Programs & Examples On #Libtool

GNU libtool is a generic library support script. Libtool hides the complexity of using shared libraries behind a consistent, portable interface.

What are libtool's .la file for?

It is a textual file that includes a description of the library.

It allows libtool to create platform-independent names.

For example, libfoo goes to:

Under Linux:

/lib/       # Symlink to shared object
/lib/     # Symlink to shared object
/lib/ # Shared object
/lib/libfoo.a        # Static library
/lib/       # 'libtool' library

Under Cygwin:

/lib/libfoo.dll.a    # Import library
/lib/libfoo.a        # Static library
/lib/       # libtool library
/bin/cygfoo_1.dll    # DLL

Under Windows MinGW:

/lib/libfoo.dll.a    # Import library
/lib/libfoo.a        # Static library
/lib/       # 'libtool' library
/bin/foo_1.dll       # DLL

So is the only file that is preserved between platforms by libtool allowing to understand what happens with:

  • Library dependencies
  • Actual file names
  • Library version and revision

Without depending on a specific platform implementation of libraries.

JavaScript inside an <img title="<a href='#' onClick='alert('Hello World!')>The Link</a>" /> possible?

When you click on the image you'll get the alert:

<img src="logo1.jpg" onClick='alert("Hello World!")'/>

if this is what you want.

What is the difference between an int and a long in C++?

For the most part, the number of bytes and range of values is determined by the CPU's architecture not by C++. However, C++ sets minimum requirements, which litb explained properly and Martin York only made a few mistakes with.

The reason why you can't use int and long interchangeably is because they aren't always the same length. C was invented on a PDP-11 where a byte had 8 bits, int was two bytes and could be handled directly by hardware instructions. Since C programmers often needed four-byte arithmetic, long was invented and it was four bytes, handled by library functions. Other machines had different specifications. The C standard imposed some minimum requirements.

Is CSS Turing complete?

One aspect of Turing completeness is the halting problem.

This means that, if CSS is Turing complete, then there's no general algorithm for determining whether a CSS program will finish running or loop forever.

But we can derive such an algorithm for CSS! Here it is:

  • If the stylesheet doesn't declare any animations, then it will halt.

  • If it does have animations, then:

    • If any animation-iteration-count is infinite, and the containing selector is matched in the HTML, then it will not halt.

    • Otherwise, it will halt.

That's it. Since we just solved the halting problem for CSS, it follows that CSS is not Turing complete.

(Other people have mentioned IE 6, which allows for embedding arbitrary JavaScript expressions in CSS; that will obviously add Turing completeness. But that feature is non-standard, and nobody in their right mind uses it anyway.)

Daniel Wagner brought up a point that I missed in the original answer. He notes that while I've covered animations, other parts of the style engine such as selector matching or layout can lead to Turing completeness as well. While it's difficult to make a formal argument about these, I'll try to outline why Turing completeness is still unlikely to happen.

First: Turing complete languages have some way of feeding data back into itself, whether it be through recursion or looping. But the design of the CSS language is hostile to this feedback:

  • @media queries can only check properties of the browser itself, such as viewport size or pixel resolution. These properties can change via user interaction or JavaScript code (e.g. resizing the browser window), but not through CSS alone.

  • ::before and ::after pseudo-elements are not considered part of the DOM, and cannot be matched in any other way.

  • Selector combinators can only inspect elements above and before the current element, so they cannot be used to create dependency cycles.

  • It's possible to shift an element away when you hover over it, but the position only updates when you move the mouse.

That should be enough to convince you that selector matching, on its own, cannot be Turing complete. But what about layout?

The modern CSS layout algorithm is very complex, with features such as Flexbox and Grid muddying the waters. But even if it were possible to trigger an infinite loop with layout, it would be hard to leverage this to perform useful computation. That's because CSS selectors inspect only the internal structure of the DOM, not how these elements are laid out on the screen. So any Turing completeness proof using the layout system must depend on layout alone.

Finally – and this is perhaps the most important reason – browser vendors have an interest in keeping CSS not Turing complete. By restricting the language, vendors allow for clever optimizations that make the web faster for everyone. Moreover, Google dedicates a whole server farm to searching for bugs in Chrome. If there were a way to write an infinite loop using CSS, then they probably would have found it already

Android getting value from selected radiobutton

radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
       public void onCheckedChanged(RadioGroup group, int checkedId)
           radioButton = (RadioButton) findViewById(checkedId);
           Toast.makeText(getBaseContext(), radioButton.getText(), Toast.LENGTH_SHORT).show();

Trim leading and trailing spaces from a string in awk

If you want to trim all spaces, only in lines that have a comma, and use awk, then the following will work for you:

awk -F, '/,/{gsub(/ /, "", $0); print} ' input.txt

If you only want to remove spaces in the second column, change the expression to

awk -F, '/,/{gsub(/ /, "", $2); print$1","$2} ' input.txt

Note that gsub substitutes the character in // with the second expression, in the variable that is the third parameter - and does so in-place - in other words, when it's done, the $0 (or $2) has been modified.

Full explanation:

-F,            use comma as field separator 
               (so the thing before the first comma is $1, etc)
/,/            operate only on lines with a comma 
               (this means empty lines are skipped)
gsub(a,b,c)    match the regular expression a, replace it with b, 
               and do all this with the contents of c
print$1","$2   print the contents of field 1, a comma, then field 2
input.txt      use input.txt as the source of lines to process

EDIT I want to point out that @BMW's solution is better, as it actually trims only leading and trailing spaces with two successive gsub commands. Whilst giving credit I will give an explanation of how it works.

gsub(/^[ \t]+/,"",$2);    - starting at the beginning (^) replace all (+ = zero or more, greedy)
                             consecutive tabs and spaces with an empty string
gsub(/[ \t]+$/,"",$2)}    - do the same, but now for all space up to the end of string ($)
1                         - ="true". Shorthand for "use default action", which is print $0
                          - that is, print the entire (modified) line

CSS Input Type Selectors - Possible to have an "or" or "not" syntax?

CSS3 has a pseudo-class called :not()

input:not([type='checkbox']) {    
    visibility: hidden;
<p>If <code>:not()</code> is supported, you'll only see the checkbox.</p>
  <li>text: (<input type="text">)</li>  
  <li>password (<input type="password">)</li>       
  <li>checkbox (<input type="checkbox">)</li> 

Multiple selectors

As Vincent mentioned, it's possible to string multiple :not()s together:


CSS4, which is supported in many of the latest browser releases, allows multiple selectors in a :not()


Legacy support

All modern browsers support the CSS3 syntax. At the time this question was asked, we needed a fall-back for IE7 and IE8. One option was to use a polyfill like IE9.js. Another was to exploit the cascade in CSS:

input {
   // styles for most inputs

input[type=checkbox] {
  // revert back to the original style

input.checkbox {
  // for completeness, this would have worked even in IE3!

How to initialize log4j properly?

Log4j by default looks for a file called or log4j.xml on the classpath.

You can control which file it uses to initialize itself by setting system properties as described here (Look for the "Default Initialization Procedure" section).

For example:

java -Dlog4j.configuration=customName ....

Will cause log4j to look for a file called customName on the classpath.

If you are having problems I find it helpful to turn on the log4j.debug:


It will print to System.out lots of helpful information about which file it used to initialize itself, which loggers / appenders got configured and how etc.

The configuration file can be a java properties file or an xml file. Here is a sample of the properties file format taken from the log4j intro documentation page:

log4j.rootLogger=debug, stdout, R


# Pattern to output the caller's file name and line number.
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n


# Keep one backup file

log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n

How to set image width to be 100% and height to be auto in react native?

function ImageX( props){
   const [state, setState] = React.useState({v:{height:1}});
   useEffect(() => {
    if(!props.source || !props.source.uri) return;
    .then(() => {
        Image.getSize(props.source.uri, (width, height) => {
          let aspectRatio =  height/width;
    .catch(error => console.log(error))
   },[props.source && props.source.uri]);
   if (state.v.height <=1) //Image not in cache (disk) yet
      return (
        <Image {...props}/>
     let neededst={v:{width:state.v.width, height:state.v.height}}
     let st={};
    assignObject(neededst, st);
     return (
       <Image {...props} style={neededst.v}/>

 function assignObject(target, source) {
  if (!source) return;
  for (let k in target) {
    let v = target[k];
    if (Object(v) === Object) assignObject(v, source[k]);
    else {
      if (source[k]) {
        try {
          Object.assign(v, source[k]);
        } catch (e) {

  for (let k in source) {
    if (!target[k]) {
      target[k] = source[k];


Using Image component from

how to clear JTable

If we use tMOdel.setRowCount(0); we can get Empty table.

DefaultTableModel tMOdel = (DefaultTableModel) jtableName.getModel();

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;

Set form backcolor to custom color

With Winforms you can use Form.BackColor to do this.
From within the Form's code:

BackColor = Color.LightPink;

If you mean a WPF Window you can use the Background property.
From within the Window's code:

Background = Brushes.LightPink;

Understanding `scale` in R

log simply takes the logarithm (base e, by default) of each element of the vector.
scale, with default settings, will calculate the mean and standard deviation of the entire vector, then "scale" each element by those values by subtracting the mean and dividing by the sd. (If you use scale(x, scale=FALSE), it will only subtract the mean but not divide by the std deviation.)

Note that this will give you the same values

   x <- runif(7)

   # Manually scaling
   (x - mean(x)) / sd(x)


How do you import a large MS SQL .sql file?

I had exactly the same issue and had been struggling for a while then finally found the solution which is to set -a parameter to the sqlcmd in order to change its default packet size:

sqlcmd -S [servername] -d [databasename] -i [scriptfilename] -a 32767

Reloading .env variables without restarting server (Laravel 5, shared hosting)

In config/database.php I changed the default DB connection from mysql to sqlite. I deleted the .env file (actually renamed it) and created the sqlite file with touch storage/database.sqlite. The migration worked with sqlite.

Then I switched back the config/database.php default DB connection to mysql and recovered the .env file. The migration worked with mysql.

It doesn't make sense I guess. Maybe was something serverside.

How can I inspect the file system of a failed `docker build`?

What I would do is comment out the Dockerfile below and including the offending line. Then you can run the container and run the docker commands by hand, and look at the logs in the usual way. E.g. if the Dockerfile is

RUN foo
RUN bar
RUN baz

and it's dying at bar I would do

RUN foo
# RUN bar
# RUN baz


$ docker build -t foo .
$ docker run -it foo bash
container# bar
...grep logs...

Angular 2 - innerHTML styling

If you are using sass as style preprocessor, you can switch back to native Sass compiler for dev dependency by:

npm install node-sass --save-dev

So that you can keep using /deep/ for development.

How do you remove columns from a data.frame?


# exclude variables v1, v2, v3
myvars <- names(mydata) %in% c("v1", "v2", "v3") 
newdata <- mydata[!myvars]

# exclude 3rd and 5th variable 
newdata <- mydata[c(-3,-5)]

# delete variables v3 and v5
mydata$v3 <- mydata$v5 <- NULL

Thought it was really clever make a list of "not to include"

Send raw ZPL to Zebra printer via USB

You can use COM, or P/Invoke from .Net, to open the Winspool.drv driver and send bytes directly to devices. But you don't want to do that; this typically works only for the one device on the one version of the one driver you test with, and breaks on everything else. Take this from long, painful, personal experience.

What you want to do is get a barcode font or library that draws barcodes using plain old GDI or GDI+ commands; there's one for .Net here. This works on all devices, even after Zebra changes the driver.

URL to load resources from the classpath in Java

In a Spring Boot app, I used the following to get the file URL,


Catch browser's "zoom" event in JavaScript

I'am replying to a 3 year old link but I guess here's a more acceptable answer,

Create .css file as,

@media screen and (max-width: 1000px) 
       // things you want to trigger when the screen is zoomed


@media screen and (max-width: 1000px) 

The above code makes the size of the font '10px' when the screen is zoomed to approximately 125%. You can check for different zoom level by changing the value of '1000px'.

How to concatenate characters in java?

System.out.print(a + "" + b + "" + c);

Oracle SQL query for Date format

you can use this command by getting your data. this will extract your data...

select * from employees where to_char(es_date,'dd/mon/yyyy')='17/jun/2003';

Center form submit buttons HTML / CSS

Try this :

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "">
    <style type="text/css">

        #btn_i {
        #formbox {
            margin:auto 0;
            text-align: center;
    <form method="post" action="">
        <div id="formbox">
            <input value="Search" title="Search" type="submit" id="btn_s"> 
            <input value="I'm Feeling Lucky" title="I'm Feeling Lucky" name="lucky" type="submit" id="btn_i">

This has 2 examples, you can use the one that fits best in your situation.

  • use text-align:center on the parent container, or create a container for this.
  • if the container has to have a fixed size, use auto left and right margins to center it in the parent container.

note that auto is used with single blocks to center them in the parent space by distrubuting the empty space to the left and right.

Importing Maven project into Eclipse

I want to import existing maven project into eclipse. I found 2 ways to do it, one is through running from command line mvn eclipse:eclipse and another is to install maven eclipse plugin from eclipse. What is the difference between the both and which one is preferable?

The maven-eclipse-plugin is a Maven plugin and has always been there (one of the first plugin available with Maven 1, one of the first plugin migrated to Maven 2). It has been during a long time the only decent way to integrateimport an existing maven project with Eclipse. Actually, it doesn't provide real integration, it just generates the .project and .classpath files (it has also WTP support) from a Maven project. I've used this plugin during years and was very happy with it (and very unsatisfied at this time by Eclipse plugins for Maven like m2eclipse).

The m2eclipse plugin is one of the Eclipse plugins for Maven. It's actually the first and most mature of the projects aimed at integrating Maven within the Eclipse IDE (this has not always been the case, it was not really usable ~2 years ago, see the feedback in Mevenide vs. M2Eclipse, Q for Eclipse/IAM). But, even if I do not use things like creating a Maven project from Eclipse or the POM editor or other fancy wizards, I have to say that this plugin is now totally usable, provides very smooth integration, has nice features... In other words, I finally switched to it :) I'd now recommend it to any user (advanced or beginners).

If I install maven eclipse plugin through the eclipse menu Help -> Install New Software, do I still need to modify my pom.xml to include the maven eclipse plugin in the plugins section?

This question is a bit confusing but the answer is no. With the m2eclipse plugin installed, just right-click the package explorer and Import... > Maven projects to import an existing maven project into Eclipse.

jQuery datepicker set selected date, on the fly

or you can simply have

$('.date-pick').datePicker().val(new Date()).trigger('change')

jQuery set checkbox checked

"checked" attribute 'ticks' the checkbox as soon as it exists. So to check/uncheck a checkbox you have to set/unset the attribute.

For checking the box:

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

For unchecking the box:


For testing the checked status:

if ($('#myCheckbox').is(':checked'))

Hope it helps...

What arguments are passed into AsyncTask<arg1, arg2, arg3>?

I'm too late to the party but thought this might help someone.

E: gnupg, gnupg2 and gnupg1 do not seem to be installed, but one of them is required for this operation

In your Dockerfile, run this first:

apt-get update && apt-get install -y gnupg2

intellij incorrectly saying no beans of type found for autowired repository

Sometimes - in my case that is - the reason is a wrong import. I accidentally imported

import org.jvnet.hk2.annotations.Service

instead of

import org.springframework.stereotype.Service

by blindly accepting the first choice in Idea's suggested imports. Took me a few minutes the first time it happend :-)

form confirm before submit

$('.testform').submit(function() {
  if ($(this).data('first-submit')) {
    return true;
  } else {
    $(this).find('.submitbtn').val('Confirm').data('first-submit', true);
    return false;

Maven: how to override the dependency added by a library

I also had trouble overruling a dependency in a third party library. I used scot's approach with the exclusion but I also added the dependency with the newer version in the pom. (I used Maven 3.3.3)

So for the stAX example it would look like this:

    <!--  STAX comes with Java 1.6 -->


sql set variable using COUNT

You want:

DECLARE @times int

SELECT @times =  COUNT(DidWin)
FROM thetable
WHERE DidWin = 1 AND Playername='Me'

You also don't need the 'as' clause.

How to add header to a dataset in R?

this should work out,

      kable(dt) %>%
      kable_styling("striped") %>%
      add_header_above(c(" " = 1, "Group 1" = 2, "Group 2" = 2, "Group 3" = 2))
kable(dt) %>%
  kable_styling(c("striped", "bordered")) %>%
  add_header_above(c(" ", "Group 1" = 2, "Group 2" = 2, "Group 3" = 2)) %>%
  add_header_above(c(" ", "Group 4" = 4, "Group 5" = 2)) %>%
  add_header_above(c(" ", "Group 6" = 6))

for more you can check the link

Remove duplicates from a List<T> in C#

If you're using .Net 3+, you can use Linq.

List<T> withDupes = LoadSomeData();
List<T> noDupes = withDupes.Distinct().ToList();

Typescript react - Could not find a declaration file for module ''react-materialize'. 'path/to/module-name.js' implicitly has an any type

Just install the necessary types for react and it should solve the error.

if you are using yarn:

yarn add @types/react @types/react-dom @types/react-router-dom -D

if you are using npm:

npm install @types/react @types/react-dom @types/react-router-dom --save-dev

Adding rows to tbody of a table using jQuery

("#tblEntAttributes tbody")

needs to be

$("#tblEntAttributes tbody").

You are not selecting the element with the correct syntax

Here's an example of both



$("#tblEntAttributes tbody").append(newRowContent);


What was the strangest coding standard rule that you were forced to follow?

Applying s_ to variables and methods which were deemed "safety critical" for software that was part of a control system. Couple this with the other rule about putting m_ on the front of member variables and you'd get something ridiculous like "s_m_blah()", which is darn annoying to write and not very readable in my opinion. In the end some 'safety expert' was supposed to gain insight by looking at the code and determining something from it by using those "s_" - in practice, they didn't know c++ too well so they couldn't do much other than make reports on the number of identifiers that we'd marked as 'safety critical'. Utter nonsense...

How to know if two arrays have the same values

I had simple integer values in a Game project
Had less number of values in each array, also, needed that original array untouched
So, I did the below, it worked fine. (Code edited to paste here)

var sourceArray = [1, 2, 3];
var targetArray = [3, 2, 1];

if (sourceArray.length !== targetArray.length) {
    // not equal
    // did something
    return false;

var newSortedSourceArray = sourceArray.slice().sort();
var newSortedTargetArray = targetArray.slice().sort();

if (newSortedSourceArray.toString() !== newSortedTargetArray.toString()) { // MAIN CHECK
    // not equal
    // did something
    return false;
else {
    // equal
    // did something
    // continued further below

// did some more work

return true;

Hope that helps.

How to check if input file is empty in jQuery

Questions : how to check File is empty or not?

Ans: I have slove this issue using this Jquery code

//If your file Is Empty :     _x000D_
      if (jQuery('#videoUploadFile').val() == '') {_x000D_
                       $('#message').html("Please Attach File");_x000D_
                   }else {_x000D_
                            alert('not work');_x000D_
<script src=""></script>_x000D_
<input type="file" id="videoUploadFile">_x000D_
<div id="message"></div>

Are nested try/except blocks in Python a good programming practice?

I don't think it's a matter of being Pythonic or elegant. It's a matter of preventing exceptions as much as you can. Exceptions are meant to handle errors that might occur in code or events you have no control over.

In this case, you have full control when checking if an item is an attribute or in a dictionary, so avoid nested exceptions and stick with your second attempt.

How to find whether or not a variable is empty in Bash?

The question asks how to check if a variable is an empty string and the best answers are already given for that.

But I landed here after a period passed programming in PHP, and I was actually searching for a check like the empty function in PHP working in a Bash shell.

After reading the answers I realized I was not thinking properly in Bash, but anyhow in that moment a function like empty in PHP would have been soooo handy in my Bash code.

As I think this can happen to others, I decided to convert the PHP empty function in Bash.

According to the PHP manual:

a variable is considered empty if it doesn't exist or if its value is one of the following:

  • "" (an empty string)
  • 0 (0 as an integer)
  • 0.0 (0 as a float)
  • "0" (0 as a string)
  • an empty array
  • a variable declared, but without a value

Of course the null and false cases cannot be converted in bash, so they are omitted.

function empty
    local var="$1"

    # Return true if:
    # 1.    var is a null string ("" as empty string)
    # 2.    a non set variable is passed
    # 3.    a declared variable or array but without a value is passed
    # 4.    an empty array is passed
    if test -z "$var"
        [[ $( echo "1" ) ]]

    # Return true if var is zero (0 as an integer or "0" as a string)
    elif [ "$var" == 0 2> /dev/null ]
        [[ $( echo "1" ) ]]

    # Return true if var is 0.0 (0 as a float)
    elif [ "$var" == 0.0 2> /dev/null ]
        [[ $( echo "1" ) ]]

    [[ $( echo "" ) ]]

Example of usage:

if empty "${var}"
        echo "empty"
        echo "not empty"

The following snippet:


    " "

for (( i=0; i<${#vars[@]}; i++ ))

    if empty "${var}"
            what="not empty"
    echo "VAR \"$var\" is $what"



VAR "" is empty
VAR "0" is empty
VAR "0.0" is empty
VAR "0" is empty
VAR "1" is not empty
VAR "string" is not empty
VAR " " is not empty

Having said that in a Bash logic the checks on zero in this function can cause side problems imho, anyone using this function should evaluate this risk and maybe decide to cut those checks off leaving only the first one.

C# 4.0 optional out/ref arguments

No, but another great alternative is having the method use a generic template class for optional parameters as follows:

public class OptionalOut<Type>
    public Type Result { get; set; }

Then you can use it as follows:

public string foo(string value, OptionalOut<int> outResult = null)
    // .. do something

    if (outResult != null) {
        outResult.Result = 100;

    return value;

public void bar ()
    string str = "bar";

    string result;
    OptionalOut<int> optional = new OptionalOut<int> ();

    // example: call without the optional out parameter
    result = foo (str);
    Console.WriteLine ("Output was {0} with no optional value used", result);

    // example: call it with optional parameter
    result = foo (str, optional);
    Console.WriteLine ("Output was {0} with optional value of {1}", result, optional.Result);

    // example: call it with named optional parameter
    foo (str, outResult: optional);
    Console.WriteLine ("Output was {0} with optional value of {1}", result, optional.Result);

What is difference between MVC, MVP & MVVM design pattern in terms of coding c#

Great Explanation from the link :

Let's First look at MVC

The input is directed at the Controller first, not the view. That input might be coming from a user interacting with a page, but it could also be from simply entering a specific url into a browser. In either case, its a Controller that is interfaced with to kick off some functionality.

There is a many-to-one relationship between the Controller and the View. That’s because a single controller may select different views to be rendered based on the operation being executed.

There is one way arrow from Controller to View. This is because the View doesn’t have any knowledge of or reference to the controller.

The Controller does pass back the Model, so there is knowledge between the View and the expected Model being passed into it, but not the Controller serving it up.

MVP – Model View Presenter

Now let’s look at the MVP pattern. It looks very similar to MVC, except for some key distinctions:

The input begins with the View, not the Presenter.

There is a one-to-one mapping between the View and the associated Presenter.

The View holds a reference to the Presenter. The Presenter is also reacting to events being triggered from the View, so its aware of the View its associated with.

The Presenter updates the View based on the requested actions it performs on the Model, but the View is not Model aware.

MVVM – Model View View Model

So with the MVC and MVP patterns in front of us, let’s look at the MVVM pattern and see what differences it holds:

The input begins with the View, not the View Model.

While the View holds a reference to the View Model, the View Model has no information about the View. This is why its possible to have a one-to-many mapping between various Views and one View Model…even across technologies. For example, a WPF View and a Silverlight View could share the same View Model.

How to connect to mysql with laravel?

Maybe you forgot to first create a table migrations:

php artisan migrate:install

Also there is a very userful package Generators, which makes a lot of work for you

Data was not saved: object references an unsaved transient instance - save the transient instance before flushing

Looks like Users that are added in your Country object, are not already present in the DB. You need to use cascade to make sure that when Country is persisted, all User which are not there in data but are associated with Country also get persisted.

Below code should help:

@ManyToOne (cascade = CascadeType.ALL)
   @JoinColumn (name = "countryId")
   private Country country;

Swift Open Link in Safari

In Swift 1.2:

@IBAction func openLink {    
    let pth = ""
    if let url = NSURL(string: pth){

Printing leading 0's in C

ZIP Code is a highly localised field, and many countries have characters in their postcodes, e.g., UK, Canada. Therefore, in this example, you should use a string / varchar field to store it if at any point you would be shipping or getting users, customers, clients, etc. from other countries.

However, in the general case, you should use the recommended answer (printf("%05d", number);).

What is InputStream & Output Stream? Why and when do we use them?

From the Java Tutorial:

A stream is a sequence of data.

A program uses an input stream to read data from a source, one item at a time:

enter image description here

A program uses an output stream to write data to a destination, one item at time:

enter image description here

The data source and data destination pictured above can be anything that holds, generates, or consumes data. Obviously this includes disk files, but a source or destination can also be another program, a peripheral device, a network socket, or an array.

Sample code from oracle tutorial:


public class CopyBytes {
    public static void main(String[] args) throws IOException {

        FileInputStream in = null;
        FileOutputStream out = null;

        try {
            in = new FileInputStream("xanadu.txt");
            out = new FileOutputStream("outagain.txt");
            int c;

            while ((c = != -1) {
        } finally {
            if (in != null) {
            if (out != null) {

This program uses byte streams to copy xanadu.txt file to outagain.txt , by writing one byte at a time

Have a look at this SE question to know more details about advanced Character streams, which are wrappers on top of Byte Streams :

byte stream and character stream

Min / Max Validator in Angular 2 Final

This question has already been answered. I'd like to extend the answer from @amd. Sometimes you might need a default value.

For example, to validate against a specific value, I'd like to provide it as follows-

<input integerMinValue="20" >

But the minimum value of a 32 bit signed integer is -2147483648. To validate against this value, I don't like to provide it. I'd like to write as follows-

<input integerMinValue >

To achieve this you can write your directive as follows

import {Directive, Input} from '@angular/core';
import {AbstractControl, NG_VALIDATORS, ValidationErrors, Validator, Validators} from '@angular/forms';

    selector: '[integerMinValue]',
    providers: [{provide: NG_VALIDATORS, useExisting: IntegerMinValidatorDirective, multi: true}]
export class IntegerMinValidatorDirective implements Validator {

    private minValue = -2147483648;

    @Input('integerMinValue') set min(value: number) {
        if (value) {
            this.minValue = +value;

    validate(control: AbstractControl): ValidationErrors | null {
        return Validators.min(this.minValue)(control);


Why has it failed to load main-class manifest attribute from a JAR file?

I discovered that I was also having this error in NetBeans. I hope the following is helpful.

  1. Make sure that when you go to Project Configuration you set the main class you intend for running.
  2. Do a Build or Clean Build
  3. Place the jar file where you wish and try: java -jar "YourProject.jar" again at the command line.

This was the problem I was getting because I had other "test" programs I was using in NetBeans and I had to make sure the Main Class under the Run portion of the Project configuration was set correctly.

many blessings, John P

How to reverse an std::string?


string reversed(temp.rbegin(), temp.rend());

EDIT: Elaborating as requested.

string::rbegin() and string::rend(), which stand for "reverse begin" and "reverse end" respectively, return reverse iterators into the string. These are objects supporting the standard iterator interface (operator* to dereference to an element, i.e. a character of the string, and operator++ to advance to the "next" element), such that rbegin() points to the last character of the string, rend() points to the first one, and advancing the iterator moves it to the previous character (this is what makes it a reverse iterator).

Finally, the constructor we are passing these iterators into is a string constructor of the form:

template <typename Iterator>
string(Iterator first, Iterator last);

which accepts a pair of iterators of any type denoting a range of characters, and initializes the string to that range of characters.

Using a .php file to generate a MySQL dump

MajorLeo's answer point me in the right direction but it didn't worked for me. I've found this site that follows the same approach and did work.

$dir = "path/to/file/";
$filename = "backup" . date("YmdHis") . ".sql.gz";

$db_host = "host";
$db_username = "username";
$db_password = "password";
$db_database = "database";

$cmd = "mysqldump -h {$db_host} -u {$db_username} --password={$db_password} {$db_database} | gzip > {$dir}{$filename}";

header("Content-type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"$filename\"");

passthru("cat {$dir}{$filename}");

I hope it helps someone else!

Tensorflow import error: No module named 'tensorflow'

deleting tensorflow from cDrive/users/envs/tensorflow and after that

conda create -n tensorflow python=3.6
 activate tensorflow
 pip install --ignore-installed --upgrade tensorflow

now its working for newer versions of python thank you

Select specific row from mysql table

SET @customerID=0;
SELECT @customerID:=@customerID+1 AS customerID

you can obtain the dataset from SQL like this and populate it into a java data structure (like a List) and then make the necessary sorting over there. (maybe with the help of a comparable interface)

jQuery UI 1.10: dialog and zIndex option

You may want to try jQuery dialog method:

$( ".selector" ).dialog( "moveToTop" );


MySQL 8.0 - Client does not support authentication protocol requested by server; consider upgrading MySQL client

I had this error for several hours an just got to the bottom of it, finally. As Zchary says, check very carefully you're passing in the right database name.

Actually, in my case, it was even worse: I was passing in all my createConnection() parameters as undefined because I was picking them up from process.env. Or so I thought! Then I realised my debug and test npm scripts worked but things failed for a normal run. Hmm...

So the point is - MySQL seems to throw this error even when the username, password, database and host fields are all undefined, which is slightly misleading..

Anyway, morale of the story - check the silly and seemingly-unlikely things first!

How can I catch an error caused by mail()?

PHPMailer handles errors nicely, also a good script to use for sending mail via SMTP...

if(!$mail->Send()) {
  echo "Mailer Error: " . $mail->ErrorInfo;
} else {
  echo "Message sent!";

What does this expression language ${pageContext.request.contextPath} exactly do in JSP EL?

For my project's setup, "${pageContext.request.contextPath}"= refers to "src/main/webapp". Another way to tell is by right clicking on your project in Eclipse and then going to Properties:

enter image description here

javascript: optional first argument in function

Call like this

my_function ("", options);

Change New Google Recaptcha (v2) Width

unfortunately none of the above worked. I finally could do it using the following stuffs: This solution works 100% (adapt it to your need)

.g-recaptcha-wrapper {_x000D_
    position: relative;_x000D_
    border: 1px solid #ededed;_x000D_
    background: #f9f9f9;_x000D_
    border-radius: 4px;_x000D_
    padding: 0;_x000D_
    #topHider {_x000D_
        position: absolute;_x000D_
        top: 0;_x000D_
        left: 0;_x000D_
        height: 2px !important;_x000D_
        width: 100%;_x000D_
        background-color: #f9f9f9;_x000D_
    #rightHider {_x000D_
        position: absolute;_x000D_
        top: 0;_x000D_
        left: 295px;_x000D_
        height: 100% !important;_x000D_
        width: 15px;_x000D_
        background-color: #f9f9f9;_x000D_
    #leftHider {_x000D_
        position: absolute;_x000D_
        top: 0;_x000D_
        left: 0;_x000D_
        height: 100% !important;_x000D_
        width: 2px;_x000D_
        background-color: #f9f9f9;_x000D_
    #bottomHider {_x000D_
        position: absolute;_x000D_
        bottom: 1px;_x000D_
        left: 0;_x000D_
        height: 2px !important;_x000D_
        width: 100%;_x000D_
        background-color: #f9f9f9;_x000D_
<div class="g-recaptcha-wrapper">_x000D_
  <re-captcha #captchaRef="reCaptcha" (resolved)="onCaptchaResolved($event)" siteKey="{{captchaSiteKey}}"></re-captcha>_x000D_
  <div id="topHider"></div>_x000D_
  <div id="rightHider"></div>_x000D_
  <div id="bottomHider"></div>_x000D_
  <div id="leftHider"></div>_x000D_

Result enter image description here

What is an unsigned char?

char and unsigned char aren't guaranteed to be 8-bit types on all platforms—they are guaranteed to be 8-bit or larger. Some platforms have 9-bit, 32-bit, or 64-bit bytes. However, the most common platforms today (Windows, Mac, Linux x86, etc.) have 8-bit bytes.

SQL how to make null values come last when sorting ascending

SELECT *          
FROM Employees
ORDER BY ISNULL(DepartmentId, 99999);

See this blog post.

How to resolve "Server Error in '/' Application" error?

It sounds like the admin has locked the "authentication" node of the web.config, which one can do in the global web.config pretty easily. Or, in a nutshell, this is working as designed.

How to count lines of Java code using IntelliJ IDEA?

Statistic plugins works fine!

Here is a quick case:

  1. Ctrl+Shift+A and serach for "Statistic" to open the panel.
  2. You will see panel as the screenshot and then click Refresh for whole project or select your project or file and Refresh on selection for only selection.


Array inside a JavaScript Object?

var data = {_x000D_
  name: "Ankit",_x000D_
  age: 24,_x000D_
  workingDay: ["Mon", "Tue", "Wed", "Thu", "Fri"]_x000D_
for (const key in data) {_x000D_
  if (data.hasOwnProperty(key)) {_x000D_
    const element = data[key];_x000D_
      console.log(key+": ", element);_x000D_

For loop example in MySQL

While loop syntax example in MySQL:

delimiter //

CREATE procedure yourdatabase.while_example()
  declare str VARCHAR(255) default '';
  declare x INT default 0;
  SET x = 1;

  WHILE x <= 5 DO
    SET str = CONCAT(str,x,',');
    SET x = x + 1;

  select str;

Which prints:

mysql> call while_example();
| str        |
| 1,2,3,4,5, |

REPEAT loop syntax example in MySQL:

delimiter //

CREATE procedure yourdb.repeat_loop_example()
  SET x = 5;
  SET str = '';

    SET str = CONCAT(str,x,',');
    SET x = x - 1;
    UNTIL x <= 0

  SELECT str;

Which prints:

mysql> call repeat_loop_example();
| str        |
| 5,4,3,2,1, |

FOR loop syntax example in MySQL:

delimiter //

CREATE procedure yourdatabase.for_loop_example()
  SET x = -5;
  SET str = '';

  loop_label: LOOP
    IF x > 0 THEN
      LEAVE loop_label;
    END IF;
    SET str = CONCAT(str,x,',');
    SET x = x + 1;
    ITERATE loop_label;

  SELECT str;


Which prints:

mysql> call for_loop_example();
| str               |
| -5,-4,-3,-2,-1,0, |
1 row in set (0.00 sec)

Do the tutorial:

If I catch you pushing this kind of MySQL for-loop constructs into production, I'm going to shoot you with the foam missile launcher. You can use a pipe wrench to bang in a nail, but doing so makes you look silly.

PHP & localStorage;

localStorage is something that is kept on the client side. There is no data transmitted to the server side.

You can only get the data with JavaScript and you can send it to the server side with Ajax.

Return Type for jdbcTemplate.queryForList(sql, object, classType)

In order to map a the result set of query to a particular Java class you'll probably be best (assuming you're interested in using the object elsewhere) off with a RowMapper to convert the columns in the result set into an object instance.

See Section of Data access with JDBC on how to use a row mapper.

In short, you'll need something like:

List<Conversation> actors = jdbcTemplate.query(
    new Object[] {userId, dateFrom, dateTo},
    new RowMapper<Conversation>() {
        public Conversation mapRow(ResultSet rs, int rowNum) throws SQLException {
            Conversation c = new Conversation();
            return c;

what is an illegal reflective access

Apart from an understanding of the accesses amongst modules and their respective packages. I believe the crux of it lies in the Module System#Relaxed-strong-encapsulation and I would just cherry-pick the relevant parts of it to try and answer the question.

What defines an illegal reflective access and what circumstances trigger the warning?

To aid in the migration to Java-9, the strong encapsulation of the modules could be relaxed.

  • An implementation may provide static access, i.e. by compiled bytecode.

  • May provide a means to invoke its run-time system with one or more packages of one or more of its modules open to code in all unnamed modules, i.e. to code on the classpath. If the run-time system is invoked in this way, and if by doing so some invocations of the reflection APIs succeed where otherwise they would have failed.

In such cases, you've actually ended up making a reflective access which is "illegal" since in a pure modular world you were not meant to do such accesses.

How it all hangs together and what triggers the warning in what scenario?

This relaxation of the encapsulation is controlled at runtime by a new launcher option --illegal-access which by default in Java9 equals permit. The permit mode ensures

The first reflective-access operation to any such package causes a warning to be issued, but no warnings are issued after that point. This single warning describes how to enable further warnings. This warning cannot be suppressed.

The modes are configurable with values debug(message as well as stacktrace for every such access), warn(message for each such access), and deny(disables such operations).

Few things to debug and fix on applications would be:-

  • Run it with --illegal-access=deny to get to know about and avoid opening packages from one module to another without a module declaration including such a directive(opens) or explicit use of --add-opens VM arg.
  • Static references from compiled code to JDK-internal APIs could be identified using the jdeps tool with the --jdk-internals option

The warning message issued when an illegal reflective-access operation is detected has the following form:

WARNING: Illegal reflective access by $PERPETRATOR to $VICTIM


$PERPETRATOR is the fully-qualified name of the type containing the code that invoked the reflective operation in question plus the code source (i.e., JAR-file path), if available, and

$VICTIM is a string that describes the member being accessed, including the fully-qualified name of the enclosing type

Questions for such a sample warning: = JDK9: An illegal reflective access operation has occurred. org.python.core.PySystemState

Last and an important note, while trying to ensure that you do not face such warnings and are future safe, all you need to do is ensure your modules are not making those illegal reflective accesses. :)

Correlation between two vectors?

To perform a linear regression between two vectors x and y follow these steps:

[p,err] = polyfit(x,y,1);   % First order polynomial
y_fit = polyval(p,x,err);   % Values on a line
y_dif = y - y_fit;          % y value difference (residuals)
SSdif = sum(y_dif.^2);      % Sum square of difference
SStot = (length(y)-1)*var(y);   % Sum square of y taken from variance
rsq = 1-SSdif/SStot;        % Correlation 'r' value. If 1.0 the correlelation is perfect

For x=[10;200;7;150] and y=[0.001;0.45;0.0007;0.2] I get rsq = 0.9181.

Reference URL:

TypeError: a bytes-like object is required, not 'str' when writing to a file in Python3

why not try opening your file as text?

with open(fname, 'rt') as f:
    lines = [x.strip() for x in f.readlines()]

Additionally here is a link for python 3.x on the official page: And this is the open function:

If you are really trying to handle it as a binary then consider encoding your string.

What is the meaning of git reset --hard origin/master?

In newer version of git (2.23+) you can use:

git switch -C master origin/master

-C is same as --force-create. Related Reference Docs

Differences between Html.TextboxFor and Html.EditorFor in MVC and Razor

TextBoxFor: It will render like text input html element corresponding to specified expression. In simple word it will always render like an input textbox irrespective datatype of the property which is getting bind with the control.

EditorFor: This control is bit smart. It renders HTML markup based on the datatype of the property. E.g. suppose there is a boolean property in model. To render this property in the view as a checkbox either we can use CheckBoxFor or EditorFor. Both will be generate the same markup.

What is the advantage of using EditorFor?

As we know, depending on the datatype of the property it generates the html markup. So suppose tomorrow if we change the datatype of property in the model, no need to change anything in the view. EditorFor control will change the html markup automatically.

How do I delete multiple rows in Entity Framework (without foreach)

context.Widgets.RemoveRange(context.Widgets.Where(w => w.WidgetId == widgetId).ToList()); db.SaveChanges();

How to access first element of JSON object array?

the event property seems to be string first you have to parse it to json :

 var req = { mandrill_events: '[{"event":"inbound","ts":1426249238}]' };
 var event = JSON.parse(req.mandrill_events);
 var ts =  event[0].ts

How can one print a size_t variable portably using the printf family?

std::size_t s = 1024;
std::cout << s; // or any other kind of stream like stringstream!

FontAwesome icons not showing. Why?

Under your reference, you have this:

<link href="//" rel="stylesheet">

Specifically, the href= part.

However, under your full html is this:

<link src="" rel="stylesheet">

Have you tried replacing src= with href= in your full html to become this?

<link href="" rel="stylesheet">

Works for me:

Detecting Browser Autofill

Here is CSS solution taken from Klarna UI team. See their nice implementation here resource

Works fine for me.

input:-webkit-autofill {
  animation-name: onAutoFillStart;
  transition: background-color 50000s ease-in-out 0s;
input:not(:-webkit-autofill) {
  animation-name: onAutoFillCancel;

What's the quickest way to multiply multiple cells by another number?

  1. Enter the multiplier in a cell
  2. Copy that cell to the clipboard
  3. Select the range you want to multiply by the multiplier
  4. (Excel 2003 or earlier) Choose Edit | Paste Special | Multiply

    (Excel 2007 or later) Click on the Paste down arrow | Paste Special | Multiply

Define global variable with webpack

Use DefinePlugin.

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

new webpack.DefinePlugin(definitions)


plugins: [
  new webpack.DefinePlugin({
    PRODUCTION: JSON.stringify(true)


console.log(`Environment is in production: ${PRODUCTION}`);

[Ljava.lang.Object; cannot be cast to

In case entire entity is being return, better solution in spring JPA is use @Query(value = "from entity where Id in :ids")

This return entity type rather than object type

Structs data type in php?

I cobbled together a 'dynamic' struct class today, had a look tonight and someone has written something similar with better handling of constructor parameters, it might be worth a look:

One of the comments on this page mentions an interesting thing in PHP - apparently you're able to cast an array as an object, which lets you refer to array elements using the arrow notation, as you would with a Struct pointer in C. The comment's example was as follows:

$z = array('foo' => 1, 'bar' => true, 'baz' => array(1,2,3));
//accessing values as properties
$y = (object)$z;
echo $y->foo;

I haven't tried this myself yet, but it may be that you could get the desired notation by just casting - if that's all you're after. These are of course 'dynamic' data structures, just syntactic sugar for accessing key/value pairs in a hash.

If you're actually looking for something more statically typed, then ASpencer's answer is the droid you're looking for (as Obi-Wan might say.)

Git Remote: Error: fatal: protocol error: bad line length character: Unab

This error message is a bit obtuse, but what it's actually trying to tell you is that the remote server didn't reply with a proper git response. Ultimately, there was a problem on the server running the git-receive-pack process.

In the Git protocol, the first four bytes should be the line length. Instead, they were the characters Unab... which is probably the beginning an error message of some kind. (ie, it's probably "Unable to..." do something).

What happens when you run ssh <host> git-receive-pack <path-to-git-repository>? You should see the error message that your git client is barfing on and you may be able to correct it.

How do I create a WPF Rounded Corner container?

You don't need a custom control, just put your container in a border element:

<Border BorderBrush="#FF000000" BorderThickness="1" CornerRadius="8">

You can replace the <Grid/> with any of the layout containers...

Change a Git remote HEAD to point to something besides master

There was almost the same question on GitHub a year ago.

The idea was to rename the master branch:

git branch -m master development
git branch -m published master
git push -f origin master 

Making master have what you want people to use, and do all other work in branches.

(a "git-symbolic-ref HEAD refs/head/published" would not be propagated to the remote repo)

This is similar to "How do I delete origin/master in Git".

As said in this thread: (emphasis mine)

"git clone" creates only a single local branch.
To do that, it looks at the HEAD ref of the remote repo, and creates a local branch with the same name as the remote branch referenced by it.

So to wrap that up, you have repo A and clone it:

  • HEAD references refs/heads/master and that exists
    -> you get a local branch called master, starting from origin/master

  • HEAD references refs/heads/anotherBranch and that exists
    -> you get a local branch called anotherBranch, starting from origin/anotherBranch

  • HEAD references refs/heads/master and that doesn't exist
    -> "git clone" complains

Not sure if there's any way to directly modify the HEAD ref in a repo.

(which is the all point of your question, I know ;) )

Maybe the only way would be a "publication for the poor", where you:

 $ git-symbolic-ref HEAD refs/head/published
 $ git-update-server-info
 $ rsync -az .git/* server:/local_path_to/git/myRepo.git/

But that would involve write access to the server, which is not always possible.

As I explain in "Git: Correct way to change Active Branch in a bare repository?", git remote set-head wouldn't change anything on the remote repo.

It would only change the remote tracking branch stored locally in your local repo, in remotes/<name>/HEAD.

With Git 2.29 (Q4 2020), "git remote set-head(man)" that failed still said something that hints the operation went through, which was misleading.

See commit 5a07c6c (17 Sep 2020) by Christian Schlack (cschlack).
(Merged by Junio C Hamano -- gitster -- in commit 39149df, 22 Sep 2020)

remote: don't show success message when set-head fails

Signed-off-by: Christian Schlack

Suppress the message 'origin/HEAD set to master' in case of an error.

$ git remote set-head origin -a
error: Not a valid ref: refs/remotes/origin/master
origin/HEAD set to master

VSCode Change Default Terminal

If you want to select the type of console, you can write this in the file "keybinding.json" (this file can be found in the following path "File-> Preferences-> Keyboard Shortcuts") `

//with this you can select what type of console you want
    "key": "ctrl+shift+t",
    "command": "shellLauncher.launch"

//and this will help you quickly change console
    "key": "ctrl+shift+j", 
    "command": "workbench.action.terminal.focusNext" 
    "key": "ctrl+shift+k", 
    "command": "workbench.action.terminal.focusPrevious" 

C# JSON Serialization of Dictionary into {key:value, ...} instead of {key:key, value:value, ...}

use property UseSimpleDictionaryFormat on DataContractJsonSerializer and set it to true.

Does the job :)

How do I create a Python function with optional arguments?

Try calling it like: obj.some_function( '1', 2, '3', g="foo", h="bar" ). After the required positional arguments, you can specify specific optional arguments by name.

Send POST parameters with MultipartFormData using Alamofire, in iOS Swift

As in Swift 3.x for upload image with parameter we can use below alamofire upload method-

static func uploadImageData(inputUrl:String,parameters:[String:Any],imageName: String,imageFile : UIImage,completion:@escaping(_:Any)->Void) {

        let imageData = UIImageJPEGRepresentation(imageFile , 0.5)

        Alamofire.upload(multipartFormData: { (multipartFormData) in

            multipartFormData.append(imageData!, withName: imageName, fileName: "swift_file\(arc4random_uniform(100)).jpeg", mimeType: "image/jpeg")

            for key in parameters.keys{
                let name = String(key)
                if let val = parameters[name!] as? String{
                    multipartFormData.append( .utf8)!, withName: name!)
        }, to:inputUrl)
        { (result) in
            switch result {
            case .success(let upload, _, _):

                upload.uploadProgress(closure: { (Progress) in

                upload.responseJSON { response in

                    if let JSON = response.result.value {

            case .failure(let encodingError):



Note: Additionally if our parameter is array of key-pairs then we can use

 var arrayOfKeyPairs = [[String:Any]]()
 let json = try? arrayOfKeyPairs, options: [.prettyPrinted])
 let jsonPresentation = String(data: json!, encoding: .utf8)

Send HTML in email via PHP

You can easily send the email with HTML content via PHP. Use the following script.

$to = '[email protected]';
$subject = "Send HTML Email Using PHP";

$htmlContent = '
    <h1>Send HTML Email Using PHP</h1>
    <p>This is a HTMl email using PHP by CodexWorld</p>

// Set content-type header for sending HTML email
$headers = "MIME-Version: 1.0" . "\r\n";
$headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";

// Additional headers
$headers .= 'From: CodexWorld<[email protected]>' . "\r\n";
$headers .= 'Cc: [email protected]' . "\r\n";
$headers .= 'Bcc: [email protected]' . "\r\n";

// Send email
    $successMsg = 'Email has sent successfully.';
    $errorMsg = 'Email sending fail.';

Source code and live demo can be found from here - Send Beautiful HTML Email using PHP

How to convert a Base64 string into a Bitmap image to show it in a ImageView?

You can just basically revert your code using some other built in methods.

byte[] decodedString = Base64.decode(encodedImage, Base64.DEFAULT);
Bitmap decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length); 

jQuery select change show/hide div event

    $('#colorselector').on('change', function() {
      if ( this.value == 'red')

Do like this for every value Also change the values... as per your parameters

Excel 2013 VBA Clear All Filters macro

I usually use this code

Sub AutoFilter_Remove()
    Sheet1.AutoFilterMode = False  'Change Sheet1 to the relevant sheet
                                   'Alternatively: Worksheets("[Your Sheet Name]").AutoFilterMode = False
End Sub

How to import functions from different js file in a Vue+webpack+vue-loader project

I was trying to organize my vue app code, and came across this question , since I have a lot of logic in my component and can not use other sub-coponents , it makes sense to use many functions in a separate js file and call them in the vue file, so here is my attempt

1)The Component (.vue file)

//MyComponent.vue file
  <div>Hello {{name}}</div>
  <button @click="function_A">Read Name</button>
  <button @click="function_B">Write Name</button>
  <button @click="function_C">Reset</button>

import Mylib from "./Mylib"; // <-- import
export default {
  name: "MyComponent",
  data() {
    return {
      name: "Bob",
      message: "click on the buttons"
  methods: {
    function_A() {
      Mylib.myfuncA(this); // <---read data
    function_B() {
      Mylib.myfuncB(this); // <---write data
    function_C() {
      Mylib.myfuncC(this); // <---write data

2)The External js file

let exports = {};

// this (vue instance) is passed as that , so we
// can read and write data from and to it as we please :)
exports.myfuncA = (that) => {
  that.message =
  "you hit ''myfuncA'' function that is located in Mylib.js  and = " +;

exports.myfuncB = (that) => {
  that.message =
  "you hit ''myfuncB'' function that is located in Mylib.js and now I will change the name to Nassim"; = "Nassim"; // <-- change name to Nassim

exports.myfuncC = (that) => {
  that.message =
  "you hit ''myfuncC'' function that is located in Mylib.js and now I will change the name back to Bob"; = "Bob"; // <-- change name to Bob

export default exports;

enter image description here 3)see it in action :


after getting more experience with Vue , I found out that you could use mixins too to split your code into different files and make it easier to code and maintain see

Can gcc output C code after preprocessing?


This is another good option to have in mind:

gcc -save-temps -c -o main.o main.c


#define INC 1

int myfunc(int i) {
    return i + INC;

and now, besides the normal output main.o, the current working directory also contains the following files:

  • main.i is the desired prepossessed file containing:

    # 1 "main.c"
    # 1 "<built-in>"
    # 1 "<command-line>"
    # 31 "<command-line>"
    # 1 "/usr/include/stdc-predef.h" 1 3 4
    # 32 "<command-line>" 2
    # 1 "main.c"
    int myfunc(int i) {
        return i + 1;
  • main.s is a bonus :-) and contains the generated assembly:

        .file   "main.c"
        .globl  myfunc
        .type   myfunc, @function
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        movl    %edi, -4(%rbp)
        movl    -4(%rbp), %eax
        addl    $1, %eax
        popq    %rbp
        .cfi_def_cfa 7, 8
        .size   myfunc, .-myfunc
        .ident  "GCC: (Ubuntu 8.3.0-6ubuntu1) 8.3.0"
        .section    .note.GNU-stack,"",@progbits

If you want to do it for a large number of files, consider using instead:


which saves the intermediate files to the same directory as the -o object output instead of the current working directory, thus avoiding potential basename conflicts.

The advantage of this option over -E is that it is easy to add it to any build script, without interfering much in the build itself.

Another cool thing about this option is if you add -v:

gcc -save-temps -c -o main.o -v main.c

it actually shows the explicit files being used instead of ugly temporaries under /tmp, so it is easy to know exactly what is going on, which includes the preprocessing / compilation / assembly steps:

/usr/lib/gcc/x86_64-linux-gnu/8/cc1 -E -quiet -v -imultiarch x86_64-linux-gnu main.c -mtune=generic -march=x86-64 -fpch-preprocess -fstack-protector-strong -Wformat -Wformat-security -o main.i
/usr/lib/gcc/x86_64-linux-gnu/8/cc1 -fpreprocessed main.i -quiet -dumpbase main.c -mtune=generic -march=x86-64 -auxbase-strip main.o -version -fstack-protector-strong -Wformat -Wformat-security -o main.s
as -v --64 -o main.o main.s

Tested in Ubuntu 19.04 amd64, GCC 8.3.0.

CMake predefined targets

CMake automatically provides a targets for the preprocessed file:

make help

shows us that we can do:

make main.i

and that target runs:

Preprocessing C source to CMakeFiles/main.dir/main.c.i
/usr/bin/cc    -E /home/ciro/bak/hello/main.c > CMakeFiles/main.dir/main.c.i

so the file can be seen at CMakeFiles/main.dir/main.c.i

Tested on cmake 3.16.1.

Count unique values using pandas groupby

This is just an add-on to the solution in case you want to compute not only unique values but other aggregate functions:


Hope you find it useful

Getting time elapsed in Objective-C

You should not rely on [NSDate date] for timing purposes since it can over- or under-report the elapsed time. There are even cases where your computer will seemingly time-travel since the elapsed time will be negative! (E.g. if the clock moved backwards during timing.)

According to Aria Haghighi in the "Advanced iOS Gesture Recognition" lecture of the Winter 2013 Stanford iOS course (34:00), you should use CACurrentMediaTime() if you need an accurate time interval.


#import <QuartzCore/QuartzCore.h>
CFTimeInterval startTime = CACurrentMediaTime();
// perform some action
CFTimeInterval elapsedTime = CACurrentMediaTime() - startTime;


let startTime = CACurrentMediaTime()
// perform some action
let elapsedTime = CACurrentMediaTime() - startTime

The reason is that [NSDate date] syncs on the server, so it could lead to "time-sync hiccups" which can lead to very difficult-to-track bugs. CACurrentMediaTime(), on the other hand, is a device time that doesn't change with these network syncs.

You will need to add the QuartzCore framework to your target's settings.

Flutter - The method was called on null

Because of your initialization wrong.

Don't do like this,

MethodName _methodName;

Do like this,

MethodName _methodName = MethodName();

How do I find Waldo with Mathematica?

My guess at a "bulletproof way to do this" (think CIA finding Waldo in any satellite image any time, not just a single image without competing elements, like striped shirts)... I would train a Boltzmann machine on many images of Waldo - all variations of him sitting, standing, occluded, etc.; shirt, hat, camera, and all the works. You don't need a large corpus of Waldos (maybe 3-5 will be enough), but the more the better.

This will assign clouds of probabilities to various elements occurring in whatever the correct arrangement, and then establish (via segmentation) what an average object size is, fragment the source image into cells of objects which most resemble individual people (considering possible occlusions and pose changes), but since Waldo pictures usually include a LOT of people at about the same scale, this should be a very easy task, then feed these segments of the pre-trained Boltzmann machine. It will give you probability of each one being Waldo. Take one with the highest probability.

This is how OCR, ZIP code readers, and strokeless handwriting recognition work today. Basically you know the answer is there, you know more or less what it should look like, and everything else may have common elements, but is definitely "not it", so you don't bother with the "not it"s, you just look of the likelihood of "it" among all possible "it"s you've seen before" (in ZIP codes for example, you'd train BM for just 1s, just 2s, just 3s, etc., then feed each digit to each machine, and pick one that has most confidence). This works a lot better than a single neural network learning features of all numbers.

Reading JSON from a file?

The json.load() method (without "s" in "load") can read a file directly:

import json

with open('strings.json') as f:
    d = json.load(f)

You were using the json.loads() method, which is used for string arguments only.

Edit: The new message is a totally different problem. In that case, there is some invalid json in that file. For that, I would recommend running the file through a json validator.

There are also solutions for fixing json like for example How do I automatically fix an invalid JSON string?.

What is stability in sorting algorithms and why is it important?

There's a few reasons why stability can be important. One is that, if two records don't need to be swapped by swapping them you can cause a memory update, a page is marked dirty, and needs to be re-written to disk (or another slow medium).

Remove table row after clicking table row delete button

you can do it like this:

    function SomeDeleteRowFunction(o) {
     //no clue what to put here?
     var p=o.parentNode.parentNode;

           <td><input type="button" value="Delete Row" onclick="SomeDeleteRowFunction(this)"></td>
           <td><input type="button" value="Delete Row" onclick="SomeDeleteRowFunction(this)"></td>
           <td><input type="button" value="Delete Row" onclick="SomeDeleteRowFunction(this)"></td>

Rotating a view in Android

You could create an animation and apply it to your button view. For example:

    // Locate view
    ImageView diskView = (ImageView) findViewById(;

    // Create an animation instance
    Animation an = new RotateAnimation(0.0f, 360.0f, pivotX, pivotY);

    // Set the animation's parameters
    an.setDuration(10000);               // duration in ms
    an.setRepeatCount(0);                // -1 = infinite repeated
    an.setRepeatMode(Animation.REVERSE); // reverses each repeat
    an.setFillAfter(true);               // keep rotation after animation

    // Aply animation to image view

How to iterate through LinkedHashMap with lists as values

You can use the entry set and iterate over the entries which allows you to access both, key and value, directly.

for (Entry<String, ArrayList<String>> entry : test1.entrySet() {
     System.out.println(entry.getKey() + "/" + entry.getValue());

I tried this but get only returns string

Why do you think so? The method get returns the type E for which the generic type parameter was chosen, in your case ArrayList<String>.

How can I parse a YAML file from a Linux shell script?

Given that Python3 and PyYAML are quite easy dependencies to meet nowadays, the following may help:

yaml() {
    python3 -c "import yaml;print(yaml.safe_load(open('$1'))$2)"

VALUE=$(yaml ~/my_yaml_file.yaml "['a_key']")

Replace Fragment inside a ViewPager

In your onCreateView method, container is actually a ViewPager instance.

So, just calling

ViewPager vpViewPager = (ViewPager) container;

will change current fragment in your ViewPager.

gcc: undefined reference to

Are you mixing C and C++? One issue that can occur is that the declarations in the .h file for a .c file need to be surrounded by:

#if defined(__cplusplus)
  extern "C" {                 // Make sure we have C-declarations in C++ programs


#if defined(__cplusplus)

Note: if unable / unwilling to modify the .h file(s) in question, you can surround their inclusion with extern "C":

extern "C" {
#include <abc.h>
} //extern

Optimistic vs. Pessimistic locking

One use case for optimistic locking is to have your application use the database to allow one of your threads / hosts to 'claim' a task. This is a technique that has come in handy for me on a regular basis.

The best example I can think of is for a task queue implemented using a database, with multiple threads claiming tasks concurrently. If a task has status 'Available', 'Claimed', 'Completed', a db query can say something like "Set status='Claimed' where status='Available'. If multiple threads try to change the status in this way, all but the first thread will fail because of dirty data.

Note that this is a use case involving only optimistic locking. So as an alternative to saying "Optimistic locking is used when you don't expect many collisions", it can also be used where you expect collisions but want exactly one transaction to succeed.

IsNull function in DB2 SQL?

COALESCE function same ISNULL function Note. you must use COALESCE function with same data type of column that you check is null.

Vim and Ctags tips and tricks

I've encapsulated tags manipulation in an experimental plugin of mine.

Regarding C++ development in vim, I've already answered there: I use my own suite, and a few other plugins.

Log4Net configuring log level

Within the definition of the appender, I believe you can do something like this:

<appender name="AdoNetAppender" type="log4net.Appender.AdoNetAppender">
    <filter type="log4net.Filter.LevelRangeFilter">
        <param name="LevelMin" value="INFO"/>
        <param name="LevelMax" value="INFO"/>

How to set the environmental variable LD_LIBRARY_PATH in linux

The file .bash_profile is only executed by login shells. You may need to put it in ~/.bashrc, or simply logout and login again.

Register comdlg32.dll gets Regsvr32: DllRegisterServer entry point was not found

Registering DLL for Fundsite

Outdated or missing comdlg32.ocx runtime library can be the problem of causing this error. Make sure comdlg32.ocx file is not corrupted otherwise Download the File comdlg32.ocx (~60 Kb Zip).

Download the file and extract the comdlg32.ocx to your the Windows\System32 folder or Windows\SysWOW64. In my case i started with Windows\System32 but it didn’t work at my end, so I again saved in Windows\SysWOW64.

Type following command from Start, Run dialog:“c:\windows>System32\regsvr32 Comdlg32.ocx “ or “c:\windows>SysWOW64\regsvr32 Comdlg32.ocx ”

Now Comdlg.ocx File is register and next step is to register the DLL

  1. Copy the Fundsite.Text.Encoding. dll into .Net Framework folder for 64bit on below path C:\Windows\Microsoft.NET\Framework64\v2.0.50727

  2. Then on command prompt and go to directory C:\Windows\Microsoft.NET\Framework64\v2.0.50727 and then run the following command as shown below.

This will register the dll successfully.

C:\Windows\\framework64\v2.0.50727>regasm "Dll Name".dll

How to draw a line in android

Another approach to draw a line programatically using ImageView

import android.os.Bundle;
import android.widget.ImageView;

public class Test extends Activity {
  ImageView drawingImageView;

  public void onCreate(Bundle savedInstanceState) {
    drawingImageView = (ImageView) this.findViewById(;
    Bitmap bitmap = Bitmap.createBitmap((int) getWindowManager()
        .getDefaultDisplay().getWidth(), (int) getWindowManager()
        .getDefaultDisplay().getHeight(), Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);

    // Line
    Paint paint = new Paint();
    int startx = 50;
    int starty = 100;
    int endx = 150;
    int endy = 210;
    canvas.drawLine(startx, starty, endx, endy, paint);


What is a None value?

The book you refer to is clearly trying to greatly simplify the meaning of None. Python variables don't have an initial, empty state – Python variables are bound (only) when they're defined. You can't create a Python variable without giving it a value.

>>> print(x)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined
>>> def test(x):
...   print(x)
>>> test()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: test() takes exactly 1 argument (0 given)
>>> def test():
...   print(x)
>>> test()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in test
NameError: global name 'x' is not defined

but sometimes you want to make a function mean different things depending on whether a variable is defined or not. You can create an argument with a default value of None:

>>> def test(x=None):
...   if x is None:
...     print('no x here')
...   else:
...     print(x)
>>> test()
no x here
>>> test('x!')

The fact that this value is the special None value is not terribly important in this case. I could've used any default value:

>>> def test(x=-1):
...   if x == -1:
...     print('no x here')
...   else:
...     print(x)
>>> test()
no x here
>>> test('x!')

…but having None around gives us two benefits:

  1. We don't have to pick a special value like -1 whose meaning is unclear, and
  2. Our function may actually need to handle -1 as a normal input.
>>> test(-1)
no x here


So the book is a little misleading mostly in its use of the word reset – assigning None to a name is a signal to a programmer that that value isn't being used or that the function should behave in some default way, but to reset a value to its original, undefined state you must use the del keyword:

>>> x = 3
>>> x
>>> del x
>>> x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined

Linq to SQL how to do "where [column] in (list of values)"


where list.Contains(item.Property)

Or in your case:

var foo = from codeData in channel.AsQueryable<CodeData>()
          where codeIDs.Contains(codeData.CodeId)
          select codeData;

But you might as well do that in dot notation:

var foo = channel.AsQueryable<CodeData>()
                 .Where(codeData => codeIDs.Contains(codeData.CodeId));

Add a background image to shape in XML Android

This is a corner image

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="">

        android:top="5dp" />

            <corners android:radius="10dp" />
                android:color="@color/white" />


Creating temporary files in bash

You might want to look at mktemp

The mktemp utility takes the given filename template and overwrites a portion of it to create a unique filename. The template may be any filename with some number of 'Xs' appended to it, for example /tmp/tfile.XXXXXXXXXX. The trailing 'Xs' are replaced with a combination of the current process number and random letters.

For more details: man mktemp

Provide static IP to docker containers via docker-compose

I was facing some difficulties with an environment variable that is with custom name (not with container name /port convention for KAPACITOR_BASE_URL and KAPACITOR_ALERTS_ENDPOINT). If we give service name in this case it wouldn't resolve the ip as

KAPACITOR_BASE_URL:  http://kapacitor:9092

In above http://[**kapacitor**]:9092 would not resolve to

I resolved the static IPs issues using subnetting configurations.

version: "3.3"

        - subnet:
        image: postgres:9.4.4
            - "5432:5432"
            - postgres_data:/var/lib/postgresql/data

        image: redis:latest
            - "6379"

        image: influxdb:latest
            - "8086:8086"
            - "8083:8083"
            - ../influxdb/influxdb.conf:/etc/influxdb/influxdb.conf
            - ../influxdb/inxdb:/var/lib/influxdb
          INFLUXDB_ADMIN_ENABLED: "true"
          INFLUXDB_USERNAME: "db_username"
          INFLUXDB_PASSWORD: "12345678"
          INFLUXDB_DB: db_customers

        image: kapacitor:latest
            - "9092:9092"
            - influxdb
            - ../kapacitor/kapacitor.conf:/etc/kapacitor/kapacitor.conf
            - ../kapacitor/kapdb:/var/lib/kapacitor
          KAPACITOR_INFLUXDB_0_URLS_0: http://influxdb:8086

        build: .
        command: bundle exec rails s -b
            - "3000:3000"
            - db
            - kapacitor
            - db
            - .:/var/app/current
          DATABASE_URL: postgres://postgres@db
          DATABASE_USERNAME: postgres
          DATABASE_PASSWORD: postgres
          INFLUX_URL: http://influxdb:8086
          INFLUX_USER: db_username
          INFLUX_PWD: 12345678


Git refusing to merge unrelated histories on rebase

I had the same problem. Try this:

git pull origin master --allow-unrelated-histories 

git push origin master

Build a simple HTTP server in C

I suggest you take a look at tiny httpd. If you want to write it from scratch, then you'll want to thoroughly read RFC 2616. Use BSD sockets to access the network at a really low level.

JavaFX Location is not set error message

I tried a fast and simple thing:

I have two packages -> app.gui and app.login

In my login class I use the mainview.fxml from app.gui so I did this in the login.fxml

FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("../gui/MainView.fxml"));

And it works :)

git push >> fatal: no configured push destination

The command (or the URL in it) to add the github repository as a remote isn't quite correct. If I understand your repository name correctly, it should be;

git remote add demo_app '[email protected]:levelone/demo_app.git'

How would I get everything before a : in a string Python

I have benchmarked these various technics under Python 3.7.0 (IPython).


  • fastest (when the split symbol c is known): pre-compiled regex.
  • fastest (otherwise): s.partition(c)[0].
  • safe (i.e., when c may not be in s): partition, split.
  • unsafe: index, regex.


import string, random, re

SYMBOLS = string.ascii_uppercase + string.digits
SIZE = 100

def create_test_set(string_length):
    for _ in range(SIZE):
        random_string = ''.join(random.choices(SYMBOLS, k=string_length))
        yield (random.choice(random_string), random_string)

for string_length in (2**4, 2**8, 2**16, 2**32):
    print("\nString length:", string_length)
    print("  regex (compiled):", end=" ")
    test_set_for_regex = ((re.compile("(.*?)" + c).match, s) for (c, s) in test_set)
    %timeit [re_match(s).group() for (re_match, s) in test_set_for_regex]
    test_set = list(create_test_set(16))
    print("  partition:       ", end=" ")
    %timeit [s.partition(c)[0] for (c, s) in test_set]
    print("  index:           ", end=" ")
    %timeit [s[:s.index(c)] for (c, s) in test_set]
    print("  split (limited): ", end=" ")
    %timeit [s.split(c, 1)[0] for (c, s) in test_set]
    print("  split:           ", end=" ")
    %timeit [s.split(c)[0] for (c, s) in test_set]
    print("  regex:           ", end=" ")
    %timeit [re.match("(.*?)" + c, s).group() for (c, s) in test_set]


String length: 16
  regex (compiled): 156 ns ± 4.41 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  partition:        19.3 µs ± 430 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
  index:            26.1 µs ± 341 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split (limited):  26.8 µs ± 1.26 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split:            26.3 µs ± 835 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  regex:            128 µs ± 4.02 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

String length: 256
  regex (compiled): 167 ns ± 2.7 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  partition:        20.9 µs ± 694 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  index:            28.6 µs ± 2.73 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split (limited):  27.4 µs ± 979 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split:            31.5 µs ± 4.86 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  regex:            148 µs ± 7.05 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

String length: 65536
  regex (compiled): 173 ns ± 3.95 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  partition:        20.9 µs ± 613 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
  index:            27.7 µs ± 515 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split (limited):  27.2 µs ± 796 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split:            26.5 µs ± 377 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  regex:            128 µs ± 1.5 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

String length: 4294967296
  regex (compiled): 165 ns ± 1.2 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  partition:        19.9 µs ± 144 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
  index:            27.7 µs ± 571 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split (limited):  26.1 µs ± 472 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split:            28.1 µs ± 1.69 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  regex:            137 µs ± 6.53 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

Cannot get OpenCV to compile because of undefined references?

follow this tutorial. i ran the file in bash. its in the tutorial

read the example from openCV


cmake_minimum_required(VERSION 3.7)
# cmake needs this line
cmake_minimum_required(VERSION 2.8)

# Define project name

# Find OpenCV, you may need to set OpenCV_DIR variable
# to the absolute path to the directory containing OpenCVConfig.cmake file
# via the command line or GUI
find_package(OpenCV REQUIRED)

# If the package has been found, several variables will
# be set, you can find the full list with descriptions
# in the OpenCVConfig.cmake file.
# Print some message showing some of them
message(STATUS "OpenCV library status:")
message(STATUS "    version: ${OpenCV_VERSION}")
message(STATUS "    libraries: ${OpenCV_LIBS}")
message(STATUS "    include path: ${OpenCV_INCLUDE_DIRS}")

    # Add OpenCV headers location to your include paths

# Declare the executable target built from your sources
add_executable(main main.cpp)

# Link your application with OpenCV libraries
target_link_libraries(main ${OpenCV_LIBS})


 * @file LinearBlend.cpp
 * @brief Simple linear blender ( dst = alpha*src1 + beta*src2 )
 * @author OpenCV team

#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include <stdio.h>

using namespace cv;

/** Global Variables */
const int alpha_slider_max = 100;
int alpha_slider;
double alpha;
double beta;

/** Matrices to store images */
Mat src1;
Mat src2;
Mat dst;

 * @function on_trackbar
 * @brief Callback for trackbar
static void on_trackbar( int, void* )
    alpha = (double) alpha_slider/alpha_slider_max ;

    beta = ( 1.0 - alpha );

    addWeighted( src1, alpha, src2, beta, 0.0, dst);

    imshow( "Linear Blend", dst );

 * @function main
 * @brief Main function
int main( void )
    /// Read images ( both have to be of the same size and type )
    src1 = imread("../data/LinuxLogo.jpg");
    src2 = imread("../data/WindowsLogo.jpg");

    if( src1.empty() ) { printf("Error loading src1 \n"); return -1; }
    if( src2.empty() ) { printf("Error loading src2 \n"); return -1; }

    /// Initialize values
    alpha_slider = 0;

    namedWindow("Linear Blend", WINDOW_AUTOSIZE); // Create Window

    char TrackbarName[50];
    sprintf( TrackbarName, "Alpha x %d", alpha_slider_max );
    createTrackbar( TrackbarName, "Linear Blend", &alpha_slider, alpha_slider_max, on_trackbar );

    /// Show some stuff
    on_trackbar( alpha_slider, 0 );

    /// Wait until user press some key
    return 0;

Tested in linux mint 17

ggplot combining two plots from different data.frames

As Baptiste said, you need to specify the data argument at the geom level. Either

#df1 is the default dataset for all geoms
(plot1 <- ggplot(df1, aes(v, p)) + 
    geom_point() +
    geom_step(data = df2)


#No default; data explicitly specified for each geom
(plot2 <- ggplot(NULL, aes(v, p)) + 
      geom_point(data = df1) +
      geom_step(data = df2)

javascript: pause setTimeout();

You could wrap window.setTimeout like this, which I think is similar to what you were suggesting in the question:

var Timer = function(callback, delay) {
    var timerId, start, remaining = delay;

    this.pause = function() {
        remaining -= - start;

    this.resume = function() {
        start =;
        timerId = window.setTimeout(callback, remaining);


var timer = new Timer(function() {
}, 1000);

// Do some stuff...

Exception : mockito wanted but not invoked, Actually there were zero interactions with this mock

You need to inject mock inside the class you're testing. At the moment you're interacting with the real object, not with the mock one. You can fix the code in a following way:

void testAbc(){
     myClass.myObj = myInteface;;
     verify(myInterface).myMethodToBeVerified(new String("a"), new String("b"));

although it would be a wiser choice to extract all initialization code into @Before

void setUp(){
     myClass = new myClass();
     myClass.myObj = myInteface;

void testAbc(){;
     verify(myInterface).myMethodToBeVerified(new String("a"), new String("b"));

Use and meaning of "in" in an if statement?

Since you claim to be used to JavaScript:

The Python in operator is similar to the JavaScript in operator.

Here's some JavaScript:

var d = {1: 2, 3: 4};
if (1 in d) {

And the equivalent Python:

d = {1: 2, 3: 4}
if 1 in d:

With objects/dicts, they're nearly identical, both checking whether 1 is a key of the object/dict. The big difference, of course, is that JavaScript is sloppily-typed, so '1' in d would be just as true.

With arrays/lists, they're very different. A JS array is an object, and its indexes are the keys, so 1 in [3, 4, 5] will be true. A Python list is completely different from a dict, and its in operator checks the values, not the indexes, which tends to be more useful. And Python extends this behavior to all iterables.

With strings, they're even more different. A JS string isn't an object, so you will get a TypeError. But a Python str or unicode will check whether the other operand is a substring. (This means 1 in '123' is illegal, because 1 can't be a substring of anything, but '1' in '123' is true.)

With objects as objects, in JS there is of course no distinction, but in Python, objects are instances of classes, not dicts. So, in JS, 1 in d will be true for an object if it has a member or method named '1', but in Python, it's up to your class what it means—Python will call d.__contains__(1), then, if that fails, it tries to use your object as an utterable (by calling its __iter__, and, if that fails, by trying to index it with integers starting from 0).

Also, note that JS's in, because it's actually checking for object membership, does the usual JS method-resolution-order search, while Python's in, because it's checking for keys of a dict, members of a sequence, etc., does no such thing. So, technically, it's probably a bit closer to the hasOwnProperty method than the in operator.

What's the difference between django OneToOneField and ForeignKey?

OneToOneField (one-to-one) realizes, in object orientation, the notion of composition, while ForeignKey (one-to-many) relates to agregation.

Export to CSV using MVC, C# and jQuery

Respect to Biff, here's a few tweaks that let me use the method to bounce CSV from jQuery/Post against the server and come back as a CSV prompt to the user.

    public FileContentResult DownloadCSV()

        var csvStringData = new StreamReader(Request.InputStream).ReadToEnd();

        csvStringData = Uri.UnescapeDataString(csvStringData.Replace("mydata=", ""));

        return File(new System.Text.UTF8Encoding().GetBytes(csvStringData), "text/csv", "report.csv");

You'll need the unescape line if you are hitting this from a form with code like the following,

    var input = $("<input>").attr("type", "hidden").attr("name", "mydata").val(data);

SQL Query NOT Between Two Dates

Your logic is backwards.

        start_date NOT BETWEEN CAST('2009-12-15' AS DATE) and CAST('2010-01-02' AS DATE)
    AND end_date NOT BETWEEN CAST('2009-12-15' AS DATE) and CAST('2010-01-02' AS DATE)

Declare and assign multiple string variables at the same time

string Camnr , Klantnr , Ordernr , Bonnr , Volgnr , Omschrijving , Startdatum , Bonprioriteit , Matsoort , Dikte , Draaibaarheid , Draaiomschrijving , Orderleverdatum , Regeltaakkode , Gebruiksvoorkeur , Regelcamprog , Regeltijd , Orderrelease;
Camnr = Klantnr = Ordernr = Bonnr = Volgnr = Omschrijving = Startdatum = Bonprioriteit = Matsoort = Dikte = Draaibaarheid = Draaiomschrijving = Orderleverdatum = Regeltaakkode = Gebruiksvoorkeur = Regelcamprog = Regeltijd = Orderrelease = string.Empty;

asterisk : Unable to connect to remote asterisk (does /var/run/asterisk.ctl exist?)

I had this problem today. It had nothing to do with any of the posted answers. I tried them all. My problem was a misconfiguration with the zaptel.conf (running old asterisk!). I had commented out some span details trying to troubleshoot a PRI issue. When the server got rebooted this issue presented itself. I was able to discover this by looking at the wanrouter messages in the logs. I noticed there were 3 errors, and the corresponding line numbers, once I corrected these issues, and ran an #asterisk -vvvvc the server came back up and everything worked.

How do I compile a .c file on my Mac?

Ondrasej is the "most right" here, IMO.
There are also gui-er ways to do it, without resorting to Xcode. I like TryC.

Mac OS X includes Developer Tools, a developing environment for making Macintosh applications. However, if someone wants to study programming using C, Xcode is too big and too complicated for beginners, to write a small sample program. TryC is very suitable for beginners.

enter image description here

You don't need to launch a huge Xcode application, or type unfamiliar commands in Terminal. Using TryC, you can write, compile and run a C, C++ and Ruby program just like TextEdit. It's only available to compile one source code file but it's enough for trying sample programs.

check if directory exists and delete in one command unix


bash -c '[ -d my_mystery_dirname ] && run_this_command'

This will work if you can run bash on the remote machine....

In bash, [ -d something ] checks if there is directory called 'something', returning a success code if it exists and is a directory. Chaining commands with && runs the second command only if the first one succeeded. So [ -d somedir ] && command runs the command only if the directory exists.

How to show android checkbox at right side?

You can do

android:gravity="right|center"//or "center_vertical" for center text
android:text="hello" />

Following line is enough


'ls' in CMD on Windows is not recognized

enter image description here


Make a dir c:\command

Second Make a ll.bat



Third Add to Path C:/commands enter image description here

Python read-only property

Notice that instance methods are also attributes (of the class) and that you could set them at the class or instance level if you really wanted to be a badass. Or that you may set a class variable (which is also an attribute of the class), where handy readonly properties won't work neatly out of the box. What I'm trying to say is that the "readonly attribute" problem is in fact more general than it's usually perceived to be. Fortunately there are conventional expectations at work that are so strong as to blind us wrt these other cases (after all, almost everything is an attribute of some sort in python).

Building upon these expectations I think the most general and lightweight approach is to adopt the convention that "public" (no leading underscore) attributes are readonly except when explicitly documented as writeable. This subsumes the usual expectation that methods won't be patched and class variables indicating instance defaults are better let alone. If you feel really paranoid about some special attribute, use a readonly descriptor as a last resource measure.

center aligning a fixed position div

You could use flexbox for this as well.

.wrapper {_x000D_
  position: fixed;_x000D_
  top: 0;_x000D_
  left: 0;_x000D_
  height: 100%;_x000D_
  width: 100%;_x000D_
  /* this is what centers your element in the fixed wrapper*/_x000D_
  display: flex;_x000D_
  flex-flow: column nowrap;_x000D_
  justify-content: center; /* aligns on vertical for column */_x000D_
  align-items: center; /* aligns on horizontal for column */_x000D_
  /* just for styling to see the limits */_x000D_
  border: 2px dashed red;_x000D_
  box-sizing: border-box;_x000D_
.element {_x000D_
  width: 200px;_x000D_
  height: 80px;_x000D_
  /* Just for styling */_x000D_
  background-color: lightyellow;_x000D_
  border: 2px dashed purple;_x000D_
<div class="wrapper"> <!-- Fixed element that spans the viewport -->_x000D_
  <div class="element">Your element</div> <!-- your actual centered element -->_x000D_

Populating a razor dropdownlist from a List<object> in MVC

Your call to DropDownListFor needs a few more parameters to flesh it out. You need a SelectList as in the following SO question:

MVC3 DropDownListFor - a simple example?

With what you have there, you've only told it where to store the data, not where to load the list from.

Android studio Error "Unsupported Modules Detected: Compilation is not supported for following modules"

In my case I cloned a git-project where both Java and Kotlin included. Then checked another branch and pressed "Sync Project with Gradle Files". Android Studio 3.0.1.

MySQL DAYOFWEEK() - my week begins with monday

Could write a udf and take a value to tell it which day of the week should be 1 would look like this (drawing on answer from John to use MOD instead of CASE):

DROP FUNCTION IF EXISTS `reporting`.`udfDayOfWeek`;
CREATE FUNCTION `reporting`.`udfDayOfWeek` (
  _date DATETIME,
  _firstDay TINYINT
) RETURNS tinyint(4)
  DECLARE _dayOfWeek, _offset TINYINT;
  SET _offset = 8 - _firstDay;
  SET _dayOfWeek = (DAYOFWEEK(_date) + _offset) MOD 7;
  IF _dayOfWeek = 0 THEN
    SET _dayOfWeek = 7;
  RETURN _dayOfWeek;

To call this function to give you the current day of week value when your week starts on a Tuesday for instance, you'd call:

SELECT udfDayOfWeek(NOW(), 3);

Nice thing about having it as a udf is you could also call it on a result set field like this:

  udfDayOfWeek(p.SignupDate, 3) AS SignupDayOfWeek,
FROM Profile p;

How do I set a textbox's value using an anchor with jQuery?

To assign value of a text box whose id is ?textbox? in jQuery please do the following


How to get bean using application context in spring boot

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

in a service class

private ApplicationContext context;

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

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

How to remove time portion of date in C# in DateTime object only?

string dt = myCalender.SelectedDate.ToString();
string date = dt.Remove(10);
displayDate.Content = date;

If you take date from calender, with this we also get time. Which is not required all time. Using this we can remove time from date.

How to cast int to enum in C++?

Spinning off the closing question, "how do I convert a to type Test::A" rather than being rigid about the requirement to have a cast in there, and answering several years late only because this seems to be a popular question and nobody else has mentioned the alternative, per the C++11 standard:

5.2.9 Static cast

... an expression e can be explicitly converted to a type T using a static_cast of the form static_cast<T>(e) if the declaration T t(e); is well-formed, for some invented temporary variable t (8.5). The effect of such an explicit conversion is the same as performing the declaration and initialization and then using the temporary variable as the result of the conversion.

Therefore directly using the form t(e) will also work, and you might prefer it for neatness:

auto result = Test(a);

Java, "Variable name" cannot be resolved to a variable

If you look at the scope of the variable 'hoursWorked' you will see that it is a member of the class (declared as private int)

The two variables you are having trouble with are passed as parameters to the constructor.

The error message is because 'hours' is out of scope in the setter.


Use SELECT CONVERT(date, '20140327')

In your case,

       CONVERT(date, [GRADUATION_DATE])     
FROM mydb

Static Classes In Java

Can a class be static in Java ?

The answer is YES, we can have static class in java. In java, we have static instance variables as well as static methods and also static block. Classes can also be made static in Java.

In java, we can’t make Top-level (outer) class static. Only nested classes can be static.

static nested class vs non-static nested class

1) Nested static class doesn’t need a reference of Outer class, but Non-static nested class or Inner class requires Outer class reference.

2) Inner class(or non-static nested class) can access both static and non-static members of Outer class. A static class cannot access non-static members of the Outer class. It can access only static members of Outer class.

see here:

Split a string by another string in C#

In order to split by a string you'll have to use the string array overload.

string data = "THExxQUICKxxBROWNxxFOX";

return data.Split(new string[] { "xx" }, StringSplitOptions.None);

Best/Most Comprehensive API for Stocks/Financial Data

Last I looked -- a couple of years ago -- there wasn't an easy option and the "solution" (which I did not agree with) was screen-scraping a number of websites. It may be easier now but I would still be surprised to see something, well, useful.

The problem here is that the data is immensely valuable (and very expensive), so while defining a method of retrieving it would be easy, getting the trading venues to part with their data would be next to impossible. Some of the MTFs (currently) provide their data for free but I'm not sure how you would get it without paying someone else, like Reuters, for it.

Mysql Compare two datetime fields

Do you want to order it?

Select * From temp where mydate > '2009-06-29 04:00:44' ORDER BY mydate;

How do you round a floating point number in Perl?

cat table |
  perl -ne '/\d+\s+(\d+)\s+(\S+)/ && print "".**int**(log($1)/log(2))."\t$2\n";' 

ImportError: No module named tensorflow

I was trying to install tensorflow GPU for a Windows 7 with pip3 for python3.5.x. Instead of doing pip3 install --upgrade tensorflow I just did pip install tensorflow and after it completed i was finally able to import tensorflow in python3.5.x.

Why do people write #!/usr/bin/env python on the first line of a Python script?

If you're running your script in a virtual environment, say venv, then executing which python while working on venv will display the path to the Python interpreter:


Note that the name of the virtual environment is embedded in the path to the Python interpreter. Therefore, hardcoding this path in your script will cause two problems:

  • If you upload the script to a repository, you're forcing other users to have the same virtual environment name. This is if they identify the problem first.
  • You won't be able to run the script across multiple virtual environments even if you had all required packages in other virtual environments.

Therefore, to add to Jonathan's answer, the ideal shebang is #!/usr/bin/env python, not just for portability across OSes but for portability across virtual environments as well!

How to redirect user's browser URL to a different page in Nodejs?

OP: "I would love if there were a way to do it where I didn't have to know the host address..."

response.writeHead(301, {
  Location: "http" + (request.socket.encrypted ? "s" : "") + "://" + + newRoom

CSS filter: make color image with transparency white

To my knowledge, there is sadly no CSS filter to colorise an element (perhaps with the use of some SVG filter magic, but I'm somewhat unfamiliar with that) and even if that wasn't the case, filters are basically only supported by webkit browsers.

With that said, you could still work around this and use a canvas to modify your image. Basically, you can draw an image element onto a canvas and then loop through the pixels, modifying the respective RGBA values to the colour you want.

However, canvases do come with some restrictions. Most importantly, you have to make sure that the image src comes from the same domain as the page. Otherwise the browser won't allow you to read or modify the pixel data of the canvas.

Here's a JSFiddle changing the colour of the JSFiddle logo.

//Base64 source, but any local source will work_x000D_
var src = "data:image/png;base64,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";_x000D_
var canvas = document.getElementById("theCanvas");_x000D_
var ctx = canvas.getContext("2d");_x000D_
var img = new Image;_x000D_
//wait for the image to load_x000D_
img.onload = function() {_x000D_
    //Draw the original image so that you can fetch the colour data_x000D_
    var imgData = ctx.getImageData(0, 0, canvas.width, canvas.height);_x000D_
    /*_x000D_ is a one-dimensional array which contains _x000D_
    the respective RGBA values for every pixel _x000D_
    in the selected region of the context _x000D_
    (note i+=4 in the loop)_x000D_
    for (var i = 0; i <; i+=4) {_x000D_[i] = 255; //Red, 0-255_x000D_[i+1] = 255; //Green, 0-255_x000D_[i+2] = 255; //Blue, 0-255_x000D_
   /* _x000D_[i+3] contains the alpha value_x000D_
   which we are going to ignore and leave_x000D_
   alone with its original value_x000D_
    ctx.clearRect(0, 0, canvas.width, canvas.height); //clear the original image_x000D_
    ctx.putImageData(imgData, 0, 0); //paint the new colorised image_x000D_
//Load the image!_x000D_
img.src = src;
body {_x000D_
    background: green;_x000D_
<canvas id="theCanvas"></canvas>

How to convert a byte array to its numeric value (Java)?

Each cell in the array is treated as unsigned int:

private int unsignedIntFromByteArray(byte[] bytes) {
int res = 0;
if (bytes == null)
    return res;

for (int i=0;i<bytes.length;i++){
    res = res | ((bytes[i] & 0xff) << i*8);
return res;

calculating the difference in months between two dates

If you want to have a result 1 between 28th Feb and 1st March:

DateTime date1, date2;
int monthSpan = (date2.Year - date1.Year) * 12 + date2.Month - date1.Month

How to check version of python modules?

In Summary:

conda list   

(It will provide all the libraries along with version details).


pip show tensorflow

(It gives complete library details).

How to turn off the Eclipse code formatter for certain sections of Java code?

Alternative method: In Eclipse 3.6, under "Line Wrapping" then "General Settings" there is an option to "Never join already wrapped lines." This means the formatter will wrap long lines but not undo any wrapping you already have.

ggplot2, change title size

+ theme(plot.title = element_text(size=22))

Here is the full set of things you can change in element_text:

element_text(family = NULL, face = NULL, colour = NULL, size = NULL,
  hjust = NULL, vjust = NULL, angle = NULL, lineheight = NULL,
  color = NULL)

R - " missing value where TRUE/FALSE needed "

check the command : NA!=NA : you'll get the result NA, hence the error message.

You have to use the function for your ifstatement to work (in general, it is always better to use this function to check for NA values) :

comments = c("no","yes",NA)
for (l in 1:length(comments)) {
    if (![l])) print(comments[l])
[1] "no"
[1] "yes"

How to get indices of a sorted array in Python

Essentially you need to do an argsort, what implementation you need depends if you want to use external libraries (e.g. NumPy) or if you want to stay pure-Python without dependencies.

The question you need to ask yourself is: Do you want the

  • indices that would sort the array/list
  • indices that the elements would have in the sorted array/list

Unfortunately the example in the question doesn't make it clear what is desired because both will give the same result:

>>> arr = np.array([1, 2, 3, 100, 5])

>>> np.argsort(np.argsort(arr))
array([0, 1, 2, 4, 3], dtype=int64)

>>> np.argsort(arr)
array([0, 1, 2, 4, 3], dtype=int64)

Choosing the argsort implementation

If you have NumPy at your disposal you can simply use the function numpy.argsort or method numpy.ndarray.argsort.

An implementation without NumPy was mentioned in some other answers already, so I'll just recap the fastest solution according to the benchmark answer here

def argsort(l):
    return sorted(range(len(l)), key=l.__getitem__)

Getting the indices that would sort the array/list

To get the indices that would sort the array/list you can simply call argsort on the array or list. I'm using the NumPy versions here but the Python implementation should give the same results

>>> arr = np.array([3, 1, 2, 4])
>>> np.argsort(arr)
array([1, 2, 0, 3], dtype=int64)

The result contains the indices that are needed to get the sorted array.

Since the sorted array would be [1, 2, 3, 4] the argsorted array contains the indices of these elements in the original.

  • The smallest value is 1 and it is at index 1 in the original so the first element of the result is 1.
  • The 2 is at index 2 in the original so the second element of the result is 2.
  • The 3 is at index 0 in the original so the third element of the result is 0.
  • The largest value 4 and it is at index 3 in the original so the last element of the result is 3.

Getting the indices that the elements would have in the sorted array/list

In this case you would need to apply argsort twice:

>>> arr = np.array([3, 1, 2, 4])
>>> np.argsort(np.argsort(arr))
array([2, 0, 1, 3], dtype=int64)

In this case :

  • the first element of the original is 3, which is the third largest value so it would have index 2 in the sorted array/list so the first element is 2.
  • the second element of the original is 1, which is the smallest value so it would have index 0 in the sorted array/list so the second element is 0.
  • the third element of the original is 2, which is the second-smallest value so it would have index 1 in the sorted array/list so the third element is 1.
  • the fourth element of the original is 4 which is the largest value so it would have index 3 in the sorted array/list so the last element is 3.

split python source code into multiple files?

I am researching module usage in python just now and thought I would answer the question Markus asks in the comments above ("How to import variables when they are embedded in modules?") from two perspectives:

  1. variable/function, and
  2. class property/method.

Here is how I would rewrite the main program to demonstrate variable reuse for Markus:

import f2
myStorage = f2.useMyVars(0) # initialze class and properties
for i in range(0,10):
    print "Hello, "
print "Display class property myVar:", myStorage.getMyVar()
print "Display global variable gMyVar:", f2.get_gMyVar()

Here is how I would rewrite the reusable module

# Module:
# Example 1: functions to store and retrieve global variables
gMyVar = 0
def print_world():
    print "World!"
def get_gMyVar():
    return gMyVar # no need for global statement 
def inc_gMyVar():
    global gMyVar
    gMyVar += 1  

# Example 2: class methods to store and retrieve properties
class useMyVars(object):
    def __init__(self, myVar):
        self.myVar = myVar
    def getMyVar(self):
        return self.myVar
    def setMyVar(self, myVar):
        self.myVar = myVar
    def print_helloWorld(self):
        print "Hello, World!"

When is executed here is what the output would look like:

%run ""
Display class property myVar: 9
Display global variable gMyVar: 10

I think the point to Markus would be:

  • To reuse a module's code more than once, put your module's code into functions or classes,
  • To reuse variables stored as properties in modules, initialize properties within a class and add "getter" and "setter" methods so variables do not have to be copied into the main program,
  • To reuse variables stored in modules, initialize the variables and use getter and setter functions. The setter functions would declare the variables as global.

Get HTML5 localStorage keys

For those mentioning using Object.keys(localStorage)... don't because it won't work in Firefox (ironically because Firefox is faithful to the spec). Consider this:

localStorage.setItem("key", "value1")
localStorage.setItem("key2", "value2")
localStorage.setItem("getItem", "value3")
localStorage.setItem("setItem", "value4")

Because key, getItem and setItem are prototypal methods Object.keys(localStorage) will only return ["key2"].

You are best to do something like this:

let t = [];
for (let i = 0; i < localStorage.length; i++) {

Get index of a key/value pair in a C# dictionary based on the value

no , there is nothing similar IndexOf for Dictionary although you can make use of ContainsKey method to get whether a key belongs to dictionary or not

Java 8 NullPointerException in Collectors.toMap

Retaining all questions ids with small tweak

Map<Integer, Boolean> answerMap =
            .collect(Collectors.toMap(Answer::getId, a -> 

docker : invalid reference format

I had a similar problem. Issue I was having was $(pwd) has a space in there which was throwing docker run off.

Change the directory name to not have spaces in there, and it should work if this is the problem

Specify an SSH key for git push for a given domain

I've cribbed together and tested with github the following approach, based on reading other answers, which combines a few techniques:

  • correct SSH config
  • git URL re-writing

The advantage of this approach is, once set up, it doesn't require any additional work to get it right - for example, you don't need to change remote URLs or remember to clone things differently - the URL rewriting makes it all work.


# Personal GitHub
  User git
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/github_id_rsa

# Work GitHub
Host github-work
  User git
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/work_github_id_rsa

Host *
  IdentitiesOnly yes


    name = My Name
    email = [email protected]

[includeIf "gitdir:~/dev/work/"]
    path = ~/dev/work/.gitconfig

[url "github-work:work-github-org/"]
    insteadOf = [email protected]:work-github-org/


    email = [email protected]

As long as you keep all your work repos under ~/dev/work and personal stuff elsewhere, git will use the correct SSH key when doing pulls/clones/pushes to the server, and it will also attach the correct email address to all of your commits.


What is the use of ObservableCollection in .net?

Explanation without Code

For those wanting an answer without any code behind it (boom-tish) with a story (to help you remember):

Normal Collections - No Notifications

Every now and then I go to NYC and my wife asks me to buy stuff. So I take a shopping list with me. The list has a lot of things on there like:

  1. Louis Vuitton handbag ($5000)
  2. Clive Christian’s Imperial Majesty Perfume ($215,000 )
  3. Gucci Sunglasses ($2000)

hahaha well I"m not buying that stuff. So I cross them off and remove them from the list and I add instead:

  1. 12 dozen Titleist golf balls.
  2. 12 lb bowling ball.

So I usually come home without the goods and she's never pleased. The thing is that she doesn't know about what i take off the list and what I add onto it; she gets no notifications.

The ObservableCollection - notifications when changes made

Now, whenever I remove something from the list: she get's a notification on her phone (i.e. sms / email etc)!

The observable collection works just the same way. If you add or remove something to or from it: someone is notified. And when they are notified, well then they call you and you'll get a ear-full. Of course the consequences are customisable via the event handler.

That sums it all up!

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

Increase the font-size of glyphicon to increase all icons size.

.glyphicon {
    font-size: 50px;

To target only one icon,

.glyphicon.glyphicon-globe {
    font-size: 75px;

Open Redis port for remote connections

1- Comment out bind

2- set requirepass yourpassword

then check if the firewall blocked your port

iptables -L -n

service iptables stop

How to round an average to 2 decimal places in PostgreSQL?

Try also the old syntax for casting,

SELECT ROUND(AVG(some_column)::numeric,2)    
FROM table;

works with any version of PostgreSQL.

There are a lack of overloads in some PostgreSQL functions, why (???): I think "it is a lack" (!), but @CraigRinger, @Catcall and the PostgreSQL team agree about "pg's historic rationale".

PS: another point about rounding is accuracy, check @IanKenney's answer.

Overloading as casting strategy

You can overload the ROUND function with,

    SELECT ROUND($1::numeric,$2);
 $$ language SQL IMMUTABLE;

Now your instruction will works fine, try (after function creation)

 SELECT round(1/3.,4); -- 0.3333 numeric

but it returns a NUMERIC type... To preserve the first commom-usage overload, we can return a FLOAT type when a TEXT parameter is offered,

    SELECT CASE WHEN $2='dec'
                THEN ROUND($1::numeric,$3)::float
                -- ... WHEN $2='hex' THEN ... WHEN $2='bin' THEN... complete!
                ELSE 'NaN'::float  -- like an error message 
 $$ language SQL IMMUTABLE;


 SELECT round(1/3.,'dec',4);   -- 0.3333 float!
 SELECT round(2.8+1/3.,'dec',1); -- 3.1 float!
 SELECT round(2.8+1/3.,'dec'::text); -- need to cast string? pg bug 

PS: checking \df round after overloadings, will show something like,

 Schema     |  Name | Result data type | Argument data types 
 myschema   | round | double precision | double precision, text, int
 myschema   | round | numeric          | double precision, int
 pg_catalog | round | double precision | double precision            
 pg_catalog | round | numeric          | numeric   
 pg_catalog | round | numeric          | numeric, int          

The pg_catalog functions are the default ones, see manual of build-in math functions.

How can I switch language in google play?

Answer below the dotted line below is the original that's now outdated.

Here is the latest information ( Thank you @deadfish ):

add &hl=<language> like &hl=pl or &hl=en

example: or

All available languages and abbreviations can be looked up here:


To change the actual local market:

Basically the market is determined automatically based on your IP. You can change some local country settings from your Gmail account settings but still IP of the country you're browsing from is more important. To go around it you'd have to Proxy-cheat. Check out some ways/sites:

To do it from an Android phone you'd need to find an app. I don't have my Droid anymore but give this a try:

How to clear the canvas for redrawing

I always use this

ctx.clearRect(0, 0, canvas.width, canvas.height)


combining clearRect and requestAnimationFrame allows for more fluid animation if that is what you're going for

Error in file(file, "rt") : cannot open the connection

close your R studio and run it again as an administrator. That did the magic for me. Hope it works for you and anyone going through this too.

how to delete a specific row in codeigniter?

a simple way:

in view(pass the id value):

<td><?php echo anchor('textarea/delete_row?id='.$row->id, 'DELETE', 'id="$row->id"'); ?></td>

in controller(receive the id):

$id = $this->input->get('id');

in model(get the passed args):

function row_delete($id){}

Actually, you should use the ajax to POST the id value to controller and delete the row, not the GET.

How to set Python's default version to 3.x on OS X?

The RIGHT and WRONG way to set Python 3 as default on a Mac

In this article author discuss three ways of setting default python:

  1. What NOT to do.
  2. What we COULD do (but also shouldn't).
  3. What we SHOULD do!

All these ways are working. You decide which is better.

Python Set Comprehension

You can get clean and clear solutions by building the appropriate predicates as helper functions. In other words, use the Python set-builder notation the same way you would write the answer with regular mathematics set-notation.

The whole idea behind set comprehensions is to let us write and reason in code the same way we do mathematics by hand.

With an appropriate predicate in hand, problem 1 simplifies to:

 low_primes = {x for x in range(1, 100) if is_prime(x)}

And problem 2 simplifies to:

 low_prime_pairs = {(x, x+2) for x in range(1,100,2) if is_prime(x) and is_prime(x+2)}

Note how this code is a direct translation of the problem specification, "A Prime Pair is a pair of consecutive odd numbers that are both prime."

P.S. I'm trying to give you the correct problem solving technique without actually giving away the answer to the homework problem.

Git - How to use .netrc file on Windows to save user and password

Is it possible to use a .netrc file on Windows?

Yes: You must:

  • define environment variable %HOME% (pre-Git 2.0, no longer needed with Git 2.0+)
  • put a _netrc file in %HOME%

If you are using Windows 7/10, in a CMD session, type:


and the %HOME% will be set to 'C:\Users\"username"'.
Go that that folder (cd %HOME%) and make a file called '_netrc'

Note: Again, for Windows, you need a '_netrc' file, not a '.netrc' file.

Its content is quite standard (Replace the <examples> with your values):

machine <hostname1>
login <login1>
password <password1>
machine <hostname2>
login <login2>
password <password2>

Luke mentions in the comments:

Using the latest version of msysgit on Windows 7, I did not need to set the HOME environment variable. The _netrc file alone did the trick.

This is indeed what I mentioned in "Trying to “install” github, .ssh dir not there":
git-cmd.bat included in msysgit does set the %HOME% environment variable:

@if not exist "%HOME%" @set HOME=%HOMEDRIVE%%HOMEPATH%
@if not exist "%HOME%" @set HOME=%USERPROFILE%

??? believes in the comments that "it seems that it won't work for http protocol"

However, I answered that netrc is used by curl, and works for HTTP protocol, as shown in this example (look for 'netrc' in the page): . Also used with HTTP protocol here: "_netrc/.netrc alternative to cURL".

A common trap with with netrc support on Windows is that git will bypass using it if an origin https url specifies a user name.

For example, if your .git/config file contains:

[remote "origin"]
     fetch = +refs/heads/*:refs/remotes/origin/*
     url = https://[email protected]/p/my-project/

Git will not resolve your credentials via _netrc, to fix this remove your username, like so:

[remote "origin"]
     fetch = +refs/heads/*:refs/remotes/origin/*
     url =

Alternative solution: With git version 1.7.9+ (January 2012): This answer from Mark Longair details the credential cache mechanism which also allows you to not store your password in plain text as shown below.

With Git 1.8.3 (April 2013):

You now can use an encrypted .netrc (with gpg).
On Windows: %HOME%/_netrc (_, not '.')

A new read-only credential helper (in contrib/) to interact with the .netrc/.authinfo files has been added.

That script would allow you to use gpg-encrypted netrc files, avoiding the issue of having your credentials stored in a plain text file.

Files with the .gpg extension will be decrypted by GPG before parsing.
Multiple -f arguments are OK. They are processed in order, and the first matching entry found is returned via the credential helper protocol.

When no -f option is given, .authinfo.gpg, .netrc.gpg, .authinfo, and .netrc files in your home directory are used in this order.

To enable this credential helper:

git config credential.helper '$shortname -f AUTHFILE1 -f AUTHFILE2'

(Note that Git will prepend "git-credential-" to the helper name and look for it in the path.)

# and if you want lots of debugging info:
git config credential.helper '$shortname -f AUTHFILE -d'

#or to see the files opened and data found:
git config credential.helper '$shortname -f AUTHFILE -v'

See a full example at "Is there a way to skip password typing when using https:// github"

With Git 2.18+ (June 2018), you now can customize the GPG program used to decrypt the encrypted .netrc file.

See commit 786ef50, commit f07eeed (12 May 2018) by Luis Marsano (``).
(Merged by Junio C Hamano -- gitster -- in commit 017b7c5, 30 May 2018)

git-credential-netrc: accept gpg option

git-credential-netrc was hardcoded to decrypt with 'gpg' regardless of the gpg.program option.
This is a problem on distributions like Debian that call modern GnuPG something else, like 'gpg2'

AngularJS multiple filter with custom filter function

Try this:

<tr ng-repeat="player in players | filter:{id: player_id, name:player_name} | filter:ageFilter">

$scope.ageFilter = function (player) {
    return (player.age > $scope.min_age && player.age < $scope.max_age);

AttributeError("'str' object has no attribute 'read'")

AttributeError("'str' object has no attribute 'read'",)

This means exactly what it says: something tried to find a .read attribute on the object that you gave it, and you gave it an object of type str (i.e., you gave it a string).

The error occurred here:

json.load (jsonofabitch)['data']['children']

Well, you aren't looking for read anywhere, so it must happen in the json.load function that you called (as indicated by the full traceback). That is because json.load is trying to .read the thing that you gave it, but you gave it jsonofabitch, which currently names a string (which you created by calling .read on the response).

Solution: don't call .read yourself; the function will do this, and is expecting you to give it the response directly so that it can do so.

You could also have figured this out by reading the built-in Python documentation for the function (try help(json.load), or for the entire module (try help(json)), or by checking the documentation for those functions on .

How to add a button to UINavigationBar?

Why not use the following: (from Draw custom Back button on iPhone Navigation Bar)

// Add left
UINavigationItem *previousItem = [[UINavigationItem alloc] initWithTitle:@"Back title"];
UINavigationItem *currentItem = [[UINavigationItem alloc] initWithTitle:@"Main Title"];
[self.navigationController.navigationBar setItems:[NSArray arrayWithObjects:previousItem, currentItem, nil] animated:YES];

// set the delegate to self
[self.navigationController.navigationBar setDelegate:self];

What is aria-label and how should I use it?


Aria is used to improve the user experience of visually impaired users. Visually impaired users navigate though application using screen reader software like JAWS, NVDA,.. While navigating through the application, screen reader software announces content to users. Aria can be used to add content in the code which helps screen reader users understand role, state, label and purpose of the control

Aria does not change anything visually. (Aria is scared of designers too).


aria-label attribute is used to communicate the label to screen reader users. Usually search input field does not have visual label (thanks to designers). aria-label can be used to communicate the label of control to screen reader users

How To Use:

<input type="edit" aria-label="search" placeholder="search">

There is no visual change in application. But screen readers can understand the purpose of control


Both aria-label and aria-labelledby is used to communicate the label. But aria-labelledby can be used to reference any label already present in the page whereas aria-label is used to communicate the label which i not displayed visually

Approach 1:

<span id="sd">Search</span>

<input type="text" aria-labelledby="sd">

Approach 2:

aria-labelledby can also be used to combine two labels for screen reader users

<span id="de">Billing Address</span>

<span id="sd">First Name</span>

<input type="text" aria-labelledby="de sd">

Trigger validation of all fields in Angular Form submit

I know, it's a tad bit too late to answer, but all you need to do is, force all forms dirty. Take a look at the following snippet:

angular.forEach($scope.myForm.$error.required, function(field) {

and then you can check if your form is valid using:

if($scope.myForm.$valid) {
    //Do something

and finally, I guess, you would want to change your route if everything looks good:


Edit: form won't register itself on the scope until submit event is trigger. Just use ng-submit directive to call a function, and wrap the above in that function, and it should work.

JPA Hibernate One-to-One relationship

I'm not sure you can use a relationship as an Id/PrimaryKey in Hibernate.

How to sort an array of objects with jquery or javascript

var array = [{id:'12', name:'Smith', value:1},{id:'13', name:'Jones', value:2}];
array.sort(function(a, b){
    var a1=, b1=;
    if(a1== b1) return 0;
    return a1> b1? 1: -1;

var array =[ ['12', ,'Smith',1],['13', 'Jones',2]];
array.sort(function(a, b){
    var a1= a[1], b1= b[1];
    if(a1== b1) return 0;
    return a1> b1? 1: -1;

Get IP address of visitors using Flask for Python

The user's IP address can be retrieved using the following snippet:

from flask import request

How do I code my submit button go to an email address

You might use Form tag with action attribute to submit the mailto.

Here is an example:

<form method="post" action="mailto:[email protected]" >
<input type="submit" value="Send Email" /> 

Multiline TextView in Android?

Why don't you declare a string instead of writing a long lines into the layout file. For this you have to declare a line of code into layout file 'android:text="@string/text"' and go to the \\app\src\main\res\values\strings.xml and add a line of code ' Your multiline text here' Also use '\n' to break the line from any point else the line will automatically be adjusted.

Spring MVC: Complex object as GET @RequestParam

I have a very similar problem. Actually the problem is deeper as I thought. I am using jquery $.post which uses Content-Type:application/x-www-form-urlencoded; charset=UTF-8 as default. Unfortunately I based my system on that and when I needed a complex object as a @RequestParam I couldn't just make it happen.

In my case I am trying to send user preferences with something like;

    {id: 'pr', preferences: p}, 
    function (response) {

On client side the actual raw data sent to the server is;


parsed as;


and the server side is;

@RequestMapping(value = "/updatePreferences")
Object updatePreferences(@RequestParam("id") String id, @RequestParam("preferences") UserPreferences preferences) {


I tried @ModelAttribute, added setter/getters, constructors with all possibilities to UserPreferences but no chance as it recognized the sent data as 5 parameters but in fact the mapped method has only 2 parameters. I also tried Biju's solution however what happens is that, spring creates an UserPreferences object with default constructor and doesn't fill in the data.

I solved the problem by sending JSon string of the preferences from the client side and handle it as if it is a String on the server side;


    {id: 'pr', preferences: JSON.stringify(p)}, 
    function (response) {


@RequestMapping(value = "/updatePreferences")
Object updatePreferences(@RequestParam("id") String id, @RequestParam("preferences") String preferencesJSon) {

        String ret = null;
        ObjectMapper mapper = new ObjectMapper();
        try {
            UserPreferences userPreferences = mapper.readValue(preferencesJSon, UserPreferences.class);
        } catch (IOException e) {

to brief, I did the conversion manually inside the REST method. In my opinion the reason why spring doesn't recognize the sent data is the content-type.

Java: Date from unix timestamp

Date d = new Date(i * 1000 + TimeZone.getDefault().getRawOffset());

Declaring an unsigned int in Java

Use char for 16 bit unsigned integers.

Where is Python's sys.path initialized from?

Python really tries hard to intelligently set sys.path. How it is set can get really complicated. The following guide is a watered-down, somewhat-incomplete, somewhat-wrong, but hopefully-useful guide for the rank-and-file python programmer of what happens when python figures out what to use as the initial values of sys.path, sys.executable, sys.exec_prefix, and sys.prefix on a normal python installation.

First, python does its level best to figure out its actual physical location on the filesystem based on what the operating system tells it. If the OS just says "python" is running, it finds itself in $PATH. It resolves any symbolic links. Once it has done this, the path of the executable that it finds is used as the value for sys.executable, no ifs, ands, or buts.

Next, it determines the initial values for sys.exec_prefix and sys.prefix.

If there is a file called pyvenv.cfg in the same directory as sys.executable or one directory up, python looks at it. Different OSes do different things with this file.

One of the values in this config file that python looks for is the configuration option home = <DIRECTORY>. Python will use this directory instead of the directory containing sys.executable when it dynamically sets the initial value of sys.prefix later. If the applocal = true setting appears in the pyvenv.cfg file on Windows, but not the home = <DIRECTORY> setting, then sys.prefix will be set to the directory containing sys.executable.

Next, the PYTHONHOME environment variable is examined. On Linux and Mac, sys.prefix and sys.exec_prefix are set to the PYTHONHOME environment variable, if it exists, superseding any home = <DIRECTORY> setting in pyvenv.cfg. On Windows, sys.prefix and sys.exec_prefix is set to the PYTHONHOME environment variable, if it exists, unless a home = <DIRECTORY> setting is present in pyvenv.cfg, which is used instead.

Otherwise, these sys.prefix and sys.exec_prefix are found by walking backwards from the location of sys.executable, or the home directory given by pyvenv.cfg if any.

If the file lib/python<version>/dyn-load is found in that directory or any of its parent directories, that directory is set to be to be sys.exec_prefix on Linux or Mac. If the file lib/python<version>/ is is found in the directory or any of its subdirectories, that directory is set to be sys.prefix on Linux, Mac, and Windows, with sys.exec_prefix set to the same value as sys.prefix on Windows. This entire step is skipped on Windows if applocal = true is set. Either the directory of sys.executable is used or, if home is set in pyvenv.cfg, that is used instead for the initial value of sys.prefix.

If it can't find these "landmark" files or sys.prefix hasn't been found yet, then python sets sys.prefix to a "fallback" value. Linux and Mac, for example, use pre-compiled defaults as the values of sys.prefix and sys.exec_prefix. Windows waits until sys.path is fully figured out to set a fallback value for sys.prefix.

Then, (what you've all been waiting for,) python determines the initial values that are to be contained in sys.path.

  1. The directory of the script which python is executing is added to sys.path. On Windows, this is always the empty string, which tells python to use the full path where the script is located instead.
  2. The contents of PYTHONPATH environment variable, if set, is added to sys.path, unless you're on Windows and applocal is set to true in pyvenv.cfg.
  3. The zip file path, which is <prefix>/lib/ on Linux/Mac and os.path.join(os.dirname(sys.executable), "") on Windows, is added to sys.path.
  4. If on Windows and no applocal = true was set in pyvenv.cfg, then the contents of the subkeys of the registry key HK_CURRENT_USER\Software\Python\PythonCore\<DLLVersion>\PythonPath\ are added, if any.
  5. If on Windows and no applocal = true was set in pyvenv.cfg, and sys.prefix could not be found, then the core contents of the of the registry key HK_CURRENT_USER\Software\Python\PythonCore\<DLLVersion>\PythonPath\ is added, if it exists;
  6. If on Windows and no applocal = true was set in pyvenv.cfg, then the contents of the subkeys of the registry key HK_LOCAL_MACHINE\Software\Python\PythonCore\<DLLVersion>\PythonPath\ are added, if any.
  7. If on Windows and no applocal = true was set in pyvenv.cfg, and sys.prefix could not be found, then the core contents of the of the registry key HK_CURRENT_USER\Software\Python\PythonCore\<DLLVersion>\PythonPath\ is added, if it exists;
  8. If on Windows, and PYTHONPATH was not set, the prefix was not found, and no registry keys were present, then the relative compile-time value of PYTHONPATH is added; otherwise, this step is ignored.
  9. Paths in the compile-time macro PYTHONPATH are added relative to the dynamically-found sys.prefix.
  10. On Mac and Linux, the value of sys.exec_prefix is added. On Windows, the directory which was used (or would have been used) to search dynamically for sys.prefix is added.

At this stage on Windows, if no prefix was found, then python will try to determine it by searching all the directories in sys.path for the landmark files, as it tried to do with the directory of sys.executable previously, until it finds something. If it doesn't, sys.prefix is left blank.

Finally, after all this, Python loads the site module, which adds stuff yet further to sys.path:

It starts by constructing up to four directories from a head and a tail part. For the head part, it uses sys.prefix and sys.exec_prefix; empty heads are skipped. For the tail part, it uses the empty string and then lib/site-packages (on Windows) or lib/pythonX.Y/site-packages and then lib/site-python (on Unix and Macintosh). For each of the distinct head-tail combinations, it sees if it refers to an existing directory, and if so, adds it to sys.path and also inspects the newly added path for configuration files.