // DEBUG PRINTS
            System.out.println(an2.getNodeName() + ": type (" + an2.getNodeType() + "):");
            if(an2.hasChildNodes()) System.out.println(an2.getFirstChild().getTextContent());
            if(an2.hasChildNodes()) System.out.println(an2.getFirstChild().getNodeValue());

Output was:

#text: type (3): foobar foobar
#text: type (3): foobar2 foobar2

Type safety: Unchecked cast

A warning is just that. A warning. Sometimes warnings are irrelevant, sometimes they're not. They're used to call your attention to something that the compiler thinks could be a problem, but may not be.

In the case of casts, it's always going to give a warning in this case. If you are absolutely certain that a particular cast will be safe, then you should consider adding an annotation like this (I'm not sure of the syntax) just before the line:

@SuppressWarnings (value="unchecked")

Highlight Anchor Links when user manually scrolls?

You can use Jquery's on method and listen for the scroll event.

Copy multiple files in Python

If you don't want to copy the whole tree (with subdirs etc), use or glob.glob("path/to/dir/*.*") to get a list of all the filenames, loop over the list and use shutil.copy to copy each file.

for filename in glob.glob(os.path.join(source_dir, '*.*')):
    shutil.copy(filename, dest_dir)

Git: How to return from 'detached HEAD' state

Use git reflog to find the hashes of previously checked out commits.

A shortcut command to get to your last checked out branch (not sure if this work correctly with detached HEAD and intermediate commits though) is git checkout -

How can I divide one column of a data frame through another?

Hadley Wickham


packages is always a saver in case of data wrangling. To add the desired division as a third variable I would use mutate()

d <- mutate(d, new = min / count2.freq)

How to create a link to another PHP page


<a href="page2.php">Link</a>

And if you need to pass a value:

<a href="page2.php?val=1">Link that pass the value 1</a>

To retrive the value put in page2.php this code:

$val = $_GET["val"];

Now the variable $val has the value 1.

ssh connection refused on Raspberry Pi

Apparently, the SSH server on Raspbian is now disabled by default. If there is no server listening for connections, it will not accept them. You can manually enable the SSH server according to this tutorial :

As of the November 2016 release, Raspbian has the SSH server disabled by default.

There are now multiple ways to enable it. Choose one:

From the desktop

  1. Launch Raspberry Pi Configuration from the Preferences menu
  2. Navigate to the Interfaces tab
  3. Select Enabled next to SSH
  4. Click OK

From the terminal with raspi-config

  1. Enter sudo raspi-config in a terminal window
  2. Select Interfacing Options
  3. Navigate to and select SSH
  4. Choose Yes
  5. Select Ok
  6. Choose Finish

Start the SSH service with systemctl

sudo systemctl enable ssh
sudo systemctl start ssh

On a headless Raspberry Pi

For headless setup, SSH can be enabled by placing a file named ssh, without any extension, onto the boot partition of the SD card. When the Pi boots, it looks for the ssh file. If it is found, SSH is enabled, and the file is deleted. The content of the file does not matter: it could contain text, or nothing at all.

How to check Network port access and display useful message?

boiled this down to a one liner sets the variable "$port389Open" to True or false - its fast and easy to replicate for a list of ports

try{$socket = New-Object Net.Sockets.TcpClient($ipAddress,389);if($socket -eq $null){$Port389Open = $false}else{Port389Open = $true;$socket.close()}}catch{Port389Open = $false}

If you want ot go really crazy you can return the an entire array-

Function StdPorts($ip){
    $rst = "" |  select IP,Port547Open,Port135Open,Port3389Open,Port389Open,Port53Open
    $rst.IP = $Ip
    try{$socket = New-Object Net.Sockets.TcpClient($ip,389);if($socket -eq $null){$rst.Port389Open = $false}else{$rst.Port389Open = $true;$socket.close();$ipscore++}}catch{$rst.Port389Open = $false}
    try{$socket = New-Object Net.Sockets.TcpClient($ip,53);if($socket -eq $null){$rst.Port53Open = $false}else{$rst.Port53Open = $true;$socket.close();$ipscore++}}catch{$rst.Port53Open = $false}
    try{$socket = New-Object Net.Sockets.TcpClient($ip,3389);if($socket -eq $null){$rst.Port3389Open = $false}else{$rst.Port3389Open = $true;$socket.close();$ipscore++}}catch{$rst.Port3389Open = $false}
    try{$socket = New-Object Net.Sockets.TcpClient($ip,547);if($socket -eq $null){$rst.Port547Open = $false}else{$rst.Port547Open = $true;$socket.close();$ipscore++}}catch{$rst.Port547Open = $false}
    try{$socket = New-Object Net.Sockets.TcpClient($ip,135);if($socket -eq $null){$rst.Port135Open = $false}else{$rst.Port135Open = $true;$socket.close();$SkipWMI = $False;$ipscore++}}catch{$rst.Port135Open = $false}
    Return $rst

Minimum 6 characters regex expression

Something along the lines of this?

<asp:TextBox id="txtUsername" runat="server" />

    ErrorMessage="Field not valid!"
    ValidationExpression="[0-9a-zA-Z]{6,}" />

UIButton Image + Text IOS

I see very complicated answers, all of them using code. However, if you are using Interface Builder, there is a very easy way to do this:

  1. Select the button and set a title and an image. Note that if you set the background instead of the image then the image will be resized if it is smaller than the button.IB basic image and title
  2. Set the position of both items by changing the edge and insets. You could even control the alignment of both in the Control section.

IB position set IB Control set

You could even use the same approach by code, without creating UILabels and UIImages inside as other solutions proposed. Always Keep It Simple!

EDIT: Attached a small example having the 3 things set (title, image and background) with correct insets Button preview

Get/pick an image from Android's built-in Gallery app programmatically

This is a complete solution. I've just updated this example code with the information provided in the answer below by @mad. Also check the solution below from @Khobaib explaining how to deal with picasa images.


I've just reviewed my original answer and created a simple Android Studio project you can checkout from github and import directly on your system.

(note that the multiple file selection still needs work)

Single Picture Selection

With support for images from file explorers thanks to user mad.

public class BrowsePictureActivity extends Activity {

    // this is the action code we use in our intent, 
    // this way we know we're looking at the response from our own action
    private static final int SELECT_PICTURE = 1;

    private String selectedImagePath;

    public void onCreate(Bundle savedInstanceState) {

                .setOnClickListener(new OnClickListener() {

                    public void onClick(View arg0) {

                        // in onCreate or any event where your want the user to
                        // select a file
                        Intent intent = new Intent();
                                "Select Picture"), SELECT_PICTURE);

    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (resultCode == RESULT_OK) {
            if (requestCode == SELECT_PICTURE) {
                Uri selectedImageUri = data.getData();
                selectedImagePath = getPath(selectedImageUri);

     * helper to retrieve the path of an image URI
    public String getPath(Uri uri) {
            // just some safety built in 
            if( uri == null ) {
                // TODO perform some logging or show user feedback
                return null;
            // try to retrieve the image from the media store first
            // this will only work for images selected from gallery
            String[] projection = { MediaStore.Images.Media.DATA };
            Cursor cursor = managedQuery(uri, projection, null, null, null);
            if( cursor != null ){
                int column_index = cursor
                String path = cursor.getString(column_index);
                return path;
            // this is our fallback here
            return uri.getPath();


Selecting Multiple Pictures

Since someone requested that information in a comment and it's better to have information gathered.

Set an extra parameter EXTRA_ALLOW_MULTIPLE on the intent:

intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);

And in the Result handling check for that parameter:

if (Intent.ACTION_SEND_MULTIPLE.equals(data.getAction()))
        && Intent.hasExtra(Intent.EXTRA_STREAM)) {
    // retrieve a collection of selected images
    ArrayList<Parcelable> list = intent.getParcelableArrayListExtra(Intent.EXTRA_STREAM);
    // iterate over these images
    if( list != null ) {
       for (Parcelable parcel : list) {
         Uri uri = (Uri) parcel;
         // TODO handle the images one by one here

Note that this is only supported by API level 18+.

Change name of folder when cloning from GitHub?

git clone <Repo> <DestinationDirectory>

Clone the repository located at Repo into the folder called DestinationDirectory on the local machine.

Git:nothing added to commit but untracked files present

Please Follow this process

First of all install git bash and create a repository on git

1) Go to working directory where the file exist which you want to push on remote and create .git folder by

$ git init

2) Add the files in your new local repository.

$ git add .

Note: while you are in same folder make sure you have placed dot after command if you putting path or not putting dot that will create ambiguity

3) Commit the files that you've staged in your local repository.

$ git commit -m "First commit"**

4) after this go to git repository and copy remote URL

$ git remote add origin *remote repository URL


$ git remote -v

Note: this will ask for and just put it as per config


$ git push origin master

this will push whole committed code to FILE.git on repository

And I think we done

Ripple effect on Android Lollipop CardView

Add these two like of code work like a charm for any view like Button, Linear Layout, or CardView Just put these two lines and see the magic...


In Javascript, how to conditionally add a member to an object?

You can add all your undefined values with no condition and then use JSON.stringify to remove them all :

const person = {
  name: undefined,
  age: 22,
  height: null

const cleaned = JSON.parse(JSON.stringify(person));

// Contents of cleaned:

// cleaned = {
//   age: 22,
//   height: null
// }

SQL QUERY replace NULL value in a row with a value from the previous known value

This will work on Snowflake (credit to Darren Gardner):

create temp table ss (id int, val int);
insert into ss (id,val) select 1, 3;
insert into ss (id,val) select 2, null;
insert into ss (id,val) select 3, 5;
insert into ss (id,val) select 4, null;
insert into ss (id,val) select 5, null;
insert into ss (id,val) select 6, 2;

select *
      ,last_value(val ignore nulls) over 
       (order by id rows between unbounded preceding and current row) as val2
  from ss;

Android draw a Horizontal line between views

It will draw Silver gray colored Line between TextView & ListView

    android:text="FaceBook Feeds" />


    android:layout_height="50dp" />

Performance of Arrays vs. Lists

if you are just getting a single value out of either (not in a loop) then both do bounds checking (you're in managed code remember) it's just the list does it twice. See the notes later for why this is likely not a big deal.

If you are using your own for(int int i = 0; i < x.[Length/Count];i++) then the key difference is as follows:

  • Array:
    • bounds checking is removed
  • Lists
    • bounds checking is performed

If you are using foreach then the key difference is as follows:

  • Array:
    • no object is allocated to manage the iteration
    • bounds checking is removed
  • List via a variable known to be List.
    • the iteration management variable is stack allocated
    • bounds checking is performed
  • List via a variable known to be IList.
    • the iteration management variable is heap allocated
    • bounds checking is performed also Lists values may not be altered during the foreach whereas the array's can be.

The bounds checking is often no big deal (especially if you are on a cpu with a deep pipeline and branch prediction - the norm for most these days) but only your own profiling can tell you if that is an issue. If you are in parts of your code where you are avoiding heap allocations (good examples are libraries or in hashcode implementations) then ensuring the variable is typed as List not IList will avoid that pitfall. As always profile if it matters.

What is the Difference Between Mercurial and Git?

Sometime last year I evaluated both git and hg for my own use, and decided to go with hg. I felt it looked like a cleaner solution, and worked better on more platforms at the time. It was mostly a toss-up, though.

More recently, I started using git because of git-svn and the ability to act as a Subversion client. This won me over and I've now switched completely to git. I think it's got a slightly higher learning curve (especially if you need to poke around the insides), but it really is a great system. I'm going to go read those two comparison articles that John posted now.

How to use SVN, Branch? Tag? Trunk?

Version Control with Subversion is the guide for beginners and old hands alike.

I don't think you can use Subversion effectively without reading at least the first few chapters of this.

LaTeX package for syntax highlighting of code in various languages

After asking a similar question I’ve created another package which uses Pygments, and offers quite a few more options than texments. It’s called minted and is quite stable and usable.

Just to show it off, here’s a code highlighted with minted:

Example code

How to remove old and unused Docker images

docker system prune -a

(You'll be asked to confirm the command. Use -f to force run, if you know what you're doing.)

How do I skip a header from CSV files in Spark?

Alternatively, you can use the spark-csv package (or in Spark 2.0 this is more or less available natively as CSV). Note that this expects the header on each file (as you desire):

schema = StructType([

df ='com.databricks.spark.csv'). \

Could not load NIB in bundle

Got this problem while transforming my old code from XCode 3x to XCode 4 and Solved it by just renaming wwwwwwww.xib into RootViewController.xib

div hover background-color change?

if you want the color to change when you have simply add the :hover pseudo

div.e:hover {

File inside jar is not visible for spring

In the spring jar package, I use new ClassPathResource(filename).getFile(), which throws the exception:

cannot be resolved to absolute file path because it does not reside in the file system: jar

But using new ClassPathResource(filename).getInputStream() will solve this problem. The reason is that the configuration file in the jar does not exist in the operating system's file tree,so must use getInputStream().

AppFabric installation failed because installer MSI returned with error code : 1603

For me the following method worked, Firstly ensure that windows update service is running from services.msc or you can run this command in an administrator Command Prompt -

net start wuauserv

Next edit the following registry from regedit -> HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\InetStp -> MajorVersion -> Change this value from 10 to 9.

Then try installing the AppFabric and it should work. Note :- revert back to registry value changes you made to ensure there are no problems in future if any.

Coarse-grained vs fine-grained

Coarse-grained and Fine-grained both think about optimizing a number of servicess. But the difference is in the level. I like to explain with an example, you will understand easily.

Fine-grained: For example, I have 100 services like findbyId, findbyCategry, findbyName...... so on. Instead of that many services why we can not provide find(id, category, on). So this way we can reduce the services. This is just an example, but the goal is how to optimize the number of services.

Coarse-grained: For example, I have 100 clients, each client have their own set of 100 services. So I have to provide 100*100 total services. It is very much difficult. Instead of that what I do is, I identify all common services which apply to most of the clients as one service set and remaining separately. For example in 100 services 50 services are common. So I have to manage 100*50 + 50 only.

How to read first N lines of a file?

If you want to read the first lines quickly and you don't care about performance you can use .readlines() which returns list object and then slice the list.

E.g. for the first 5 lines:

with open("pathofmyfileandfileandname") as myfile:
    firstNlines=myfile.readlines()[0:5] #put here the interval you want

Note: the whole file is read so is not the best from the performance point of view but it is easy to use, fast to write and easy to remember so if you want just perform some one-time calculation is very convenient

print firstNlines

One advantage compared to the other answers is the possibility to select easily the range of lines e.g. skipping the first 10 lines [10:30] or the lasts 10 [:-10] or taking only even lines [::2].

Laravel Eloquent - distinct() and count() not working properly together

A more generic answer that would have saved me time, and hopefully others:

Does not work (returns count of all rows):


The fix:


Using JQuery hover with HTML image map

Although jQuery Maphilight plugin does the job, it relies on the outdated verbose imagemap in your html. I would prefer to keep the mapcoordinates external. This could be as JS with the jquery imagemap plugin but it lacks hover states. A nice solution is googles geomap visualisation in flash and JS. But the opensource future for this kind of vectordata however is svg, considering svg support accross all modern browsers, and googles svgweb for a flash convert for IE, why not a jquery plugin to add links and hoverstates to a svg map, like the JS demo here? That way you also avoid the complex step of transforming a vectormap to a imagemap coordinates.

Java 8 - Difference between Optional.flatMap and

You can refer below link to understand in detail (best explanation which I could find):

Both map and flatMap - accept Function. The return type of map() is a single value whereas flatMap is returning stream of values

<R> Stream<R> map(Function<? super T, ? extends R> mapper)

<R> Stream<R> flatMap(Function<? super T, ? extends Stream<? extends R>> mapper)

How to tell if a string contains a certain character in JavaScript?

ES6 contains inbuilt method (includes) in String's prototype, which can be used to check if string contains another string or not.

var str = 'To be, or not to be, that is the question.';_x000D_
console.log(str.includes('To be')); 

Following polyfill can be used to add this method in non-supported browsers. (Source)

if (!String.prototype.includes) {_x000D_
  String.prototype.includes = function(search, start) {_x000D_
    'use strict';_x000D_
    if (typeof start !== 'number') {_x000D_
      start = 0;_x000D_
    if (start + search.length > this.length) {_x000D_
      return false;_x000D_
    } else {_x000D_
      return this.indexOf(search, start) !== -1;_x000D_

How do I find my host and username on mysql?

Default user for MySQL is "root", and server "localhost".

nvarchar(max) vs NText

You should apparently use nvarchar(max):


Spring schemaLocation fails when there is no internet connection

I had ran into this similar problem as well. In my case, my resolution is quite different. Here's my spring context xml file:

<beans xmlns=""

I'm not specifying any xsd version as I want spring to use the latest xsd version inside spring dependencies. The spring version my application used was spring-beans-4.3.1.RELEASE.jar:4.3.1.RELEASE and when I assembly my application into jar, all spring dependencies exist in my classpath. However, I received following error during startup of my spring application context:

org.xml.sax.SAXParseException: schema_reference.4: Failed to read schema document '', because 1) could not find the document; 2) the document could not be read; 3) the root element of the document is not <xsd:schema>.

After some hard time troubleshooting, I found the issue is due to the index.list inside the META-INF folder of my jar file. With index.list file, spring namespace handlers cannot be located to parse the spring application context xml correctly. You can read more about this spring issue SPR-5705

By removing indexing from my maven-jar-plugin, I manage to resolve the issue. Hope this will save some times for people having the same problem.

Getting "method not valid without suitable object" error when trying to make a HTTP request in VBA?

For reading REST data, at least OData Consider Microsoft Power Query. You won't be able to write data. However, you can read data very well.

How to grep for contents after pattern?

You can use grep, as the other answers state. But you don't need grep, awk, sed, perl, cut, or any external tool. You can do it with pure bash.

Try this (semicolons are there to allow you to put it all on one line):

$ while read line;
    if [[ "${line%%:\ *}" == "potato" ]];
      echo ${line##*:\ };
  done< file.txt

## tells bash to delete the longest match of ": " in $line from the front.

$ while read line; do echo ${line##*:\ }; done< file.txt

or if you wanted the key rather than the value, %% tells bash to delete the longest match of ": " in $line from the end.

$ while read line; do echo ${line%%:\ *}; done< file.txt

The substring to split on is ":\ " because the space character must be escaped with the backslash.

You can find more like these at the linux documentation project.

Remove table row after clicking table row delete button

As @gaurang171 mentioned, we can use .closest() which will return the first ancestor, or the closest to our delete button, and use .remove() to remove it.

This is how we can implement it using jQuery click event instead of using JavaScript onclick.


<table id="myTable">
  <th width="30%" style="color:red;">ID</th>
  <th width="25%" style="color:red;">Name</th>
  <th width="25%" style="color:red;">Age</th>
  <th width="1%"></th>

  <td width="30%" style="color:red;">SSS-001</td>
  <td width="25%" style="color:red;">Ben</td>
  <td width="25%" style="color:red;">25</td>
  <td><button type='button' class='btnDelete'>x</button></td>

  <td width="30%" style="color:red;">SSS-002</td>
  <td width="25%" style="color:red;">Anderson</td>
  <td width="25%" style="color:red;">47</td>
  <td><button type='button' class='btnDelete'>x</button></td>

  <td width="30%" style="color:red;">SSS-003</td>
  <td width="25%" style="color:red;">Rocky</td>
  <td width="25%" style="color:red;">32</td>
  <td><button type='button' class='btnDelete'>x</button></td>

  <td width="30%" style="color:red;">SSS-004</td>
  <td width="25%" style="color:red;">Lee</td>
  <td width="25%" style="color:red;">15</td>
  <td><button type='button' class='btnDelete'>x</button></td>



Try in JSFiddle: click here.

"SDK Platform Tools component is missing!"

I have been faced with a similar problem with SDK 24.0.2, and ADT 23.0, on windows 7 and Eclipse Luna (4.4.0). The android SDK Manager comes with default Proxy IP of (localhost) and port 8081. So as you try to run the SDK Managers as advised by earlier solutions, it will try to connect through the default proxy settings, which keep on failing( least on my system). Therefore, if you do not need proxy settings, simply clear default proxy settings (i.e. remove proxy server IP and Port, leaving the fields empty). Otherwise set them as necessary. To access these settings in eclipse, go Window-> Android SDK Manager->Tools->Options.

Hope this helps someone.

Looping through a Scripting.Dictionary using index/item number

Adding to assylias's answer - assylias shows us D.ITEMS is a method that returns an array. Knowing that, we don't need the variant array a(i) [See caveat below]. We just need to use the proper array syntax.

For i = 0 To d.Count - 1
    s = d.Items()(i)
    Debug.Print s
Next i()

KEYS works the same way

For i = 0 To d.Count - 1
    Debug.Print d.Keys()(i), d.Items()(i)
Next i

This syntax is also useful for the SPLIT function which may help make this clearer. SPLIT also returns an array with lower bounds at 0. Thus, the following prints "C".

Debug.Print Split("A,B,C,D", ",")(2)

SPLIT is a function. Its parameters are in the first set of parentheses. Methods and Functions always use the first set of parentheses for parameters, even if no parameters are needed. In the example SPLIT returns the array {"A","B","C","D"}. Since it returns an array we can use a second set of parentheses to identify an element within the returned array just as we would any array.

Caveat: This shorter syntax may not be as efficient as using the variant array a() when iterating through the entire dictionary since the shorter syntax invokes the dictionary's Items method with each iteration. The shorter syntax is best for plucking a single item by number from a dictionary.

Rebasing a Git merge commit

There are two options here.

One is to do an interactive rebase and edit the merge commit, redo the merge manually and continue the rebase.

Another is to use the --rebase-merges option on git rebase, which is described as follows from the manual:

By default, a rebase will simply drop merge commits from the todo list, and put the rebased commits into a single, linear branch. With --rebase-merges, the rebase will instead try to preserve the branching structure within the commits that are to be rebased, by recreating the merge commits. Any resolved merge conflicts or manual amendments in these merge commits will have to be resolved/re-applied manually."

Remove 'b' character do in front of a string literal in Python 3

Decoding is redundant

You only had this "error" in the first place, because of a misunderstanding of what's happening.

You get the b because you encoded to utf-8 and now it's a bytes object.

 >> type("text".encode("utf-8"))
 >> <class 'bytes'>


  1. You can just print the string first
  2. Redundantly decode it after encoding

How do I force "git pull" to overwrite local files?

Reset the index and the head to origin/master, but do not reset the working tree:

git reset origin/master

Replacing &nbsp; from javascript dom text node

I think when you define a function with "var foo = function() {...};", the function is only defined after that line. In other words, try this:

var replaceHtmlEntites = (function() {
  var translate_re = /&(nbsp|amp|quot|lt|gt);/g;
  var translate = {
    "nbsp": " ",
    "amp" : "&",
    "quot": "\"",
    "lt"  : "<",
    "gt"  : ">"
  return function(s) {
    return ( s.replace(translate_re, function(match, entity) {
      return translate[entity];
    }) );

var cleanText = text.replace(/^\xa0*([^\xa0]*)\xa0*$/g,"");
cleanText = replaceHtmlEntities(text);

Edit: Also, only use "var" the first time you declare a variable (you're using it twice on the cleanText variable).

Edit 2: The problem is the spelling of the function name. You have "var replaceHtmlEntites =". It should be "var replaceHtmlEntities ="

How can I make a button redirect my page to another page?

This is here:

 <button onClick="window.location='page_name.php';" value="click here" />

Get average color of image via Javascript

All-In-One Solution

I would personally combine Color Thief along with this modified version of Name that Color to obtain a more-than-sufficient array of dominant color results for images.


Consider the following image:

enter image description here

You can use the following code to extract image data relating to the dominant color:

let color_thief = new ColorThief();
let sample_image = new Image();

sample_image.onload = () => {
  let result ='#' + color_thief.getColor(sample_image).map(x => {
    const hex = x.toString(16);
    return hex.length === 1 ? '0' + hex : hex;
  console.log(result[0]); // #f0c420     : Dominant HEX/RGB value of closest match
  console.log(result[1]); // Moon Yellow : Dominant specific color name of closest match
  console.log(result[2]); // #ffff00     : Dominant HEX/RGB value of shade of closest match
  console.log(result[3]); // Yellow      : Dominant color name of shade of closest match
  console.log(result[4]); // false       : True if exact color match

sample_image.crossOrigin = 'anonymous';
sample_image.src = document.getElementById('sample-image').src;

Is there a better way to run a command N times in bash?

A little bit naive but this is what I usually remember off the top of my head:

for i in 1 2 3; do
  some commands

Very similar to @joe-koberg's answer. His is better especially if you need many repetitions, just harder for me to remember other syntax because in last years I'm not using bash a lot. I mean not for scripting at least.

How to test if a double is an integer

Here is a good solution:

if (variable == (int)variable) {

Count how many files in directory PHP

$files = glob('uploads/*');
$count = 0;
$totalCount = 0;
$subFileCount = 0;
foreach ($files as $file) 
    global $count, $totalCount;
        $totalCount += getFileCount($file);

function getFileCount($dir)
    global $subFileCount;
        $subfiles = glob($dir.'/*');
            foreach ($subfiles as $file) 
    return $subFileCount;

$totalFilesCount = $count + $totalCount; 
echo 'Total Files Count ' . $totalFilesCount;

Rendering HTML inside textarea

With an editable div you can use the method document.execCommand (more details) to easily provide the support for the tags you specified and for some other functionality..

#text {_x000D_
    width : 500px;_x000D_
 min-height : 100px;_x000D_
 border : 2px solid;_x000D_
<div id="text" contenteditable="true"></div>_x000D_
<button onclick="document.execCommand('bold');">toggle bold</button>_x000D_
<button onclick="document.execCommand('italic');">toggle italic</button>_x000D_
<button onclick="document.execCommand('underline');">toggle underline</button>

css display table cell requires percentage width

You just need to add 'table-layout: fixed;'

.table {
   display: table;
   height: 100px;
   width: 100%;
   table-layout: fixed;

iPhone UIView Animation Best Practice

Here is Code for Smooth animation, might Be helpful for many developers.
I found this snippet of code from this tutorial.

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
[animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];
[animation setAutoreverses:YES];
[animation setFromValue:[NSNumber numberWithFloat:1.3f]];
[animation setToValue:[NSNumber numberWithFloat:1.f]];
[animation setDuration:2.f];
[animation setRemovedOnCompletion:NO];

[animation setFillMode:kCAFillModeForwards];
[[self.myView layer] addAnimation:animation forKey:@"scale"];/// add here any Controller that you want t put Smooth animation.

sass --watch with automatic minify?

If you are using JetBrains editors like IntelliJ IDEA, PhpStorm, WebStorm etc. Use the following settings in Settings > File Watchers. enter image description here

  1. Convert style.scss to style.css set the arguments

    --no-cache --update $FileName$:$FileNameWithoutExtension$.css

    and output paths to refresh

  2. Convert style.scss to compressed style.min.css set the arguments

    --no-cache --update $FileName$:$FileNameWithoutExtension$.min.css --style compressed

    and output paths to refresh


Gradle does not find tools.jar

For me this error ocurred after trying to use audioplayers flutter library. To solve i got tools.jar of the folder:

C:\Program Files\Android\Android Studio\jre\lib

and pasted on

C:\Program Files\Java\jre1.8.0_181\lib.

After this the build worked fine.

Convert DOS line endings to Linux line endings in Vim

:g/Ctrl-v Ctrl-m/s///

CtrlM is the character \r, or carriage return, which DOS line endings add. CtrlV tells Vim to insert a literal CtrlM character at the command line.

Taken as a whole, this command replaces all \r with nothing, removing them from the ends of lines.

How to save a pandas DataFrame table as a png

Pandas allows you to plot tables using matplotlib (details here). Usually this plots the table directly onto a plot (with axes and everything) which is not what you want. However, these can be removed first:

import matplotlib.pyplot as plt
import pandas as pd
from pandas.table.plotting import table # EDIT: see deprecation warnings below

ax = plt.subplot(111, frame_on=False) # no visible frame
ax.xaxis.set_visible(False)  # hide the x axis
ax.yaxis.set_visible(False)  # hide the y axis

table(ax, df)  # where df is your data frame


The output might not be the prettiest but you can find additional arguments for the table() function here. Also thanks to this post for info on how to remove axes in matplotlib.


Here is a (admittedly quite hacky) way of simulating multi-indexes when plotting using the method above. If you have a multi-index data frame called df that looks like:

first  second
bar    one       1.991802
       two       0.403415
baz    one      -1.024986
       two      -0.522366
foo    one       0.350297
       two      -0.444106
qux    one      -0.472536
       two       0.999393
dtype: float64

First reset the indexes so they become normal columns

df = df.reset_index() 
    first second       0
0   bar    one  1.991802
1   bar    two  0.403415
2   baz    one -1.024986
3   baz    two -0.522366
4   foo    one  0.350297
5   foo    two -0.444106
6   qux    one -0.472536
7   qux    two  0.999393

Remove all duplicates from the higher order multi-index columns by setting them to an empty string (in my example I only have duplicate indexes in "first"):

df.ix[df.duplicated('first') , 'first'] = '' # see deprecation warnings below
  first second         0
0   bar    one  1.991802
1          two  0.403415
2   baz    one -1.024986
3          two -0.522366
4   foo    one  0.350297
5          two -0.444106
6   qux    one -0.472536
7          two  0.999393

Change the column names over your "indexes" to the empty string

new_cols = df.columns.values
new_cols[:2] = '',''  # since my index columns are the two left-most on the table
df.columns = new_cols 

Now call the table function but set all the row labels in the table to the empty string (this makes sure the actual indexes of your plot are not displayed):

table(ax, df, rowLabels=['']*df.shape[0], loc='center')

et voila:

enter image description here

Your not-so-pretty but totally functional multi-indexed table.


As pointed out in the comments, the import statement for table:

from import table

is now deprecated in newer versions of pandas in favour of:

from pandas.plotting import table 


The ix indexer has now been fully deprecated so we should use the loc indexer instead. Replace:

df.ix[df.duplicated('first') , 'first'] = ''


df.loc[df.duplicated('first') , 'first'] = ''

Plot smooth line with PyPlot

For this example spline works well, but if the function is not smooth inherently and you want to have smoothed version you can also try:

from scipy.ndimage.filters import gaussian_filter1d

ysmoothed = gaussian_filter1d(y, sigma=2)
plt.plot(x, ysmoothed)

if you increase sigma you can get a more smoothed function.

Proceed with caution with this one. It modifies the original values and may not be what you want.

Jdbctemplate query for string: EmptyResultDataAccessException: Incorrect result size: expected 1, actual 0

Ok, I figured it out. I just wrapped it in a try catch and send back null.

    public String test() {
            String cert=null;
            String sql = "select ID_NMB_SRZ from codb_owner.TR_LTM_SLS_RTN 
                     where id_str_rt = '999' and ID_NMB_SRZ = '60230009999999'";
            try {
                Object o = (String) jdbc.queryForObject(sql, String.class);
                cert = (String) o;
            } catch (EmptyResultDataAccessException e) {
            return cert;

Multiple modals overlay

The other solutions did not work for me out of the box. I think perhaps because I am using a more recent version of Bootstrap (3.3.2).... the overlay was appearing on top of the modal dialog.

I refactored the code a bit and commented out the part that was adjusting the modal-backdrop. This fixed the issue.

    var $body = $('body');
    var OPEN_MODALS_COUNT = 'fv_open_modals';
    var Z_ADJUSTED = 'fv-modal-stack';
    var defaultBootstrapModalZindex = 1040;

    // keep track of the number of open modals                   
    if ($ === undefined) {
        $, 0);

    $body.on('', '.modal', function (event)
        if (!$(this).hasClass(Z_ADJUSTED))  // only if z-index not already set
            // Increment count & mark as being adjusted
            $, $ + 1);

            // Set Z-Index
            $(this).css('z-index', defaultBootstrapModalZindex + (1 * $;

            //// BackDrop z-index   (Doesn't seem to be necessary with Bootstrap 3.3.2 ...)
            //$('.modal-backdrop').not( '.' + Z_ADJUSTED )
            //        .css('z-index', 1039 + (10 * $
            //        .addClass(Z_ADJUSTED);
    $body.on('', '.modal', function (event)
        // Decrement count & remove adjusted class
        $, $ - 1);
        // Fix issue with scrollbar being shown when any modal is hidden
        if($ > 0)

As a side note, if you want to use this in AngularJs, just put the code inside of your module's .run() method.

How to store file name in database, with other info while uploading image to server using PHP?

<form method="post" action="addMember.php" enctype="multipart/form-data">
              Please Enter the Band Members Name.
              Band Member or Affiliates Name:
            <input type="text" name="nameMember"/>
              Please Enter the Band Members Position. Example:Drums.
              Band Position:
            <input type="text" name="bandMember"/>
              Please Upload a Photo of the Member in gif or jpeg format. The file name should be named after the Members name. If the same file name is uploaded twice it will be overwritten! Maxium size of File is 35kb.
            <input type="hidden" name="size" value="350000">
            <input type="file" name="photo"> 
              Please Enter any other information about the band member here.
              Other Member Information:
<textarea rows="10" cols="35" name="aboutMember">
              Please Enter any other Bands the Member has been in.
              Other Bands:
            <input type="text" name="otherBands" size=30 />
            <input TYPE="submit" name="upload" title="Add data to the Database" value="Add Member"/>

save it as addMember.php


//This is the directory where images will be saved
$target = "your directory";
$target = $target . basename( $_FILES['photo']['name']);

//This gets all the other information from the form

// Connects to your Database
mysql_connect("yourhost", "username", "password") or die(mysql_error()) ;
mysql_select_db("dbName") or die(mysql_error()) ;

//Writes the information to the database
mysql_query("INSERT INTO tableName (nameMember,bandMember,photo,aboutMember,otherBands)
VALUES ('$name', '$bandMember', '$pic', '$about', '$bands')") ;

//Writes the photo to the server
if(move_uploaded_file($_FILES['photo']['tmp_name'], $target))

//Tells you if its all ok
echo "The file ". basename( $_FILES['photo']['name']). " has been uploaded, and your information has been added to the directory";
else {

//Gives and error if its not
echo "Sorry, there was a problem uploading your file.";

in the above code one little bug ,i fixed that bug.

What is base 64 encoding used for?

Mostly, I've seen it used to encode binary data in contexts that can only handle ascii - or a simple - character sets.

Determine project root from a running node.js application

Old question, I know, however no question mention to use progress.argv. The argv array includes a full pathname and filename (with or without .js extension) that was used as parameter to be executed by node. Because this also can contain flags, you must filter this.

This is not an example you can directly use (because of using my own framework) but I think it gives you some idea how to do it. I also use a cache method to avoid that calling this function stress the system too much, especially when no extension is specified (and a file exist check is required), for example:

node myfile


node myfile.js

That's the reason I cache it, see also code below.

function getRootFilePath()
        if( !isDefined( oData.SU_ROOT_FILE_PATH ) )
            var sExt = false;

            each( process.argv, function( i, v )
                 // Skip invalid and provided command line options
                if( !!v && isValidString( v ) && v[0] !== '-' )
                    sExt = getFileExt( v );

                    if( ( sExt === 'js' ) || ( sExt === '' && fileExists( v+'.js' )) )

                        var a = uniformPath( v ).split("/"); 

                         // Chop off last string, filename

                         // Cache it so we don't have to do it again.

                         // Found, skip loop
                        return true;
            }, true ); // <-- true is: each in reverse order

        return oData.SU_ROOT_FILE_PATH || '';

Writing a string to a cell in excel

I've had a few cranberry-vodkas tonight so I might be missing something...Is setting the range necessary? Why not use:

Activeworkbook.Sheets("Game").Range("A1").value = "Subtotal"

Does this fail as well?

Looks like you tried something similar:

'Worksheets("Game").Range("A1") = "Asdf"

However, Worksheets is a collection, so you can't reference "Game". I think you need to use the Sheets object instead.

Check whether specific radio button is checked

1.You don't need the @ prefix for attribute names any more:

Note: In jQuery 1.3 [@attr] style selectors were removed (they were previously deprecated in jQuery 1.2). Simply remove the ‘@’ symbol from your selectors in order to make them work again.

2.Your selector queries radio buttons by name, but that attribute is not defined in your HTML structure.

Android read text raw resource file

Here is an implementation in Kotlin

    try {
        val inputStream: InputStream = this.getResources().openRawResource(R.raw.**)
        val inputStreamReader = InputStreamReader(inputStream)
        val sb = StringBuilder()
        var line: String?
        val br = BufferedReader(inputStreamReader)
        line = br.readLine()
        while (line != null) {
            line = br.readLine()

        var content : String = sb.toString()
        Log.d(TAG, content)
    } catch (e:Exception){
        Log.d(TAG, e.toString())

Best Python IDE on Linux

Probably the new PyCharm from the makers of IntelliJ and ReSharper.

Unable to negotiate with XX.XXX.XX.XX: no matching host key type found. Their offer: ssh-dss

You can also add -oHostKeyAlgorithms=+ssh-dss in your ssh line:

ssh -oHostKeyAlgorithms=+ssh-dss user@host

Find and Replace Inside a Text File from a Bash Command

If the file you are working on is not so big, and temporarily storing it in a variable is no problem, then you can use Bash string substitution on the whole file at once - there's no need to go over it line by line:

echo "${file_contents//abc/XYZ}" > /tmp/file.txt

The whole file contents will be treated as one long string, including linebreaks.

XYZ can be a variable eg $replacement, and one advantage of not using sed here is that you need not be concerned that the search or replace string might contain the sed pattern delimiter character (usually, but not necessarily, /). A disadvantage is not being able to use regular expressions or any of sed's more sophisticated operations.

How can I recover a lost commit in Git?

git reflog is your friend. Find the commit that you want to be on in that list and you can reset to it (for example:git reset --hard e870e41).

(If you didn't commit your changes... you might be in trouble - commit early, and commit often!)

How to display HTML <FORM> as inline element?

Add a inline wrapper.

<div style='display:flex'>
 <p>Read this sentence</p>
 <input type='submit' value='or push this button' />
    <p>Message here</p>

Add params to given URL in Python

Use the various urlparse functions to tear apart the existing URL, urllib.urlencode() on the combined dictionary, then urlparse.urlunparse() to put it all back together again.

Or just take the result of urllib.urlencode() and concatenate it to the URL appropriately.

How to join two tables by multiple columns in SQL?

SELECT E.CaseNum, E.FileNum, E.ActivityNum, E.Grade, V.Score
FROM Evaluation E
ON E.CaseNum = V.CaseNum AND E.FileNum = V.FileNum AND E.ActivityNum = V.ActivityNum

Differences between key, superkey, minimal superkey, candidate key and primary key

I have always found it difficult to remember all the keys; so I keep the below notes handy, hope they help someone! Let me know if it can be improved.

  • Key: An attribute or combination of attributes that uniquely identify an entity/record in a relational table.

  • PK: A single key that is unique and not-null. It is one of the candidate keys.

  • Foreign Key: FK is a key in one table (child) that uniquely identifies a row of another table (parent). A FK is not-unique in the child table. It is a candidate key in the parent table. Referential integrity is maintained as the value in FK is present as a value in PK in parent table else it is NULL.

  • Unique Key: A unique key that may or may not be NULL

  • Natural key: PK in OLTP. It may be a PK in OLAP.

  • Surrogate Key: It is the Surrogate PK in OLAP acting as the substitute of the PK in OLTP. Artificial key generated internally in OLAP.

  • Composite Key: PK made up of multiple attributes

  • SuperKey: A key that can be uniquely used to identify a database record, that may contain extra attributes that are not necessary to uniquely identify records.

  • Candidate Key: A candidate key can be uniquely used to identify a database record without any extraneous data. They are Not Null and unique. It is a minimal super-key.

  • Alternate Key: A candidate key that is not the primary key is called an alternate key.

  • Candidate Key/s with Extraneous data: Consider that can be used to identify a record in the Employee table but candidate key alone is sufficient for this task. So becomes the extraneous data.

Note that the PK, Foreign Key, Unique Key, Natural key, Surrogate Key, Composite Key are defined as Database objects; where the Natural key is a PK in the OLTP and could be a PK in the target OLAP. For the rest of the keys, it's up to the DB designer/architect to decide whether unique/not-null/referential integrity constraints need to enforced or not.

Below I have tried to use set theory to simplify the representation of the membership of the keys w.r.t. each other.

key = { All of the below keys   }
PK  = { PK  }
Foreign Key = { Key with Not Null constraint    }
Unique Key  = { {Candidate Key/s}, {attributes containing NULL} }
Natural key = { PK  }
Surrogate Key   = { PK  }
Composite Key   = { PK  }
Super Key   = { {Candidate Key/s}, {Candidate Key/s with Extraneous data}   }
Candidate Key   = { PK, {Alternate Key/s}   }
Alternate Key   = { {Candidate Keys} - PK   }
Candidate Key/s with Extraneous data    = {     }

I have summarized it below:

Database Keys

Notes: an-overview-of-the-database-keys-primary-key-composite-key-surrogate-key-et-al

Android: resizing imageview in XML

for example:

<ImageView android:id="@+id/image_view"     

Add property android:scaleType="fitCenter" and android:adjustViewBounds="true".

How to make custom dialog with rounded corners in android

simplest way is to use from

CardView and its card:cardCornerRadius

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



And when you are creating your Dialog

dialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));

Read a text file using Node.js?

You'll want to use the process.argv array to access the command-line arguments to get the filename and the FileSystem module (fs) to read the file. For example:

// Make sure we got a filename on the command line.
if (process.argv.length < 3) {
  console.log('Usage: node ' + process.argv[1] + ' FILENAME');
// Read the file and print its contents.
var fs = require('fs')
  , filename = process.argv[2];
fs.readFile(filename, 'utf8', function(err, data) {
  if (err) throw err;
  console.log('OK: ' + filename);

To break that down a little for you process.argv will usually have length two, the zeroth item being the "node" interpreter and the first being the script that node is currently running, items after that were passed on the command line. Once you've pulled a filename from argv then you can use the filesystem functions to read the file and do whatever you want with its contents. Sample usage would look like this:

$ node ./cat.js file.txt
OK: file.txt
This is file.txt!

[Edit] As @wtfcoder mentions, using the "fs.readFile()" method might not be the best idea because it will buffer the entire contents of the file before yielding it to the callback function. This buffering could potentially use lots of memory but, more importantly, it does not take advantage of one of the core features of node.js - asynchronous, evented I/O.

The "node" way to process a large file (or any file, really) would be to use and process each available chunk as it is available from the operating system. However, reading the file as such requires you to do your own (possibly) incremental parsing/processing of the file and some amount of buffering might be inevitable.

ASP.NET file download from server

Simple solution for downloading a file from the server:

protected void btnDownload_Click(object sender, EventArgs e)
            string FileName = "Durgesh.jpg"; // It's a file name displayed on downloaded file on client side.

            System.Web.HttpResponse response = System.Web.HttpContext.Current.Response;
            response.ContentType = "image/jpeg";
            response.AddHeader("Content-Disposition", "attachment; filename=" + FileName + ";");

What does it mean to "program to an interface"?

Let's start out with some definitions first:

Interface n. The set of all signatures defined by an object's operations is called the interface to the object

Type n. A particular interface

A simple example of an interface as defined above would be all the PDO object methods such as query(), commit(), close() etc., as a whole, not separately. These methods, i.e. its interface define the complete set of messages, requests that can be sent to the object.

A type as defined above is a particular interface. I will use the made-up shape interface to demonstrate: draw(), getArea(), getPerimeter() etc..

If an object is of the Database type we mean that it accepts messages/requests of the database interface, query(), commit() etc.. Objects can be of many types. You can have a database object be of the shape type as long as it implements its interface, in which case this would be sub-typing.

Many objects can be of many different interfaces/types and implement that interface differently. This allows us to substitute objects, letting us choose which one to use. Also known as polymorphism.

The client will only be aware of the interface and not the implementation.

So in essence programming to an interface would involve making some type of abstract class such as Shape with the interface only specified i.e. draw(), getCoordinates(), getArea() etc.. And then have different concrete classes implement those interfaces such as a Circle class, Square class, Triangle class. Hence program to an interface not an implementation.

AngularJS: Uncaught Error: [$injector:modulerr] Failed to instantiate module?

For people who find this old posting on the web by searching for the error message, there is another possible cause of the problem.

You could just have a typo in your call to the script, even if you have already done the things described in the other excellent answer. So check to make sure you can used the right spelling in your script tags.

Angular ng-repeat Error "Duplicates in a repeater are not allowed."

The solution is actually described here:

AngularJS does not allow duplicates in a ng-repeat directive. This means if you are trying to do the following, you will get an error.

// This code throws the error "Duplicates in a repeater are not allowed.
// Repeater: row in [1,1,1] key: number:1"
<div ng-repeat="row in [1,1,1]">

However, changing the above code slightly to define an index to determine uniqueness as below will get it working again.

// This will work
<div ng-repeat="row in [1,1,1] track by $index">

Official docs are here:

SQL Error: ORA-12899: value too large for column

example : 1 and 2 table is available

1 table delete entry and select nor 2 table records and insert to no 1 table . when delete time no 1 table dont have second table records example emp id not available means this errors appeared

Convert categorical data in pandas dataframe

What I do is, I replace values.

Like this-

df['col'].replace(to_replace=['category_1', 'category_2', 'category_3'], value=[1, 2, 3], inplace=True)

In this way, if the col column has categorical values, they get replaced by the numerical values.

JS strings "+" vs concat method

In JS, "+" concatenation works by creating a new String object.

For example, with...

var s = "Hello";

...we have one object s.


s = s + " World";

Now, s is a new object.

2nd method: String.prototype.concat

CSS :not(:last-child):after selector

Every things seems correct. You might want to use the following css selector instead of what you used.

ul > li:not(:last-child):after

Difference between "char" and "String" in Java

A char simply contains a single alphabet and a string has a full word or number of words woth having a escape sequence inserted in the end automatically to tell the compiler that string has been ended here.(0)

Load text file as strings using numpy.loadtxt()

Is it essential that you need a NumPy array? Otherwise you could speed things up by loading the data as a nested list.

def load(fname):
    ''' Load the file using std open'''
    f = open(fname,'r')

    data = []
    for line in f.readlines():
        data.append(line.replace('\n','').split(' '))


    return data

For a text file with 4000x4000 words this is about 10 times faster than loadtxt.

Export and import table dump (.sql) using pgAdmin

If you have Git bash installed, you can do something like this:

/c/Program\ Files\ \(x86\)/PostgreSQL/9.3/bin/psql -U <pg_role_name> -d <pg_database_name> < <path_to_your>.sql

Div height 100% and expands to fit content

I'm not entirely sure that I've understood the question because this is a fairly straightforward answer, but here goes... :)

Have you tried setting the overflow property of the container to visible or auto?

#some_div {
    overflow: visible;

Adding that should push the black container to whatever size your dynamic container requires. I prefer visible to auto because auto seems to come with scroll bars...

What is the difference between HTTP 1.1 and HTTP 2.0?

HTTP 2.0 is a binary protocol that multiplexes numerous streams going over a single (normally TLS-encrypted) TCP connection.

The contents of each stream are HTTP 1.1 requests and responses, just encoded and packed up differently. HTTP2 adds a number of features to manage the streams, but leaves old semantics untouched.

Firebase cloud messaging notification not received by device

In my case, I manually killed some google play services and forgot about it.

Later, I have to restart the device, after that I can receive notification without any problem.

unable to set private key file: './cert.pem' type PEM

I had the same issue, eventually I found a solution that works without splitting the file, by following Petter Ivarrson's answer

My problem was when converting .p12 certificate to .pem. I used:

openssl pkcs12 -in cert.p12 -out cert.pem

This converts and exports all certificates (CA + CLIENT) together with a private key into one file.

The problem was when I tried to verify if the hashes of certificate and key are matching by running:

// Get certificate HASH
openssl x509 -noout -modulus -in cert.pem | openssl md5

// Get private key HASH
openssl rsa -noout -modulus -in cert.pem | openssl md5

This displayed different hashes and that was the reason CURL failed. See here:

I guess that was because all certificates are inside a file (CA + CLIENT) and CURL takes CA certificate instead of CLIENT one. Because CA is first in the list.

So the solution was to export only CLIENT certificate together with private key:

openssl pkcs12 -in cert.p12 -out cert.pem -clcerts

Now when I re-run the verification:
openssl x509 -noout -modulus -in cert.pem | openssl md5
openssl rsa -noout -modulus -in cert.pem | openssl md5


So I was able to make a curl request by running

curl -ivk --cert ./cert.pem:KeyChoosenByMeWhenIrunOpenSSL

without problems!!!

That being said... I think the best solution is to split the certificates into separate file and use them separately like Petter Ivarsson wrote:

curl --insecure --key key.pem --cacert ca.pem --cert client.pem:KeyChoosenByMeWhenIrunOpenSSL

How to build jars from IntelliJ properly?

If you are using third party libraries with your project or if you have problems with creating MANIFEST.MF file properly, there can be conflicts when running JAR files generated using

File > Project Structure > Artifacts > '+' > JAR > From modules with dependencies > .....

method mentioned above.

Instead I suggest you to create an empty JAR and add all other elements to the output root manually. A wonderful blog article for this method can be found here: I tried the steps mentioned there and everything worked fine for me!

How can I ssh directly to a particular directory?

You could add

cd /some/directory/somewhere/named/Foo

to your .bashrc file (or .profile or whatever you call it) at the other host. That way, no matter what you do or where you ssh from, whenever you log onto that server, it will cd to the proper directory for you, and all you have to do is use ssh like normal.

Of curse, rogeriopvl's solution works too, but it's a tad bit more verbose, and you have to remember to do it every time (unless you make an alias) so it seems a bit less "fun".

How to use awk sort by column 3

try this -

awk '{print $0|"sort -t',' -nk3 "}' user.csv


sort -t',' -nk3 user.csv

Output of git branch in tree like fashion

The following example shows commit parents as well:

git log --graph --all \
--format='%C(cyan dim) %p %Cred %h %C(white dim) %s %Cgreen(%cr)%C(cyan dim) <%an>%C(bold yellow)%d%Creset'

How to check if a date is in a given range?

It's not necessary to convert to timestamp to do the comparison, given that the strings are validated as dates in 'YYYY-MM-DD' canonical format.

This test will work:

( ( $date_from_user >= $start_date ) && ( $date_from_user <= $end_date ) )


$start_date     = '2009-06-17';
$end_date       = '2009-09-05';
$date_from_user = '2009-08-28';

NOTE: Comparing strings like this does allow for "non-valid" dates e.g. (December 32nd ) '2009-13-32' and for weirdly formatted strings '2009/3/3', such that a string comparison will NOT be equivalent to a date or timestamp comparison. This works ONLY if the date values in the strings are in a CONSISTENT and CANONICAL format.

EDIT to add a note here, elaborating on the obvious.

By CONSISTENT, I mean for example that the strings being compared must be in identical format: the month must always be two characters, the day must always be two characters, and the separator character must always be a dash. We can't reliably compare "strings" that aren't four character year, two character month, two character day. If we had a mix of one character and two character months in the strings, for example, we'd get unexpected result when we compared, '2009-9-30' to '2009-10-11'. We humanly see "9" as being less than "10", but a string comparison will see '2009-9' as greater than '2009-1'. We don't necessarily need to have a dash separator characters; we could just as reliably compare strings in 'YYYYMMDD' format; if there is a separator character, it has to always be there and always be the same.

By CANONICAL, I mean that a format that will result in strings that will be sorted in date order. That is, the string will have a representation of "year" first, then "month", then "day". We can't reliably compare strings in 'MM-DD-YYYY' format, because that's not canonical. A string comparison would compare the MM (month) before it compared YYYY (year) since the string comparison works from left to right.) A big benefit of the 'YYYY-MM-DD' string format is that it is canonical; dates represented in this format can reliably be compared as strings.


If you do go for the php timestamp conversion, be aware of the limitations.

On some platforms, php does not support timestamp values earlier than 1970-01-01 and/or later than 2038-01-19. (That's the nature of the unix timestamp 32-bit integer.) Later versions pf php (5.3?) are supposed to address that.

The timezone can also be an issue, if you aren't careful to use the same timezone when converting from string to timestamp and from timestamp back to string.


user authentication libraries for node.js?

I was basically looking for the same thing. Specifically, I wanted the following:

  1. To use express.js, which wraps Connect's middleware capability
  2. "Form based" authentication
  3. Granular control over which routes are authenticated
  4. A database back-end for users/passwords
  5. Use sessions

What I ended up doing was creating my own middleware function check_auth that I pass as an argument to each route I want authenticated. check_auth merely checks the session and if the user is not logged in, then redirects them to the login page, like so:

function check_auth(req, res, next) {

  //  if the user isn't logged in, redirect them to a login page
  if(!req.session.login) {
    return; // the buck stops here... we do not call next(), because
            // we don't want to proceed; instead we want to show a login page

  //  the user is logged in, so call next()

Then for each route, I ensure this function is passed as middleware. For example:

app.get('/tasks', check_auth, function(req, res) {
    // snip

Finally, we need to actually handle the login process. This is straightforward:

app.get('/login', function(req, res) {
  res.render("login", {layout:false});
});'/login', function(req, res) {

  // here, I'm using mongoose.js to search for the user in mongodb
  var user_query = UserModel.findOne({}, function(err, user){
    if(err) {
      res.render("login", {layout:false, locals:{ error:err } });

    if(!user || user.password != req.body.password) {
          locals:{ error:"Invalid login!", }
    } else {
      // successful login; store the session info
      req.session.login =;

At any rate, this approach was mostly designed to be flexible and simple. I'm sure there are numerous ways to improve it. If you have any, I'd very much like your feedback.

EDIT: This is a simplified example. In a production system, you'd never want to store & compare passwords in plain text. As a commenter points out, there are libs that can help manage password security.

Why can't I have "public static const string S = "stuff"; in my Class?

const is similar to static we can access both varables with class name but diff is static variables can be modified and const can not.

Field 'id' doesn't have a default value?

As a developer it is highly recommended to use STRICT mode because it will allow you to see issues/errors/warnings that may come about instead of just working around it by turning off strict mode. It's also better practice.

Strict mode is a great tool to see messy, sloppy code.

adb uninstall failed

Seems like you have an app that contains a hidden Device Administrator like this one here:

you can only uninstall such an app when you disable the device admin first. You can use to disable it or do it by your own by sending the intent to the app that invokes the receiver that will disable the device admin.

How do I push a new local branch to a remote Git repository and track it too?

For greatest flexibility, you could use a custom Git command. For example, create the following Python script somewhere in your $PATH under the name git-publish and make it executable:

#!/usr/bin/env python3

import argparse
import subprocess
import sys

def publish(args):
    return['git', 'push', '--set-upstream', args.remote, args.branch]).returncode

def parse_args():
    parser = argparse.ArgumentParser(description='Push and set upstream for a branch')
    parser.add_argument('-r', '--remote', default='origin',
                        help="The remote name (default is 'origin')")
    parser.add_argument('-b', '--branch', help='The branch name (default is whatever HEAD is pointing to)',
    return parser.parse_args()

def main():
    args = parse_args()
    return publish(args)

if __name__ == '__main__':

Then git publish -h will show you usage information:

usage: git-publish [-h] [-r REMOTE] [-b BRANCH]

Push and set upstream for a branch

optional arguments:
  -h, --help            show this help message and exit
  -r REMOTE, --remote REMOTE
                        The remote name (default is 'origin')
  -b BRANCH, --branch BRANCH
                        The branch name (default is whatever HEAD is pointing to)

How do you 'redo' changes after 'undo' with Emacs?

Beware of an undo-tree quirk for redo!

Many popular “starter kits” (prelude, purcell, spacemacs) come bundled with undo-tree. Most (all?) even auto-enable it. As mentioned, undo-tree is a handy way to visualize and traverse the undo/redo tree. Prelude even gives it a key-chord (uu), and also C-x u.

The problem is: undo-tree seems to wreck Emacs’ default and well-known binding for redo: C-g C-/.

Instead, you can use these symmetrical keys for undo/redo:

C-/     undo
C-S-/   redo

These are useful since sometimes you want to quickly redo without opening up the visualizer.

How to fire AJAX request Periodically?

Yes, you could use either the JavaScript setTimeout() method or setInterval() method to invoke the code that you would like to run. Here's how you might do it with setTimeout:

function executeQuery() {
    url: 'url/path/here',
    success: function(data) {
      // do something with the return value here if you like
  setTimeout(executeQuery, 5000); // you could choose not to continue on failure...

$(document).ready(function() {
  // run the first time; all subsequent calls will take care of themselves
  setTimeout(executeQuery, 5000);

How can I use ":" as an AWK field separator?

AWK works as a text interpreter that goes linewise for the whole document and that goes fieldwise for each line. Thus $1, $2...$n are references to the fields of each line ($1 is the first field, $2 is the second field, and so on...).

You can define a field separator by using the "-F" switch under the command line or within two brackets with "FS=...".

Now consider the answer of Jürgen:

echo "1: " | awk -F  ":" '/1/ {print $1}'

Above the field, boundaries are set by ":" so we have two fields $1 which is "1" and $2 which is the empty space. After comes the regular expression "/1/" that instructs the filter to output the first field only when the interpreter stumbles upon a line containing such an expression (I mean 1).

The output of the "echo" command is one line that contains "1", so the filter will work...

When dealing with the following example:

echo "1: " | awk '/1/ -F ":" {print $1}'

The syntax is messy and the interpreter chose to ignore the part F ":" and switches to the default field splitter which is the empty space, thus outputting "1:" as the first field and there will be not a second field!

The answer of Jürgen contains the good syntax...

How to check the exit status using an if statement

If you are writing a function, which is always preferred, you should propagate the error like this:

function() {
    if some_command; then
        echo worked
        return $?

This will propagate the error to the caller, so that he can do things like function && next as expected.

ASP.NET MVC - Getting QueryString values

I recommend using the ValueProvider property of the controller, much in the way that UpdateModel/TryUpdateModel do to extract the route, query, and form parameters required. This will keep your method signatures from potentially growing very large and being subject to frequent change. It also makes it a little easier to test since you can supply a ValueProvider to the controller during unit tests.

Enter key pressed event handler

In WPF, TextBox element will not get opportunity to use "Enter" button for creating KeyUp Event until you will not set property: AcceptsReturn="True".

But, it would`t solve the problem with handling KeyUp Event in TextBox element. After pressing "ENTER" you will get a new text line in TextBox.

I had solved problem of using KeyUp Event of TextBox element by using Bubble event strategy. It's short and easy. You have to attach a KeyUp Event handler in some (any) parent element:


<Window x:Class="TextBox_EnterButtomEvent.MainWindow"
    Title="MainWindow" Height="350" Width="525">
<Grid KeyUp="Grid_KeyUp">
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height ="0.3*"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
    <TextBlock Grid.Row="1" Grid.Column="1" Padding="0" TextWrapping="WrapWithOverflow">
        Input text end press ENTER:
    <TextBox Grid.Row="2" Grid.Column="1" HorizontalAlignment="Stretch"/>
    <TextBlock Grid.Row="4" Grid.Column="1" Padding="0" TextWrapping="WrapWithOverflow">
        You have entered:
    <TextBlock Name="txtBlock" Grid.Row="5" Grid.Column="1" HorizontalAlignment="Stretch"/>

C# logical part (KeyUp Event handler is attached to a grid element):

public partial class MainWindow : Window
    public MainWindow()

    private void Grid_KeyUp(object sender, KeyEventArgs e)
        if(e.Key == Key.Enter)
            TextBox txtBox = e.Source as TextBox;
            if(txtBox != null)
                this.txtBlock.Text = txtBox.Text;
                this.txtBlock.Background = new SolidColorBrush(Colors.LightGray);


Image with result

Set initially selected item in Select list in Angular2

Okay, so I figured out what the problem was, and the approach I believe works best. In my case, because the two objects weren't identical from a Javascript perspective, as in: they may have shared the same values, but they were different actual objects, e.g. originalObject was instantiated entirely separately from objects which was essentially an array of reference data (to populate the dropdown).

I found that the approach that worked best for me was to compare a unique property of the objects, rather than directly compare the two entire objects. This comparison is done in the bound property selected:

<select [ngModel]="originalObject">
    <option *ngFor="let object of objects" [ngValue]="object" [selected]="object.uniqueId === originalObject.uniqueId">{{}}</option>

How to merge rows in a column into one cell in excel?

I present to you my ConcatenateRange VBA function (thanks Jean for the naming advice!) . It will take a range of cells (any dimension, any direction, etc.) and merge them together into a single string. As an optional third parameter, you can add a seperator (like a space, or commas sererated).

In this case, you'd write this to use it:


Function ConcatenateRange(ByVal cell_range As range, _
                    Optional ByVal separator As String) As String

Dim newString As String
Dim cell As Variant

For Each cell in cell_range
    If Len(cell) <> 0 Then
        newString = newString & (separator & cell)
    End if

If Len(newString) <> 0 Then
    newString = Right$(newString, (Len(newString) - Len(separator)))
End If

ConcatenateRange = newString

End Function

Return first N key:value pairs from dict

For Python 3.8 the correct answer should be:

import more_itertools

d = {'a': 3, 'b': 2, 'c': 3, 'd': 4, 'e': 5}

first_n = more_itertools.take(3, d.items())

Whose output is:

[('a', 3), ('b', 2), ('c', 3)]

After pip install more-itertools of course.

Facebook Architecture

"Knowing about sites which handles such massive traffic gives lots of pointers for architects etc. to keep in mind certain stuff while designing new sites"

I think you can probably learn a lot from the design of Facebook, just as you can from the design of any successful large software system. However, it seems to me that you should not keep the current design of Facebook in mind when designing new systems.

Why do you want to be able to handle the traffic that Facebook has to handle? Odds are that you will never have to, no matter how talented a programmer you may be. Facebook itself was not designed from the start for such massive scalability, which is perhaps the most important lesson to learn from it.

If you want to learn about a non-trivial software system I can recommend the book "Dissecting a C# Application" about the development of the SharpDevelop IDE. It is out of print, but it is available for free online. The book gives you a glimpse into a real application and provides insights about IDEs which are useful for a programmer.

Argument Exception "Item with Same Key has already been added"

If you want "insert or replace" semantics, use this syntax:

A[key] = value;     // <-- insert or replace semantics

It's more efficient and readable than calls involving "ContainsKey()" or "Remove()" prior to "Add()".

So in your case:

rct3Features[items[0]] = items[1];

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

This works in Python 2.x.

For Python 3 look in the docs:

import urllib.request

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

Determine if Android app is being used for the first time

     * @author ALGO
    import java.util.UUID;

    import android.content.Context;

    public class Util {
        // ===========================================================
        // ===========================================================

        private static final String INSTALLATION = "INSTALLATION";

        public synchronized static boolean isFirstLaunch(Context context) {
            String sID = null;
            boolean launchFlag = false;
            if (sID == null) {
                File installation = new File(context.getFilesDir(), INSTALLATION);
                try {
                    if (!installation.exists()) {

                    sID = readInstallationFile(installation);
launchFlag = true;
                } catch (Exception e) {
                    throw new RuntimeException(e);
            return launchFlag;

        private static String readInstallationFile(File installation) throws IOException {
            RandomAccessFile f = new RandomAccessFile(installation, "r");// read only mode
            byte[] bytes = new byte[(int) f.length()];

            return new String(bytes);

        private static void writeInstallationFile(File installation) throws IOException {
            FileOutputStream out = new FileOutputStream(installation);
            String id = UUID.randomUUID().toString();

> Usage (in class extending


How to resolve "Waiting for Debugger" message?

Not sure if this is what you are looking for, but try putting:


in the application tag in the AndroidManifest.xml

Remove attribute "checked" of checkbox

try something like this FIDDLE

        navigator.device.capture.captureImage(function(mediaFiles) {

        $("#captureImage").prop('checked', false);


Postgresql : syntax error at or near "-"

i was trying trying to GRANT read-only privileges to a particular table to a user called walters-ro. So when i ran the sql command # GRANT SELECT ON table_name TO walters-ro; --- i got the following error..`syntax error at or near “-”

The solution to this was basically putting the user_name into double quotes since there is a dash(-) between the name.

# GRANT SELECT ON table_name TO "walters-ro";

That solved the problem.

Why can't I inherit static classes?

A workaround you can do is not use static classes but hide the constructor so the classes static members are the only thing accessible outside the class. The result is an inheritable "static" class essentially:

public class TestClass<T>
    protected TestClass()
    { }

    public static T Add(T x, T y)
        return (dynamic)x + (dynamic)y;

public class TestClass : TestClass<double>
    // Inherited classes will also need to have protected constructors to prevent people from creating instances of them.
    protected TestClass()
    { }

TestClass.Add(3.0, 4.0)
TestClass<int>.Add(3, 4)

// Creating a class instance is not allowed because the constructors are inaccessible.
// new TestClass();
// new TestClass<int>();

Unfortunately because of the "by-design" language limitation we can't do:

public static class TestClass<T>
    public static T Add(T x, T y)
        return (dynamic)x + (dynamic)y;

public static class TestClass : TestClass<double>

Could not load file or assembly ... The parameter is incorrect

You can either clean, build or rebuild your application or simply delete Temporary ASP.NET Files at C:\Users\YOUR USERNAME\AppData\Local\Temp

This works like magic. In my case i had an assembly binding issue saying Could not load file bla bla bla

you can also see solution 2 as

How do I get only directories using Get-ChildItem?


Get-ChildItem -dir #lists only directories
Get-ChildItem -file #lists only files

If you prefer aliases, use

ls -dir #lists only directories
ls -file #lists only files


dir -dir #lists only directories
dir -file #lists only files

To recurse subdirectories as well, add -r option.

ls -dir -r #lists only directories recursively
ls -file -r #lists only files recursively 

Tested on PowerShell 4.0, PowerShell 5.0 (Windows 10), PowerShell Core 6.0 (Windows 10, Mac, and Linux), and PowerShell 7.0 (Windows 10, Mac, and Linux).

Note: On PowerShell Core, symlinks are not followed when you specify the -r switch. To follow symlinks, specify the -FollowSymlink switch with -r.

Note 2: PowerShell is now cross-platform, since version 6.0. The cross-platform version was originally called PowerShell Core, but the the word "Core" has been dropped since PowerShell 7.0+.

Get-ChildItem documentation:

Accessing MVC's model property from Javascript

You could take your entire server-side model and turn it into a Javascript object by doing the following:

var model = @Html.Raw(Json.Encode(Model));

In your case if you just want the FloorPlanSettings object, simply pass the Encode method that property:

var floorplanSettings = @Html.Raw(Json.Encode(Model.FloorPlanSettings));

Best way to remove items from a collection

If you want to access members of the collection by one of their properties, you might consider using a Dictionary<T> or KeyedCollection<T> instead. This way you don't have to search for the item you're looking for.

Otherwise, you could at least do this:

foreach (SPRoleAssignment spAssignment in workspace.RoleAssignments)
    if (spAssignment.Member.Name == shortName)

how to call scalar function in sql server 2008

For Scalar Function Syntax is

Select dbo.Function_Name(parameter_name)

Select dbo.Department_Employee_Count('HR')

Changing a specific column name in pandas DataFrame

For renaming the columns here is the simple one which will work for both Default(0,1,2,etc;) and existing columns but not much useful for a larger data sets(having many columns).

For a larger data set we can slice the columns that we need and apply the below code:

df.columns = ['new_name','new_name1','old_name']

Difference between Constructor and ngOnInit

The constructor is called when Angular "instanciates/constructs" the component. The ngOnInit method is a hook which represents the initialization part of the component lifecycle. A good practice is to use it only for service injection:

    service1: Service1,
    service2: Service2

Even if it is possible, you should not do some "work" inside. If you want to launch some action which have to occur at component "initialization", use ngOnInit:


Moreover, actions that involve input properties, coming from a parent component, can't be done in the contructor. They should be placed in ngOnInit method or another hook. It is the same for element related to the view (the DOM), for example, viewchild elements:

@Input itemFromParent: string;
@ViewChild('childView') childView;

    console.log(itemFromParent); // KO
    // childView is undefined here

    console.log(itemFromParent); // OK
    // childView is undefined here, you can manipulate here