Programs & Examples On #State server

npm start error with create-react-app

This is to help others completely new to react and who area having problems just starting a first app even though they did a fresh install and try using npm install and the other fixes I saw around the forums.

Running it on Windows 10 with all the latest npm create-react-app installed and got failure after failure on a simple npm start in a simple my-app demo folder.

Spent a long time with what looks similar to the OP error at first but is slightly different. This starts with ERRNO 4058 and continues with code 'ENOENT' syscall: 'spawn cmd', path: ''cmd' ...

Eventually worked out from github create-react-app forum that a quick fix for this is registering cmd in the "path" variable. To do this go to System Properties>Environment variables. Click on path variable edit and and add new entry of C:\Windows\System32. Restart CMD prompt and I was good to go.

how to make window.open pop up Modal?

You can't make window.open modal and I strongly recommend you not to go that way. Instead you can use something like jQuery UI's dialog widget.

UPDATE:

You can use load() method:

$("#dialog").load("resource.php").dialog({options});

This way it would be faster but the markup will merge into your main document so any submit will be applied on the main window.

And you can use an IFRAME:

$("#dialog").append($("<iframe></iframe>").attr("src", "resource.php")).dialog({options});

This is slower, but will submit independently.

Android List View Drag and Drop sort

Now it's pretty easy to implement for RecyclerView with ItemTouchHelper. Just override onMove method from ItemTouchHelper.Callback:

 @Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
    mMovieAdapter.swap(viewHolder.getAdapterPosition(), target.getAdapterPosition());
    return true;
}

Pretty good tutorial on this can be found at medium.com : Drag and Swipe with RecyclerView

Proper use cases for Android UserManager.isUserAGoat()?

Android R Update:

From Android R, this method always returns false. Google says that this is done "to protect goat privacy":

/**
 * Used to determine whether the user making this call is subject to
 * teleportations.
 *
 * <p>As of {@link android.os.Build.VERSION_CODES#LOLLIPOP}, this method can
 * now automatically identify goats using advanced goat recognition technology.</p>
 *
 * <p>As of {@link android.os.Build.VERSION_CODES#R}, this method always returns
 * {@code false} in order to protect goat privacy.</p>
 *
 * @return Returns whether the user making this call is a goat.
 */
public boolean isUserAGoat() {
    if (mContext.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.R) {
        return false;
    }
    return mContext.getPackageManager()
            .isPackageAvailable("com.coffeestainstudios.goatsimulator");
}

Previous answer:

From their source, the method used to return false until it was changed in API 21.

/**
 * Used to determine whether the user making this call is subject to
 * teleportations.
 * @return whether the user making this call is a goat 
 */
public boolean isUserAGoat() {
    return false;
}

It looks like the method has no real use for us as developers. Someone has previously stated that it might be an Easter egg.

In API 21 the implementation was changed to check if there is an installed app with the package com.coffeestainstudios.goatsimulator

/**
 * Used to determine whether the user making this call is subject to
 * teleportations.
 *
 * <p>As of {@link android.os.Build.VERSION_CODES#LOLLIPOP}, this method can
 * now automatically identify goats using advanced goat recognition technology.</p>
 *
 * @return Returns true if the user making this call is a goat.
 */
public boolean isUserAGoat() {
    return mContext.getPackageManager()
            .isPackageAvailable("com.coffeestainstudios.goatsimulator");
}

Here is the source and the change.

Using sessions & session variables in a PHP Login Script

Firstly, the PHP documentation has some excellent information on sessions.

Secondly, you will need some way to store the credentials for each user of your website (e.g. a database). It is a good idea not to store passwords as human-readable, unencrypted plain text. When storing passwords, you should use PHP's crypt() hashing function. This means that if any credentials are compromised, the passwords are not readily available.

Most log-in systems will hash/crypt the password a user enters then compare the result to the hash in the storage system (e.g. database) for the corresponding username. If the hash of the entered password matches the stored hash, the user has entered the correct password.

You can use session variables to store information about the current state of the user - i.e. are they logged in or not, and if they are you can also store their unique user ID or any other information you need readily available.

To start a PHP session, you need to call session_start(). Similarly, to destroy a session and its data, you need to call session_destroy() (for example, when the user logs out):

// Begin the session
session_start();

// Use session variables
$_SESSION['userid'] = $userid;

// E.g. find if the user is logged in
if($_SESSION['userid']) {
    // Logged in
}
else {
    // Not logged in
}

// Destroy the session
if($log_out)
    session_destroy();

I would also recommend that you take a look at this. There's some good, easy to follow information on creating a simple log-in system there.

How do I import modules or install extensions in PostgreSQL 9.1+?

The extensions available for each version of Postgresql vary. An easy way to check which extensions are available is, as has been already mentioned:

SELECT * FROM pg_available_extensions;

If the extension that you are looking for is available, you can install it using:

CREATE EXTENSION 'extensionName';

or if you want to drop it use:

DROP EXTENSION 'extensionName';

With psql you can additionally check if the extension has been successfully installed using \dx, and find more details about the extension using \dx+ extensioName. It returns additional information about the extension, like which packages are used with it.

If the extension is not available in your Postgres version, then you need to download the necessary binary files and libraries and locate it them at /usr/share/conrib

jQuery multiple conditions within if statement

Try

if (!(i == 'InvKey' || i == 'PostDate')) {

or

if (i != 'InvKey' || i != 'PostDate') {

that says if i does not equals InvKey OR PostDate

Sorting a Dictionary in place with respect to keys

While Dictionary is implemented as a hash table, SortedDictionary is implemented as a Red-Black Tree.

If you don't take advantage of the order in your algorithm and only need to sort the data before output, using SortedDictionary would have negative impact on performance.

You can "sort" the dictionary like this:

Dictionary<string, int> dictionary = new Dictionary<string, int>();
// algorithm
return new SortedDictionary<string, int>(dictionary);

JQuery get all elements by class name

With the code in the question, you're only dealing interacting with the first of the four entries returned by that selector.

Code below as a fiddle: https://jsfiddle.net/c4nhpqgb/

I want to be overly clear that you have four items that matched that selector, so you need to deal with each explicitly. Using eq() is a little more explicit making this point than the answers using map, though map or each is what you'd probably use "in real life" (jquery docs for eq here).

<html>
    <head>
        <script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js" ></script>
    </head>

    <body>
        <div class="mbox">Block One</div>
        <div class="mbox">Block Two</div>
        <div class="mbox">Block Three</div>
        <div class="mbox">Block Four</div>

        <div id="outige"></div>
        <script>
            // using the $ prefix to use the "jQuery wrapped var" convention
            var i, $mvar = $('.mbox');

            // convenience method to display unprocessed html on the same page
            function logit( string )
            {
                var text = document.createTextNode( string );
                $('#outige').append(text);
                $('#outige').append("<br>");
            }

            logit($mvar.length);

            for (i=0; i<$mvar.length; i++)    {
                logit($mvar.eq(i).html());
            }
        </script>
    </body>

</html>

Output from logit calls (after the initial four div's display):

4
Block One
Block Two
Block Three
Block Four

Pagination using MySQL LIMIT, OFFSET

Use .. LIMIT :pageSize OFFSET :pageStart

Where :pageStart is bound to the_page_index (i.e. 0 for the first page) * number_of_items_per_pages (e.g. 4) and :pageSize is bound to number_of_items_per_pages.

To detect for "has more pages", either use SQL_CALC_FOUND_ROWS or use .. LIMIT :pageSize OFFSET :pageStart + 1 and detect a missing last (pageSize+1) record. Needless to say, for pages with an index > 0, there exists a previous page.

If the page index value is embedded in the URL (e.g. in "prev page" and "next page" links) then it can be obtained via the appropriate $_GET item.

Change color of Label in C#

You can try this with Color.FromArgb:

Random rnd = new Random();
lbl.ForeColor = Color.FromArgb(rnd.Next(255), rnd.Next(255), rnd.Next(255));

Creating a file only if it doesn't exist in Node.js

This method is no longer recommended. fs.exists is deprecated. See comments.

Here are some options:

1) Have 2 "fs" calls. The first one is the "fs.exists" call, and the second is "fs.write / read, etc"

//checks if the file exists. 
//If it does, it just calls back.
//If it doesn't, then the file is created.
function checkForFile(fileName,callback)
{
    fs.exists(fileName, function (exists) {
        if(exists)
        {
            callback();
        }else
        {
            fs.writeFile(fileName, {flag: 'wx'}, function (err, data) 
            { 
                callback();
            })
        }
    });
}

function writeToFile()
{
    checkForFile("file.dat",function()
    {
       //It is now safe to write/read to file.dat
       fs.readFile("file.dat", function (err,data) 
       {
          //do stuff
       });
    });
}

2) Or Create an empty file first:

--- Sync:

//If you want to force the file to be empty then you want to use the 'w' flag:

var fd = fs.openSync(filepath, 'w');

//That will truncate the file if it exists and create it if it doesn't.

//Wrap it in an fs.closeSync call if you don't need the file descriptor it returns.

fs.closeSync(fs.openSync(filepath, 'w'));

--- ASync:

var fs = require("fs");
fs.open(path, "wx", function (err, fd) {
    // handle error
    fs.close(fd, function (err) {
        // handle error
    });
});

3) Or use "touch": https://github.com/isaacs/node-touch

How to set the max size of upload file

put this in your application.yml file to allow uploads of files up to 900 MB

server:
  servlet:
    multipart:
      enabled: true
      max-file-size: 900000000  #900M
      max-request-size: 900000000

Include in SELECT a column that isn't actually in the database

You may want to use:

SELECT Name, 'Unpaid' AS Status FROM table;

The SELECT clause syntax, as defined in MSDN: SELECT Clause (Transact-SQL), is as follows:

SELECT [ ALL | DISTINCT ]
[ TOP ( expression ) [ PERCENT ] [ WITH TIES ] ] 
<select_list> 

Where the expression can be a constant, function, any combination of column names, constants, and functions connected by an operator or operators, or a subquery.

Export JAR with Netbeans

You need to enable the option

Project Properties -> Build -> Packaging -> Build JAR after compiling

(but this is enabled by default)

How to iterate through property names of Javascript object?

In JavaScript 1.8.5, Object.getOwnPropertyNames returns an array of all properties found directly upon a given object.

Object.getOwnPropertyNames ( obj )

and another method Object.keys, which returns an array containing the names of all of the given object's own enumerable properties.

Object.keys( obj )

I used forEach to list values and keys in obj, same as for (var key in obj) ..

Object.keys(obj).forEach(function (key) {
      console.log( key , obj[key] );
});

This all are new features in ECMAScript , the mothods getOwnPropertyNames, keys won't supports old browser's.

What is middleware exactly?

There is a common definition in web application development which is (and I'm making this wording up but it seems to fit): A component which is designed to modify an HTTP request and/or response but does not (usually) serve the response in its entirety, designed to be chained together to form a pipeline of behavioral changes during request processing.

Examples of tasks that are commonly implemented by middleware:

  • Gzip response compression
  • HTTP authentication
  • Request logging

The key point here is that none of these is fully responsible for responding to the client. Instead each changes the behavior in some way as part of the pipeline, leaving the actual response to come from something later in the sequence (pipeline).

Usually, the middlewares are run before some sort of "router", which examines the request (often the path) and calls the appropriate code to generate the response.

Personally, I hate the term "middleware" for its genericity but it is in common use.

Here is an additional explanation specifically applicable to Ruby on Rails.

npm install -g less does not work: EACCES: permission denied

For my mac environment

sudo chown -R $USER /usr/local/lib/node_modules

solve the issue

Allow anything through CORS Policy

Simply you can add rack-cors gem https://rubygems.org/gems/rack-cors/versions/0.4.0

1st Step: add gem to your Gemfile:

gem 'rack-cors', :require => 'rack/cors'

and then save and run bundle install

2nd Step: update your config/application.rb file by adding this:

config.middleware.insert_before 0, Rack::Cors do
      allow do
        origins '*'
        resource '*', :headers => :any, :methods => [:get, :post, :options]
      end
    end

for more details you can go to https://github.com/cyu/rack-cors Specailly if you don't use rails 5.

Unable to import a module that is definitely installed

It's the python path problem.

In my case, I have python installed in:

/Library/Frameworks/Python.framework/Versions/2.6/bin/python,

and there is no site-packages directory within the python2.6.

The package(SOAPpy) I installed by pip is located

/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/

And site-package is not in the python path, all I did is add site-packages to PYTHONPATH permanently.

  1. Open up Terminal
  2. Type open .bash_profile
  3. In the text file that pops up, add this line at the end:

    export PYTHONPATH=$PYTHONPATH:/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/

  4. Save the file, restart the Terminal, and you're done

Excel SUMIF between dates

I found another way to work around this issue that I thought I would share.

In my case I had a years worth of daily columns (i.e. Jan-1, Jan-2... Dec-31), and I had to extract totals for each month. I went about it this way: Sum the entire year, Subtract out the totals for the dates prior and the dates after. It looks like this for February's totals:

=SUM($P3:$NP3)-(SUMIF($P$2:$NP$2, ">2/28/2014",$P3:$NP3)+SUMIF($P$2:$NP$2, "<2/1/2014",$P3:$NP3))

Where $P$2:$NP$2 contained my date values and $P3:$NP3 was the first row of data I am totaling. So SUM($P3:$NP3) is my entire year's total and I subtract (the sum of two sumifs):

SUMIF($P$2:$NP$2, ">2/28/2014",$P3:$NP3), which totals all the months after February and SUMIF($P$2:$NP$2, "<2/1/2014",$P3:$NP3), which totals all the months before February.

Install pdo for postgres Ubuntu

PDO driver for PostgreSQL is now included in the debian package php5-dev. The above steps using Pecl no longer works.

How to read files and stdout from a running Docker container

You can view the filesystem of the container at

/var/lib/docker/devicemapper/mnt/$CONTAINER_ID/rootfs/

and you can just

tail -f mylogfile.log

jquery dialog save cancel button styling

These solutions are all very well if you only have one dialog in the page at any one time, however if you want to style multiple dialogs at once then try:

$("#element").dialog({
    buttons: {
        'Save': function() {},
        'Cancel': function() {}
    }
})
.dialog("widget")
.find(".ui-dialog-buttonpane button")
.eq(0).addClass("btnSave").end()
.eq(1).addClass("btnCancel").end();

Instead of globally selecting buttons, this gets the widget object and finds it's button pane, then individually styles each button. This saves lot's of pain when you have several dialogs on one page

How to assign a select result to a variable?

I just had the same problem and...

declare @userId uniqueidentifier
set @userId = (select top 1 UserId from aspnet_Users)

or even shorter:

declare @userId uniqueidentifier
SELECT TOP 1 @userId = UserId FROM aspnet_Users

Using malloc for allocation of multi-dimensional arrays with different row lengths

malloc does not allocate on specific boundaries, so it must be assumed that it allocates on a byte boundary.

The returned pointer can then not be used if converted to any other type, since accessing that pointer will probably produce a memory access violation by the CPU, and the application will be immediately shut down.

JavaScript error (Uncaught SyntaxError: Unexpected end of input)

This error is mainly caused by empty returned ajax calls, when trying to parse an empty JSON.

To solve this test if the returned data is empty

$.ajax({
    url: url,
    type: "get",
    dataType: "json",
    success: function (response) {

        if(response.data.length == 0){
            // EMPTY
        }else{
            var obj =jQuery.parseJSON(response.data);
            console.log(obj);
        }
    }
});

How to calculate date difference in JavaScript?

<html lang="en">
<head>
<script>
function getDateDiff(time1, time2) {
  var str1= time1.split('/');
  var str2= time2.split('/');

  //                yyyy   , mm       , dd
  var t1 = new Date(str1[2], str1[0]-1, str1[1]);
  var t2 = new Date(str2[2], str2[0]-1, str2[1]);

  var diffMS = t1 - t2;    
  console.log(diffMS + ' ms');

  var diffS = diffMS / 1000;    
  console.log(diffS + ' ');

  var diffM = diffS / 60;
  console.log(diffM + ' minutes');

  var diffH = diffM / 60;
  console.log(diffH + ' hours');

  var diffD = diffH / 24;
  console.log(diffD + ' days');
  alert(diffD);
}

//alert(getDateDiff('10/18/2013','10/14/2013'));
</script>
</head>
<body>
  <input type="button" 
       onclick="getDateDiff('10/18/2013','10/14/2013')" 
       value="clickHere()" />

</body>
</html>

What does "dereferencing" a pointer mean?

Code and explanation from Pointer Basics:

The dereference operation starts at the pointer and follows its arrow over to access its pointee. The goal may be to look at the pointee state or to change the pointee state. The dereference operation on a pointer only works if the pointer has a pointee -- the pointee must be allocated and the pointer must be set to point to it. The most common error in pointer code is forgetting to set up the pointee. The most common runtime crash because of that error in the code is a failed dereference operation. In Java the incorrect dereference will be flagged politely by the runtime system. In compiled languages such as C, C++, and Pascal, the incorrect dereference will sometimes crash, and other times corrupt memory in some subtle, random way. Pointer bugs in compiled languages can be difficult to track down for this reason.

void main() {   
    int*    x;  // Allocate the pointer x
    x = malloc(sizeof(int));    // Allocate an int pointee,
                            // and set x to point to it
    *x = 42;    // Dereference x to store 42 in its pointee   
}

Nodejs send file in response

Here's an example program that will send myfile.mp3 by streaming it from disk (that is, it doesn't read the whole file into memory before sending the file). The server listens on port 2000.

[Update] As mentioned by @Aftershock in the comments, util.pump is gone and was replaced with a method on the Stream prototype called pipe; the code below reflects this.

var http = require('http'),
    fileSystem = require('fs'),
    path = require('path');

http.createServer(function(request, response) {
    var filePath = path.join(__dirname, 'myfile.mp3');
    var stat = fileSystem.statSync(filePath);

    response.writeHead(200, {
        'Content-Type': 'audio/mpeg',
        'Content-Length': stat.size
    });

    var readStream = fileSystem.createReadStream(filePath);
    // We replaced all the event handlers with a simple call to readStream.pipe()
    readStream.pipe(response);
})
.listen(2000);

Taken from http://elegantcode.com/2011/04/06/taking-baby-steps-with-node-js-pumping-data-between-streams/

How to add many functions in ONE ng-click?

Follow the below

ng-click="anyFunction()"

anyFunction() {
   // call another function here
   anotherFunction();
}

How do I combine two lists into a dictionary in Python?

If there are duplicate keys in the first list that map to different values in the second list, like a 1-to-many relationship, but you need the values to be combined or added or something instead of updating, you can do this:

i = iter(["a", "a", "b", "c", "b"])
j = iter([1,2,3,4,5])
k = list(zip(i, j))
for (x,y) in k:
    if x in d:
        d[x] = d[x] + y #or whatever your function needs to be to combine them
    else:
        d[x] = y

In that example, d == {'a': 3, 'c': 4, 'b': 8}

Parsing a CSV file using NodeJS

this is my solution to get csv file from external url

const parse = require( 'csv-parse/lib/sync' );
const axios = require( 'axios' );
const readCSV = ( module.exports.readCSV = async ( path ) => {
try {
   const res = await axios( { url: path, method: 'GET', responseType: 'blob' } );
   let records = parse( res.data, {
      columns: true,
      skip_empty_lines: true
    } );

    return records;
 } catch ( e ) {
   console.log( 'err' );
 }

} );
readCSV('https://urltofilecsv');

Getting parts of a URL (Regex)

I like the regex that was published in "Javascript: The Good Parts". Its not too short and not too complex. This page on github also has the JavaScript code that uses it. But it an be adapted for any language. https://gist.github.com/voodooGQ/4057330

Is there a 'box-shadow-color' property?

You can do this with CSS Variable

.box-shadow {
    --box-shadow-color: #000; /* Declaring the variable */
    width: 30px;                
    height: 30px;
    box-shadow: 1px 1px 25px var(--box-shadow-color); /* Calling the variable */

}

.box-shadow:hover  {
    --box-shadow-color: #ff0000; /* Changing the value of the variable */
}

Best way to read a large file into a byte array in C#?

I would think this:

byte[] file = System.IO.File.ReadAllBytes(fileName);

Pretty-Print JSON Data to a File using Python

You could redirect a file to python and open using the tool and to read it use more.

The sample code will be,

cat filename.json | python -m json.tool | more

What are the different types of keys in RDBMS?

(I) Super Key – An attribute or a combination of attribute that is used to identify the records uniquely is known as Super Key. A table can have many Super Keys.

E.g. of Super Key

  1. ID
  2. ID, Name
  3. ID, Address
  4. ID, Department_ID
  5. ID, Salary
  6. Name, Address
  7. Name, Address, Department_ID

So on as any combination which can identify the records uniquely will be a Super Key.

(II) Candidate Key – It can be defined as minimal Super Key or irreducible Super Key. In other words an attribute or a combination of attribute that identifies the record uniquely but none of its proper subsets can identify the records uniquely.

E.g. of Candidate Key

  1. ID
  2. Name, Address

For above table we have only two Candidate Keys (i.e. Irreducible Super Key) used to identify the records from the table uniquely. ID Key can identify the record uniquely and similarly combination of Name and Address can identify the record uniquely, but neither Name nor Address can be used to identify the records uniquely as it might be possible that we have two employees with similar name or two employees from the same house.

(III) Primary Key – A Candidate Key that is used by the database designer for unique identification of each row in a table is known as Primary Key. A Primary Key can consist of one or more attributes of a table.

E.g. of Primary Key - Database designer can use one of the Candidate Key as a Primary Key. In this case we have “ID” and “Name, Address” as Candidate Key, we will consider “ID” Key as a Primary Key as the other key is the combination of more than one attribute.

(IV) Foreign Key – A foreign key is an attribute or combination of attribute in one base table that points to the candidate key (generally it is the primary key) of another table. The purpose of the foreign key is to ensure referential integrity of the data i.e. only values that are supposed to appear in the database are permitted.

E.g. of Foreign Key – Let consider we have another table i.e. Department Table with Attributes “Department_ID”, “Department_Name”, “Manager_ID”, ”Location_ID” with Department_ID as an Primary Key. Now the Department_ID attribute of Employee Table (dependent or child table) can be defined as the Foreign Key as it can reference to the Department_ID attribute of the Departments table (the referenced or parent table), a Foreign Key value must match an existing value in the parent table or be NULL.

(V) Composite Key – If we use multiple attributes to create a Primary Key then that Primary Key is called Composite Key (also called a Compound Key or Concatenated Key).

E.g. of Composite Key, if we have used “Name, Address” as a Primary Key then it will be our Composite Key.

(VI) Alternate Key – Alternate Key can be any of the Candidate Keys except for the Primary Key.

E.g. of Alternate Key is “Name, Address” as it is the only other Candidate Key which is not a Primary Key.

(VII) Secondary Key – The attributes that are not even the Super Key but can be still used for identification of records (not unique) are known as Secondary Key.

E.g. of Secondary Key can be Name, Address, Salary, Department_ID etc. as they can identify the records but they might not be unique.

How to get POST data in WebAPI?

I had a problem with sending a request with multiple parameters.

I've solved it by sending a class, with the old parameters as properties.

<form action="http://localhost:12345/api/controller/method" method="post">
    <input type="hidden" name="name1" value="value1" />
    <input type="hidden" name="name2" value="value2" />
    <input type="submit" name="submit" value="Submit" />
</form>

Model class:

public class Model {
    public string Name1 { get; set; }
    public string Name2 { get; set; }
}

Controller:

public void method(Model m) {
    string name = m.Name1;
}

$http get parameters does not work

The 2nd parameter in the get call is a config object. You want something like this:

$http
    .get('accept.php', {
        params: {
            source: link,
            category_id: category
        }
     })
     .success(function (data,status) {
          $scope.info_show = data
     });

See the Arguments section of http://docs.angularjs.org/api/ng.$http for more detail

How to loop through a checkboxlist and to find what's checked and not checked?

Try something like this:

foreach (ListItem listItem in clbIncludes.Items)
{
    if (listItem.Selected) { 
        //do some work 
    }
    else { 
        //do something else 
    }
}

Using JavaScript to display a Blob

I guess you had an error in the inline code of your image. Try this :

_x000D_
_x000D_
var image = document.createElement('img');_x000D_
    _x000D_
image.src="data:image/gif;base64,R0lGODlhDwAPAKECAAAAzMzM/////wAAACwAAAAADwAPAAACIISPeQHsrZ5ModrLlN48CXF8m2iQ3YmmKqVlRtW4MLwWACH+H09wdGltaXplZCBieSBVbGVhZCBTbWFydFNhdmVyIQAAOw==";_x000D_
    _x000D_
image.width=100;_x000D_
image.height=100;_x000D_
image.alt="here should be some image";_x000D_
    _x000D_
document.body.appendChild(image);
_x000D_
_x000D_
_x000D_

Helpful link :http://dean.edwards.name/my/base64-ie.html

How to sort with lambda in Python

Use

a = sorted(a, key=lambda x: x.modified, reverse=True)
#             ^^^^

On Python 2.x, the sorted function takes its arguments in this order:

sorted(iterable, cmp=None, key=None, reverse=False)

so without the key=, the function you pass in will be considered a cmp function which takes 2 arguments.

JQUERY: Uncaught Error: Syntax error, unrecognized expression

If you're using jQuery 2.1.4 or above, try this:

$("#" + this.d);

Or, you can define var before using it. It makes your code simpler.

var d = this.d
$("#" + d);

Android - Start service on boot

Looks very similar to mine but I use the full package name for the receiver:

<receiver android:name=".StartupIntentReceiver">

I have:

<receiver android:name="com.your.package.AutoStart"> 

How to return a boolean method in java?

Best way would be to declare Boolean variable within the code block and return it at end of code, like this:

public boolean Test(){
    boolean booleanFlag= true; 
    if (A>B)
    {booleanFlag= true;}
    else 
    {booleanFlag = false;}
    return booleanFlag;

}

I find this the best way.

Post parameter is always null

I had a similar issue where the request object for my Web API method was always null. I noticed that since the controller action name was prefixed with "Get", Web API treated this as a HTTP GET rather than a POST. After renaming the controller action, it now works as intended.

Build a basic Python iterator

This question is about iterable objects, not about iterators. In Python, sequences are iterable too so one way to make an iterable class is to make it behave like a sequence, i.e. give it __getitem__ and __len__ methods. I have tested this on Python 2 and 3.

class CustomRange:

    def __init__(self, low, high):
        self.low = low
        self.high = high

    def __getitem__(self, item):
        if item >= len(self):
            raise IndexError("CustomRange index out of range")
        return self.low + item

    def __len__(self):
        return self.high - self.low


cr = CustomRange(0, 10)
for i in cr:
    print(i)

Dynamically add event listener

I aso find this extremely confusing. as @EricMartinez points out Renderer2 listen() returns the function to remove the listener:

ƒ () { return element.removeEventListener(eventName, /** @type {?} */ (handler), false); }

If i´m adding a listener

this.listenToClick = this.renderer.listen('document', 'click', (evt) => {
    alert('Clicking the document');
})

I´d expect my function to execute what i intended, not the total opposite which is remove the listener.

// I´d expect an alert('Clicking the document'); 
this.listenToClick();
// what you actually get is removing the listener, so nothing...

In the given scenario, It´d actually make to more sense to name it like:

// Add listeners
let unlistenGlobal = this.renderer.listen('document', 'click', (evt) => {
    console.log('Clicking the document', evt);
})

let removeSimple = this.renderer.listen(this.myButton.nativeElement, 'click', (evt) => {
    console.log('Clicking the button', evt);
});

There must be a good reason for this but in my opinion it´s very misleading and not intuitive.

Python extract pattern matches

You can also use a capture group (?P<user>pattern) and access the group like a dictionary match['user'].

string = '''someline abc\n
            someother line\n
            name my_user_name is valid\n
            some more lines\n'''

pattern = r'name (?P<user>.*) is valid'
matches = re.search(pattern, str(string), re.DOTALL)
print(matches['user'])

# my_user_name

laravel foreach loop in controller

Hi, this will throw an error:

foreach ($product->sku as $sku){ 
// Code Here
}

because you cannot loop a model with a specific column ($product->sku) from the table.
So you must loop on the whole model:

foreach ($product as $p) {
// code
}

Inside the loop you can retrieve whatever column you want just adding "->[column_name]"

foreach ($product as $p) {
echo $p->sku;
}

Have a great day

How do I pass command-line arguments to a WinForms application?

The best way to work with args for your winforms app is to use

string[] args = Environment.GetCommandLineArgs();

You can probably couple this with the use of an enum to solidify the use of the array througout your code base.

"And you can use this anywhere in your application, you aren’t just restricted to using it in the main() method like in a console application."

Found at:HERE

Identify if a string is a number

Use these extension methods to clearly distinguish between a check if the string is numerical and if the string only contains 0-9 digits

public static class ExtensionMethods
{
    /// <summary>
    /// Returns true if string could represent a valid number, including decimals and local culture symbols
    /// </summary>
    public static bool IsNumeric(this string s)
    {
        decimal d;
        return decimal.TryParse(s, System.Globalization.NumberStyles.Any, System.Globalization.CultureInfo.CurrentCulture, out d);
    }

    /// <summary>
    /// Returns true only if string is wholy comprised of numerical digits
    /// </summary>
    public static bool IsNumbersOnly(this string s)
    {
        if (s == null || s == string.Empty)
            return false;

        foreach (char c in s)
        {
            if (c < '0' || c > '9') // Avoid using .IsDigit or .IsNumeric as they will return true for other characters
                return false;
        }

        return true;
    }
}

SQL comment header examples

The header that we currently use looks like this:

---------------------------------------------------
-- Produced By   : Our company  
-- URL       : www.company.com  
-- Author        : me   
-- Date      : yesterday    
-- Purpose       : to do something  
-- Called by     : some other process   
-- Modifications : some other guy - today - to fix my bug   
------------------------------------------------------------

On a side note, any comments that I place within the SQL i always use the format:

/* Comment */

As in the past I had problems where scripting (by SQL Server) does funny things wrapping lines round and comments starting -- have commented out required SQL.... but that might just be me.

How to make a movie out of images in python

I use the ffmpeg-python binding. You can find more information here.

import ffmpeg
(
    ffmpeg
    .input('/path/to/jpegs/*.jpg', pattern_type='glob', framerate=25)
    .output('movie.mp4')
    .run()
)

Show hide div using codebehind

Another method (which it appears no-one has mentioned thus far), is to add an additional KeyValue pair to the element's Style array. i.e

Div.Style.Add("display", "none");

This has the added benefit of merely hiding the element, rather than preventing it from being written to the DOM to begin with - unlike the "Visible" property. i.e.

Div.Visible = false

results in the div never being written to the DOM.

Edit: This should be done in the 'code-behind', I.e. The *.aspx.cs file.

Bold & Non-Bold Text In A Single UILabel?

I've adopted Crazy Yoghurt's answer to swift's extensions.

extension UILabel {

    func boldRange(_ range: Range<String.Index>) {
        if let text = self.attributedText {
            let attr = NSMutableAttributedString(attributedString: text)
            let start = text.string.characters.distance(from: text.string.startIndex, to: range.lowerBound)
            let length = text.string.characters.distance(from: range.lowerBound, to: range.upperBound)
            attr.addAttributes([NSFontAttributeName: UIFont.boldSystemFont(ofSize: self.font.pointSize)], range: NSMakeRange(start, length))
            self.attributedText = attr
        }
    }

    func boldSubstring(_ substr: String) {
        if let text = self.attributedText {
            var range = text.string.range(of: substr)
            let attr = NSMutableAttributedString(attributedString: text)
            while range != nil {
                let start = text.string.characters.distance(from: text.string.startIndex, to: range!.lowerBound)
                let length = text.string.characters.distance(from: range!.lowerBound, to: range!.upperBound)
                var nsRange = NSMakeRange(start, length)
                let font = attr.attribute(NSFontAttributeName, at: start, effectiveRange: &nsRange) as! UIFont
                if !font.fontDescriptor.symbolicTraits.contains(.traitBold) {
                    break
                }
                range = text.string.range(of: substr, options: NSString.CompareOptions.literal, range: range!.upperBound..<text.string.endIndex, locale: nil)
            }
            if let r = range {
                boldRange(r)
            }
        }
    }
}

May be there is not good conversion between Range and NSRange, but I didn't found something better.

Using R to download zipped data file, extract, and import data

rio() would be very suitable for this - it uses the file extension of a file name to determine what kind of file it is, so it will work with a large variety of file types. I've also used unzip() to list the file names within the zip file, so its not necessary to specify the file name(s) manually.

library(rio)

# create a temporary directory
td <- tempdir()

# create a temporary file
tf <- tempfile(tmpdir=td, fileext=".zip")

# download file from internet into temporary location
download.file("http://download.companieshouse.gov.uk/BasicCompanyData-part1.zip", tf)

# list zip archive
file_names <- unzip(tf, list=TRUE)

# extract files from zip file
unzip(tf, exdir=td, overwrite=TRUE)

# use when zip file has only one file
data <- import(file.path(td, file_names$Name[1]))

# use when zip file has multiple files
data_multiple <- lapply(file_names$Name, function(x) import(file.path(td, x)))

# delete the files and directories
unlink(td)

How to set ANDROID_HOME path in ubuntu?

better way is to reuse ANDROID_HOME variable in path variable. if your ANDROID_HOME variable changes you just have to make change at one place.

export ANDROID_HOME=/home/arshid/Android/Sdk
export PATH=$PATH:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools

server error:405 - HTTP verb used to access this page is not allowed

In the Facebook app control panel make sure you have a forward slash on the end of any specified URL if you are only specifying a folder name

i.e.

Page Tab URL: http://mypagetabserver.com/custom_tab/

Remove all padding and margin table HTML and CSS

I find the most perfectly working answer is this

.noBorder {
    border: 0px;
    padding:0; 
    margin:0;
    border-collapse: collapse;
}

How to play ringtone/alarm sound in Android

For the future googlers: use RingtoneManager.getActualDefaultRingtoneUri() instead of RingtoneManager.getDefaultUri(). According to its name, it would return the actual uri, so you can freely use it. From documentation of getActualDefaultRingtoneUri():

Gets the current default sound's Uri. This will give the actual sound Uri, instead of using this, most clients can use DEFAULT_RINGTONE_URI.

Meanwhile getDefaultUri() says this:

Returns the Uri for the default ringtone of a particular type. Rather than returning the actual ringtone's sound Uri, this will return the symbolic Uri which will resolved to the actual sound when played.

Python datetime - setting fixed hour and minute after using strptime to get day,month,year

Use datetime.replace:

from datetime import datetime
dt = datetime.strptime('26 Sep 2012', '%d %b %Y')
newdatetime = dt.replace(hour=11, minute=59)

How to get a index value from foreach loop in jstl

I face Similar problem now I understand we have some more option : varStatus="loop", Here will be loop will variable which will hold the index of lop.

It can use for use to read for Zeor base index or 1 one base index.

${loop.count}` it will give 1 starting base index.

${loop.index} it will give 0 base index as normal Index of array start from 0.

For Example :

<c:forEach var="currentImage" items="${cityBannerImages}" varStatus="loop">
<picture>
   <source srcset="${currentImage}" media="(min-width: 1000px)"></source>
   <source srcset="${cityMobileImages[loop.count]}" media="(min-width:600px)"></source>
   <img srcset="${cityMobileImages[loop.count]}" alt=""></img>
</picture>
</c:forEach>

For more Info please refer this link

Could not find method compile() for arguments Gradle

In my case, all the compile statements has somehow arranged in a single line. separating them in individual lines has fixed the issue.

Gitignore not working

I solved my problem doing the following:

First of all, I am a windows user, but i have faced similar issue. So, I am posting my solution here.

There is one simple reason why sometimes the .gitignore doesn`t work like it is supposed to. It is due to the EOL conversion behavior.

Here is a quick fix for that

Edit > EOL Conversion > Windows Format > Save

You can blame your text editor settings for that.

For example:

As i am a windows developer, I typically use Notepad++ for editing my text unlike Vim users.

So what happens is, when i open my .gitignore file using Notepad++, it looks something like this:

## Ignore Visual Studio temporary files, build results, and
## files generated by popular Visual Studio add-ons.
##
## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore


# See https://help.github.com/ignore-files/ for more about ignoring files.

# User-specific files
*.suo
*.user
*.userosscache
*.sln.docstates
*.dll
*.force
# User-specific files (MonoDevelop/Xamarin Studio)
*.userprefs

If i open the same file using the default Notepad, this is what i get

## Ignore Visual Studio temporary files, build results, and ## files generated by popular Visual Studio add-ons. ## ## Get latest from  https://github.com/github/gitignore/blob/master/VisualStudio.gitignore # See https://help.github.com/ignore-files/ for more about ignoring files. # User-specific files *.suo *.user *.userosscache 

So, you might have already guessed by looking at the output. Everything in the .gitignore has become a one liner, and since there is a ## in the start, it acts as if everything is commented.

The way to fix this is simple: Just open your .gitignore file with Notepad++ , then do the following

Edit > EOL Conversion > Windows Format > Save

The next time you open the same file with the windows default notepad, everything should be properly formatted. Try it and see if this works for you.

Set the layout weight of a TextView programmatically

In the earlier answers weight is passed to the constructor of a new SomeLayoutType.LayoutParams object. Still in many cases it's more convenient to use existing objects - it helps to avoid dealing with parameters we are not interested in.

An example:

// Get our View (TextView or anything) object:
View v = findViewById(R.id.our_view); 

// Get params:
LinearLayout.LayoutParams loparams = (LinearLayout.LayoutParams) v.getLayoutParams();

// Set only target params:
loparams.height = 0;
loparams.weight = 1;
v.setLayoutParams(loparams);

How to render a DateTime in a specific format in ASP.NET MVC 3?

I use the following approach to inline format and display a date property from the model.

@Html.ValueFor(model => model.MyDateTime, "{0:dd/MM/yyyy}")

Otherwise when populating a TextBox or Editor you could do like @Darin suggested, decorated the attribute with a [DisplayFormat] attribute.

Saving results with headers in Sql Server Management Studio

Got here when looking for a way to make SSMS properly escape CSV separators when exporting results.

Guess what? - this is actually an option, and it is unchecked by default. So by default, you get broken CSV files (and may not even realize it, esp. if your export is large and your data doesn't have commas normally) - and you have to go in and click a checkbox so that your CSVs export correctly!

To me, this seems like a monumentally stupid design choice and an apt metaphor for Microsoft's approach to software in general ("broken by default, requires meaningless ritualistic actions to make trivial functionality work").

But I will gladly donate $100 to a charity of respondent's choice if someone can give me one valid real-life reason for this option to exist (i.e., an actual scenario where it was useful).

How do I load an org.w3c.dom.Document from XML in a string?

To manipulate XML in Java, I always tend to use the Transformer API:

import javax.xml.transform.Source;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.stream.StreamSource;

public static Document loadXMLFrom(String xml) throws TransformerException {
    Source source = new StreamSource(new StringReader(xml));
    DOMResult result = new DOMResult();
    TransformerFactory.newInstance().newTransformer().transform(source , result);
    return (Document) result.getNode();
}   

What is the backslash character (\\)?

\ is used for escape sequences in programming languages.

\n prints a newline
\\ prints a backslash
\" prints "
\t prints a tabulator
\b moves the cursor one back

Foreign key referring to primary keys across multiple tables?

I know this is long stagnant topic, but in case anyone searches here is how I deal with multi table foreign keys. With this technique you do not have any DBA enforced cascade operations, so please make sure you deal with DELETE and such in your code.

Table 1 Fruit
pk_fruitid, name
1, apple
2, pear

Table 2 Meat
Pk_meatid, name
1, beef
2, chicken

Table 3 Entity's
PK_entityid, anme
1, fruit
2, meat
3, desert

Table 4 Basket (Table using fk_s)
PK_basketid, fk_entityid, pseudo_entityrow
1, 2, 2 (Chicken - entity denotes meat table, pseudokey denotes row in indictaed table)
2, 1, 1 (Apple)
3, 1, 2 (pear)
4, 3, 1 (cheesecake)

SO Op's Example would look like this

deductions
--------------
type    id      name
1      khce1   gold
2      khsn1   silver

types
---------------------
1 employees_ce
2 employees_sn

How can I echo HTML in PHP?

This is how I do it:

<?php if($contition == true){ ?>
         <input type="text" value="<?php echo $value_stored_in_php_variable; ?>" />
<?php }else{ ?>
         <p>No input here </p>
<?php } ?>

How to animate GIFs in HTML document?

try

_x000D_
_x000D_
<img src="https://cdn.glitch.com/0e4d1ff3-5897-47c5-9711-d026c01539b8%2Fbddfd6e4434f42662b009295c9bab86e.gif?v=1573157191712" alt="this slowpoke moves"  width="250" alt="404 image"/>
_x000D_
_x000D_
_x000D_

and switch the src with your source. If the alt pops up, try a different url. If it doesn't work, restart your computer or switch your browser.

Add/delete row from a table

I would try formatting your table correctly first off like so:

I cannot help but thinking that formatting the table could at the very least not do any harm.

<table>
   <thead>
      <th>Header1</th>
      ......
   </thead>
   <tbody>
       <tr><td>Content1</td>....</tr>
       ......
   </tbody>
</table>

Synchronizing a local Git repository with a remote one

git fetch --prune

-p, --prune
After fetching, remove any remote-tracking branches which no longer exist on the remote. prune options

Extract images from PDF without resampling, in python?

After reading the posts using pyPDF2.

The error while using @sylvain's code NotImplementedError: unsupported filter /DCTDecode must come from the method .getData(): It is solved when using ._data instead, by @Alex Paramonov.

So far I have only met "DCTDecode" cases, but I am sharing the adapted code that include remarks from the different posts: From zilb by @Alex Paramonov, sub_obj['/Filter'] being a list, by @mxl.

Hope it can help the pyPDF2 users. Follow the code:

    import sys
    import PyPDF2, traceback
    import zlib
    try:
        from PIL import Image
    except ImportError:
        import Image

    pdf_path = 'path_to_your_pdf_file.pdf'
    input1 = PyPDF2.PdfFileReader(open(pdf_path, "rb"))
    nPages = input1.getNumPages()

    for i in range(nPages) :
        page0 = input1.getPage(i)

        if '/XObject' in page0['/Resources']:
            try:
                xObject = page0['/Resources']['/XObject'].getObject()
            except :
                xObject = []

            for obj_name in xObject:
                sub_obj = xObject[obj_name]
                if sub_obj['/Subtype'] == '/Image':
                    zlib_compressed = '/FlateDecode' in sub_obj.get('/Filter', '')
                    if zlib_compressed:
                       sub_obj._data = zlib.decompress(sub_obj._data)

                    size = (sub_obj['/Width'], sub_obj['/Height'])
                    data = sub_obj._data#sub_obj.getData()
                    try :
                        if sub_obj['/ColorSpace'] == '/DeviceRGB':
                            mode = "RGB"
                        elif sub_obj['/ColorSpace'] == '/DeviceCMYK':
                            mode = "CMYK"
                            # will cause errors when saving (might need convert to RGB first)
                        else:
                            mode = "P"

                        fn = 'p%03d-%s' % (i + 1, obj_name[1:])
                        if '/Filter' in sub_obj:
                            if '/FlateDecode' in sub_obj['/Filter']:
                                img = Image.frombytes(mode, size, data)
                                img.save(fn + ".png")
                            elif '/DCTDecode' in sub_obj['/Filter']:
                                img = open(fn + ".jpg", "wb")
                                img.write(data)
                                img.close()
                            elif '/JPXDecode' in sub_obj['/Filter']:
                                img = open(fn + ".jp2", "wb")
                                img.write(data)
                                img.close()
                            elif '/CCITTFaxDecode' in sub_obj['/Filter']:
                                img = open(fn + ".tiff", "wb")
                                img.write(data)
                                img.close()
                            elif '/LZWDecode' in sub_obj['/Filter'] :
                                img = open(fn + ".tif", "wb")
                                img.write(data)
                                img.close()
                            else :
                                print('Unknown format:', sub_obj['/Filter'])
                        else:
                            img = Image.frombytes(mode, size, data)
                            img.save(fn + ".png")
                    except:
                        traceback.print_exc()
        else:
            print("No image found for page %d" % (i + 1))

Button inside of anchor link works in Firefox but not in Internet Explorer?

Since this is only an issue in IE, to resolve this, I'm first detecting if the browser is IE and if so, use a jquery click event. I put this code into a global file so it's fixed throughout the site.

if (navigator.appName === 'Microsoft Internet Explorer')
{
    $('a input.button').click(function()
    {
        window.location = $(this).closest('a').attr('href');
    });
}

This way we only have the overhead of assigning click events to linked input buttons for IE. note: The above code is inside a document ready function to make sure the page is completely loaded before assigning click events.

I also assigned class names to my input buttons to save some overhead when using IE so I can search for

$('a input.button')

instead of

$('a input[type=button]')

.

<a href="some_link"><input type="button" class="button" value="some value" /></a>

On top of all that, I'm also utilizing CSS to make the buttons look clickable when your mouse hovers over it:

input.button {cursor: pointer}

strdup() - what does it do in C?

The statement:

strcpy(ptr2, ptr1);

is equivalent to (other than the fact this changes the pointers):

while(*ptr2++ = *ptr1++);

Whereas:

ptr2 = strdup(ptr1);

is equivalent to:

ptr2 = malloc(strlen(ptr1) + 1);
if (ptr2 != NULL) strcpy(ptr2, ptr1);

So, if you want the string which you have copied to be used in another function (as it is created in heap section), you can use strdup, else strcpy is enough,

Regular expression search replace in Sublime Text 2

By the way, in the question above:

For:

Hello, my name is bob

Find part:

my name is (\w)+

With replace part:

my name used to be \1

Would return:

Hello, my name used to be b

Change find part to:

my name is (\w+)

And replace will be what you expect:

Hello, my name used to be bob

While (\w)+ will match "bob", it is not the grouping you want for replacement.

Is it possible to get multiple values from a subquery?

A Subquery in the Select clause, as in your case, is also known as a Scalar Subquery, which means that it's a form of expression. Meaning that it can only return one value.

I'm afraid you can't return multiple columns from a single Scalar Subquery, no.

Here's more about Oracle Scalar Subqueries:

http://docs.oracle.com/cd/B19306_01/server.102/b14200/expressions010.htm#i1033549

How to Add Stacktrace or debug Option when Building Android Studio Project

In Android Studios 2.1.1, the command-line Options is under "Build, Execution, Deployment">"Compiler"

enter image description here

How to select the Date Picker In Selenium WebDriver

From Java 8 you can use this simple method for picking a random date from the date picker

List<WebElement> datePickerDays = driver.findElements(By.tagName("td"));
datePickerDays.stream().filter(e->e.getText().equals(whichDateYouWantToClick)).findFirst().get().click();

Get age from Birthdate

JsFiddle

You can calculate with Dates.

var birthdate = new Date("1990/1/1");
var cur = new Date();
var diff = cur-birthdate; // This is the difference in milliseconds
var age = Math.floor(diff/31557600000); // Divide by 1000*60*60*24*365.25

LISTAGG function: "result of string concatenation is too long"

Managing overflows in LISTAGG

We can use the Database 12c SQL pattern matching function, MATCH_RECOGNIZE, to return a list of values that does not exceed limit.

Example code and more explanation in below link.

https://blogs.oracle.com/datawarehousing/entry/managing_overflows_in_listagg

"Could not get any response" response when using postman with subdomain

In my case, The issue was that for UAT environment, API URL will start with Http instead of https. Also, the backend assigns different ports for both Http and https.

for example,

http://10.12.12.31:2001/api/example. - is correct for me

https://10.12.12.31:2002/api/example. - is wrong for me

Because I was using https and 2002 port for hitting the UAT environment. So I am getting could not get any response error in postman.

Get parent directory of running script

If your script is located in /var/www/dir/index.php then the following would return:

dirname(__FILE__); // /var/www/dir

or

dirname( dirname(__FILE__) ); // /var/www

Edit

This is a technique used in many frameworks to determine relative paths from the app_root.

File structure:

 /var/
      www/
          index.php
          subdir/
                 library.php

index.php is my dispatcher/boostrap file that all requests are routed to:

define(ROOT_PATH, dirname(__FILE__) ); // /var/www

library.php is some file located an extra directory down and I need to determine the path relative to the app root (/var/www/).

$path_current = dirname( __FILE__ ); // /var/www/subdir
$path_relative = str_replace(ROOT_PATH, '', $path_current); // /subdir

There's probably a better way to calculate the relative path then str_replace() but you get the idea.

Installing a pip package from within a Jupyter Notebook not working

Try using some shell magic: %%sh %%sh pip install geocoder let me know if it works, thanks

How do I find a default constraint using INFORMATION_SCHEMA?

Is the COLUMN_DEFAULT column of INFORMATION_SCHEMA.COLUMNS what you are looking for?

How do I set the default font size in Vim?

Add Regular to syntax and use gfn:

set gfn= Monospace\ Regular:h13

./configure : /bin/sh^M : bad interpreter

When you write your script on windows environment and you want to run it on unix environnement you need to be careful about the encodage :

dos2unix $filePath

Listview Scroll to the end of the list after updating the list

Using : Set the head of the list to it bottom lv.setStackFromBottom(true);

Worked for me and the list is scrolled to the bottom automatically when it is first brought into visibility. The list then scrolls as it should with TRANSCRIPT_MODE_ALWAYS_SCROLL.

Rotate an image in image source in html

This CSS seems to work in Safari and Chrome:

div#div2
{
-webkit-transform:rotate(90deg); /* Chrome, Safari, Opera */
transform:rotate(90deg); /* Standard syntax */
}

and in the body:

<div id="div2"><img src="image.jpg"  ></div>

But this (and the .rotate90 example above) pushes the rotated image higher up on the page than if it were un-rotated. Not sure how to control placement of the image relative to text or other rotated images.

Using grep to help subset a data frame in R

It's pretty straightforward using [ to extract:

grep will give you the position in which it matched your search pattern (unless you use value = TRUE).

grep("^G45", My.Data$x)
# [1] 2

Since you're searching within the values of a single column, that actually corresponds to the row index. So, use that with [ (where you would use My.Data[rows, cols] to get specific rows and columns).

My.Data[grep("^G45", My.Data$x), ]
#      x y
# 2 G459 2

The help-page for subset shows how you can use grep and grepl with subset if you prefer using this function over [. Here's an example.

subset(My.Data, grepl("^G45", My.Data$x))
#      x y
# 2 G459 2

As of R 3.3, there's now also the startsWith function, which you can again use with subset (or with any of the other approaches above). According to the help page for the function, it's considerably faster than using substring or grepl.

subset(My.Data, startsWith(as.character(x), "G45"))
#      x y
# 2 G459 2

Reminder - \r\n or \n\r?

\r\n

Odd to say I remember it because it is the opposite of the typewriter I used.
Well if it was normal I had no need to remember it... :-)

typewriter from wikipedia *Image from Wikipedia

In the typewriter when you finish to digit the line you use the carriage return lever, that before makes roll the drum, the newline, and after allow you to manually operate the carriage return.

You can listen from this record from freesound.org the sound of the paper feeding in the beginning, and at around -1:03 seconds from the end, after the bell warning for the end of the line sound of the drum that rolls and after the one of the carriage return.

Can an Option in a Select tag carry multiple values?

its possible to have multiple values in a select option as shown below.

<select id="ddlEmployee" class="form-control">
    <option value="">-- Select --</option>
    <option value="1" data-city="Washington" data-doj="20-06-2011">John</option>
    <option value="2" data-city="California" data-doj="10-05-2015">Clif</option>
    <option value="3" data-city="Delhi" data-doj="01-01-2008">Alexander</option>
</select>

you can get selected value on change event using jquery as shown below.

$("#ddlEmployee").change(function () {
     alert($(this).find(':selected').data('city'));
});

You can find more details in this LINK

What is DOM Event delegation?

It's basically how association is made to the element. .click applies to the current DOM, while .on (using delegation) will continue to be valid for new elements added to the DOM after event association.

Which is better to use, I'd say it depends on the case.

Example:

<ul id="todo">
   <li>Do 1</li>
   <li>Do 2</li>
   <li>Do 3</li>
   <li>Do 4</li>
</ul>

.Click Event:

$("li").click(function () {
   $(this).remove ();
});

Event .on:

$("#todo").on("click", "li", function () {
   $(this).remove();
});

Note that I've separated the selector in the .on. I'll explain why.

Let us suppose that after this association, let us do the following:

$("#todo").append("<li>Do 5</li>");

That is where you will notice the difference.

If the event was associated via .click, task 5 will not obey the click event, and so it will not be removed.

If it was associated via .on, with the selector separate, it will obey.

Recommendations of Python REST (web services) framework?

Something to be careful about when designing a RESTful API is the conflation of GET and POST, as if they were the same thing. It's easy to make this mistake with Django's function-based views and CherryPy's default dispatcher, although both frameworks now provide a way around this problem (class-based views and MethodDispatcher, respectively).

HTTP-verbs are very important in REST, and unless you're very careful about this, you'll end up falling into a REST anti-pattern.

Some frameworks that get it right are web.py, Flask and Bottle. When combined with the mimerender library (full disclosure: I wrote it), they allow you to write nice RESTful webservices:

import web
import json
from mimerender import mimerender

render_xml = lambda message: '<message>%s</message>'%message
render_json = lambda **args: json.dumps(args)
render_html = lambda message: '<html><body>%s</body></html>'%message
render_txt = lambda message: message

urls = (
    '/(.*)', 'greet'
)
app = web.application(urls, globals())

class greet:
    @mimerender(
        default = 'html',
        html = render_html,
        xml  = render_xml,
        json = render_json,
        txt  = render_txt
    )
    def GET(self, name):
        if not name: 
            name = 'world'
        return {'message': 'Hello, ' + name + '!'}

if __name__ == "__main__":
    app.run()

The service's logic is implemented only once, and the correct representation selection (Accept header) + dispatch to the proper render function (or template) is done in a tidy, transparent way.

$ curl localhost:8080/x
<html><body>Hello, x!</body></html>

$ curl -H "Accept: application/html" localhost:8080/x
<html><body>Hello, x!</body></html>

$ curl -H "Accept: application/xml" localhost:8080/x
<message>Hello, x!</message>

$ curl -H "Accept: application/json" localhost:8080/x
{'message':'Hello, x!'}

$ curl -H "Accept: text/plain" localhost:8080/x
Hello, x!

Update (April 2012): added information about Django's class-based views, CherryPy's MethodDispatcher and Flask and Bottle frameworks. Neither existed back when the question was asked.

Laravel: Get Object From Collection By Attribute

Elegant solution for finding a value (http://betamode.de/2013/10/17/laravel-4-eloquent-check-if-there-is-a-model-with-certain-key-value-pair-in-a-collection/) can be adapted:

$desired_object_key = $food->array_search(24, $food->lists('id'));
if ($desired_object_key !== false) {
   $desired_object = $food[$desired_object_key];
}

How do I get AWS_ACCESS_KEY_ID for Amazon?

  1. Open the AWS Console
  2. Click on your username near the top right and select My Security Credentials
  3. Click on Users in the sidebar
  4. Click on your username
  5. Click on the Security Credentials tab
  6. Click Create Access Key
  7. Click Show User Security Credentials

How to send password securely over HTTP?

You can use a challenge response scheme. Say the client and server both know a secret S. Then the server can be sure that the client knows the password (without giving it away) by:

  1. Server sends a random number, R, to client.
  2. Client sends H(R,S) back to the server (where H is a cryptographic hash function, like SHA-256)
  3. Server computes H(R,S) and compares it to the client's response. If they match, the server knows the client knows the password.

Edit:

There is an issue here with the freshness of R and the fact that HTTP is stateless. This can be handled by having the server create a secret, call it Q, that only the server knows. Then the protocol goes like this:

  1. Server generates random number R. It then sends to the client H(R,Q) (which cannot be forged by the client).
  2. Client sends R, H(R,Q), and computes H(R,S) and sends all of it back to the server (where H is a cryptographic hash function, like SHA-256)
  3. Server computes H(R,S) and compares it to the client's response. Then it takes R and computes (again) H(R,Q). If the client's version of H(R,Q) and H(R,S) match the server's re-computation, the server deems the client authenticated.

To note, since H(R,Q) cannot be forged by the client, H(R,Q) acts as a cookie (and could therefore be implemented actually as a cookie).

Another Edit:

The previous edit to the protocol is incorrect as anyone who has observed H(R,Q) seems to be able to replay it with the correct hash. The server has to remember which R's are no longer fresh. I'm CW'ing this answer so you guys can edit away at this and work out something good.

Git error on commit after merge - fatal: cannot do a partial commit during a merge

If you are using Source tree or other GUI ensure all files are checked (after merge).

How to count frequency of characters in a string?

If this does not need to be super-fast just create an array of integers, one integer for each letter (only alphabetic so 2*26 integers? or any binary data possible?). go through the string one char at a time, get the index of the responsible integer (e.g. if you only have alphabetic chars you can have 'A' be at index 0 and get that index by subtracting any 'A' to 'Z' by 'A' just as an example of how you can get reasonably fast indices) and increment the value in that index.

There are various micro-optimizations to make this faster (if necessary).

How do I create a new column from the output of pandas groupby().sum()?

How do I create a new column with Groupby().Sum()?

There are two ways - one straightforward and the other slightly more interesting.


Everybody's Favorite: GroupBy.transform() with 'sum'

@Ed Chum's answer can be simplified, a bit. Call DataFrame.groupby rather than Series.groupby. This results in simpler syntax.

# The setup.
df[['Date', 'Data3']]

         Date  Data3
0  2015-05-08      5
1  2015-05-07      8
2  2015-05-06      6
3  2015-05-05      1
4  2015-05-08     50
5  2015-05-07    100
6  2015-05-06     60
7  2015-05-05    120

df.groupby('Date')['Data3'].transform('sum')

0     55
1    108
2     66
3    121
4     55
5    108
6     66
7    121
Name: Data3, dtype: int64 

It's a tad faster,

df2 = pd.concat([df] * 12345)

%timeit df2['Data3'].groupby(df['Date']).transform('sum')
%timeit df2.groupby('Date')['Data3'].transform('sum')

10.4 ms ± 367 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
8.58 ms ± 559 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)

Unconventional, but Worth your Consideration: GroupBy.sum() + Series.map()

I stumbled upon an interesting idiosyncrasy in the API. From what I tell, you can reproduce this on any major version over 0.20 (I tested this on 0.23 and 0.24). It seems like you consistently can shave off a few milliseconds of the time taken by transform if you instead use a direct function of GroupBy and broadcast it using map:

df.Date.map(df.groupby('Date')['Data3'].sum())

0     55
1    108
2     66
3    121
4     55
5    108
6     66
7    121
Name: Date, dtype: int64

Compare with

df.groupby('Date')['Data3'].transform('sum')

0     55
1    108
2     66
3    121
4     55
5    108
6     66
7    121
Name: Data3, dtype: int64

My tests show that map is a bit faster if you can afford to use the direct GroupBy function (such as mean, min, max, first, etc). It is more or less faster for most general situations upto around ~200 thousand records. After that, the performance really depends on the data.

(Left: v0.23, Right: v0.24)

Nice alternative to know, and better if you have smaller frames with smaller numbers of groups. . . but I would recommend transform as a first choice. Thought this was worth sharing anyway.

Benchmarking code, for reference:

import perfplot

perfplot.show(
    setup=lambda n: pd.DataFrame({'A': np.random.choice(n//10, n), 'B': np.ones(n)}),
    kernels=[
        lambda df: df.groupby('A')['B'].transform('sum'),
        lambda df:  df.A.map(df.groupby('A')['B'].sum()),
    ],
    labels=['GroupBy.transform', 'GroupBy.sum + map'],
    n_range=[2**k for k in range(5, 20)],
    xlabel='N',
    logy=True,
    logx=True
)

VBA - Range.Row.Count

Probably a better solution is work upwards from the bottom:

k=sh.Range("A1048576").end(xlUp).row

Convert output of MySQL query to utf8

Addition:

When using the MySQL client library, then you should prevent a conversion back to your connection's default charset. (see mysql_set_character_set()[1])

In this case, use an additional cast to binary:

SELECT column1, CAST(CONVERT(column2 USING utf8) AS binary)
FROM my_table
WHERE my_condition;

Otherwise, the SELECT statement converts to utf-8, but your client library converts it back to a (potentially different) default connection charset.

Android Layout Weight

i would suppose to set the EditTexts width to wrap_content and put the two buttons into a LinearLayout whose width is fill_parent and weight set to 1.

Java: Find .txt files in specified folder

You can use the listFiles() method provided by the java.io.File class.

import java.io.File;
import java.io.FilenameFilter;

public class Filter {

    public File[] finder( String dirName){
        File dir = new File(dirName);

        return dir.listFiles(new FilenameFilter() { 
                 public boolean accept(File dir, String filename)
                      { return filename.endsWith(".txt"); }
        } );

    }

}

UIScrollView scroll to bottom programmatically

CGFloat yOffset = scrollView.contentOffset.y;

CGFloat height = scrollView.frame.size.height;

CGFloat contentHeight = scrollView.contentSize.height;

CGFloat distance = (contentHeight  - height) - yOffset;

if(distance < 0)
{
    return ;
}

CGPoint offset = scrollView.contentOffset;

offset.y += distance;

[scrollView setContentOffset:offset animated:YES];

android start activity from service

I had the same problem, and want to let you know that none of the above worked for me. What worked for me was:

 Intent dialogIntent = new Intent(this, myActivity.class);
 dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 this.startActivity(dialogIntent);

and in one my subclasses, stored in a separate file I had to:

public static Service myService;

myService = this;

new SubService(myService);

Intent dialogIntent = new Intent(myService, myActivity.class);
dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
myService.startActivity(dialogIntent);

All the other answers gave me a nullpointerexception.

vertical & horizontal lines in matplotlib

This may be a common problem for new users of Matplotlib to draw vertical and horizontal lines. In order to understand this problem, you should be aware that different coordinate systems exist in Matplotlib.

The method axhline and axvline are used to draw lines at the axes coordinate. In this coordinate system, coordinate for the bottom left point is (0,0), while the coordinate for the top right point is (1,1), regardless of the data range of your plot. Both the parameter xmin and xmax are in the range [0,1].

On the other hand, method hlines and vlines are used to draw lines at the data coordinate. The range for xmin and xmax are the in the range of data limit of x axis.

Let's take a concrete example,

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0, 5, 100)
y = np.sin(x)

fig, ax = plt.subplots()

ax.plot(x, y)
ax.axhline(y=0.5, xmin=0.0, xmax=1.0, color='r')
ax.hlines(y=0.6, xmin=0.0, xmax=1.0, color='b')

plt.show()

It will produce the following plot: enter image description here

The value for xmin and xmax are the same for the axhline and hlines method. But the length of produced line is different.

dd: How to calculate optimal blocksize?

The optimal block size depends on various factors, including the operating system (and its version), and the various hardware buses and disks involved. Several Unix-like systems (including Linux and at least some flavors of BSD) define the st_blksize member in the struct stat that gives what the kernel thinks is the optimal block size:

#include <sys/stat.h>
#include <stdio.h>

int main(void)
{
    struct stat stats;

    if (!stat("/", &stats))
    {
        printf("%u\n", stats.st_blksize);
    }
}

The best way may be to experiment: copy a gigabyte with various block sizes and time that. (Remember to clear kernel buffer caches before each run: echo 3 > /proc/sys/vm/drop_caches).

However, as a rule of thumb, I've found that a large enough block size lets dd do a good job, and the differences between, say, 64 KiB and 1 MiB are minor, compared to 4 KiB versus 64 KiB. (Though, admittedly, it's been a while since I did that. I use a mebibyte by default now, or just let dd pick the size.)

How to find item with max value using linq?

With EF or LINQ to SQL:

var item = db.Items.OrderByDescending(i => i.Value).FirstOrDefault();

With LINQ to Objects I suggest to use morelinq extension MaxBy (get morelinq from nuget):

var item = items.MaxBy(i => i.Value);

How can I change the image of an ImageView?

Just to go a little bit further in the matter, you can also set a bitmap directly, like this:

ImageView imageView = new ImageView(this);  
Bitmap bImage = BitmapFactory.decodeResource(this.getResources(), R.drawable.my_image);
imageView.setImageBitmap(bImage);

Of course, this technique is only useful if you need to change the image.

Increase max_execution_time in PHP?

Theres a setting max_input_time (on Apache) for many webservers that defines how long they will wait for post data, regardless of the size. If this time runs out the connection is closed without even touching the php.

So your problem is not necessarily solvable with php only but you will need to change the server settings too.

Directing print output to a .txt file

Suppose my input file is "input.txt" and output file is "output.txt".

Let's consider the input file has details to read:

5
1 2 3 4 5

Code:

import sys

sys.stdin = open("input", "r")
sys.stdout = open("output", "w")

print("Reading from input File : ")
n = int(input())
print("Value of n is :", n)

arr = list(map(int, input().split()))
print(arr)

So this will read from input file and output will be displayed in output file.

For more details please see https://www.geeksforgeeks.org/inputoutput-external-file-cc-java-python-competitive-programming/

Formatting Phone Numbers in PHP

Assuming that your phone numbers always have this exact format, you can use this snippet:

$from = "+11234567890";
$to = sprintf("%s-%s-%s",
              substr($from, 2, 3),
              substr($from, 5, 3),
              substr($from, 8));

Create a Date with a set timezone without using a string representation

One line solution

new Date(new Date(1422524805305).getTime() - 330*60*1000)

Instead of 1422524805305, use the timestamp in milliseconds Instead of 330, use your timezone offset in minutes wrt. GMT (eg India +5:30 is 5*60+30 = 330 minutes)

Complete list of reasons why a css file might not be working

I don't think the problem lies in the sample you posted - we'd need to see the CSS, or verify its location etc!

But why not try stripping it down to one CSS rule - put it in the HEAD section, then if it works, move that rule to the external file. Then re-introduce the other rules to make sure there's nothing missing or taking precedence over your CSS.

Returning value from Thread

With small modifications to your code, you can achieve it in a more generic way.

 final Handler responseHandler = new Handler(Looper.getMainLooper()){
            @Override
            public void handleMessage(Message msg) {
                //txtView.setText((String) msg.obj);
                Toast.makeText(MainActivity.this,
                        "Result from UIHandlerThread:"+(int)msg.obj,
                        Toast.LENGTH_LONG)
                        .show();
            }
        };

        HandlerThread handlerThread = new HandlerThread("UIHandlerThread"){
            public void run(){
                Integer a = 2;
                Message msg = new Message();
                msg.obj = a;
                responseHandler.sendMessage(msg);
                System.out.println(a);
            }
        };
        handlerThread.start();

Solution :

  1. Create a Handler in UI Thread,which is called as responseHandler
  2. Initialize this Handler from Looper of UI Thread.
  3. In HandlerThread, post message on this responseHandler
  4. handleMessgae shows a Toast with value received from message. This Message object is generic and you can send different type of attributes.

With this approach, you can send multiple values to UI thread at different point of times. You can run (post) many Runnable objects on this HandlerThread and each Runnable can set value in Message object, which can be received by UI Thread.

Is the order of elements in a JSON list preserved?

Some JavaScript engines keep keys in insertion order. V8, for instance, keeps all keys in insertion order except for keys that can be parsed as unsigned 32-bit integers.

This means that if you run either of the following:

var animals = {};
animals['dog'] = true;
animals['bear'] = true;
animals['monkey'] = true;
for (var animal in animals) {
  if (animals.hasOwnProperty(animal)) {
    $('<li>').text(animal).appendTo('#animals');
  }
}
var animals = JSON.parse('{ "dog": true, "bear": true, "monkey": true }');
for (var animal in animals) {
  $('<li>').text(animal).appendTo('#animals');
}

You'll consistently get dog, bear, and monkey in that order, on Chrome, which uses V8. Node.js also uses V8. This will hold true even if you have thousands of items. YMMV with other JavaScript engines.

Demo here and here.

Mongoose, update values in array of objects

There is one thing to remember, when you are searching the object in array on the basis of more than one condition then use $elemMatch

Person.update(
   {
     _id: 5,
     grades: { $elemMatch: { grade: { $lte: 90 }, mean: { $gt: 80 } } }
   },
   { $set: { "grades.$.std" : 6 } }
)

here is the docs

Get image dimensions

You can use the getimagesize function like this:

list($width, $height) = getimagesize('path to image');
echo "width: " . $width . "<br />";
echo "height: " .  $height;

Check if a string is a date value

new Date(date) === 'Invalid Date' only works in Firefox and Chrome. IE8 (the one I have on my machine for testing purposes) gives NaN.

As was stated to the accepted answer, Date.parse(date) will also work for numbers. So to get around that, you could also check that it is not a number (if that's something you want to confirm).

var parsedDate = Date.parse(date);

// You want to check again for !isNaN(parsedDate) here because Dates can be converted
// to numbers, but a failed Date parse will not.
if (isNaN(date) && !isNaN(parsedDate)) {
    /* do your work */
}

Is there a way to make a DIV unselectable?

Also in IOS if you want to get rid of gray semi-transparent overlays appearing ontouch, add css:

-webkit-tap-highlight-color: rgba(0,0,0,0);
-webkit-touch-callout: none;

Cause of a process being a deadlock victim

Here is how this particular deadlock problem actually occurred and how it was actually resolved. This is a fairly active database with 130K transactions occurring daily. The indexes in the tables in this database were originally clustered. The client requested us to make the indexes nonclustered. As soon as we did, the deadlocking began. When we reestablished the indexes as clustered, the deadlocking stopped.

In Python, how do I loop through the dictionary and change the value if it equals something?

You could create a dict comprehension of just the elements whose values are None, and then update back into the original:

tmp = dict((k,"") for k,v in mydict.iteritems() if v is None)
mydict.update(tmp)

Update - did some performance tests

Well, after trying dicts of from 100 to 10,000 items, with varying percentage of None values, the performance of Alex's solution is across-the-board about twice as fast as this solution.

Accurate way to measure execution times of php scripts

Here is my script to measure average time

<?php

$times = [];
$nbrOfLoops = 4;
for ($i = 0; $i < $nbrOfLoops; ++$i) {
    $start = microtime(true);
    sleep(1);
    $times[] = microtime(true) - $start;
}

echo 'Average: ' . (array_sum($times) / count($times)) . 'seconds';

How can I safely create a nested directory?

Try the os.path.exists function

if not os.path.exists(dir):
    os.mkdir(dir)

How to reverse a singly linked list using only two pointers?

To swap two variables without the use of a temporary variable,

a = a xor b
b = a xor b
a = a xor b

fastest way is to write it in one line

a = a ^ b ^ (b=a)

Similarly,

using two swaps

swap(a,b)
swap(b,c)

solution using xor

a = a^b^c
b = a^b^c
c = a^b^c
a = a^b^c

solution in one line

c = a ^ b ^ c ^ (a=b) ^ (b=c)
b = a ^ b ^ c ^ (c=a) ^ (a=b)
a = a ^ b ^ c ^ (b=c) ^ (c=a)

The same logic is used to reverse a linked list.

typedef struct List
{
 int info;
 struct List *next;
}List;


List* reverseList(List *head)
{
 p=head;
 q=p->next;
 p->next=NULL;
 while(q)
 {
    q = (List*) ((int)p ^ (int)q ^ (int)q->next ^ (int)(q->next=p) ^ (int)(p=q));
 }
 head = p;
 return head;
}  

How to convert a number to string and vice versa in C++

In C++17, new functions std::to_chars and std::from_chars are introduced in header charconv.

std::to_chars is locale-independent, non-allocating, and non-throwing.

Only a small subset of formatting policies used by other libraries (such as std::sprintf) is provided.

From std::to_chars, same for std::from_chars.

The guarantee that std::from_chars can recover every floating-point value formatted by to_chars exactly is only provided if both functions are from the same implementation

 // See en.cppreference.com for more information, including format control.
#include <cstdio>
#include <cstddef>
#include <cstdlib>
#include <cassert>
#include <charconv>

using Type =  /* Any fundamental type */ ;
std::size_t buffer_size = /* ... */ ;

[[noreturn]] void report_and_exit(int ret, const char *output) noexcept 
{
    std::printf("%s\n", output);
    std::exit(ret);
}
void check(const std::errc &ec) noexcept
{
    if (ec ==  std::errc::value_too_large)
        report_and_exit(1, "Failed");
}
int main() {
    char buffer[buffer_size];        
    Type val_to_be_converted, result_of_converted_back;

    auto result1 = std::to_chars(buffer, buffer + buffer_size,  val_to_be_converted);
    check(result1.ec);
    *result1.ptr = '\0';

    auto result2 = std::from_chars(buffer, result1.ptr, result_of_converted_back);
    check(result2.ec);

    assert(val_to_be_converted == result_of_converted_back);
    report_and_exit(0, buffer);
}

Although it's not fully implemented by compilers, it definitely will be implemented.

Loading basic HTML in Node.js

I just found one way using the fs library. I'm not certain if it's the cleanest though.

var http = require('http'),
    fs = require('fs');


fs.readFile('./index.html', function (err, html) {
    if (err) {
        throw err; 
    }       
    http.createServer(function(request, response) {  
        response.writeHeader(200, {"Content-Type": "text/html"});  
        response.write(html);  
        response.end();  
    }).listen(8000);
});

The basic concept is just raw file reading and dumping the contents. Still open to cleaner options, though!

Select multiple columns by labels in pandas

Just pick the columns you want directly....

df[['A','E','I','C']]

Send POST parameters with MultipartFormData using Alamofire, in iOS Swift

In Alamofire 4 it is important to add the body data before you add the file data!

let parameters = [String: String]()
[...]
self.manager.upload(
    multipartFormData: { multipartFormData in
        for (key, value) in parameters {
            multipartFormData.append(value.data(using: .utf8)!, withName: key)
        }
        multipartFormData.append(imageData, withName: "user", fileName: "user.jpg", mimeType: "image/jpeg")
    },
    to: path,
    [...]
)

Laravel: getting a a single value from a MySQL query

On laravel 5.6 it has a very simple solution:

User::where('username', $username)->first()->groupName;

It will return groupName as a string.

IF-THEN-ELSE statements in postgresql

case when field1>0 then field2/field1 else 0 end as field3

C++ error 'Undefined reference to Class::Function()'

In the definition of your Card class, a declaration for a default construction appears:

class Card
{
    // ...

    Card(); // <== Declaration of default constructor!

    // ...
};

But no corresponding definition is given. In fact, this function definition (from card.cpp):

void Card() {
//nothing
}

Does not define a constructor, but rather a global function called Card that returns void. You probably meant to write this instead:

Card::Card() {
//nothing
}

Unless you do that, since the default constructor is declared but not defined, the linker will produce error about undefined references when a call to the default constructor is found.


The same applies to your constructor accepting two arguments. This:

void Card(Card::Rank rank, Card::Suit suit) {
    cardRank = rank;
    cardSuit = suit;
}

Should be rewritten into this:

Card::Card(Card::Rank rank, Card::Suit suit) {
    cardRank = rank;
    cardSuit = suit;
}

And the same also applies for other member functions: it seems you did not add the Card:: qualifier before the member function names in their definitions. Without it, those functions are global functions rather than definitions of member functions.


Your destructor, on the other hand, is declared but never defined. Just provide a definition for it in card.cpp:

Card::~Card() { }

When is a CDATA section necessary within a script tag?

Do not use CDATA in HTML4 but you should use CDATA in XHTML and must use CDATA in XML if you have unescaped symbols like < and >.

Razor HtmlHelper Extensions (or other namespaces for views) Not Found

As the accepted answer suggests you can add "using" to all views by adding to section of config file.

But for a single view you could just use

@using SomeNamespace.Extensions

Oracle SQL Developer spool output?

You can export the query results to a text file (or insert statements, or even pdf) by right-clicking on Query Result row (any row) and choose Export

using Sql Developer 3.0

See SQL Developer downloads for latest versions

No connection could be made because the target machine actively refused it (PHP / WAMP)

following steps worked for me.

  1. Go to wamp\apps\phpmyadmin
  2. search config.inc.php
  3. search 127.0.0.1 and replace with "localhost".

Objective-C declared @property attributes (nonatomic, copy, strong, weak)

Great answers! One thing that I would like to clarify deeper is nonatomic/atomic. The user should understand that this property - "atomicity" spreads only on the attribute's reference and not on it's contents. I.e. atomic will guarantee the user atomicity for reading/setting the pointer and only the pointer to the attribute. For example:

@interface MyClass: NSObject
@property (atomic, strong) NSDictionary *dict;
...

In this case it is guaranteed that the pointer to the dict will be read/set in the atomic manner by different threads. BUT the dict itself (the dictionary dict pointing to) is still thread unsafe, i.e. all read/add operations to the dictionary are still thread unsafe.

If you need thread safe collection you either have bad architecture (more often) OR real requirement (more rare). If it is "real requirement" - you should either find good&tested thread safe collection component OR be prepared for trials and tribulations writing your own one. It latter case look at "lock-free", "wait-free" paradigms. Looks like rocket-science at a first glance, but could help you achieving fantastic performance in comparison to "usual locking".

Removing array item by value

w/o flip:

<?php
foreach ($items as $key => $value) {
    if ($id === $value) {
        unset($items[$key]);
    }
}

What's the difference between <mvc:annotation-driven /> and <context:annotation-config /> in servlet?

<context:annotation-config> declares support for general annotations such as @Required, @Autowired, @PostConstruct, and so on.

<mvc:annotation-driven /> declares explicit support for annotation-driven MVC controllers (i.e. @RequestMapping, @Controller, although support for those is the default behaviour), as well as adding support for declarative validation via @Valid and message body marshalling with @RequestBody/ResponseBody.

Convert java.util.date default format to Timestamp in Java

You can use DateFormat(java.text.*) to parse the date:

DateFormat df = new SimpleDateFormat("EEE MMM dd kk:mm:ss z yyyy", Locale.ENGLISH);
Date d = df.parse("Mon May 27 11:46:15 IST 2013")

You will have to change the locale to match your own (with this you will get 10:46:15). Then you can use the same code you have to convert it to a timestamp.

How can I pipe stderr, and not stdout?

This also works (and I find it a tiny bit easier to remember)

command 2> /dev/fd/1 | grep 'something'

More info about /dev/fd directory here

Change value of input onchange?

for jQuery we can use below:

by input name:

$('input[name="textboxname"]').val('some value');

by input class:

$('input[type=text].textboxclass').val('some value');

by input id:

$('#textboxid').val('some value');

Unique constraint violation during insert: why? (Oracle)

It looks like you are not providing a value for the primary key field DB_ID. If that is a primary key, you must provide a unique value for that column. The only way not to provide it would be to create a database trigger that, on insert, would provide a value, most likely derived from a sequence.

If this is a restoration from another database and there is a sequence on this new instance, it might be trying to reuse a value. If the old data had unique keys from 1 - 1000 and your current sequence is at 500, it would be generating values that already exist. If a sequence does exist for this table and it is trying to use it, you would need to reconcile the values in your table with the current value of the sequence.

You can use SEQUENCE_NAME.CURRVAL to see the current value of the sequence (if it exists of course)

How do I decode a base64 encoded string?

The m000493 method seems to perform some kind of XOR encryption. This means that the same method can be used for both encrypting and decrypting the text. All you have to do is reverse m0001cd:

string p0 = Encoding.UTF8.GetString(Convert.FromBase64String("OBFZDT..."));

string result = m000493(p0, "_p0lizei.");
//    result == "gaia^unplugged^Ta..."

with return m0001cd(builder3.ToString()); changed to return builder3.ToString();.

How do I make the first letter of a string uppercase in JavaScript?

We could get the first character with one of my favorite RegExp, looks like a cute smiley: /^./

String.prototype.capitalize = function () {
  return this.replace(/^./, function (match) {
    return match.toUpperCase();
  });
};

And for all coffee-junkies:

String::capitalize = ->
  @replace /^./, (match) ->
    match.toUpperCase()

...and for all guys who think that there's a better way of doing this, without extending native prototypes:

var capitalize = function (input) {
  return input.replace(/^./, function (match) {
    return match.toUpperCase();
  });
};

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

Quotes:

"url: http://www.example-site.com/"

To clarify, I meant “quote the value” and originally thought the entire thing was the value. If http://www.example-site.com/ is the value, just quote it like so:

url: "http://www.example-site.com/"

Scala how can I count the number of occurrences in a list

scala> val list = List(1,2,4,2,4,7,3,2,4)
list: List[Int] = List(1, 2, 4, 2, 4, 7, 3, 2, 4)

scala> println(list.filter(_ == 2).size)
3

How to find the size of a table in SQL?

Combining the answers from ratty's and Haim's posts (including comments) I've come up with this, which for SQL Server seems to be the most elegant so far:

-- DROP TABLE #tmpTableSizes
CREATE TABLE #tmpTableSizes
(
    tableName varchar(100),
    numberofRows varchar(100),
    reservedSize varchar(50),
    dataSize varchar(50),
    indexSize varchar(50),
    unusedSize varchar(50)
)
insert #tmpTableSizes
EXEC sp_MSforeachtable @command1="EXEC sp_spaceused '?'"


select  * from #tmpTableSizes
order by cast(LEFT(reservedSize, LEN(reservedSize) - 4) as int)  desc

This gives you a list of all your tables in order of reserved size, ordered from largest to smallest.

Why do I get "Cannot redirect after HTTP headers have been sent" when I call Response.Redirect()?

There is one simple answer for this: You have been output something else, like text, or anything related to output from your page before you send your header. This affect why you get that error.

Just check your code for posible output or you can put the header on top of your method so it will be send first.

How to save a bitmap on internal storage

To save file into directory

  public static Uri saveImageToInternalStorage(Context mContext, Bitmap bitmap){

    String mTimeStamp = new SimpleDateFormat("ddMMyyyy_HHmm").format(new Date());

    String mImageName = "snap_"+mTimeStamp+".jpg";

    ContextWrapper wrapper = new ContextWrapper(mContext);

    File file = wrapper.getDir("Images",MODE_PRIVATE);

    file = new File(file, "snap_"+ mImageName+".jpg");

    try{

        OutputStream stream = null;

        stream = new FileOutputStream(file);

        bitmap.compress(Bitmap.CompressFormat.JPEG,100,stream);

        stream.flush();

        stream.close();

    }catch (IOException e) 
    {
        e.printStackTrace();
    }

    Uri mImageUri = Uri.parse(file.getAbsolutePath());

    return mImageUri;
}

required permission

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

How do I hide the PHP explode delimiter from submitted form results?

<select name="FakeName" id="Fake-ID" aria-required="true" required>  <?php $options=nl2br(file_get_contents("employees.txt")); $options=explode("<br />",$options);  foreach ($options as $item_array) { echo "<option value='".$item_array"'>".$item_array"</option>";  } ?> </select> 

How to insert blank lines in PDF?

You can trigger a newline by inserting Chunk.NEWLINE into your document. Here's an example.

public static void main(String args[]) {
    try {
        // create a new document
        Document document = new Document( PageSize.A4, 20, 20, 20, 20 );
        PdfWriter.getInstance( document, new FileOutputStream( "HelloWorld.pdf" ) );

        document.open();

        document.add( new Paragraph( "Hello, World!" ) );
        document.add( new Paragraph( "Hello, World!" ) );

        // add a couple of blank lines
        document.add( Chunk.NEWLINE );
        document.add( Chunk.NEWLINE );

        // add one more line with text
        document.add( new Paragraph( "Hello, World!" ) );

        document.close();
    }
    catch (Exception e) {
        e.printStackTrace();
    }
}

Below is a screen shot showing part of the PDF that the code above produces.

Hello PDF with blank lines inserted

Remove menubar from Electron app

Before this line at main.js:

mainWindow = new BrowserWindow({width: 800, height: 900})

mainWindow.setMenu(null) //this will r menu bar

Log4j: How to configure simplest possible file logging?

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="false">

   <appender name="fileAppender" class="org.apache.log4j.RollingFileAppender">
      <param name="Threshold" value="INFO" />
      <param name="File" value="sample.log"/>
      <layout class="org.apache.log4j.PatternLayout">
         <param name="ConversionPattern" value="%d %-5p  [%c{1}] %m %n" />
      </layout>
   </appender>

  <root> 
    <priority value ="debug" /> 
    <appender-ref ref="fileAppender" /> 
  </root> 

</log4j:configuration>

Log4j can be a bit confusing. So lets try to understand what is going on in this file: In log4j you have two basic constructs appenders and loggers.

Appenders define how and where things are appended. Will it be logged to a file, to the console, to a database, etc.? In this case you are specifying that log statements directed to fileAppender will be put in the file sample.log using the pattern specified in the layout tags. You could just as easily create a appender for the console or the database. Where the console appender would specify things like the layout on the screen and the database appender would have connection details and table names.

Loggers respond to logging events as they bubble up. If an event catches the interest of a specific logger it will invoke its attached appenders. In the example below you have only one logger the root logger - which responds to all logging events by default. In addition to the root logger you can specify more specific loggers that respond to events from specific packages. These loggers can have their own appenders specified using the appender-ref tags or will otherwise inherit the appenders from the root logger. Using more specific loggers allows you to fine tune the logging level on specific packages or to direct certain packages to other appenders.

So what this file is saying is:

  1. Create a fileAppender that logs to file sample.log
  2. Attach that appender to the root logger.
  3. The root logger will respond to any events at least as detailed as 'debug' level
  4. The appender is configured to only log events that are at least as detailed as 'info'

The net out is that if you have a logger.debug("blah blah") in your code it will get ignored. A logger.info("Blah blah"); will output to sample.log.

The snippet below could be added to the file above with the log4j tags. This logger would inherit the appenders from <root> but would limit the all logging events from the package org.springframework to those logged at level info or above.

  <!-- Example Package level Logger -->
    <logger name="org.springframework">
        <level value="info"/>
    </logger>   

Passing an array of parameters to a stored procedure

I'd consider passing your IDs as an XML string, and then you could shred the XML into a temp table to join against, or you could also query against the XML directly using SP_XML_PREPAREDOCUMENT and OPENXML.

JavaScript: Check if mouse button down?

I think the best approach to this is to keep your own record of the mouse button state, as follows:

var mouseDown = 0;
document.body.onmousedown = function() { 
    mouseDown = 1;
}
document.body.onmouseup = function() {
    mouseDown = 0;
}

and then, later in your code:

if (mouseDown == 1) {
    // the mouse is down, do what you have to do.
}

How to switch to new window in Selenium for Python?

On top of the answers already given, to open a new tab the javascript command window.open() can be used.

For example:

# Opens a new tab
self.driver.execute_script("window.open()")

# Switch to the newly opened tab
self.driver.switch_to.window(self.driver.window_handles[1])

# Navigate to new URL in new tab
self.driver.get("https://google.com")
# Run other commands in the new tab here

You're then able to close the original tab as follows

# Switch to original tab
self.driver.switch_to.window(self.driver.window_handles[0])

# Close original tab
self.driver.close()

# Switch back to newly opened tab, which is now in position 0
self.driver.switch_to.window(self.driver.window_handles[0])

Or close the newly opened tab

# Close current tab
self.driver.close()

# Switch back to original tab
self.driver.switch_to.window(self.driver.window_handles[0])

Hope this helps.

Python: Removing spaces from list objects

result = map(str.strip, hello)

How to create and handle composite primary key in JPA

Key class:

@Embeddable
@Access (AccessType.FIELD)
public class EntryKey implements Serializable {

    public EntryKey() {
    }

    public EntryKey(final Long id, final Long version) {
        this.id = id;
        this.version = version;
    }

    public Long getId() {
        return this.id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public Long getVersion() {
        return this.version;
    }

    public void setVersion(Long version) {
        this.version = version;
    }

    public boolean equals(Object other) {
        if (this == other)
            return true;
        if (!(other instanceof EntryKey))
            return false;
        EntryKey castOther = (EntryKey) other;
        return id.equals(castOther.id) && version.equals(castOther.version);
    }

    public int hashCode() {
        final int prime = 31;
        int hash = 17;
        hash = hash * prime + this.id.hashCode();
        hash = hash * prime + this.version.hashCode();
        return hash;
    }

    @Column (name = "ID")
    private Long id;
    @Column (name = "VERSION")
    private Long operatorId;
}

Entity class:

@Entity
@Table (name = "YOUR_TABLE_NAME")
public class Entry implements Serializable {

    @EmbeddedId
    public EntryKey getKey() {
        return this.key;
    }

    public void setKey(EntryKey id) {
        this.id = id;
    }

    ...

    private EntryKey key;
    ...
}

How can I duplicate it with another Version?

You can detach entity which retrieved from provider, change the key of Entry and then persist it as a new entity.

What is Haskell used for in the real world?

I have a cool one, facebook created a automated tool for rewriting PHP code. They parse the source into an abstract syntax tree, do some transformations:

if ($f == false) -> if (false == $f)

I don't know why, but that seems to be their particular style and then they pretty print it.

https://github.com/facebook/lex-pass

We use haskell for making small domain specific languages. Huge amounts of data processing. Web development. Web spiders. Testing applications. Writing system administration scripts. Backend scripts, which communicate with other parties. Monitoring scripts (we have a DSL which works nicely together with munin, makes it much easier to write correct monitor code for your applications.)

All kind of stuff actually. It is just a everyday general purpose language with some very powerful and useful features, if you are somewhat mathematically inclined.

Radio Buttons "Checked" Attribute Not Working

This might be it:

Is there a bug with radio buttons in jQuery 1.9.1?

In short: Don't use attr() but prop() for checking radio buttons. God I hate JS...

Getting 404 Not Found error while trying to use ErrorDocument

The ErrorDocument directive, when supplied a local URL path, expects the path to be fully qualified from the DocumentRoot. In your case, this means that the actual path to the ErrorDocument is

ErrorDocument 404 /hellothere/error/404page.html

How do I create a timeline chart which shows multiple events? Eg. Metallica Band members timeline on wiki

As mentioned in the earlier comment, stacked bar chart does the trick, though the data needs to be setup differently.(See image below)

Duration column = End - Start

  1. Once done, plot your stacked bar chart using the entire data.
  2. Mark start and end range to no fill.
  3. Right click on the X Axis and change Axis options manually. (This did cause me some issues, till I realized I couldn't manipulate them to enter dates, :) yeah I am newbie, excel masters! :))

enter image description here

how to check for datatype in node js- specifically for integer

i have used it in this way and its working fine

quantity=prompt("Please enter the quantity","1");
quantity=parseInt(quantity);
if (!isNaN( quantity ))
{
    totalAmount=itemPrice*quantity;

}
return totalAmount;

Integer value in TextView

Consider using String#format with proper format specifications (%d or %f) instead.

int value = 10;

textView.setText(String.format("%d",value));

This will handle fraction separator and locale specific digits properly

"Thinking in AngularJS" if I have a jQuery background?

I find this question interesting, because my first serious exposure to JavaScript programming was Node.js and AngularJS. I never learned jQuery, and I guess that's a good thing, because I don't have to unlearn anything. In fact, I actively avoid jQuery solutions to my problems, and instead, solely look for an "AngularJS way" to solve them. So, I guess my answer to this question would essentially boil down to, "think like someone who never learned jQuery" and avoid any temptation to incorporate jQuery directly (obviously AngularJS uses it to some extent behind the scenes).

How can I check out a GitHub pull request with git?

That gist does describe what happend when you do a git fetch:

Obviously, change the github url to match your project's URL. It ends up looking like this:

[remote "origin"]
    fetch = +refs/heads/*:refs/remotes/origin/*
    url = [email protected]:joyent/node.git
    fetch = +refs/pull/*/head:refs/remotes/origin/pr/*

Now fetch all the pull requests:

$ git fetch origin
From github.com:joyent/node
 * [new ref]         refs/pull/1000/head -> origin/pr/1000
 * [new ref]         refs/pull/1002/head -> origin/pr/1002
 * [new ref]         refs/pull/1004/head -> origin/pr/1004
 * [new ref]         refs/pull/1009/head -> origin/pr/1009
...

To check out a particular pull request:

$ git checkout pr/999
Branch pr/999 set up to track remote branch pr/999 from origin.
Switched to a new branch 'pr/999'

You have various scripts listed in issues 259 to automate that task.
The git-extras project proposes the command git-pr (implemented in PR 262)

git-pr(1) -- Checks out a pull request locally

SYNOPSIS

git-pr <number> [<remote>]
git-pr clean

DESCRIPTION

Creates a local branch based on a GitHub pull request number, and switch to that branch afterwards.

The name of the remote to fetch from. Defaults to origin.

EXAMPLES

This checks out the pull request 226 from origin:

$ git pr 226

remote: Counting objects: 12, done.
remote: Compressing objects: 100% (9/9), done.
remote: Total 12 (delta 3), reused 9 (delta 3)
Unpacking objects: 100% (12/12), done.
From https://github.com/visionmedia/git-extras
  * [new ref] refs/pull/226/head -> pr/226
Switched to branch 'pr/226'

Adding a guideline to the editor in Visual Studio

If you are a user of the free Visual Studio Express edition the right key is in

HKEY_CURRENT_USER\Software\Microsoft\VCExpress\9.0\Text Editor

{note the VCExpress instead of VisualStudio) but it works! :)

AngularJS ng-class if-else expression

This is the best and reliable way to do this. Here is a simple example and after that you can develop your custom logic:

//In .ts
public showUploadButton:boolean = false;

if(some logic)
{
    //your logic
    showUploadButton = true;
}

//In template
<button [class]="showUploadButton ? 'btn btn-default': 'btn btn-info'">Upload</button>

How to get JavaScript variable value in PHP

This could be a little tricky thing but the secure way is to set a javascript cookie, then picking it up by php cookie variable.Then Assign this php variable to an php session that will hold the data more securely than cookie.Then delete the cookie using javascript and redirect the page to itself. Given that you have added an php command to catch the variable, you will get it.

Sum the digits of a number

You can try this

def sumDigits(number):
    sum = 0
    while(number>0):
        lastdigit = number%10
        sum += lastdigit
        number = number//10

    return sum

How to open the command prompt and insert commands using Java?

The following works for me on Snow Leopard:

Runtime rt = Runtime.getRuntime();
String[] testArgs = {"touch", "TEST"};
rt.exec(testArgs);

Thing is, if you want to read the output of that command, you need to read the input stream of the process. For instance,

Process pr = rt.exec(arguments);
BufferedReader r = new BufferedReader(new InputStreamReader(pr.getInputStream()));

Allows you to read the line-by-line output of the command pretty easily.

The problem might also be that MS-DOS does not interpret your order of arguments to mean "start a new command prompt". Your array should probably be:

{"start", "cmd.exe", "\c"}

To open commands in the new command prompt, you'd have to use the Process reference. But I'm not sure why you'd want to do that when you can just use exec, as the person before me commented.

Create an array or List of all dates between two dates

LINQ:

Enumerable.Range(0, 1 + end.Subtract(start).Days)
          .Select(offset => start.AddDays(offset))
          .ToArray(); 

For loop:

var dates = new List<DateTime>();

for (var dt = start; dt <= end; dt = dt.AddDays(1))
{
   dates.Add(dt);
}

EDIT: As for padding values with defaults in a time-series, you could enumerate all the dates in the full date-range, and pick the value for a date directly from the series if it exists, or the default otherwise. For example:

var paddedSeries = fullDates.ToDictionary(date => date, date => timeSeries.ContainsDate(date) 
                                               ? timeSeries[date] : defaultValue);

.NET / C# - Convert char[] to string

One other way:

char[] chars = {'a', ' ', 's', 't', 'r', 'i', 'n', 'g'};
string s = string.Join("", chars);
//we get "a string"
// or for fun:
string s = string.Join("_", chars);
//we get "a_ _s_t_r_i_n_g"

How Spring Security Filter Chain works

UsernamePasswordAuthenticationFilter is only used for /login, and latter filters are not?

No, UsernamePasswordAuthenticationFilter extends AbstractAuthenticationProcessingFilter, and this contains a RequestMatcher, that means you can define your own processing url, this filter only handle the RequestMatcher matches the request url, the default processing url is /login.

Later filters can still handle the request, if the UsernamePasswordAuthenticationFilter executes chain.doFilter(request, response);.

More details about core fitlers

Does the form-login namespace element auto-configure these filters?

UsernamePasswordAuthenticationFilter is created by <form-login>, these are Standard Filter Aliases and Ordering

Does every request (authenticated or not) reach FilterSecurityInterceptor for non-login url?

It depends on whether the before fitlers are successful, but FilterSecurityInterceptor is the last fitler normally.

Does configuring two http elements create two springSecurityFitlerChains?

Yes, every fitlerChain has a RequestMatcher, if the RequestMatcher matches the request, the request will be handled by the fitlers in the fitler chain.

The default RequestMatcher matches all request if you don't config the pattern, or you can config the specific url (<http pattern="/rest/**").

If you want to konw more about the fitlers, I think you can check source code in spring security. doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)

What is the difference between char array and char pointer in C?

What is the difference between char array vs char pointer in C?

C99 N1256 draft

There are two different uses of character string literals:

  1. Initialize char[]:

    char c[] = "abc";      
    

    This is "more magic", and described at 6.7.8/14 "Initialization":

    An array of character type may be initialized by a character string literal, optionally enclosed in braces. Successive characters of the character string literal (including the terminating null character if there is room or if the array is of unknown size) initialize the elements of the array.

    So this is just a shortcut for:

    char c[] = {'a', 'b', 'c', '\0'};
    

    Like any other regular array, c can be modified.

  2. Everywhere else: it generates an:

    So when you write:

    char *c = "abc";
    

    This is similar to:

    /* __unnamed is magic because modifying it gives UB. */
    static char __unnamed[] = "abc";
    char *c = __unnamed;
    

    Note the implicit cast from char[] to char *, which is always legal.

    Then if you modify c[0], you also modify __unnamed, which is UB.

    This is documented at 6.4.5 "String literals":

    5 In translation phase 7, a byte or code of value zero is appended to each multibyte character sequence that results from a string literal or literals. The multibyte character sequence is then used to initialize an array of static storage duration and length just sufficient to contain the sequence. For character string literals, the array elements have type char, and are initialized with the individual bytes of the multibyte character sequence [...]

    6 It is unspecified whether these arrays are distinct provided their elements have the appropriate values. If the program attempts to modify such an array, the behavior is undefined.

6.7.8/32 "Initialization" gives a direct example:

EXAMPLE 8: The declaration

char s[] = "abc", t[3] = "abc";

defines "plain" char array objects s and t whose elements are initialized with character string literals.

This declaration is identical to

char s[] = { 'a', 'b', 'c', '\0' },
t[] = { 'a', 'b', 'c' };

The contents of the arrays are modifiable. On the other hand, the declaration

char *p = "abc";

defines p with type "pointer to char" and initializes it to point to an object with type "array of char" with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to modify the contents of the array, the behavior is undefined.

GCC 4.8 x86-64 ELF implementation

Program:

#include <stdio.h>

int main(void) {
    char *s = "abc";
    printf("%s\n", s);
    return 0;
}

Compile and decompile:

gcc -ggdb -std=c99 -c main.c
objdump -Sr main.o

Output contains:

 char *s = "abc";
8:  48 c7 45 f8 00 00 00    movq   $0x0,-0x8(%rbp)
f:  00 
        c: R_X86_64_32S .rodata

Conclusion: GCC stores char* it in .rodata section, not in .text.

If we do the same for char[]:

 char s[] = "abc";

we obtain:

17:   c7 45 f0 61 62 63 00    movl   $0x636261,-0x10(%rbp)

so it gets stored in the stack (relative to %rbp).

Note however that the default linker script puts .rodata and .text in the same segment, which has execute but no write permission. This can be observed with:

readelf -l a.out

which contains:

 Section to Segment mapping:
  Segment Sections...
   02     .text .rodata

How to get JSON data from the URL (REST API) to UI using jQuery or plain JavaScript?

You can use native JS so you don't have to rely on external libraries.

(I will use some ES2015 syntax, a.k.a ES6, modern javascript) What is ES2015?

fetch('/api/rest/abc')
    .then(response => response.json())
    .then(data => {
        // Do what you want with your data
    });

You can also capture errors if any:

fetch('/api/rest/abc')
    .then(response => response.json())
    .then(data => {
        // Do what you want with your data
    })
    .catch(err => {
        console.error('An error ocurred', err);
    });

By default it uses GET and you don't have to specify headers, but you can do all that if you want. For further reference: Fetch API reference

Binary Data in JSON String. Something better than Base64

The problem with UTF-8 is that it is not the most space efficient encoding. Also, some random binary byte sequences are invalid UTF-8 encoding. So you can't just interpret a random binary byte sequence as some UTF-8 data because it will be invalid UTF-8 encoding. The benefit of this constrain on the UTF-8 encoding is that it makes it robust and possible to locate multi byte chars start and end whatever byte we start looking at.

As a consequence, if encoding a byte value in the range [0..127] would need only one byte in UTF-8 encoding, encoding a byte value in the range [128..255] would require 2 bytes ! Worse than that. In JSON, control chars, " and \ are not allowed to appear in a string. So the binary data would require some transformation to be properly encoded.

Let see. If we assume uniformly distributed random byte values in our binary data then, on average, half of the bytes would be encoded in one bytes and the other half in two bytes. The UTF-8 encoded binary data would have 150% of the initial size.

Base64 encoding grows only to 133% of the initial size. So Base64 encoding is more efficient.

What about using another Base encoding ? In UTF-8, encoding the 128 ASCII values is the most space efficient. In 8 bits you can store 7 bits. So if we cut the binary data in 7 bit chunks to store them in each byte of an UTF-8 encoded string, the encoded data would grow only to 114% of the initial size. Better than Base64. Unfortunately we can't use this easy trick because JSON doesn't allow some ASCII chars. The 33 control characters of ASCII ( [0..31] and 127) and the " and \ must be excluded. This leaves us only 128-35 = 93 chars.

So in theory we could define a Base93 encoding which would grow the encoded size to 8/log2(93) = 8*log10(2)/log10(93) = 122%. But a Base93 encoding would not be as convenient as a Base64 encoding. Base64 requires to cut the input byte sequence in 6bit chunks for which simple bitwise operation works well. Beside 133% is not much more than 122%.

This is why I came independently to the common conclusion that Base64 is indeed the best choice to encode binary data in JSON. My answer presents a justification for it. I agree it isn't very attractive from the performance point of view, but consider also the benefit of using JSON with it's human readable string representation easy to manipulate in all programming languages.

If performance is critical than a pure binary encoding should be considered as replacement of JSON. But with JSON my conclusion is that Base64 is the best.

Removing duplicates in the lists

def remove_duplicates(A):
   [A.pop(count) for count,elem in enumerate(A) if A.count(elem)!=1]
   return A

A list comprehesion to remove duplicates

Android Studio: Gradle: error: cannot find symbol variable

If you are using multiple flavors?

-make sure the resource file is not declared/added both in only one of the flavors and in main.

Example: a_layout_file.xml file containing the symbol variable(s)

src:

flavor1/res/layout/(no file)

flavor2/res/layout/a_layout_file.xml

main/res/layout/a_layout_file.xml

This setup will give the error: cannot find symbol variable, this is because the resource file can only be in both flavors or only in the main.

@HostBinding and @HostListener: what do they do and what are they for?

A quick tip that helps me remember what they do -

HostBinding('value') myValue; is exactly the same as [value]="myValue"

And

HostListener('click') myClick(){ } is exactly the same as (click)="myClick()"


HostBinding and HostListener are written in directives and the other ones (...) and [..] are written inside templates (of components).

How to efficiently remove duplicates from an array without using Set

There exists many solution of this problem.

  1. The sort approach

    • You sort your array and resolve only unique items
  2. The set approach

    • You declare a HashSet where you put all item then you have only unique ones.
  3. You create a boolean array that represent the items all ready returned, (this depend on your data in the array).

If you deal with large amount of data i would pick the 1. solution. As you do not allocate additional memory and sorting is quite fast. For small set of data the complexity would be n^2 but for large i will be n log n.

Difference between return 1, return 0, return -1 and exit?

return n from your main entry function will terminate your process and report to the parent process (the one that executed your process) the result of your process. 0 means SUCCESS. Other codes usually indicates a failure and its meaning.

When do you use POST and when do you use GET?

From w3schools.com:

What is HTTP?

The Hypertext Transfer Protocol (HTTP) is designed to enable communications between clients and servers.

HTTP works as a request-response protocol between a client and server.

A web browser may be the client, and an application on a computer that hosts a web site may be the server.

Example: A client (browser) submits an HTTP request to the server; then the server returns a response to the client. The response contains status information about the request and may also contain the requested content.

Two HTTP Request Methods: GET and POST

Two commonly used methods for a request-response between a client and server are: GET and POST.

GET – Requests data from a specified resource POST – Submits data to be processed to a specified resource

Here we distinguish the major differences:

enter image description here

Regex date validation for yyyy-mm-dd

you can test this expression:

^\d{4}[\-\/\s]?((((0[13578])|(1[02]))[\-\/\s]?(([0-2][0-9])|(3[01])))|(((0[469])|(11))[\-\/\s]?(([0-2][0-9])|(30)))|(02[\-\/\s]?[0-2][0-9]))$

Description:
validates a yyyy-mm-dd, yyyy mm dd, or yyyy/mm/dd date

makes sure day is within valid range for the month - does NOT validate Feb. 29 on a leap year, only that Feb. Can have 29 days

Matches (tested) : 0001-12-31 | 9999 09 30 | 2002/03/03

Programmatic equivalent of default(Type)

The Expressions can help here:

    private static Dictionary<Type, Delegate> lambdasMap = new Dictionary<Type, Delegate>();

    private object GetTypedNull(Type type)
    {
        Delegate func;
        if (!lambdasMap.TryGetValue(type, out func))
        {
            var body = Expression.Default(type);
            var lambda = Expression.Lambda(body);
            func = lambda.Compile();
            lambdasMap[type] = func;
        }
        return func.DynamicInvoke();
    }

I did not test this snippet, but i think it should produce "typed" nulls for reference types..

Concatenate rows of two dataframes in pandas

Thanks to @EdChum I was struggling with same problem especially when indexes do not match. Unfortunatly in pandas guide this case is missed (when you for example delete some rows)

import pandas as pd
t=pd.DataFrame()
t['a']=[1,2,3,4]
t=t.loc[t['a']>1] #now index starts from 1

u=pd.DataFrame()
u['b']=[1,2,3] #index starts from 0

#option 1
#keep index of t
u.index = t.index 

#option 2
#index of t starts from 0
t.reset_index(drop=True, inplace=True)

#now concat will keep number of rows 
r=pd.concat([t,u], axis=1)

Add JavaScript object to JavaScript object

var jsonIssues = [
 {ID:'1',Name:'Some name',Notes:'NOTES'},
 {ID:'2',Name:'Some name 2',Notes:'NOTES 2'}
];

If you want to add to the array then you can do this

jsonIssues[jsonIssues.length] = {ID:'3',Name:'Some name 3',Notes:'NOTES 3'};

Or you can use the push technique that the other guy posted, which is also good.

DIV height set as percentage of screen?

Try using Viewport Height

div {
    height:100vh; 
}

It is already discussed here in detail

How to check if a String contains only ASCII?

You can do it with java.nio.charset.Charset.

import java.nio.charset.Charset;

public class StringUtils {

  public static boolean isPureAscii(String v) {
    return Charset.forName("US-ASCII").newEncoder().canEncode(v);
    // or "ISO-8859-1" for ISO Latin 1
    // or StandardCharsets.US_ASCII with JDK1.7+
  }

  public static void main (String args[])
    throws Exception {

     String test = "Réal";
     System.out.println(test + " isPureAscii() : " + StringUtils.isPureAscii(test));
     test = "Real";
     System.out.println(test + " isPureAscii() : " + StringUtils.isPureAscii(test));

     /*
      * output :
      *   Réal isPureAscii() : false
      *   Real isPureAscii() : true
      */
  }
}

Detect non-ASCII character in a String

What is the difference between compare() and compareTo()?

The main difference is in the use of the interfaces:

Comparable (which has compareTo()) requires the objects to be compared (in order to use a TreeMap, or to sort a list) to implement that interface. But what if the class does not implement Comparable and you can't change it because it's part of a 3rd party library? Then you have to implement a Comparator, which is a bit less convenient to use.

Showing the stack trace from a running Python application

pyringe is a debugger that can interact with running python processes, print stack traces, variables, etc. without any a priori setup.

While I've often used the signal handler solution in the past, it can still often be difficult to reproduce the issue in certain environments.