Programs & Examples On #Commonjs

CommonJS is a project whose goal is to move JavaScript outside the browser.

Field 'browser' doesn't contain a valid alias configuration

In my case I was using invalid templateUrl.By correcting it problem solved.

@Component({
        selector: 'app-edit-feather-object',
        templateUrl: ''
    })

Difference between "module.exports" and "exports" in the CommonJs Module System

node does something like this:

module.exports = exports = {}

module.exports and exports refer to same object.

This is done just for convenience. so instead of writing something like this

module.exports.PI = 3.14

we can write

exports.PI = 3.14

so it is ok to add a property to exports but assigning it to a different object is not ok

exports.add = function(){
.
.
} 

? this is OK and same as module.exports.add = function(){...}

exports = function(){
.
.
} 

? this is not ok and and empty object will be returned as module.exports still refers to {} and exports refer to different object.

module.exports vs exports in Node.js

why both are used here

I believe they just want to be clear that module.exports, exports, and nano point to the same function - allowing you to use either variable to call the function within the file. nano provides some context to what the function does.

exports won't be exported (only module.exports will), so why bother overwriting that as well?

The verbosity trade-off limits the risk of future bugs, such as using exports instead of module.exports within the file. It also provides clarification that module.exports and exports are in fact pointing to the same value.


module.exports vs exports

As long as you don't reassign module.exports or exports (and instead add values to the object they both refer to), you won't have any issues and can safely use exports to be more concise.

When assigning either to a non-object, they are now pointing to different places which can be confusing unless you intentionally want module.exports to be something specific (such as a function).

Setting exports to a non-object doesn't make much sense as you'll have to set module.exports = exports at the end to be able to use it in other files.

let module = { exports: {} };
let exports = module.exports;

exports.msg = 'hi';
console.log(module.exports === exports); // true

exports = 'yo';
console.log(module.exports === exports); // false

exports = module.exports;
console.log(module.exports === exports); // true

module.exports = 'hello';
console.log(module.exports === exports); // false

module.exports = exports;
console.log(module.exports === exports); // true

Why assign module.exports to a function?

More concise! Compare how much shorter the 2nd example is:

helloWorld1.js: module.exports.hello = () => console.log('hello world');

app1.js: let sayHello = require('./helloWorld1'); sayHello.hello; // hello world

helloWorld2.js: module.exports = () => console.log('hello world');

app2.js: let sayHello = require('./helloWorld2'); sayHello; // hello world

Relation between CommonJS, AMD and RequireJS?

Quoting

AMD:

  • One browser-first approach
  • Opting for asynchronous behavior and simplified backwards compatibility
  • It doesn't have any concept of File I/O.
  • It supports objects, functions, constructors, strings, JSON and many other types of modules.

CommonJS:

  • One server-first approach
  • Assuming synchronous behavior
  • Cover a broader set of concerns such as I/O, File system, Promises and more.
  • Supports unwrapped modules, it can feel a little more close to the ES.next/Harmony specifications, freeing you of the define() wrapper that AMD enforces.
  • Only support objects as modules.

Node.js - use of module.exports as a constructor

In my opinion, some of the node.js examples are quite contrived.

You might expect to see something more like this in the real world

// square.js
function Square(width) {

  if (!(this instanceof Square)) {
    return new Square(width);
  }

  this.width = width;
};

Square.prototype.area = function area() {
  return Math.pow(this.width, 2);
};

module.exports = Square;

Usage

var Square = require("./square");

// you can use `new` keyword
var s = new Square(5);
s.area(); // 25

// or you can skip it!
var s2 = Square(10);
s2.area(); // 100

For the ES6 people

class Square {
  constructor(width) {
    this.width = width;
  }
  area() {
    return Math.pow(this.width, 2);
  }
}

export default Square;

Using it in ES6

import Square from "./square";
// ...

When using a class, you must use the new keyword to instatiate it. Everything else stays the same.

Drawing Circle with OpenGL

I have done it using the following code,

glBegin(GL.GL_LINE_LOOP);
     for(int i =0; i <= 300; i++){
         double angle = 2 * Math.PI * i / 300;
         double x = Math.cos(angle);
         double y = Math.sin(angle);
         gl.glVertex2d(x,y);
     }
glEnd();

JQuery ajax call default timeout value

There doesn't seem to be a standardized default value. I have the feeling the default is 0, and the timeout event left totally dependent on browser and network settings.

For IE, there is a timeout property for XMLHTTPRequests here. It defaults to null, and it says the network stack is likely to be the first to time out (which will not generate an ontimeout event by the way).

Sql query to insert datetime in SQL Server

Management studio creates scripts like:

insert table1 (foodate) values(CAST(N'2012-06-18 10:34:09.000' AS DateTime))

How to include static library in makefile

use

LDFLAGS= -L<Directory where the library resides> -l<library name>

Like :

LDFLAGS = -L. -lmine

for ensuring static compilation you can also add

LDFLAGS = -static

Or you can just get rid of the whole library searching, and link with with it directly.

say you have main.c fun.c

and a static library libmine.a

then you can just do in your final link line of the Makefile

$(CC) $(CFLAGS) main.o fun.o libmine.a

Use of the MANIFEST.MF file in Java

The content of the Manifest file in a JAR file created with version 1.0 of the Java Development Kit is the following.

Manifest-Version: 1.0

All the entries are as name-value pairs. The name of a header is separated from its value by a colon. The default manifest shows that it conforms to version 1.0 of the manifest specification. The manifest can also contain information about the other files that are packaged in the archive. Exactly what file information is recorded in the manifest will depend on the intended use for the JAR file. The default manifest file makes no assumptions about what information it should record about other files, so its single line contains data only about itself. Special-Purpose Manifest Headers

Depending on the intended role of the JAR file, the default manifest may have to be modified. If the JAR file is created only for the purpose of archival, then the MANIFEST.MF file is of no purpose. Most uses of JAR files go beyond simple archiving and compression and require special information to be in the manifest file. Summarized below are brief descriptions of the headers that are required for some special-purpose JAR-file functions

Applications Bundled as JAR Files: If an application is bundled in a JAR file, the Java Virtual Machine needs to be told what the entry point to the application is. An entry point is any class with a public static void main(String[] args) method. This information is provided in the Main-Class header, which has the general form:

Main-Class: classname

The value classname is to be replaced with the application's entry point.

Download Extensions: Download extensions are JAR files that are referenced by the manifest files of other JAR files. In a typical situation, an applet will be bundled in a JAR file whose manifest references a JAR file (or several JAR files) that will serve as an extension for the purposes of that applet. Extensions may reference each other in the same way. Download extensions are specified in the Class-Path header field in the manifest file of an applet, application, or another extension. A Class-Path header might look like this, for example:

Class-Path: servlet.jar infobus.jar acme/beans.jar

With this header, the classes in the files servlet.jar, infobus.jar, and acme/beans.jar will serve as extensions for purposes of the applet or application. The URLs in the Class-Path header are given relative to the URL of the JAR file of the applet or application.

Package Sealing: A package within a JAR file can be optionally sealed, which means that all classes defined in that package must be archived in the same JAR file. A package might be sealed to ensure version consistency among the classes in your software or as a security measure. To seal a package, a Name header needs to be added for the package, followed by a Sealed header, similar to this:

Name: myCompany/myPackage/
Sealed: true

The Name header's value is the package's relative pathname. Note that it ends with a '/' to distinguish it from a filename. Any headers following a Name header, without any intervening blank lines, apply to the file or package specified in the Name header. In the above example, because the Sealed header occurs after the Name: myCompany/myPackage header, with no blank lines between, the Sealed header will be interpreted as applying (only) to the package myCompany/myPackage.

Package Versioning: The Package Versioning specification defines several manifest headers to hold versioning information. One set of such headers can be assigned to each package. The versioning headers should appear directly beneath the Name header for the package. This example shows all the versioning headers:

Name: java/util/
Specification-Title: "Java Utility Classes" 
Specification-Version: "1.2"
Specification-Vendor: "Sun Microsystems, Inc.".
Implementation-Title: "java.util" 
Implementation-Version: "build57"
Implementation-Vendor: "Sun Microsystems, Inc."

Get list of JSON objects with Spring RestTemplate

In my case I preferred to extract a String then browse the context using JsonNode interface

    var response =  restTemplate.exchange("https://my-url", HttpMethod.GET, entity,  String.class);
    if (response.getStatusCode() == HttpStatus.OK) {
        var jsonString = response.getBody();
        ObjectMapper mapper = new ObjectMapper();
        JsonNode actualObj = mapper.readTree(jsonString);           
        
        System.out.println(actualObj);  
    }

or quickly

ObjectNode actualObj= restTemplate.getForObject("https://my-url", ObjectNode.class);

then read inner data with path expression i.e.

boolean b = actualObj.at("/0/states/0/no_data").asBoolean();

What does it mean when a PostgreSQL process is "idle in transaction"?

As mentioned here: Re: BUG #4243: Idle in transaction it is probably best to check your pg_locks table to see what is being locked and that might give you a better clue where the problem lies.

Open a folder using Process.Start

Do you have a lot of applications running when you are trying this? I encounter weird behavior at work sometimes because my system runs out of GDI Handles as I have so many windows open (our apps use alot).

When this happens, windows and context menus no long appear until I close something to free up some GDI handles.

The default limit in XP and Vista is 10000. It is not uncommon for my DevStudio to have 1500 GDI handles, so if you have a couple of copies of Dev studio open, it can eat them up pretty quickly. You can add a column in TaskManager to see how many handles are being used by each process.

There is a registry tweak you can do to increase the limit.

For more information see http://msdn.microsoft.com/en-us/library/ms724291(VS.85).aspx

Get characters after last / in url

Very simply:

$id = substr($url, strrpos($url, '/') + 1);

strrpos gets the position of the last occurrence of the slash; substr returns everything after that position.


As mentioned by redanimalwar if there is no slash this doesn't work correctly since strrpos returns false. Here's a more robust version:

$pos = strrpos($url, '/');
$id = $pos === false ? $url : substr($url, $pos + 1);

MySQL date formats - difficulty Inserting a date

The date format for mysql insert query is YYYY-MM-DD

example:

INSERT INTO table_name (date_column) VALUE ('YYYY-MM-DD');

Eclipse cannot load SWT libraries

Simply specify the path to the libraries:

echo "-Djava.library.path=/usr/lib/jni/" >> /etc/eclipse.ini

Resizing a button

Another alternative is that you are allowed to have multiple classes in a tag. Consider:

 <div class="button big">This is a big button</div>
 <div class="button small">This is a small button</div>

And the CSS:

 .button {
     /* all your common button styles */
 }

 .big {
     height: 60px;
     width: 100px;
 }
 .small {
     height: 40px;
     width: 70px;
 }

and so on.

Android button background color

Try this

<androidx.appcompat.widget.AppCompatButton
    android:layout_width="wrap_content"
    android:layout_height="34dp"
    android:text="Check Out"
    android:textAllCaps="true"
    android:background="#54c2bc"
    android:textColor="#FFFFFF"
    android:textSize="9sp"/>

How to implement private method in ES6 class with Traceur

Have you considered using factory functions? They usually are a much better alternative to classes or constructor functions in Javascript. Here is an example of how it works:

function car () {

    var privateVariable = 4

    function privateFunction () {}

    return {

        color: 'red',

        drive: function (miles) {},

        stop: function() {}

        ....

    }

}

Thanks to closures you have access to all private functions and variabels inside the returned object, but you can not access them from outside.

How to declare a local variable in Razor?

You can also use:

@if(string.IsNullOrEmpty(Model.CreatorFullName))
{
...your code...
}

No need for a variable in the code

How to animate the change of image in an UIImageView?

There are a few different approaches here: UIAnimations to my recollection it sounds like your challenge.

Edit: too lazy of me:)

In the post, I was referring to this method:

[newView setFrame:CGRectMake( 0.0f, 480.0f, 320.0f, 480.0f)]; //notice this is OFF screen!
[UIView beginAnimations:@"animateTableView" context:nil];
[UIView setAnimationDuration:0.4];
[newView setFrame:CGRectMake( 0.0f, 0.0f, 320.0f, 480.0f)]; //notice this is ON screen!
[UIView commitAnimations];

But instead of animation the frame, you animate the alpha:

[newView setAlpha:0.0]; // set it to zero so it is all gone.
[UIView beginAnimations:@"animateTableView" context:nil];
[UIView setAnimationDuration:0.4];
[newView setAlpha:0.5]; //this will change the newView alpha from its previous zero value to 0.5f
[UIView commitAnimations];

Equal height rows in CSS Grid Layout

Short Answer

If the goal is to create a grid with equal height rows, where the tallest cell in the grid sets the height for all rows, here's a quick and simple solution:

  • Set the container to grid-auto-rows: 1fr

How it works

Grid Layout provides a unit for establishing flexible lengths in a grid container. This is the fr unit. It is designed to distribute free space in the container and is somewhat analogous to the flex-grow property in flexbox.

If you set all rows in a grid container to 1fr, let's say like this:

grid-auto-rows: 1fr;

... then all rows will be equal height.

It doesn't really make sense off-the-bat because fr is supposed to distribute free space. And if several rows have content with different heights, then when the space is distributed, some rows would be proportionally smaller and taller.

Except, buried deep in the grid spec is this little nugget:

7.2.3. Flexible Lengths: the fr unit

...

When the available space is infinite (which happens when the grid container’s width or height is indefinite), flex-sized (fr) grid tracks are sized to their contents while retaining their respective proportions.

The used size of each flex-sized grid track is computed by determining the max-content size of each flex-sized grid track and dividing that size by the respective flex factor to determine a “hypothetical 1fr size”.

The maximum of those is used as the resolved 1fr length (the flex fraction), which is then multiplied by each grid track’s flex factor to determine its final size.

So, if I'm reading this correctly, when dealing with a dynamically-sized grid (e.g., the height is indefinite), grid tracks (rows, in this case) are sized to their contents.

The height of each row is determined by the tallest (max-content) grid item.

The maximum height of those rows becomes the length of 1fr.

That's how 1fr creates equal height rows in a grid container.


Why flexbox isn't an option

As noted in the question, equal height rows are not possible with flexbox.

Flex items can be equal height on the same row, but not across multiple rows.

This behavior is defined in the flexbox spec:

6. Flex Lines

In a multi-line flex container, the cross size of each line is the minimum size necessary to contain the flex items on the line.

In other words, when there are multiple lines in a row-based flex container, the height of each line (the "cross size") is the minimum height necessary to contain the flex items on the line.

Loop through each cell in a range of cells when given a Range object

Sub LoopRange()

    Dim rCell As Range
    Dim rRng As Range

    Set rRng = Sheet1.Range("A1:A6")

    For Each rCell In rRng.Cells
        Debug.Print rCell.Address, rCell.Value
    Next rCell

End Sub

How to git-cherry-pick only changes to certain files?

Use git merge --squash branch_name this will get all changes from the other branch and will prepare a commit for you. Now remove all unneeded changes and leave the one you want. And git will not know that there was a merge.

React Native android build failed. SDK location not found

For Windows Users

One simple solution is to set the SDK path to the Enviroment Variables list.

  1. Head over to the Enviromnent variables. (Your PC > Properties )
  2. Create New System variables
  3. Set the Variable name to ANDROID_HOME
  4. Set the Variable value to your Android Sdk Location
  5. Press OK (3 times for 3 dialog boxes)

Note:

Your Android Sdk is generally located in

C:\Users\YourUserName\AppData\Local\Android\Sdk

Make sure to close your current terminal because your terminal holds all of your pre-existing Environment Variables.

Java Returning method which returns arraylist?

MyClass obj = new MyClass();
ArrayList<Integer> numbers = obj.myNumbers();

How can I easily add storage to a VirtualBox machine with XP installed?

Take a look at CloneVDI from the VirtualBox site... 100% painless!

Merge two rows in SQL

There might be neater methods, but the following could be one approach:

SELECT    t.fk,
          (
             SELECT t1.Field1 
             FROM   `table` t1 
             WHERE  t1.fk = t.fk AND t1.Field1 IS NOT NULL
             LIMIT  1
          ) Field1,
          (
             SELECT t2.Field2
             FROM   `table` t2 
             WHERE  t2.fk = t.fk AND t2.Field2 IS NOT NULL
             LIMIT  1
          ) Field2
FROM      `table` t
WHERE     t.fk = 3
GROUP BY  t.fk;

Test Case:

CREATE TABLE `table` (fk int, Field1 varchar(10), Field2 varchar(10));

INSERT INTO `table` VALUES (3, 'ABC', NULL);
INSERT INTO `table` VALUES (3, NULL, 'DEF');
INSERT INTO `table` VALUES (4, 'GHI', NULL);
INSERT INTO `table` VALUES (4, NULL, 'JKL');
INSERT INTO `table` VALUES (5, NULL, 'MNO');

Result:

+------+--------+--------+
| fk   | Field1 | Field2 |
+------+--------+--------+
|    3 | ABC    | DEF    |
+------+--------+--------+
1 row in set (0.01 sec)

Running the same query without the WHERE t.fk = 3 clause, it would return the following result-set:

+------+--------+--------+
| fk   | Field1 | Field2 |
+------+--------+--------+
|    3 | ABC    | DEF    |
|    4 | GHI    | JKL    |
|    5 | NULL   | MNO    |
+------+--------+--------+
3 rows in set (0.01 sec)

How to predict input image using trained model in Keras?

keras predict_classes (docs) outputs A numpy array of class predictions. Which in your model case, the index of neuron of highest activation from your last(softmax) layer. [[0]] means that your model predicted that your test data is class 0. (usually you will be passing multiple image, and the result will look like [[0], [1], [1], [0]] )

You must convert your actual label (e.g. 'cancer', 'not cancer') into binary encoding (0 for 'cancer', 1 for 'not cancer') for binary classification. Then you will interpret your sequence output of [[0]] as having class label 'cancer'

Calling dynamic function with dynamic number of parameters

Couldn't you just pass the arguments array along?

function mainfunc (func){
    // remove the first argument containing the function name
    arguments.shift();
    window[func].apply(null, arguments);
}

function calledfunc1(args){
    // Do stuff here
}

function calledfunc2(args){
    // Do stuff here
}

mainfunc('calledfunc1','hello','bye');
mainfunc('calledfunc2','hello','bye','goodbye');

Do HttpClient and HttpClientHandler have to be disposed between requests?

Since it doesn't appear that anyone has mentioned it here yet, the new best way to manage HttpClient and HttpClientHandler in .NET Core 2.1 is using HttpClientFactory.

It solves most of the aforementioned issues and gotchas in a clean and easy-to-use way. From Steve Gordon's great blog post:

Add the following packages to your .Net Core (2.1.1 or later) project:

Microsoft.AspNetCore.All
Microsoft.Extensions.Http

Add this to Startup.cs:

services.AddHttpClient();

Inject and use:

[Route("api/[controller]")]
public class ValuesController : Controller
{
    private readonly IHttpClientFactory _httpClientFactory;

    public ValuesController(IHttpClientFactory httpClientFactory)
    {
        _httpClientFactory = httpClientFactory;
    }

    [HttpGet]
    public async Task<ActionResult> Get()
    {
        var client = _httpClientFactory.CreateClient();
        var result = await client.GetStringAsync("http://www.google.com");
        return Ok(result);
    }
}

Explore the series of posts in Steve's blog for lots more features.

JavaScript check if variable exists (is defined/initialized)

It depends if you just care that the variable has been defined or if you want it to have a meaningful value.

Checking if the type is undefined will check if the variable has been defined yet.

=== null or !== null will only check if the value of the variable is exactly null.

== null or != null will check if the value is undefined or null.

if(value) will check if the variable is undefined, null, 0, or an empty string.

How to use Selenium with Python?

There are a lot of sources for selenium - here is good one for simple use Selenium, and here is a example snippet too Selenium Examples

You can find a lot of good sources to use selenium, it's not too hard to get it set up and start using it.

jQuery check if it is clicked or not

Using jQuery, I would suggest a shorter solution.

var elementClicked;
$("element").click(function(){
   elementClicked = true;
});
if( elementClicked != true ) {
    alert("element not clicked");
}else{
    alert("element clicked");
}

("element" here is to be replaced with the actual name tag)

Animation fade in and out

Please try the below code for repeated fade-out/fade-in animation

AlphaAnimation anim = new AlphaAnimation(1.0f, 0.3f);
    anim.setRepeatCount(Animation.INFINITE);
    anim.setRepeatMode(Animation.REVERSE);
    anim.setDuration(300);
view.setAnimation(anim); // to start animation
view.setAnimation(null); // to stop animation

Single line sftp from terminal

Update Sep 2017 - tl;dr

Download a single file from a remote ftp server to your machine:

sftp {user}@{host}:{remoteFileName} {localFileName}

Upload a single file from your machine to a remote ftp server:

sftp {user}@{host}:{remote_dir} <<< $'put {local_file_path}'

Original answer:

Ok, so I feel a little dumb. But I figured it out. I almost had it at the top with:

sftp user@host remoteFile localFile

The only documentation shown in the terminal is this:

sftp [user@]host[:file ...]
sftp [user@]host[:dir[/]]

However, I came across this site which shows the following under the synopsis:

sftp [-vC1 ] [-b batchfile ] [-o ssh_option ] [-s subsystem | sftp_server ] [-B buffer_size ] [-F ssh_config ] [-P sftp_server path ] [-R num_requests ] [-S program ] host 
sftp [[user@]host[:file [file]]] 
sftp [[user@]host[:dir[/]]]

So the simple answer is you just do : after your user and host then the remote file and local filename. Incredibly simple!

Single line, sftp copy remote file:

sftp username@hostname:remoteFileName localFileName
sftp kyle@kylesserver:/tmp/myLogFile.log /tmp/fileNameToUseLocally.log

Update Feb 2016

In case anyone is looking for the command to do the reverse of this and push a file from your local computer to a remote server in one single line sftp command, user @Thariama below posted the solution to accomplish that. Hat tip to them for the extra code.

sftp {user}@{host}:{remote_dir} <<< $'put {local_file_path}'

how to use "tab space" while writing in text file

You can use \t to create a tab in a file.

Get the short Git version hash

git log -1 --abbrev-commit

will also do it.

git log --abbrev-commit

will list the log entries with abbreviated SHA-1 checksum.

How to save an activity state using save instance state?

To get activity state data stored in onCreate(), first you have to save data in savedInstanceState by overriding SaveInstanceState(Bundle savedInstanceState) method.

When activity destroy SaveInstanceState(Bundle savedInstanceState) method gets called and there you save data you want to save. And you get same in onCreate() when activity restart.(savedInstanceState wont be null since you have saved some data in it before activity get destroyed)

jQuery Cross Domain Ajax

Here is the snippets from my code.. If it solves your problems..

Client Code :

Set jsonpCallBack : 'photos' and dataType:'jsonp'

 $('document').ready(function() {
            var pm_url = 'http://localhost:8080/diztal/rest/login/test_cor?sessionKey=4324234';
            $.ajax({
                crossDomain: true,
                url: pm_url,
                type: 'GET',
                dataType: 'jsonp',
                jsonpCallback: 'photos'
            });
        });
        function photos (data) {
            alert(data);
            $("#twitter_followers").html(data.responseCode);
        };

Server Side Code (Using Rest Easy)

@Path("/test_cor")
@GET
@Produces(MediaType.TEXT_PLAIN)
public String testCOR(@QueryParam("sessionKey") String sessionKey, @Context HttpServletRequest httpRequest) {
    ResponseJSON<LoginResponse> resp = new ResponseJSON<LoginResponse>();
    resp.setResponseCode(sessionKey);
    resp.setResponseText("Wrong Passcode");
    resp.setResponseTypeClass("Login");
    Gson gson = new Gson();
    return "photos("+gson.toJson(resp)+")"; // CHECK_THIS_LINE
}

How do I find a particular value in an array and return its index?

Here is a very simple way to do it by hand. You could also use the <algorithm>, as Peter suggests.

#include <iostream>
int find(int arr[], int len, int seek)
{
    for (int i = 0; i < len; ++i)
    {
        if (arr[i] == seek) return i;
    }
    return -1;
}
int main()
{
    int arr[ 5 ] = { 4, 1, 3, 2, 6 };
    int x = find(arr,5,3);
    std::cout << x << std::endl;    
}

How to disable HTML button using JavaScript?

If you have the button object, called b: b.disabled=false;

ArrayList: how does the size increase?

Lets look at this code (jdk1.8)

@Test
    public void testArraySize() throws Exception {
        List<String> list = new ArrayList<>();
        list.add("ds");
        list.add("cx");
        list.add("cx");
        list.add("ww");
        list.add("ds");
        list.add("cx");
        list.add("cx");
        list.add("ww");
        list.add("ds");
        list.add("cx");
        list.add("last");
    }

1)Put break point on the line when "last" is inserted

2)Go to the add method of ArrayList You will see

ensureCapacityInternal(size + 1);  // Increments modCount!!
        elementData[size++] = e;

3) Go to ensureCapacityInternal method this method call ensureExplicitCapacity

4)

private void ensureExplicitCapacity(int minCapacity) {
        modCount++;

        // overflow-conscious code
        if (minCapacity - elementData.length > 0)
            grow(minCapacity);
    }
            return true;

In our example minCapacity is equal to 11 11-10 > 0 therefore You need grow method

5)

private void grow(int minCapacity) {
        // overflow-conscious code
        int oldCapacity = elementData.length;
        int newCapacity = oldCapacity + (oldCapacity >> 1);
        if (newCapacity - minCapacity < 0)
            newCapacity = minCapacity;
        if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);
        // minCapacity is usually close to size, so this is a win:
        elementData = Arrays.copyOf(elementData, newCapacity);
    }

Lets describe each step:

1) oldCapacity = 10 because we didn't put this param when ArrayList was init ,therefore it will use default capacity(10)

2) int newCapacity = oldCapacity + (oldCapacity >> 1); Here newCapacity is equal to oldCapacity plus oldCapacity with right shift by one (oldCapacity is 10 this is the binary representation 00001010 moving one bit to right we will get 00000101 which is 5 in decimal therefore newCapacity is 10 + 5 = 15)

3)

if (newCapacity - minCapacity < 0)
                newCapacity = minCapacity;

For example your init capacity is 1, when you add the second element into arrayList newCapacity will be equal to 1(oldCapacity) + 0 (moved to right by one bit) = 1 In this case newCapacity is less than minCapacity and elementData(array object inside arrayList) can't hold new element therefore newCapacity is equal to minCapacity

4)

if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);

Check if array size reach MAX_ARRAY_SIZE (which is Integer.MAX - 8) Why the maximum array size of ArrayList is Integer.MAX_VALUE - 8?

5) Finally it copy old values to the newArray with length 15

ImportError: No module named Image

On a system with both Python 2 and 3 installed and with pip2-installed Pillow failing to provide Image, it is possible to install PIL for Python 2 in a way that will solve ImportError: No module named Image:

easy_install-2.7 --user PIL

or

sudo easy_install-2.7 PIL

Convert a String to Modified Camel Case in Java or Title Case as is otherwise called

I used the below to solve this problem.

import org.apache.commons.lang.StringUtils;
StringUtils.capitalize(MyString);

Thanks to Ted Hopp for rightly pointing out that the question should have been TITLE CASE instead of modified CAMEL CASE.

Camel Case is usually without spaces between words.

How to iterate over a TreeMap?

Just to point out the generic way to iterate over any map:

 private <K, V> void iterateOverMap(Map<K, V> map) {
    for (Map.Entry<K, V> entry : map.entrySet()) {
        System.out.println("key ->" + entry.getKey() + ", value->" + entry.getValue());
    }
    }

SQL Server: Database stuck in "Restoring" state

this one did work :

http://social.msdn.microsoft.com/Forums/en/sqldatabaseengine/thread/8dd1b91d-3e14-4486-abe6-e3a550bfe457

I had a situation where my database showed restoring state and I couldn't run any queries and couldn't connect with our software.

What I did to get out of this situation is:

  1. Stop all SQL related services from windows services.

  2. I opened the DATA folder where the Ldf and Mdf files resides in the SQL directory, normally its like : "C:\Program Files***********\MSSQL\DATA

  3. Then I copied both the Ldf and Mdf files of the database: [db name].mdf and [db name]_log.ldf

I copied both of these files to another folder.

  1. Then I started all the SQL related services (in step 1) again from windows services.

  2. Started my MS SQL Management studio with normal login.

  3. Right click on the culprit database and hit DELETE (to delete the database at all).

  4. All the LDF and MDF files related to this database have gone from DATA folder (mentioned in step 2).

  5. Created a new database with the same name (same name of the one I deleted in step 6 - the culprit database).

  6. Then [database name]->right click -> tasks -> Take Offline.

  7. I then Copied both the files (from step 3) back to the DATA folder (step 2).

  8. [database name]->right click -> tasks -> Bring Online.

'uint32_t' identifier not found error

Boost.Config offers these typedefs for toolsets that do not provide them natively. The documentation for this specific functionality is here: Standard Integer Types

How to check if JavaScript object is JSON

You could make your own constructor for JSON parsing:

var JSONObj = function(obj) { $.extend(this, JSON.parse(obj)); }
var test = new JSONObj('{"a": "apple"}');
//{a: "apple"}

Then check instanceof to see if it needed parsing originally

test instanceof JSONObj

Bootstrap collapse animation not smooth

Padding around the collapsing div must be 0

Error:Execution failed for task ':app:dexDebug'. com.android.ide.common.process.ProcessException

For me I had multiple versions of the same library included in /app/libs. I was using Parse and I had both ParseFacebookUtilsV3-1.9.0.jar and ParseFacebookUtilsV4-1.9.0.jar.

Deleting the V3 jar solves the problem.

How to create the most compact mapping n ? isprime(n) up to a limit N?

bool isPrime(int n)
{
    // Corner cases
    if (n <= 1)  return false;
    if (n <= 3)  return true;

    // This is checked so that we can skip 
    // middle five numbers in below loop
    if (n%2 == 0 || n%3 == 0) return false;

    for (int i=5; i*i<=n; i=i+6)
        if (n%i == 0 || n%(i+2) == 0)
           return false;

    return true;
}

this is just c++ implementation of above AKS algorithm

How do I get the backtrace for all the threads in GDB?

Is there a command that does?

thread apply all where

optional parameters in SQL Server stored proc?

You can declare like this

CREATE PROCEDURE MyProcName
    @Parameter1 INT = 1,
    @Parameter2 VARCHAR (100) = 'StringValue',
    @Parameter3 VARCHAR (100) = NULL
AS

/* check for the NULL / default value (indicating nothing was passed */
if (@Parameter3 IS NULL)
BEGIN
    /* whatever code you desire for a missing parameter*/
    INSERT INTO ........
END

/* and use it in the query as so*/
SELECT *
FROM Table
WHERE Column = @Parameter

JavaScript global event mechanism

One should preserve the previously associated onerror callback as well

<script type="text/javascript">

(function() {
    var errorCallback = window.onerror;
    window.onerror = function () {
        // handle error condition
        errorCallback && errorCallback.apply(this, arguments);
    };
})();

</script>

BackgroundWorker vs background Thread

What's perplexing to me is that the visual studio designer only allows you to use BackgroundWorkers and Timers that don't actually work with the service project.

It gives you neat drag and drop controls onto your service but... don't even try deploying it. Won't work.

Services: Only use System.Timers.Timer System.Windows.Forms.Timer won't work even though it's available in the toolbox

Services: BackgroundWorkers will not work when it's running as a service Use System.Threading.ThreadPools instead or Async calls

How do I clear my local working directory in Git?

You could create a commit which contains an empty working copy.

This is a generally safe, non-destructive approach because it does not involve the use of any brute-force reset mechanisms. First you hide all managed content with git checkout empty, then you are free to manually review and remove whatever unmanaged content remains.

## create a stand-alone, tagged, empty commit
true | git mktree | xargs git commit-tree | xargs git tag empty

## clear the working copy
git checkout empty

Your working copy should now be clear of any managed content. All that remains are unmanaged files and the .git folder itself.

To re-populate your working copy...

git checkout master ## or whatever branch you will be using

If you're a forward thinking individual, you might start your repository off on the right foot by basing everything on an initial empty commit...

git init
git commit --allow-empty --allow-empty-message -m ""
git tag empty
...

There are various uses for a tagged empty worktree. My favorite at the moment is to depopulate the root under a set of git worktree subfolders.

PowerShell script to check the status of a URL

You must update the Windows PowerShell to minimum of version 4.0 for the script below to work.


[array]$SiteLinks = "http://mypage.global/Chemical/test.html"
"http://maypage2:9080/portal/site/hotpot/test.json"


foreach($url in $SiteLinks) {

   try {
      Write-host "Verifying $url" -ForegroundColor Yellow
      $checkConnection = Invoke-WebRequest -Uri $url
      if ($checkConnection.StatusCode -eq 200) {
         Write-Host "Connection Verified!" -ForegroundColor Green
      }

   } 
   catch [System.Net.WebException] {
      $exceptionMessage = $Error[0].Exception
      if ($exceptionMessage -match "503") {
         Write-Host "Server Unavaiable" -ForegroundColor Red
      }
      elseif ($exceptionMessage -match "404") {
         Write-Host "Page Not found" -ForegroundColor Red
      }


   }
}

In plain English, what does "git reset" do?

Please be aware, this is a simplified explanation intended as a first step in seeking to understand this complex functionality.

May be helpful for visual learners who want to visualise what their project state looks like after each of these commands:


For those who use Terminal with colour turned on (git config --global color.ui auto):

git reset --soft A and you will see B and C's stuff in green (staged and ready to commit)

git reset --mixed A (or git reset A) and you will see B and C's stuff in red (unstaged and ready to be staged (green) and then committed)

git reset --hard A and you will no longer see B and C's changes anywhere (will be as if they never existed)


Or for those who use a GUI program like 'Tower' or 'SourceTree'

git reset --soft A and you will see B and C's stuff in the 'staged files' area ready to commit

git reset --mixed A (or git reset A) and you will see B and C's stuff in the 'unstaged files' area ready to be moved to staged and then committed

git reset --hard A and you will no longer see B and C's changes anywhere (will be as if they never existed)

How to print pandas DataFrame without index

Similar to many of the answers above that use df.to_string(index=False), I often find it necessary to extract a single column of values in which case you can specify an individual column with .to_string using the following:

data = pd.DataFrame({'col1': np.random.randint(0, 100, 10), 
    'col2': np.random.randint(50, 100, 10), 
    'col3': np.random.randint(10, 10000, 10)})

print(data.to_string(columns=['col1'], index=False)

print(data.to_string(columns=['col1', 'col2'], index=False))

Which provides an easy to copy (and index free) output for use pasting elsewhere (Excel). Sample output:

col1  col2    
49    62    
97    97    
87    94    
85    61    
18    55

What to do about Eclipse's "No repository found containing: ..." error messages?

Install the latest STS, export its site list and import it into yours.

How can I restore the MySQL root user’s full privileges?

Just insert or update mysql.user with value Y in each column privileges.

How to fill color in a cell in VBA?

  1. Use conditional formatting instead of VBA to highlight errors.

  2. Using a VBA loop like the one you posted will take a long time to process

  3. the statement If cell.Value = "#N/A" Then will never work. If you insist on using VBA to highlight errors, try this instead.

    Sub ColorCells()

    Dim Data As Range
    Dim cell As Range
    Set currentsheet = ActiveWorkbook.Sheets("Comparison")
    Set Data = currentsheet.Range("A2:AW1048576")
    
    For Each cell In Data
    
    If IsError(cell.Value) Then
       cell.Interior.ColorIndex = 3
    End If
    Next
    
    End Sub
    
  4. Be prepared for a long wait, since the procedure loops through 51 million cells

  5. There are more efficient ways to achieve what you want to do. Update your question if you have a change of mind.

Calculating powers of integers

Well you can simply use Math.pow(a,b) as you have used earlier and just convert its value by using (int) before it. Below could be used as an example to it.

int x = (int) Math.pow(a,b);

where a and b could be double or int values as you want. This will simply convert its output to an integer value as you required.

SyntaxError: Cannot use import statement outside a module

Recently have the issue. The fix which work for me was to added this to babel.config.json in the plugins section

["@babel/plugin-transform-modules-commonjs", {
    "allowTopLevelThis": true,
    "loose": true,
    "lazy": true
  }],

I had some imported module with // and the error "cannot use import outside a module".

Bash script prints "Command Not Found" on empty lines

You can use bash -x scriptname.sh to trace it.

PHP post_max_size overrides upload_max_filesize

The normal method to send a file upload is POST, thus also post_max_size should be 16 Mb or more.

Incidentally, also memory_limit plays a role. It should be bigger than 16Mb, but since the default value is 128Mb, you won't see this problem. Example php.ini configuration:

post_max_size = 16M
upload_max_filesize = 16M
memory_limit = 128M

Change these value in php.ini if you've access to it, otherwise you can try to change them in an .htaccess file.

php_value upload_max_filesize 16M
php_value post_max_size 16M 

This will work only if the AllowOverride settings permit it. Otherwise, you've to ask to your hosting company.

Performance differences between ArrayList and LinkedList

Ignore this answer for now. The other answers, particularly that of aix, are mostly correct. Over the long term they're the way to bet. And if you have enough data (on one benchmark on one machine, it seemed to be about one million entries) ArrayList and LinkedList do currently work as advertized. However, there are some fine points that apply in the early 21st century.

Modern computer technology seems, by my testing, to give an enormous edge to arrays. Elements of an array can be shifted and copied at insane speeds. As a result arrays and ArrayList will, in most practical situations, outperform LinkedList on inserts and deletes, often dramatically. In other words, ArrayList will beat LinkedList at its own game.

The downside of ArrayList is it tends to hang onto memory space after deletions, where LinkedList gives up space as it gives up entries.

The bigger downside of arrays and ArrayList is they fragment free memory and overwork the garbage collector. As an ArrayList expands, it creates new, bigger arrays, copies the old array to the new one, and frees the old one. Memory fills with big contiguous chunks of free memory that are not big enough for the next allocation. Eventually there's no suitable space for that allocation. Even though 90% of memory is free, no individual piece is big enough to do the job. The GC will work frantically to move things around, but if it takes too long to rearrange the space, it will throw an OutOfMemoryException. If it doesn't give up, it can still slow your program way down.

The worst of it is this problem can be hard to predict. Your program will run fine one time. Then, with a bit less memory available, with no warning, it slows or stops.

LinkedList uses small, dainty bits of memory and GC's love it. It still runs fine when you're using 99% of your available memory.

So in general, use ArrayList for smaller sets of data that are not likely to have most of their contents deleted, or when you have tight control over creation and growth. (For instance, creating one ArrayList that uses 90% of memory and using it without filling it for the duration of the program is fine. Continually creating and freeing ArrayList instances that use 10% of memory will kill you.) Otherwise, go with LinkedList (or a Map of some sort if you need random access). If you have very large collections (say over 100,000 elements), no concerns about the GC, and plan lots of inserts and deletes and no random access, run a few benchmarks to see what's fastest.

How to select a single column with Entity Framework?

You could use the LINQ select clause and reference the property that relates to your Name column.

How do you push a tag to a remote repository using Git?

git push --follow-tags

This is a sane option introduced in Git 1.8.3:

git push --follow-tags

It pushes both commits and only tags that are both:

  • annotated
  • reachable (an ancestor) from the pushed commits

This is sane because:

It is for those reasons that --tags should be avoided.

Git 2.4 has added the push.followTags option to turn that flag on by default which you can set with:

git config --global push.followTags true

or by adding followTags = true to the [push] section of your ~/.gitconfig file.

"SSL certificate verify failed" using pip to install packages

 pip3 install --trusted-host pypi.org --trusted-host files.pythonhosted.org <app>

What is the dual table in Oracle?

The DUAL is special one row, one column table present by default in all Oracle databases. The owner of DUAL is SYS.

DUAL is a table automatically created by Oracle Database along with the data functions. It is always used to get the operating systems functions(like date, time, arithmetic expression., etc.)

SELECT SYSDATE from dual;  

How can I truncate a string to the first 20 words in PHP?

If you code on Laravel just use Illuminate\Support\Str

here is example

Str::words($category->publication->title, env('WORDS_COUNT_HOME'), '...')

Hope this was helpful.

Finding element's position relative to the document

You can use element.getBoundingClientRect() to retrieve element position relative to the viewport.

Then use document.documentElement.scrollTop to calculate the viewport offset.

The sum of the two will give the element position relative to the document:

element.getBoundingClientRect().top + document.documentElement.scrollTop

Calling jQuery method from onClick attribute in HTML

Don't do this!

Stay away from putting the events inline with the elements! If you don't, you're missing the point of JQuery (or one of the biggest ones at least).

The reason why it's easy to define click() handlers one way and not the other is that the other way is simply not desirable. Since you're just learning JQuery, stick to the convention. Now is not the time in your learning curve for JQuery to decide that everyone else is doing it wrong and you have a better way!

EF Code First "Invalid column name 'Discriminator'" but no inheritance

I get the error in another situation, and here are the problem and the solution:

I have 2 classes derived from a same base class named LevledItem:

public partial class Team : LeveledItem
{
   //Everything is ok here!
}
public partial class Story : LeveledItem
{
   //Everything is ok here!
}

But in their DbContext, I copied some code but forget to change one of the class name:

public class MFCTeamDbContext : DbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //Other codes here
        modelBuilder.Entity<LeveledItem>()
            .Map<Team>(m => m.Requires("Type").HasValue(ItemType.Team));
    }

public class ProductBacklogDbContext : DbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //Other codes here
        modelBuilder.Entity<LeveledItem>()
            .Map<Team>(m => m.Requires("Type").HasValue(ItemType.Story));
    }

Yes, the second Map< Team> should be Map< Story>. And it cost me half a day to figure it out!

How to remove text from a string?

Ex:-

var value="Data-123";
var removeData=value.replace("Data-","");
alert(removeData);

Hopefully this will work for you.

javax.crypto.IllegalBlockSizeException : Input length must be multiple of 16 when decrypting with padded cipher

The algorithm you are using, "AES", is a shorthand for "AES/ECB/NoPadding". What this means is that you are using the AES algorithm with 128-bit key size and block size, with the ECB mode of operation and no padding.

In other words: you are only able to encrypt data in blocks of 128 bits or 16 bytes. That's why you are getting that IllegalBlockSizeException exception.

If you want to encrypt data in sizes that are not multiple of 16 bytes, you are either going to have to use some kind of padding, or a cipher-stream. For instance, you could use CBC mode (a mode of operation that effectively transforms a block cipher into a stream cipher) by specifying "AES/CBC/NoPadding" as the algorithm, or PKCS5 padding by specifying "AES/ECB/PKCS5", which will automatically add some bytes at the end of your data in a very specific format to make the size of the ciphertext multiple of 16 bytes, and in a way that the decryption algorithm will understand that it has to ignore some data.

In any case, I strongly suggest that you stop right now what you are doing and go study some very introductory material on cryptography. For instance, check Crypto I on Coursera. You should understand very well the implications of choosing one mode or another, what are their strengths and, most importantly, their weaknesses. Without this knowledge, it is very easy to build systems which are very easy to break.


Update: based on your comments on the question, don't ever encrypt passwords when storing them at a database!!!!! You should never, ever do this. You must HASH the passwords, properly salted, which is completely different from encrypting. Really, please, don't do what you are trying to do... By encrypting the passwords, they can be decrypted. What this means is that you, as the database manager and who knows the secret key, you will be able to read every password stored in your database. Either you knew this and are doing something very, very bad, or you didn't know this, and should get shocked and stop it.

Setting up JUnit with IntelliJ IDEA

  1. Create and setup a "tests" folder
    • In the Project sidebar on the left, right-click your project and do New > Directory. Name it "test" or whatever you like.
    • Right-click the folder and choose "Mark Directory As > Test Source Root".
  2. Adding JUnit library
    • Right-click your project and choose "Open Module Settings" or hit F4. (Alternatively, File > Project Structure, Ctrl-Alt-Shift-S is probably the "right" way to do this)
    • Go to the "Libraries" group, click the little green plus (look up), and choose "From Maven...".
    • Search for "junit" -- you're looking for something like "junit:junit:4.11".
    • Check whichever boxes you want (Sources, JavaDocs) then hit OK.
    • Keep hitting OK until you're back to the code.
  3. Write your first unit test

    • Right-click on your test folder, "New > Java Class", call it whatever, e.g. MyFirstTest.
    • Write a JUnit test -- here's mine:

      import org.junit.Assert;
      import org.junit.Test;
      
      public class MyFirstTest {
          @Test
          public void firstTest() {
              Assert.assertTrue(true);
          }
      }
      
  4. Run your tests
    • Right-click on your test folder and choose "Run 'All Tests'". Presto, testo.
    • To run again, you can either hit the green "Play"-style button that appeared in the new section that popped on the bottom of your window, or you can hit the green "Play"-style button in the top bar.

Remove blue border from css custom-styled button in Chrome

Use either this:

:active {
    outline:none;
}

or this if that doesn't work:

:active {
   outline:none !important;
}

This works for me (FF and Chrome, at least). Instead of targeting the :focus state, just target the :active state and that will remove the aesthetically obtrusive highlighting in your browser when a user clicks a link. But it will still retain the focus states when a user with disabilities tabs or shift-tabs through a page. Both parties are happy. :)

Installing Bower on Ubuntu

First of all install nodejs:

sudo apt-get install nodejs

Then install npm:

sudo apt-get install npm

Then install bower:

npm install -g bower

For any of the npm package tutorial visit: https://www.npmjs.com/

Here just search the package and you can find how to install, documentation and tutorials as well.

P.S. This is just a very common solution. If your problem still exists you can try the advanced one.

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

If you wish to do this server side (without jquery), you can use lodash 4.3.0:

a = _.pickBy({ b: (someCondition? 5 : undefined) }, _.negate(_.isUndefined));

And this works using lodash 3.10.1

a = _.pick({ b: (someCondition? 5 : undefined) }, _.negate(_.isUndefined));

how to convert a string to an array in php

With explode function of php

$array=explode(" ",$str); 

This is a quick example for you http://codepad.org/Pbg4n76i

MySQL dump by query

Combining much of above here is my real practical example, selecting records based on both meterid & timestamp. I have needed this command for years. Executes really quickly.

mysqldump -uuser -ppassword main_dbo trHourly --where="MeterID =5406 AND TIMESTAMP<'2014-10-13 05:00:00'" --no-create-info --skip-extended-insert | grep  '^INSERT' > 5406.sql

Static variable inside of a function in C

A static variable inside a function has a lifespan as long as your program runs. It won't be allocated every time your function is called and deallocated when your function returns.

Commenting in a Bash script inside a multiline command

The backslash escapes the #, interpreting it as its literal character instead of a comment character.

Saving a select count(*) value to an integer (SQL Server)

[update] -- Well, my own foolishness provides the answer to this one. As it turns out, I was deleting the records from myTable before running the select COUNT statement.

How did I do that and not notice? Glad you asked. I've been testing a sql unit testing platform (tsqlunit, if you're interested) and as part of one of the tests I ran a truncate table statement, then the above. After the unit test is over everything is rolled back, and records are back in myTable. That's why I got a record count outside of my tests.

Sorry everyone...thanks for your help.

Stripping non printable characters from a string in python

Based on @Ber's answer, I suggest removing only control characters as defined in the Unicode character database categories:

import unicodedata
def filter_non_printable(s):
    return ''.join(c for c in s if not unicodedata.category(c).startswith('C'))

How to use Sublime over SSH

Use FileZilla

This applies to Mac and Windows users (I use on Mac) . I've used several of the listed answers over the years and have found that FileZilla suits my needs well when editing files on a remote host that I have SSH access to. It's also quick to setup.

  • I config a new server connection
  • connect to the server
  • right click on the file I'd like to edit and select View/Edit.

This brings up my default editor (Sublime) but it will work with any editor you have installed.

  • Once I save the file, Filezilla automatically prompts me asking if I'd like to "Upload this file back to the server", I click "Yes" and then it's updated.

Extract subset of key-value pairs from Python dictionary object?

You could try:

dict((k, bigdict[k]) for k in ('l', 'm', 'n'))

... or in Python 3 Python versions 2.7 or later (thanks to Fábio Diniz for pointing that out that it works in 2.7 too):

{k: bigdict[k] for k in ('l', 'm', 'n')}

Update: As Håvard S points out, I'm assuming that you know the keys are going to be in the dictionary - see his answer if you aren't able to make that assumption. Alternatively, as timbo points out in the comments, if you want a key that's missing in bigdict to map to None, you can do:

{k: bigdict.get(k, None) for k in ('l', 'm', 'n')}

If you're using Python 3, and you only want keys in the new dict that actually exist in the original one, you can use the fact to view objects implement some set operations:

{k: bigdict[k] for k in bigdict.keys() & {'l', 'm', 'n'}}

Python class inherits object

Is there any reason for a class declaration to inherit from object?

In Python 3, apart from compatibility between Python 2 and 3, no reason. In Python 2, many reasons.


Python 2.x story:

In Python 2.x (from 2.2 onwards) there's two styles of classes depending on the presence or absence of object as a base-class:

  1. "classic" style classes: they don't have object as a base class:

    >>> class ClassicSpam:      # no base class
    ...     pass
    >>> ClassicSpam.__bases__
    ()
    
  2. "new" style classes: they have, directly or indirectly (e.g inherit from a built-in type), object as a base class:

    >>> class NewSpam(object):           # directly inherit from object
    ...    pass
    >>> NewSpam.__bases__
    (<type 'object'>,)
    >>> class IntSpam(int):              # indirectly inherit from object...
    ...    pass
    >>> IntSpam.__bases__
    (<type 'int'>,) 
    >>> IntSpam.__bases__[0].__bases__   # ... because int inherits from object  
    (<type 'object'>,)
    

Without a doubt, when writing a class you'll always want to go for new-style classes. The perks of doing so are numerous, to list some of them:

  • Support for descriptors. Specifically, the following constructs are made possible with descriptors:

    1. classmethod: A method that receives the class as an implicit argument instead of the instance.
    2. staticmethod: A method that does not receive the implicit argument self as a first argument.
    3. properties with property: Create functions for managing the getting, setting and deleting of an attribute.
    4. __slots__: Saves memory consumptions of a class and also results in faster attribute access. Of course, it does impose limitations.
  • The __new__ static method: lets you customize how new class instances are created.

  • Method resolution order (MRO): in what order the base classes of a class will be searched when trying to resolve which method to call.

  • Related to MRO, super calls. Also see, super() considered super.

If you don't inherit from object, forget these. A more exhaustive description of the previous bullet points along with other perks of "new" style classes can be found here.

One of the downsides of new-style classes is that the class itself is more memory demanding. Unless you're creating many class objects, though, I doubt this would be an issue and it's a negative sinking in a sea of positives.


Python 3.x story:

In Python 3, things are simplified. Only new-style classes exist (referred to plainly as classes) so, the only difference in adding object is requiring you to type in 8 more characters. This:

class ClassicSpam:
    pass

is completely equivalent (apart from their name :-) to this:

class NewSpam(object):
     pass

and to this:

class Spam():
    pass

All have object in their __bases__.

>>> [object in cls.__bases__ for cls in {Spam, NewSpam, ClassicSpam}]
[True, True, True]

So, what should you do?

In Python 2: always inherit from object explicitly. Get the perks.

In Python 3: inherit from object if you are writing code that tries to be Python agnostic, that is, it needs to work both in Python 2 and in Python 3. Otherwise don't, it really makes no difference since Python inserts it for you behind the scenes.

CSS float right not working correctly

you need to wrap your text inside div and float it left while wrapper div should have height, and I've also added line height for vertical alignment

<div style="border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: gray;height:30px;">
   <div style="float:left;line-height:30px;">Contact Details</div>

    <button type="button" class="edit_button" style="float: right;">My Button</button>

</div>

also js fiddle here =) http://jsfiddle.net/xQgSm/

Changing nav-bar color after scrolling?

_x000D_
_x000D_
$(window).on('activate.bs.scrollspy', function (e,obj) {_x000D_
_x000D_
  if ((window.innerHeight + window.pageYOffset) >= document.body.offsetHeight) {_x000D_
    return;_x000D_
  }_x000D_
  _x000D_
  var isBGLight = $(obj.relatedTarget).hasClass('nav_white');_x000D_
  var isBGDark = $(obj.relatedTarget).hasClass('nav_blue');_x000D_
  $('.menu').removeClass('nav_white');_x000D_
  $('.menu').removeClass('nav_blue');_x000D_
  if(isBGDark)_x000D_
  {_x000D_
    $('.menu').addClass('nav_white');_x000D_
  }else if(isBGLight)_x000D_
  {_x000D_
    $('.menu').addClass('nav_blue');_x000D_
  }_x000D_
  /*var isScrolled = $(document).scrollTop() > 1;_x000D_
    $('.menu').toggleClass('scrolled', isScrolled);_x000D_
    $(".demos").toggleClass("demo");_x000D_
    $(".demos").toggleClass("demo1");_x000D_
  var posicionActual = $(document).scrollTop();_x000D_
  $.each($('.nav_transparent'),function(){_x000D_
    if ($(this).position().top < posicionActual){_x000D_
      $("nav.menu").removeClass("nav_white");_x000D_
      $("nav.menu").removeClass("nav_blue");_x000D_
      $("nav.menu").addClass("nav_transparent");_x000D_
      $(".demos").removeClass("demo");_x000D_
      $(".demos").addClass("demo1");_x000D_
      $(".cls").removeClass("cls2");_x000D_
      $(".cls").addClass("cls1");_x000D_
      $(".cl").removeClass("cl2");_x000D_
      $(".cl").addClass("cl1");_x000D_
      $(".hamb-bottom").css({"background-color": "#fff"});_x000D_
      $(".hamb-middle").css({"background-color": "#fff"});_x000D_
      $(".hamb-top").css({"background-color": "#fff"});_x000D_
    }_x000D_
  });_x000D_
  $.each($('.nav_blue'),function(){_x000D_
    if ($(this).position().top <= posicionActual){_x000D_
      $("nav.menu").removeClass("nav_transparent");_x000D_
      $("nav.menu").removeClass("nav_white");_x000D_
      $("nav.menu").addClass("nav_blue");_x000D_
      $(".demos").removeClass("demo1");_x000D_
      $(".demos").addClass("demo");_x000D_
      $(".cls").removeClass("cls2");_x000D_
      $(".cls").addClass("cls1");_x000D_
      $(".cl").removeClass("cl2");_x000D_
      $(".cl").addClass("cl1");_x000D_
      $(".hamb-bottom").css({"background-color": "#fff"});_x000D_
      $(".hamb-middle").css({"background-color": "#fff"});_x000D_
      $(".hamb-top").css({"background-color": "#fff"});_x000D_
    }_x000D_
  });_x000D_
  $.each($('.nav_white'),function(){_x000D_
    if ($(this).position().top <= posicionActual){_x000D_
      $("nav.menu").removeClass("nav_blue");_x000D_
      $("nav.menu").removeClass("nav_transparent");_x000D_
      $("nav.menu").addClass("nav_white");_x000D_
      $(".demos").removeClass("demo");_x000D_
      $(".demos").addClass("demo1");_x000D_
      $(".cls").removeClass("cls1");_x000D_
      $(".cls").addClass("cls2");_x000D_
      $(".cl").removeClass("cl1");_x000D_
      $(".cl").addClass("cl2");_x000D_
      $(".hamb-bottom").css({"background-color": "#4285f4"});_x000D_
      $(".hamb-middle").css({"background-color": "#4285f4"});_x000D_
      $(".hamb-top").css({"background-color": "#4285f4"});_x000D_
    }_x000D_
  });*/_x000D_
});_x000D_
$(window).on("scroll", function(){_x000D_
  if($(document).scrollTop() < 10)_x000D_
    {_x000D_
      $('.nav').removeClass('nav_white');_x000D_
      $('.nav').removeClass('nav_blue');_x000D_
      $('.nav').removeClass('nav_transparent');_x000D_
      $('.nav').addClass('nav_transparent');_x000D_
  }_x000D_
});
_x000D_
_x000D_
_x000D_

the solutions, maybe

how to display full stored procedure code?

Normally speaking you'd use a DB manager application like pgAdmin, browse to the object you're interested in, and right click your way to "script as create" or similar.

Are you trying to do this... without a management app?

SVN "Already Locked Error"

After discussing with the hosting of my SVN repository they gave me the following answer.

Apparently my repository is replicated to a remote repository using SVNSYNC. SVNSYNC has known limitations with enforcing locking across the replicated repositories and this is where the problem lies.

The locks were introduced by the AnkhSVN plugin in Visual Studio.

As the locks appears to be on the remote repository this explains why I can't actually see them using SVN commands.

The locks are being removed via the hosting company and hopefully all will soon be well again.

Simple way to measure cell execution time in ipython notebook

Use cell magic and this project on github by Phillip Cloud:

Load it by putting this at the top of your notebook or put it in your config file if you always want to load it by default:

%install_ext https://raw.github.com/cpcloud/ipython-autotime/master/autotime.py
%load_ext autotime

If loaded, every output of subsequent cell execution will include the time in min and sec it took to execute it.

How to go back to previous page if back button is pressed in WebView?

Webview in Activity,Below code worked for me , Finish the activity the after load the Url in webview.in onbackpressed it go to the previous activity

 webView = (WebView) findViewById(R.id.info_webView);
 webView.loadUrl(value);
 finish();

Python: PIP install path, what is the correct location for this and other addons?

Modules go in site-packages and executables go in your system's executable path. For your environment, this path is /usr/local/bin/.

To avoid having to deal with this, simply use easy_install, distribute or pip. These tools know which files need to go where.

SQL Server 2008: How to query all databases sizes?

SELECT
    DB.name,
    SUM(CASE WHEN type = 0 THEN MF.size * 8 / 1024 ELSE 0 END) AS DataFileSizeMB,
    SUM(CASE WHEN type = 1 THEN MF.size * 8 / 1024 ELSE 0 END) AS LogFileSizeMB
FROM
    sys.master_files MF
    JOIN sys.databases DB ON DB.database_id = MF.database_id
GROUP BY DB.name
ORDER BY DataFileSizeMB DESC

Retrieving data from a POST method in ASP.NET

The data from the request (content, inputs, files, querystring values) is all on this object HttpContext.Current.Request
To read the posted content

StreamReader reader = new StreamReader(HttpContext.Current.Request.InputStream);
string requestFromPost = reader.ReadToEnd();

To navigate through the all inputs

foreach (string key in HttpContext.Current.Request.Form.AllKeys)
{
   string value = HttpContext.Current.Request.Form[key];
}

Get Image Height and Width as integer values?

Like this :

imageCreateFromPNG($var);
//I don't know where from you get your image, here it's in the png case
// and then :
list($width, $height) = getimagesize($image);
echo $width;
echo $height;

React - changing an uncontrolled input

Set a value to 'name' property in initial state.

_x000D_
_x000D_
this.state={ name:''};
_x000D_
_x000D_
_x000D_

Init function in javascript and how it works

Self invoking anonymous function (SIAF)

Self-invoking functions runs instantly, even if DOM isn't completely ready.

jQuery document.ready vs self calling anonymous function

Compare and contrast REST and SOAP web services?

SOAP brings it’s own protocol and focuses on exposing pieces of application logic (not data) as services. SOAP exposes operations. SOAP is focused on accessing named operations, each implement some business logic through different interfaces.

Though SOAP is commonly referred to as “web services” this is a misnomer. SOAP has very little if anything to do with the Web. REST provides true “Web services” based on URIs and HTTP.

By way of illustration here are few calls and their appropriate home with commentary.

getUser(User);

This is a rest operation as you are accessing a resource (data).

switchCategory(User, OldCategory, NewCategory)

REST permits many different data formats where as SOAP only permits XML. While this may seem like it adds complexity to REST because you need to handle multiple formats, in my experience it has actually been quite beneficial. JSON usually is a better fit for data and parses much faster. REST allows better support for browser clients due to it’s support for JSON.

Java/Groovy - simple date reformatting

oldDate is not in the format of the SimpleDateFormat you are using to parse it.

Try this format: dd-MMM-yyyy - It matches what you're trying to parse.

What is the difference between json.dump() and json.dumps() in python?

The functions with an s take string parameters. The others take file streams.

Converting pixels to dp

This should give you the conversion dp to pixels:

public static int dpToPx(int dp)
{
    return (int) (dp * Resources.getSystem().getDisplayMetrics().density);
}

This should give you the conversion pixels to dp:

public static int pxToDp(int px)
{
    return (int) (px / Resources.getSystem().getDisplayMetrics().density);
}

Linq select object from list depending on objects attribute

if a.Correct is a bool flag for the correct answer then you need.

Answer answer = Answers.Single(a => a.Correct);

Form inside a table

Use the "form" attribute, if you want to save your markup:

<form method="GET" id="my_form"></form>

<table>
    <tr>
        <td>
            <input type="text" name="company" form="my_form" />
            <button type="button" form="my_form">ok</button>
        </td>
    </tr>
</table>

(*Form fields outside of the < form > tag)

how to attach url link to an image?

"How to attach url link to an image?"

You do it like this:

<a href="http://www.google.com"><img src="http://www.google.com/intl/en_ALL/images/logo.gif"/></a>

See it in action.

Getting char from string at specified index

Getting one char from string at specified index

Dim pos As Integer
Dim outStr As String
pos = 2 
Dim outStr As String
outStr = Left(Mid("abcdef", pos), 1)

outStr="b"

How to check for palindrome using Python logic

If the string has an uppercase or non-alphabetic character then the function converts all characters to lowercase and removes all non-alphabetic characters using regex finally it applies palindrome check recursively:

import re

rules = [
    lambda s: any(x.isupper() for x in s),
    lambda s: not s.isalpha()
]


def is_palindrome(s):
    if any(rule(s) for rule in rules):
        s = re.sub(r'[^\w]', '', s).lower()
    if len(s) < 2:
        return True
    if s[0] != s[-1]:
        return False
    return is_palindrome(s[1:-1])


string = 'Are we not drawn onward, we few, drawn onward to new era?'

print(is_palindrome(string))

the output is True for the input above.

When use getOne and findOne methods Spring Data JPA

The getOne methods returns only the reference from DB (lazy loading). So basically you are outside the transaction (the Transactional you have been declare in service class is not considered), and the error occur.

ESLint - "window" is not defined. How to allow global variables in package.json

Add .eslintrc in the project root.

{
  "globals": {
    "document": true,
    "foo": true,
    "window": true
  }
}

What exactly should be set in PYTHONPATH?

Here is what I learned: PYTHONPATH is a directory to add to the Python import search path "sys.path", which is made up of current dir. CWD, PYTHONPATH, standard and shared library, and customer library. For example:

% python3 -c "import sys;print(sys.path)"
['', 
'/home/username/Documents/DjangoTutorial/mySite', 
'/usr/lib/python3.6', '/usr/lib/python3.6/lib-dynload', 
'/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages']

where the first path '' denotes the current dir., the 2nd path is via

%export PYTHONPATH=/home/username/Documents/DjangoTutorial/mySite 

which can be added to ~/.bashrc to make it permanent, and the rest are Python standard and dynamic shared library plus third-party library such as django.

As said not to mess with PYTHONHOME, even setting it to '' or 'None' will cause python3 shell to stop working:

% export PYTHONHOME=''
% python3
Fatal Python error: Py_Initialize: Unable to get the locale encoding
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007f18a44ff740 (most recent call first):
Aborted (core dumped)

Note that if you start a Python script, the CWD will be the script's directory. For example:

username@bud:~/Documents/DjangoTutorial% python3 mySite/manage.py runserver
==== Printing sys.path ====
/home/username/Documents/DjangoTutorial/mySite # CWD is where manage.py resides
/usr/lib/python3.6
/usr/lib/python3.6/lib-dynload
/usr/local/lib/python3.6/dist-packages
/usr/lib/python3/dist-packages

You can also append a path to sys.path at run-time: Suppose you have a file Fibonacci.py in ~/Documents/Python directory:

username@bud:~/Documents/DjangoTutorial% python3 
>>> sys.path.append("/home/username/Documents")
>>> print(sys.path)
['', '/usr/lib/python3.6', '/usr/lib/python3.6/lib-dynload', 
'/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages', 
'/home/username/Documents']
>>> from Python import Fibonacci as fibo

or via

% PYTHONPATH=/home/username/Documents:$PYTHONPATH
% python3
>>> print(sys.path)
['', 
'/home/username/Documents', '/home/username/Documents/DjangoTutorial/mySite', 
'/usr/lib/python3.6', '/usr/lib/python3.6/lib-dynload', 
'/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages']
>>> from Python import Fibonacci as fibo

Is it worth using Python's re.compile?

Regular Expressions are compiled before being used when using the second version. If you are going to executing it many times it is definatly better to compile it first. If not compiling every time you match for one off's is fine.

How can I repeat a character in Bash?

This is the longer version of what Eliah Kagan was espousing:

while [ $(( i-- )) -gt 0 ]; do echo -n "  "; done

Of course you can use printf for that as well, but not really to my liking:

printf "%$(( i*2 ))s"

This version is Dash compatible:

until [ $(( i=i-1 )) -lt 0 ]; do echo -n "  "; done

with i being the initial number.

Can I scale a div's height proportionally to its width using CSS?

For anyone looking for a scalable solution: I wrote a small helper utility in SASS to generate responsive proportional rectangles for different breakpoints. Take a look at SASS Proportions

Hope it helps anybody!

is it possible to get the MAC address for machine using nmap

With the recent version of nmap 6.40, it will automatically show you the MAC address. example:

nmap 192.168.0.1-255

this command will scan your network from 192.168.0.1 to 255 and will display the hosts with their MAC address on your network.

in case you want to display the mac address for a single client, use this command make sure you are on root or use "sudo"

sudo nmap -Pn 192.168.0.1

this command will display the host MAC address and the open ports.

hope that is helpful.

Getting list of parameter names inside python function

locals() returns a dictionary with local names:

def func(a,b,c):
    print(locals().keys())

prints the list of parameters. If you use other local variables those will be included in this list. But you could make a copy at the beginning of your function.

How do I purge a linux mail box with huge number of emails?

Just use:

mail
d 1-15
quit

Which will delete all messages between number 1 and 15. to delete all, use the d *.

I just used this myself on ubuntu 12.04.4, and it worked like a charm.

For example:

eric@dev ~ $ mail
Heirloom Mail version 12.4 7/29/08.  Type ? for help.
"/var/spool/mail/eric": 2 messages 2 new
>N  1 Cron Daemon           Tue Jul 29 17:43  23/1016  "Cron <eric@ip-10-0-1-51> /usr/bin/php /var/www/sandbox/eric/c"
 N  2 Cron Daemon           Tue Jul 29 17:44  23/1016  "Cron <eric@ip-10-0-1-51> /usr/bin/php /var/www/sandbox/eric/c"
& d *
& quit

Then check your mail again:

eric@dev ~ $ mail
No mail for eric
eric@dev ~ $

What is tripping you up is you are using x or exit to quit which rolls back the changes during that session.

compareTo() vs. equals()

A difference is that "foo".equals((String)null) returns false while "foo".compareTo((String)null) == 0 throws a NullPointerException. So they are not always interchangeable even for Strings.

Updating records codeigniter

How to update in codeignitor?

whenever you want to update same status with multiple rows you use where_in insteam of where or if you want to change only single record can use where.

below is my code

$conditionArray = array(1, 3, 4, 6);
$this->db->where_in("ip_id", $conditionArray);
$this->db->update($this->table, array("status" => 'active'));

its working perfect.

Is there a method to generate a UUID with go language

On Linux, you can read from /proc/sys/kernel/random/uuid:

package main

import "io/ioutil"
import "fmt"

func main() {
    u, _ := ioutil.ReadFile("/proc/sys/kernel/random/uuid")
    fmt.Println(string(u))
}

No external dependencies!

$ go run uuid.go 
3ee995e3-0c96-4e30-ac1e-f7f04fd03e44

AttributeError: Module Pip has no attribute 'main'

I faced the same error while using pip on anaconda3 4.4.0 (python 3.6) on windows.

I fixed the problem by the following command:

easy_install pip==18.*  ### installing the latest version pip

Or if lower version pip required, mention the same in the command.

Or you can try installing the lower version and then upgrading the same to latest version as follow:

easy_install pip==9.0.1

easy_install --upgrade pip

PHP GuzzleHttp. How to make a post request with params?

Since Marco's answer is deprecated, you must use the following syntax (according jasonlfunk's comment) :

$client = new \GuzzleHttp\Client();
$response = $client->request('POST', 'http://www.example.com/user/create', [
    'form_params' => [
        'email' => '[email protected]',
        'name' => 'Test user',
        'password' => 'testpassword',
    ]
]);

Request with POST files

$response = $client->request('POST', 'http://www.example.com/files/post', [
    'multipart' => [
        [
            'name'     => 'file_name',
            'contents' => fopen('/path/to/file', 'r')
        ],
        [
            'name'     => 'csv_header',
            'contents' => 'First Name, Last Name, Username',
            'filename' => 'csv_header.csv'
        ]
    ]
]);

REST verbs usage with params

// PUT
$client->put('http://www.example.com/user/4', [
    'body' => [
        'email' => '[email protected]',
        'name' => 'Test user',
        'password' => 'testpassword',
    ],
    'timeout' => 5
]);

// DELETE
$client->delete('http://www.example.com/user');

Async POST data

Usefull for long server operations.

$client = new \GuzzleHttp\Client();
$promise = $client->requestAsync('POST', 'http://www.example.com/user/create', [
    'form_params' => [
        'email' => '[email protected]',
        'name' => 'Test user',
        'password' => 'testpassword',
    ]
]);
$promise->then(
    function (ResponseInterface $res) {
        echo $res->getStatusCode() . "\n";
    },
    function (RequestException $e) {
        echo $e->getMessage() . "\n";
        echo $e->getRequest()->getMethod();
    }
);

Set headers

According to documentation, you can set headers :

// Set various headers on a request
$client->request('GET', '/get', [
    'headers' => [
        'User-Agent' => 'testing/1.0',
        'Accept'     => 'application/json',
        'X-Foo'      => ['Bar', 'Baz']
    ]
]);

More information for debugging

If you want more details information, you can use debug option like this :

$client = new \GuzzleHttp\Client();
$response = $client->request('POST', 'http://www.example.com/user/create', [
    'form_params' => [
        'email' => '[email protected]',
        'name' => 'Test user',
        'password' => 'testpassword',
    ],
    // If you want more informations during request
    'debug' => true
]);

Documentation is more explicits about new possibilities.

Regular expression: zero or more occurrences of optional character /

/*

If your delimiters are slash-based, escape it:

\/*

* means "0 or more of the previous repeatable pattern", which can be a single character, a character class or a group.

How do I make case-insensitive queries on Mongodb?

  1. With Mongoose (and Node), this worked:

    • User.find({ email: /^[email protected]$/i })

    • User.find({ email: new RegExp(`^${emailVariable}$`, 'i') })

  2. In MongoDB, this worked:

Both lines are case-insensitive. The email in the DB could be [email protected] and both lines will still find the object in the DB.

Likewise, we could use /^[email protected]$/i and it would still find email: [email protected] in the DB.

Write a function that returns the longest palindrome in a given string

I was asked this question recently. Here's the solution I [eventually] came up with. I did it in JavaScript because it's pretty straightforward in that language.

The basic concept is that you walk the string looking for the smallest multi-character palindrome possible (either a two or three character one). Once you have that, expand the borders on both sides until it stops being a palindrome. If that length is longer than current longest one, store it and move along.

// This does the expanding bit.
function getsize(s, start, end) {
    var count = 0, i, j;
    for (i = start, j = end; i >= 0 && j < s.length; i--, j++) {
        if (s[i] !== s[j]) {
            return count;
        }
        count = j - i + 1; // keeps track of how big the palindrome is
    }
    return count;
}

function getBiggestPalindrome(s) {
    // test for simple cases
    if (s === null || s === '') { return 0; }
    if (s.length === 1) { return 1; }
    var longest = 1;
    for (var i = 0; i < s.length - 1; i++) {
        var c = s[i]; // the current letter
        var l; // length of the palindrome
        if (s[i] === s[i+1]) { // this is a 2 letter palindrome
            l = getsize(s, i, i+1);
        }
        if (i+2 < s.length && s[i] === s[i+2]) { // 3 letter palindrome
            l = getsize(s, i+1, i+1);
        }
        if (l > longest) { longest = l; }
    }
    return longest;
}

This could definitely be cleaned up and optimized a little more, but it should have pretty good performance in all but the worst case scenario (a string of the same letter).

How do I use setsockopt(SO_REUSEADDR)?

I think you should use SO_LINGER options (with timeout 0). In this case, you connection will close immediately after closing your program; and next restart will be able to bind again.

example:

linger lin;
lin.l_onoff = 0;
lin.l_linger = 0;
setsockopt(fd, SOL_SOCKET, SO_LINGER, (const char *)&lin, sizeof(int));

see definition: http://man7.org/linux/man-pages/man7/socket.7.html

SO_LINGER
          Sets or gets the SO_LINGER option.  The argument is a linger
          structure.

              struct linger {
                  int l_onoff;    /* linger active */
                  int l_linger;   /* how many seconds to linger for */
              };

          When enabled, a close(2) or shutdown(2) will not return until
          all queued messages for the socket have been successfully sent
          or the linger timeout has been reached.  Otherwise, the call
          returns immediately and the closing is done in the background.
          When the socket is closed as part of exit(2), it always
          lingers in the background.

More about SO_LINGER: TCP option SO_LINGER (zero) - when it's required

How to get request URL in Spring Boot RestController

Allows getting any URL on your system, not just a current one.

import org.springframework.hateoas.mvc.ControllerLinkBuilder
...
ControllerLinkBuilder linkBuilder = ControllerLinkBuilder.linkTo(methodOn(YourController.class).getSomeEntityMethod(parameterId, parameterTwoId))

URI methodUri = linkBuilder.Uri()
String methodUrl = methodUri.getPath()

Change a Git remote HEAD to point to something besides master

First, create the new branch you would like to set as your default, for example:

$>git branch main

Next, push that branch to the origin:

$>git push origin main

Now when you login to your GitHub account, you can go to your repository and choose Settings>Default Branch and choose "main."

Then, if you so choose, you can delete the master branch:

$>git push origin :master

Bad File Descriptor with Linux Socket write() Bad File Descriptor C

In general, when "Bad File Descriptor" is encountered, it means that the socket file descriptor you passed into the API is not valid, which has multiple possible reasons:

  1. The fd is already closed somewhere.
  2. The fd has a wrong value, which is inconsistent with the value obtained from socket() api

rebase in progress. Cannot commit. How to proceed or stop (abort)?

Mine was an error that popped up from BitBucket. Ran git am --skip fixed it.

How to find keys of a hash?

I wanted to use the top rated answer above

Object.prototype.keys = function () ...

However when using in conjunction with the google maps API v3, google maps is non-functional.

for (var key in h) ...

works well.

Implement a simple factory pattern with Spring 3 annotations

Why not add the interface FactoryBean to MyServiceFactory (to tell Spring that it's a factory), add a register(String service, MyService instance) then, have each of the services call:

@Autowired
MyServiceFactory serviceFactory;

@PostConstruct
public void postConstruct() {
    serviceFactory.register(myName, this);
}

This way, you can separate each service provider into modules if necessary, and Spring will automagically pick up any deployed and available service providers.

Can't get Gulp to run: cannot find module 'gulp-util'

If you have a package.json, you can install all the current project dependencies using:

npm install

Can I get the name of the current controller in the view?

controller_path holds the path of the controller used to serve the current view. (ie: admin/settings).

and

controller_name holds the name of the controller used to serve the current view. (ie: settings).

pandas unique values multiple columns

here's another way


import numpy as np
set(np.concatenate(df.values))

Converting array to list in Java

In Java 8, you can use streams:

int[] spam = new int[] { 1, 2, 3 };
Arrays.stream(spam)
      .boxed()
      .collect(Collectors.toList());

Unix command to check the filesize

Here's yet another option to add to the mix:

$ du -b file.txt

That is: estimate file space usage of file.txt in bytes.

How could I create a function with a completion handler in Swift?

I'm a little confused about custom made completion handlers. In your example:

Say you have a download function to download a file from network,and want to be notified when download task has finished.

typealias CompletionHandler = (success:Bool) -> Void

func downloadFileFromURL(url: NSURL,completionHandler: CompletionHandler) {

    // download code.

    let flag = true // true if download succeed,false otherwise

    completionHandler(success: flag)
}

Your // download code will still be ran asynchronously. Why wouldn't the code go straight to your let flag = true and completion Handler(success: flag) without waiting for your download code to be finished?

How to Implement Custom Table View Section Headers and Footers with Storyboard

What about a solution where the header is based on a view array :

class myViewController: UIViewController {
    var header: [UILabel] = myStringArray.map { (thisTitle: String) -> UILabel in
        let headerView = UILabel()
            headerView.text = thisTitle
    return(headerView)
}

Next in the delegate :

extension myViewController: UITableViewDelegate {
    func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
        return(header[section])
    }
}

Open URL in new window with JavaScript

Use window.open():

<a onclick="window.open(document.URL, '_blank', 'location=yes,height=570,width=520,scrollbars=yes,status=yes');">
  Share Page
</a>

This will create a link titled Share Page which opens the current url in a new window with a height of 570 and width of 520.

Getting file size in Python?

os.path.getsize(path)

Return the size, in bytes, of path. Raise os.error if the file does not exist or is inaccessible.

java.lang.ClassNotFoundException: org.eclipse.core.runtime.adaptor.EclipseStarter

You might be launching your application from a Product file which is not linked to the plugin file. Reset your workspace and launch using the MANIFEST.MF > Overview > Testing > Launch.

How to check if String is null

You can check with null or Number.

First, add a reference to Microsoft.VisualBasic in your application.

Then, use the following code:

bool b = Microsoft.VisualBasic.Information.IsNumeric("null");
bool c = Microsoft.VisualBasic.Information.IsNumeric("abc");

In the above, b and c should both be false.

How can I check if a value is a json object?

var checkJSON = function(m) {

   if (typeof m == 'object') { 
      try{ m = JSON.stringify(m); }
      catch(err) { return false; } }

   if (typeof m == 'string') {
      try{ m = JSON.parse(m); }
      catch (err) { return false; } }

   if (typeof m != 'object') { return false; }
   return true;

};


checkJSON(JSON.parse('{}'));      //true
checkJSON(JSON.parse('{"a":0}')); //true
checkJSON('{}');                  //true
checkJSON('{"a":0}');             //true
checkJSON('x');                   //false
checkJSON('');                    //false
checkJSON();                      //false

How to delete columns that contain ONLY NAs?

Another option is the janitor package:

df <- remove_empty_cols(df)

https://github.com/sfirke/janitor

iOS start Background Thread

Enable NSZombieEnabled to know which object is being released and then accessed. Then check if the getResultSetFromDB: has anything to do with that. Also check if docids has anything inside and if it is being retained.

This way you can be sure there is nothing wrong.

C# DataTable.Select() - How do I format the filter criteria to include null?

try this:

var result = from r in myDataTable.AsEnumerable()  
            where r.Field<string>("Name") != "n/a" &&  
                  r.Field<string>("Name") != "" select r;  
DataTable dtResult = result.CopyToDataTable();  

Placing an image to the top right corner - CSS

You can just do it like this:

#content {
    position: relative;
}
#content img {
    position: absolute;
    top: 0px;
    right: 0px;
}

<div id="content">
    <img src="images/ribbon.png" class="ribbon"/>
    <div>some text...</div>
</div>

postgresql: INSERT INTO ... (SELECT * ...)

As Henrik wrote you can use dblink to connect remote database and fetch result. For example:

psql dbtest
CREATE TABLE tblB (id serial, time integer);
INSERT INTO tblB (time) VALUES (5000), (2000);

psql postgres
CREATE TABLE tblA (id serial, time integer);

INSERT INTO tblA
    SELECT id, time 
    FROM dblink('dbname=dbtest', 'SELECT id, time FROM tblB')
    AS t(id integer, time integer)
    WHERE time > 1000;

TABLE tblA;
 id | time 
----+------
  1 | 5000
  2 | 2000
(2 rows)

PostgreSQL has record pseudo-type (only for function's argument or result type), which allows you query data from another (unknown) table.

Edit:

You can make it as prepared statement if you want and it works as well:

PREPARE migrate_data (integer) AS
INSERT INTO tblA
    SELECT id, time
    FROM dblink('dbname=dbtest', 'SELECT id, time FROM tblB')
    AS t(id integer, time integer)
    WHERE time > $1;

EXECUTE migrate_data(1000);
-- DEALLOCATE migrate_data;

Edit (yeah, another):

I just saw your revised question (closed as duplicate, or just very similar to this).

If my understanding is correct (postgres has tbla and dbtest has tblb and you want remote insert with local select, not remote select with local insert as above):

psql dbtest

SELECT dblink_exec
(
    'dbname=postgres',
    'INSERT INTO tbla
        SELECT id, time
        FROM dblink
        (
            ''dbname=dbtest'',
            ''SELECT id, time FROM tblb''
        )
        AS t(id integer, time integer)
        WHERE time > 1000;'
);

I don't like that nested dblink, but AFAIK I can't reference to tblB in dblink_exec body. Use LIMIT to specify top 20 rows, but I think you need to sort them using ORDER BY clause first.

How do I set up a simple delegate to communicate between two view controllers?

Simple example...

Let's say the child view controller has a UISlider and we want to pass the value of the slider back to the parent via a delegate.

In the child view controller's header file, declare the delegate type and its methods:

ChildViewController.h

#import <UIKit/UIKit.h>

// 1. Forward declaration of ChildViewControllerDelegate - this just declares
// that a ChildViewControllerDelegate type exists so that we can use it
// later.
@protocol ChildViewControllerDelegate;

// 2. Declaration of the view controller class, as usual
@interface ChildViewController : UIViewController

// Delegate properties should always be weak references
// See http://stackoverflow.com/a/4796131/263871 for the rationale
// (Tip: If you're not using ARC, use `assign` instead of `weak`)
@property (nonatomic, weak) id<ChildViewControllerDelegate> delegate;

// A simple IBAction method that I'll associate with a close button in
// the UI. We'll call the delegate's childViewController:didChooseValue: 
// method inside this handler.
- (IBAction)handleCloseButton:(id)sender;

@end

// 3. Definition of the delegate's interface
@protocol ChildViewControllerDelegate <NSObject>

- (void)childViewController:(ChildViewController*)viewController 
             didChooseValue:(CGFloat)value;

@end

In the child view controller's implementation, call the delegate methods as required.

ChildViewController.m

#import "ChildViewController.h"

@implementation ChildViewController

- (void)handleCloseButton:(id)sender {
    // Xcode will complain if we access a weak property more than 
    // once here, since it could in theory be nilled between accesses
    // leading to unpredictable results. So we'll start by taking
    // a local, strong reference to the delegate.
    id<ChildViewControllerDelegate> strongDelegate = self.delegate;

    // Our delegate method is optional, so we should 
    // check that the delegate implements it
    if ([strongDelegate respondsToSelector:@selector(childViewController:didChooseValue:)]) {
        [strongDelegate childViewController:self didChooseValue:self.slider.value];
    }
}

@end

In the parent view controller's header file, declare that it implements the ChildViewControllerDelegate protocol.

RootViewController.h

#import <UIKit/UIKit.h>
#import "ChildViewController.h"

@interface RootViewController : UITableViewController <ChildViewControllerDelegate>

@end

In the parent view controller's implementation, implement the delegate methods appropriately.

RootViewController.m

#import "RootViewController.h"

@implementation RootViewController

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    ChildViewController *detailViewController = [[ChildViewController alloc] init];
    // Assign self as the delegate for the child view controller
    detailViewController.delegate = self;
    [self.navigationController pushViewController:detailViewController animated:YES];
}

// Implement the delegate methods for ChildViewControllerDelegate
- (void)childViewController:(ChildViewController *)viewController didChooseValue:(CGFloat)value {

    // Do something with value...

    // ...then dismiss the child view controller
    [self.navigationController popViewControllerAnimated:YES];
}

@end

Hope this helps!

Any way to make a WPF textblock selectable?

There is an alternative solution that might be adaptable to the RichTextBox oultined in this blog post - it used a trigger to swap out the control template when the use hovers over the control - should help with performance

What is the difference between .py and .pyc files?

.pyc contain the compiled bytecode of Python source files. The Python interpreter loads .pyc files before .py files, so if they're present, it can save some time by not having to re-compile the Python source code. You can get rid of them if you want, but they don't cause problems, they're not big, and they may save some time when running programs.

Best way to save a trained model in PyTorch?

It depends on what you want to do.

Case # 1: Save the model to use it yourself for inference: You save the model, you restore it, and then you change the model to evaluation mode. This is done because you usually have BatchNorm and Dropout layers that by default are in train mode on construction:

torch.save(model.state_dict(), filepath)

#Later to restore:
model.load_state_dict(torch.load(filepath))
model.eval()

Case # 2: Save model to resume training later: If you need to keep training the model that you are about to save, you need to save more than just the model. You also need to save the state of the optimizer, epochs, score, etc. You would do it like this:

state = {
    'epoch': epoch,
    'state_dict': model.state_dict(),
    'optimizer': optimizer.state_dict(),
    ...
}
torch.save(state, filepath)

To resume training you would do things like: state = torch.load(filepath), and then, to restore the state of each individual object, something like this:

model.load_state_dict(state['state_dict'])
optimizer.load_state_dict(state['optimizer'])

Since you are resuming training, DO NOT call model.eval() once you restore the states when loading.

Case # 3: Model to be used by someone else with no access to your code: In Tensorflow you can create a .pb file that defines both the architecture and the weights of the model. This is very handy, specially when using Tensorflow serve. The equivalent way to do this in Pytorch would be:

torch.save(model, filepath)

# Then later:
model = torch.load(filepath)

This way is still not bullet proof and since pytorch is still undergoing a lot of changes, I wouldn't recommend it.

How do I perform a Perl substitution on a string while keeping the original?

If you write Perl with use strict;, then you'll find that the one line syntax isn't valid, even when declared.

With:

my ($newstring = $oldstring) =~ s/foo/bar/;

You get:

Can't declare scalar assignment in "my" at script.pl line 7, near ") =~"
Execution of script.pl aborted due to compilation errors.

Instead, the syntax that you have been using, while a line longer, is the syntactically correct way to do it with use strict;. For me, using use strict; is just a habit now. I do it automatically. Everyone should.

#!/usr/bin/env perl -wT

use strict;

my $oldstring = "foo one foo two foo three";
my $newstring = $oldstring;
$newstring =~ s/foo/bar/g;

print "$oldstring","\n";
print "$newstring","\n";

How can I disable selected attribute from select2() dropdown Jquery?

The below code also works fine for Select2 3.x

For Enable Select Box:

$('#foo').select2('enable');

For Disable Select Box:

$('#foo').select2('disable');

jsfiddle: http://jsfiddle.net/DcunN/

Installing mysql-python on Centos

Step 1 - Install package

# yum install MySQL-python
Loaded plugins: auto-update-debuginfo, langpacks, presto, refresh-packagekit
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package MySQL-python.i686 0:1.2.3-3.fc15 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package              Arch         Version                 Repository      Size
================================================================================
Installing:
 MySQL-python         i686         1.2.3-3.fc15            fedora          78 k

Transaction Summary
================================================================================
Install       1 Package(s)

Total download size: 78 k
Installed size: 220 k
Is this ok [y/N]: y
Downloading Packages:
Setting up and reading Presto delta metadata
Processing delta metadata
Package(s) data still to download: 78 k
MySQL-python-1.2.3-3.fc15.i686.rpm                       |  78 kB     00:00     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : MySQL-python-1.2.3-3.fc15.i686                               1/1 

Installed:
  MySQL-python.i686 0:1.2.3-3.fc15                                              

Complete!

Step 2 - Test working

import MySQLdb
db = MySQLdb.connect("localhost","myusername","mypassword","mydb" )
cursor = db.cursor()
cursor.execute("SELECT VERSION()")
data = cursor.fetchone()    
print "Database version : %s " % data    
db.close()

Ouput:

Database version : 5.5.20 

Javascript button to insert a big black dot (•) into a html textarea

Just access the element and append it to the value.

<input
     type="button" 
     onclick="document.getElementById('myTextArea').value += '•'" 
     value="Add •">

See a live demo.

For the sake of keeping things simple, I haven't written unobtrusive JS. For a production system you should.

Also it needs to be a UTF8 character.

Browsers generally submit forms using the encoding they received the page in. Serve your page as UTF-8 if you want UTF-8 data submitted back.

Initialize empty vector in structure - c++

The default vector constructor will create an empty vector. As such, you should be able to write:

struct user r = { string(), vector<unsigned char>() };

Note, I've also used the default string constructor instead of "".

You might want to consider making user a class and adding a default constructor that does this for you:

class User {
  User() {}
  string username;
  vector<unsigned char> password;
};

Then just writing:

User r;

Will result in a correctly initialized user.

Detecting installed programs via registry

In addition to all the registry keys mentioned above, you may also have to look at HKEY_CURRENT_USER\Software\Microsoft\Installer\Products for programs installed just for the current user.

"No Content-Security-Policy meta tag found." error in my phonegap application

There are errors in your meta tag.

Yours:

<meta http-equiv="Content-Security-Policy" content="default-src *; style-src 'self' 'unsafe-inline'; script-src: 'self' 'unsafe-inline' 'unsafe-eval'>

Corrected:

<meta http-equiv="Content-Security-Policy" content="default-src *; style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline' 'unsafe-eval'"/>

Note the colon after "script-src", and the end double-quote of the meta tag.

SQL Stored Procedure set variables using SELECT

One advantage your current approach does have is that it will raise an error if multiple rows are returned by the predicate. To reproduce that you can use.

SELECT @currentTerm = currentterm,
       @termID = termid,
       @endDate = enddate
FROM   table1
WHERE  iscurrent = 1

IF( @@ROWCOUNT <> 1 )
  BEGIN
      RAISERROR ('Unexpected number of matching rows',
                 16,
                 1)

      RETURN
  END  

Convert an image to grayscale in HTML/CSS

You don't need use so many prefixes for full use, because if you choose prefix for old firefox, you don't need use prefix for new firefox.

So for full use, enough use this code:

img.grayscale {
    filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0\'/></filter></svg>#grayscale"); /* Firefox 10+, Firefox on Android */
    filter: gray; /* IE6-9 */
    -webkit-filter: grayscale(100%); /* Chrome 19+, Safari 6+, Safari 6+ iOS */
}

img.grayscale.disabled {
    filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'1 0 0 0 0, 0 1 0 0 0, 0 0 1 0 0, 0 0 0 1 0\'/></filter></svg>#grayscale");
    filter: none;
    -webkit-filter: grayscale(0%);
}

Set QLineEdit to accept only numbers

The best is QSpinBox.

And for a double value use QDoubleSpinBox.

QSpinBox myInt;
myInt.setMinimum(-5);
myInt.setMaximum(5);
myInt.setSingleStep(1);// Will increment the current value with 1 (if you use up arrow key) (if you use down arrow key => -1)
myInt.setValue(2);// Default/begining value
myInt.value();// Get the current value
//connect(&myInt, SIGNAL(valueChanged(int)), this, SLOT(myValueChanged(int)));

webpack command not working

Installing webpack with -g option installs webpack in a folder in

C:\Users\<.profileusername.>\AppData\Roaming\npm\node_modules

same with webpack-cli and webpack-dev-server

Outside the global node_modules a link is created for webpack to be run from commandline

C:\Users\<.profileusername.>\AppData\Roaming\npm

to make this work locally, I did the following

  1. renamed the webpack folder in global node_modules to _old
  2. installed webpack locally within project
  3. edited the command link webpack.cmd and pointed the webpack.js to look into my local node_modules folder within my application

Problem with this approach is you'd have to maintain links for each project you have. Theres no other way since you are using the command line editor to run webpack command when installing with a -g option.

So if you had proj1, proj2 and proj3 all with their local node_modules and local webpack installed( not using -g when installing), then you'd have to create non-generic link names instead of just webpack.

example here would be to create webpack_proj1.cmd, webpack_proj2.cmd and webpack_proj3.cmd and in each cmd follow point 2 and 3 above

PS: dont forget to update your package.json with these changes or else you'll get errors as it won't find webpack command

Build error: You must add a reference to System.Runtime

I needed to download and install the Windows 8.0 (and not 8.1) SDK to make the error disappear on my TeamCity server.

https://developer.microsoft.com/en-us/windows/downloads/windows-8-sdk

What are the nuances of scope prototypal / prototypical inheritance in AngularJS?

Quick answer:
A child scope normally prototypically inherits from its parent scope, but not always. One exception to this rule is a directive with scope: { ... } -- this creates an "isolate" scope that does not prototypically inherit. This construct is often used when creating a "reusable component" directive.

As for the nuances, scope inheritance is normally straightfoward... until you need 2-way data binding (i.e., form elements, ng-model) in the child scope. Ng-repeat, ng-switch, and ng-include can trip you up if you try to bind to a primitive (e.g., number, string, boolean) in the parent scope from inside the child scope. It doesn't work the way most people expect it should work. The child scope gets its own property that hides/shadows the parent property of the same name. Your workarounds are

  1. define objects in the parent for your model, then reference a property of that object in the child: parentObj.someProp
  2. use $parent.parentScopeProperty (not always possible, but easier than 1. where possible)
  3. define a function on the parent scope, and call it from the child (not always possible)

New AngularJS developers often do not realize that ng-repeat, ng-switch, ng-view, ng-include and ng-if all create new child scopes, so the problem often shows up when these directives are involved. (See this example for a quick illustration of the problem.)

This issue with primitives can be easily avoided by following the "best practice" of always have a '.' in your ng-models – watch 3 minutes worth. Misko demonstrates the primitive binding issue with ng-switch.

Having a '.' in your models will ensure that prototypal inheritance is in play. So, use

<input type="text" ng-model="someObj.prop1">

<!--rather than
<input type="text" ng-model="prop1">`
-->


L-o-n-g answer:

JavaScript Prototypal Inheritance

Also placed on the AngularJS wiki: https://github.com/angular/angular.js/wiki/Understanding-Scopes

It is important to first have a solid understanding of prototypal inheritance, especially if you are coming from a server-side background and you are more familiar with class-ical inheritance. So let's review that first.

Suppose parentScope has properties aString, aNumber, anArray, anObject, and aFunction. If childScope prototypically inherits from parentScope, we have:

prototypal inheritance

(Note that to save space, I show the anArray object as a single blue object with its three values, rather than an single blue object with three separate gray literals.)

If we try to access a property defined on the parentScope from the child scope, JavaScript will first look in the child scope, not find the property, then look in the inherited scope, and find the property. (If it didn't find the property in the parentScope, it would continue up the prototype chain... all the way up to the root scope). So, these are all true:

childScope.aString === 'parent string'
childScope.anArray[1] === 20
childScope.anObject.property1 === 'parent prop1'
childScope.aFunction() === 'parent output'

Suppose we then do this:

childScope.aString = 'child string'

The prototype chain is not consulted, and a new aString property is added to the childScope. This new property hides/shadows the parentScope property with the same name. This will become very important when we discuss ng-repeat and ng-include below.

property hiding

Suppose we then do this:

childScope.anArray[1] = '22'
childScope.anObject.property1 = 'child prop1'

The prototype chain is consulted because the objects (anArray and anObject) are not found in the childScope. The objects are found in the parentScope, and the property values are updated on the original objects. No new properties are added to the childScope; no new objects are created. (Note that in JavaScript arrays and functions are also objects.)

follow the prototype chain

Suppose we then do this:

childScope.anArray = [100, 555]
childScope.anObject = { name: 'Mark', country: 'USA' }

The prototype chain is not consulted, and child scope gets two new object properties that hide/shadow the parentScope object properties with the same names.

more property hiding

Takeaways:

  • If we read childScope.propertyX, and childScope has propertyX, then the prototype chain is not consulted.
  • If we set childScope.propertyX, the prototype chain is not consulted.

One last scenario:

delete childScope.anArray
childScope.anArray[1] === 22  // true

We deleted the childScope property first, then when we try to access the property again, the prototype chain is consulted.

after removing a child property


Angular Scope Inheritance

The contenders:

  • The following create new scopes, and inherit prototypically: ng-repeat, ng-include, ng-switch, ng-controller, directive with scope: true, directive with transclude: true.
  • The following creates a new scope which does not inherit prototypically: directive with scope: { ... }. This creates an "isolate" scope instead.

Note, by default, directives do not create new scope -- i.e., the default is scope: false.

ng-include

Suppose we have in our controller:

$scope.myPrimitive = 50;
$scope.myObject    = {aNumber: 11};

And in our HTML:

<script type="text/ng-template" id="/tpl1.html">
<input ng-model="myPrimitive">
</script>
<div ng-include src="'/tpl1.html'"></div>

<script type="text/ng-template" id="/tpl2.html">
<input ng-model="myObject.aNumber">
</script>
<div ng-include src="'/tpl2.html'"></div>

Each ng-include generates a new child scope, which prototypically inherits from the parent scope.

ng-include child scopes

Typing (say, "77") into the first input textbox causes the child scope to get a new myPrimitive scope property that hides/shadows the parent scope property of the same name. This is probably not what you want/expect.

ng-include with a primitive

Typing (say, "99") into the second input textbox does not result in a new child property. Because tpl2.html binds the model to an object property, prototypal inheritance kicks in when the ngModel looks for object myObject -- it finds it in the parent scope.

ng-include with an object

We can rewrite the first template to use $parent, if we don't want to change our model from a primitive to an object:

<input ng-model="$parent.myPrimitive">

Typing (say, "22") into this input textbox does not result in a new child property. The model is now bound to a property of the parent scope (because $parent is a child scope property that references the parent scope).

ng-include with $parent

For all scopes (prototypal or not), Angular always tracks a parent-child relationship (i.e., a hierarchy), via scope properties $parent, $$childHead and $$childTail. I normally don't show these scope properties in the diagrams.

For scenarios where form elements are not involved, another solution is to define a function on the parent scope to modify the primitive. Then ensure the child always calls this function, which will be available to the child scope due to prototypal inheritance. E.g.,

// in the parent scope
$scope.setMyPrimitive = function(value) {
     $scope.myPrimitive = value;
}

Here is a sample fiddle that uses this "parent function" approach. (The fiddle was written as part of this answer: https://stackoverflow.com/a/14104318/215945.)

See also https://stackoverflow.com/a/13782671/215945 and https://github.com/angular/angular.js/issues/1267.

ng-switch

ng-switch scope inheritance works just like ng-include. So if you need 2-way data binding to a primitive in the parent scope, use $parent, or change the model to be an object and then bind to a property of that object. This will avoid child scope hiding/shadowing of parent scope properties.

See also AngularJS, bind scope of a switch-case?

ng-repeat

Ng-repeat works a little differently. Suppose we have in our controller:

$scope.myArrayOfPrimitives = [ 11, 22 ];
$scope.myArrayOfObjects    = [{num: 101}, {num: 202}]

And in our HTML:

<ul><li ng-repeat="num in myArrayOfPrimitives">
       <input ng-model="num">
    </li>
<ul>
<ul><li ng-repeat="obj in myArrayOfObjects">
       <input ng-model="obj.num">
    </li>
<ul>

For each item/iteration, ng-repeat creates a new scope, which prototypically inherits from the parent scope, but it also assigns the item's value to a new property on the new child scope. (The name of the new property is the loop variable's name.) Here's what the Angular source code for ng-repeat actually is:

childScope = scope.$new();  // child scope prototypically inherits from parent scope
...
childScope[valueIdent] = value;  // creates a new childScope property

If item is a primitive (as in myArrayOfPrimitives), essentially a copy of the value is assigned to the new child scope property. Changing the child scope property's value (i.e., using ng-model, hence child scope num) does not change the array the parent scope references. So in the first ng-repeat above, each child scope gets a num property that is independent of the myArrayOfPrimitives array:

ng-repeat with primitives

This ng-repeat will not work (like you want/expect it to). Typing into the textboxes changes the values in the gray boxes, which are only visible in the child scopes. What we want is for the inputs to affect the myArrayOfPrimitives array, not a child scope primitive property. To accomplish this, we need to change the model to be an array of objects.

So, if item is an object, a reference to the original object (not a copy) is assigned to the new child scope property. Changing the child scope property's value (i.e., using ng-model, hence obj.num) does change the object the parent scope references. So in the second ng-repeat above, we have:

ng-repeat with objects

(I colored one line gray just so that it is clear where it is going.)

This works as expected. Typing into the textboxes changes the values in the gray boxes, which are visible to both the child and parent scopes.

See also Difficulty with ng-model, ng-repeat, and inputs and https://stackoverflow.com/a/13782671/215945

ng-controller

Nesting controllers using ng-controller results in normal prototypal inheritance, just like ng-include and ng-switch, so the same techniques apply. However, "it is considered bad form for two controllers to share information via $scope inheritance" -- http://onehungrymind.com/angularjs-sticky-notes-pt-1-architecture/ A service should be used to share data between controllers instead.

(If you really want to share data via controllers scope inheritance, there is nothing you need to do. The child scope will have access to all of the parent scope properties. See also Controller load order differs when loading or navigating)

directives

  1. default (scope: false) - the directive does not create a new scope, so there is no inheritance here. This is easy, but also dangerous because, e.g., a directive might think it is creating a new property on the scope, when in fact it is clobbering an existing property. This is not a good choice for writing directives that are intended as reusable components.
  2. scope: true - the directive creates a new child scope that prototypically inherits from the parent scope. If more than one directive (on the same DOM element) requests a new scope, only one new child scope is created. Since we have "normal" prototypal inheritance, this is like ng-include and ng-switch, so be wary of 2-way data binding to parent scope primitives, and child scope hiding/shadowing of parent scope properties.
  3. scope: { ... } - the directive creates a new isolate/isolated scope. It does not prototypically inherit. This is usually your best choice when creating reusable components, since the directive cannot accidentally read or modify the parent scope. However, such directives often need access to a few parent scope properties. The object hash is used to set up two-way binding (using '=') or one-way binding (using '@') between the parent scope and the isolate scope. There is also '&' to bind to parent scope expressions. So, these all create local scope properties that are derived from the parent scope. Note that attributes are used to help set up the binding -- you can't just reference parent scope property names in the object hash, you have to use an attribute. E.g., this won't work if you want to bind to parent property parentProp in the isolated scope: <div my-directive> and scope: { localProp: '@parentProp' }. An attribute must be used to specify each parent property that the directive wants to bind to: <div my-directive the-Parent-Prop=parentProp> and scope: { localProp: '@theParentProp' }.
    Isolate scope's __proto__ references Object. Isolate scope's $parent references the parent scope, so although it is isolated and doesn't inherit prototypically from the parent scope, it is still a child scope.
    For the picture below we have
    <my-directive interpolated="{{parentProp1}}" twowayBinding="parentProp2"> and
    scope: { interpolatedProp: '@interpolated', twowayBindingProp: '=twowayBinding' }
    Also, assume the directive does this in its linking function: scope.someIsolateProp = "I'm isolated"
    isolated scope
    For more information on isolate scopes see http://onehungrymind.com/angularjs-sticky-notes-pt-2-isolated-scope/
  4. transclude: true - the directive creates a new "transcluded" child scope, which prototypically inherits from the parent scope. The transcluded and the isolated scope (if any) are siblings -- the $parent property of each scope references the same parent scope. When a transcluded and an isolate scope both exist, isolate scope property $$nextSibling will reference the transcluded scope. I'm not aware of any nuances with the transcluded scope.
    For the picture below, assume the same directive as above with this addition: transclude: true
    transcluded scope

This fiddle has a showScope() function that can be used to examine an isolate and transcluded scope. See the instructions in the comments in the fiddle.


Summary

There are four types of scopes:

  1. normal prototypal scope inheritance -- ng-include, ng-switch, ng-controller, directive with scope: true
  2. normal prototypal scope inheritance with a copy/assignment -- ng-repeat. Each iteration of ng-repeat creates a new child scope, and that new child scope always gets a new property.
  3. isolate scope -- directive with scope: {...}. This one is not prototypal, but '=', '@', and '&' provide a mechanism to access parent scope properties, via attributes.
  4. transcluded scope -- directive with transclude: true. This one is also normal prototypal scope inheritance, but it is also a sibling of any isolate scope.

For all scopes (prototypal or not), Angular always tracks a parent-child relationship (i.e., a hierarchy), via properties $parent and $$childHead and $$childTail.

Diagrams were generated with "*.dot" files, which are on github. Tim Caswell's "Learning JavaScript with Object Graphs" was the inspiration for using GraphViz for the diagrams.

How to access JSON Object name/value?

I think you should mention dataType: 'json' in ajax config and to access that value:

data[0].name

Go build: "Cannot find package" (even though GOPATH is set)

Have you tried adding the absolute directory of go to your 'path'?

export PATH=$PATH:/directory/to/go/

Ripple effect on Android Lollipop CardView

I managed to get the ripple effect on the cardview by :

<android.support.v7.widget.CardView 
    xmlns:card_view="http://schemas.android.com/apk/res-auto" 
    android:clickable="true" 
    android:foreground="@drawable/custom_bg"/>

and for the custom_bg that you can see in above code, you have to define a xml file for both lollipop(in drawable-v21 package) and pre-lollipop(in drawable package) devices. for custom_bg in drawable-v21 package the code is:

<ripple 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:color="?android:attr/colorControlHighlight">
<item
    android:id="@android:id/mask"
    android:drawable="@android:color/white"/>
</ripple>

for custom_bg in the drawable package, code is:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

<item android:state_pressed="true">
    <shape>
        <solid android:color="@color/colorHighlight"></solid>
    </shape>
</item>
<item>
    <shape>
        <solid android:color="@color/navigation_drawer_background"></solid>
    </shape>
</item>
</selector>

so on pre-lollipop devices you will have a solid click effect and on lollipop devices you will have a ripple effect on the cardview.

What are bitwise shift (bit-shift) operators and how do they work?

Let's say we have a single byte:

0110110

Applying a single left bitshift gets us:

1101100

The leftmost zero was shifted out of the byte, and a new zero was appended to the right end of the byte.

The bits don't rollover; they are discarded. That means if you left shift 1101100 and then right shift it, you won't get the same result back.

Shifting left by N is equivalent to multiplying by 2N.

Shifting right by N is (if you are using ones' complement) is the equivalent of dividing by 2N and rounding to zero.

Bitshifting can be used for insanely fast multiplication and division, provided you are working with a power of 2. Almost all low-level graphics routines use bitshifting.

For example, way back in the olden days, we used mode 13h (320x200 256 colors) for games. In Mode 13h, the video memory was laid out sequentially per pixel. That meant to calculate the location for a pixel, you would use the following math:

memoryOffset = (row * 320) + column

Now, back in that day and age, speed was critical, so we would use bitshifts to do this operation.

However, 320 is not a power of two, so to get around this we have to find out what is a power of two that added together makes 320:

(row * 320) = (row * 256) + (row * 64)

Now we can convert that into left shifts:

(row * 320) = (row << 8) + (row << 6)

For a final result of:

memoryOffset = ((row << 8) + (row << 6)) + column

Now we get the same offset as before, except instead of an expensive multiplication operation, we use the two bitshifts...in x86 it would be something like this (note, it's been forever since I've done assembly (editor's note: corrected a couple mistakes and added a 32-bit example)):

mov ax, 320; 2 cycles
mul word [row]; 22 CPU Cycles
mov di,ax; 2 cycles
add di, [column]; 2 cycles
; di = [row]*320 + [column]

; 16-bit addressing mode limitations:
; [di] is a valid addressing mode, but [ax] isn't, otherwise we could skip the last mov

Total: 28 cycles on whatever ancient CPU had these timings.

Vrs

mov ax, [row]; 2 cycles
mov di, ax; 2
shl ax, 6;  2
shl di, 8;  2
add di, ax; 2    (320 = 256+64)
add di, [column]; 2
; di = [row]*(256+64) + [column]

12 cycles on the same ancient CPU.

Yes, we would work this hard to shave off 16 CPU cycles.

In 32 or 64-bit mode, both versions get a lot shorter and faster. Modern out-of-order execution CPUs like Intel Skylake (see http://agner.org/optimize/) have very fast hardware multiply (low latency and high throughput), so the gain is much smaller. AMD Bulldozer-family is a bit slower, especially for 64-bit multiply. On Intel CPUs, and AMD Ryzen, two shifts are slightly lower latency but more instructions than a multiply (which may lead to lower throughput):

imul edi, [row], 320    ; 3 cycle latency from [row] being ready
add  edi, [column]      ; 1 cycle latency (from [column] and edi being ready).
; edi = [row]*(256+64) + [column],  in 4 cycles from [row] being ready.

vs.

mov edi, [row]
shl edi, 6               ; row*64.   1 cycle latency
lea edi, [edi + edi*4]   ; row*(64 + 64*4).  1 cycle latency
add edi, [column]        ; 1 cycle latency from edi and [column] both being ready
; edi = [row]*(256+64) + [column],  in 3 cycles from [row] being ready.

Compilers will do this for you: See how GCC, Clang, and Microsoft Visual C++ all use shift+lea when optimizing return 320*row + col;.

The most interesting thing to note here is that x86 has a shift-and-add instruction (LEA) that can do small left shifts and add at the same time, with the performance as an add instruction. ARM is even more powerful: one operand of any instruction can be left or right shifted for free. So scaling by a compile-time-constant that's known to be a power-of-2 can be even more efficient than a multiply.


OK, back in the modern days... something more useful now would be to use bitshifting to store two 8-bit values in a 16-bit integer. For example, in C#:

// Byte1: 11110000
// Byte2: 00001111

Int16 value = ((byte)(Byte1 >> 8) | Byte2));

// value = 000011111110000;

In C++, compilers should do this for you if you used a struct with two 8-bit members, but in practice they don't always.

Angular JS Uncaught Error: [$injector:modulerr]

I previously had the same issue, but I realized that I didn't include the "app.js" (the main application) inside my main page (index.html). So even when you include all the dependencies required by AngularJS, you might end up with that error in the console. So always make sure to include the necessary files inside your main page and you shouldn't have that issue.

Hope this helps.

What is ADT? (Abstract Data Type)

Before defining abstract data types, let us considers the different view of system-defined data types. We all know that by default all primitive data types (int, float, etc.) support basic operations such as addition and subtraction. The system provides the implementations for the primitive data types. For user-defined data types, we also need to define operations. The implementation for these operations can be done when we want to actually use them. That means in general, user-defined data types are defined along with their operations.

To simplify the process of solving problems, we combine the data structures with their operations and we call this "Abstract Data Type". (ADT's).

Commonly used ADT'S include: Linked List, Stacks, Queues, Binary Tree, Dictionaries, Disjoint Sets (Union and find), Hash Tables and many others.

ADT's consist of two types:

1. Declaration of data.

2. Declaration of operation.

Highlight a word with jQuery

You need to get the content of the p tag and replace all the dolors in it with the highlighted version.

You don't even need to have jQuery for this. :-)

How can I get an object's absolute position on the page in Javascript?

var cumulativeOffset = function(element) {
    var top = 0, left = 0;
    do {
        top += element.offsetTop  || 0;
        left += element.offsetLeft || 0;
        element = element.offsetParent;
    } while(element);

    return {
        top: top,
        left: left
    };
};

(Method shamelessly stolen from PrototypeJS; code style, variable names and return value changed to protect the innocent)

Parse JSON file using GSON

Imo, the best way to parse your JSON response with GSON would be creating classes that "match" your response and then use Gson.fromJson() method.
For example:

class Response {
    Map<String, App> descriptor;
    // standard getters & setters...
}

class App {
  String name;
  int age;
  String[] messages;
  // standard getters & setters...
}

Then just use:

Gson gson = new Gson();
Response response = gson.fromJson(yourJson, Response.class);

Where yourJson can be a String, any Reader, a JsonReader or a JsonElement.

Finally, if you want to access any particular field, you just have to do:

String name = response.getDescriptor().get("app3").getName();

You can always parse the JSON manually as suggested in other answers, but personally I think this approach is clearer, more maintainable in long term and it fits better with the whole idea of JSON.

How to set Internet options for Android emulator?

-http-proxy can be set in eclipse this way:

  1. Menu Window
  2. Submenu Preferences
  3. In Preferences Dialog Click Android in left part Click Launch Near Default Emulator Options: input ur -http-proxy

C#: easiest way to populate a ListBox from a List

Is this what you are looking for:

myListBox.DataSource = MyList;

Difference between float and decimal data type

Floating-Point Types (Approximate Value) - FLOAT, DOUBLE

The FLOAT and DOUBLE types represent approximate numeric data values. MySQL uses four bytes for single-precision values and eight bytes for double-precision values.

For FLOAT, the SQL standard permits an optional specification of the precision (but not the range of the exponent) in bits following the keyword FLOAT in parentheses. MySQL also supports this optional precision specification, but the precision value is used only to determine storage size. A precision from 0 to 23 results in a 4-byte single-precision FLOAT column. A precision from 24 to 53 results in an 8-byte double-precision DOUBLE column.

MySQL permits a nonstandard syntax: FLOAT(M,D) or REAL(M,D) or DOUBLE PRECISION(M,D). Here, “(M,D)” means than values can be stored with up to M digits in total, of which D digits may be after the decimal point. For example, a column defined as FLOAT(7,4) will look like -999.9999 when displayed. MySQL performs rounding when storing values, so if you insert 999.00009 into a FLOAT(7,4) column, the approximate result is 999.0001.

Because floating-point values are approximate and not stored as exact values, attempts to treat them as exact in comparisons may lead to problems. They are also subject to platform or implementation dependencies.

For maximum portability, code requiring storage of approximate numeric data values should use FLOAT or DOUBLE PRECISION with no specification of precision or number of digits.

https://dev.mysql.com/doc/refman/5.5/en/floating-point-types.html

Problems with Floating-Point Values

Floating-point numbers sometimes cause confusion because they are approximate and not stored as exact values. A floating-point value as written in an SQL statement may not be the same as the value represented internally. Attempts to treat floating-point values as exact in comparisons may lead to problems. They are also subject to platform or implementation dependencies. The FLOAT and DOUBLE data types are subject to these issues. For DECIMAL columns, MySQL performs operations with a precision of 65 decimal digits, which should solve most common inaccuracy problems.

The following example uses DOUBLE to demonstrate how calculations that are done using floating-point operations are subject to floating-point error.

mysql> CREATE TABLE t1 (i INT, d1 DOUBLE, d2 DOUBLE);
mysql> INSERT INTO t1 VALUES (1, 101.40, 21.40), (1, -80.00, 0.00),
    -> (2, 0.00, 0.00), (2, -13.20, 0.00), (2, 59.60, 46.40),
    -> (2, 30.40, 30.40), (3, 37.00, 7.40), (3, -29.60, 0.00),
    -> (4, 60.00, 15.40), (4, -10.60, 0.00), (4, -34.00, 0.00),
    -> (5, 33.00, 0.00), (5, -25.80, 0.00), (5, 0.00, 7.20),
    -> (6, 0.00, 0.00), (6, -51.40, 0.00);

mysql> SELECT i, SUM(d1) AS a, SUM(d2) AS b
    -> FROM t1 GROUP BY i HAVING a <> b;

+------+-------+------+
| i    | a     | b    |
+------+-------+------+
|    1 |  21.4 | 21.4 |
|    2 |  76.8 | 76.8 |
|    3 |   7.4 |  7.4 |
|    4 |  15.4 | 15.4 |
|    5 |   7.2 |  7.2 |
|    6 | -51.4 |    0 |
+------+-------+------+

The result is correct. Although the first five records look like they should not satisfy the comparison (the values of a and b do not appear to be different), they may do so because the difference between the numbers shows up around the tenth decimal or so, depending on factors such as computer architecture or the compiler version or optimization level. For example, different CPUs may evaluate floating-point numbers differently.

If columns d1 and d2 had been defined as DECIMAL rather than DOUBLE, the result of the SELECT query would have contained only one row—the last one shown above.

The correct way to do floating-point number comparison is to first decide on an acceptable tolerance for differences between the numbers and then do the comparison against the tolerance value. For example, if we agree that floating-point numbers should be regarded the same if they are same within a precision of one in ten thousand (0.0001), the comparison should be written to find differences larger than the tolerance value:

mysql> SELECT i, SUM(d1) AS a, SUM(d2) AS b FROM t1
    -> GROUP BY i HAVING ABS(a - b) > 0.0001;
+------+-------+------+
| i    | a     | b    |
+------+-------+------+
|    6 | -51.4 |    0 |
+------+-------+------+
1 row in set (0.00 sec)

Conversely, to get rows where the numbers are the same, the test should find differences within the tolerance value:

mysql> SELECT i, SUM(d1) AS a, SUM(d2) AS b FROM t1
    -> GROUP BY i HAVING ABS(a - b) <= 0.0001;
+------+------+------+
| i    | a    | b    |
+------+------+------+
|    1 | 21.4 | 21.4 |
|    2 | 76.8 | 76.8 |
|    3 |  7.4 |  7.4 |
|    4 | 15.4 | 15.4 |
|    5 |  7.2 |  7.2 |
+------+------+------+
5 rows in set (0.03 sec)

Floating-point values are subject to platform or implementation dependencies. Suppose that you execute the following statements:

CREATE TABLE t1(c1 FLOAT(53,0), c2 FLOAT(53,0));
INSERT INTO t1 VALUES('1e+52','-1e+52');
SELECT * FROM t1;

On some platforms, the SELECT statement returns inf and -inf. On others, it returns 0 and -0.

An implication of the preceding issues is that if you attempt to create a replication slave by dumping table contents with mysqldump on the master and reloading the dump file into the slave, tables containing floating-point columns might differ between the two hosts.

https://dev.mysql.com/doc/refman/5.5/en/problems-with-float.html

Get selected value from combo box in C# WPF

XAML:

<ComboBox Height="23" HorizontalAlignment="Left" Margin="19,123,0,0" Name="comboBox1" VerticalAlignment="Top" Width="33" ItemsSource="{Binding}" AllowDrop="True" AlternationCount="1">
    <ComboBoxItem Content="1" Name="ComboBoxItem1" />
    <ComboBoxItem Content="2" Name="ComboBoxItem2" />
    <ComboBoxItem Content="3" Name="ComboBoxItem3" />
</ComboBox>

C#:

if (ComboBoxItem1.IsSelected)
{
    // Your code
}
else if (ComboBoxItem2.IsSelected)
{
    // Your code
}
else if(ComboBoxItem3.IsSelected)
{
    // Your code
}

null check in jsf expression language

Use empty (it checks both nullness and emptiness) and group the nested ternary expression by parentheses (EL is in certain implementations/versions namely somewhat problematic with nested ternary expressions). Thus, so:

styleClass="#{empty obj.validationErrorMap ? ' ' :  
 (obj.validationErrorMap.contains('key') ? 'highlight_field' : 'highlight_row')}"

If still in vain (I would then check JBoss EL configs), use the "normal" EL approach:

styleClass="#{empty obj.validationErrorMap ? ' ' :  
 (obj.validationErrorMap['key'] ne null ? 'highlight_field' : 'highlight_row')}"

Update: as per the comments, the Map turns out to actually be a List (please work on your naming conventions). To check if a List contains an item the "normal" EL way, use JSTL fn:contains (although not explicitly documented, it works for List as well).

styleClass="#{empty obj.validationErrorMap ? ' ' :  
 (fn:contains(obj.validationErrorMap, 'key') ? 'highlight_field' : 'highlight_row')}"

Create a List of primitive int?

Try using the ArrayIntList from the apache framework. It works exactly like an arraylist, except it can hold primitive int.

More details here -

https://commons.apache.org/dormant/commons-primitives/apidocs/org/apache/commons/collections/primitives/ArrayIntList.html

How to run vbs as administrator from vbs?

Add this to the beginning of your file:

Set WshShell = WScript.CreateObject("WScript.Shell")
If WScript.Arguments.Length = 0 Then
  Set ObjShell = CreateObject("Shell.Application")
  ObjShell.ShellExecute "wscript.exe" _
    , """" & WScript.ScriptFullName & """ RunAsAdministrator", , "runas", 1
  WScript.Quit
End if

Deleting specific rows from DataTable

<asp:GridView ID="grd_item_list" runat="server" AutoGenerateColumns="false" Width="100%" CssClass="table table-bordered table-hover" OnRowCommand="grd_item_list_RowCommand">
    <Columns>
        <asp:TemplateField HeaderText="No">
            <ItemTemplate>
                <%# Container.DataItemIndex + 1 %>
            </ItemTemplate>
        </asp:TemplateField>            
        <asp:TemplateField HeaderText="Actions">
            <ItemTemplate>                    
                <asp:Button ID="remove_itemIndex" OnClientClick="if(confirm('Are You Sure to delete?')==true){ return true;} else{ return false;}" runat="server" class="btn btn-primary" Text="REMOVE" CommandName="REMOVE_ITEM" CommandArgument='<%# Container.DataItemIndex+1 %>' />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

 **This is the row binding event**

protected void grd_item_list_RowCommand(object sender, GridViewCommandEventArgs e) {

    item_list_bind_structure();

    if (ViewState["item_list"] != null)
        dt = (DataTable)ViewState["item_list"];


    if (e.CommandName == "REMOVE_ITEM") {
        var RowNum = Convert.ToInt32(e.CommandArgument.ToString()) - 1;

        DataRow dr = dt.Rows[RowNum];
        dr.Delete();

    }

    grd_item_list.DataSource = dt;
    grd_item_list.DataBind();
}

postgresql - add boolean column to table set default

Just for future reference, if you already have a boolean column and you just want to add a default do:

ALTER TABLE users
  ALTER COLUMN priv_user SET DEFAULT false;

What are the aspect ratios for all Android phone and tablet devices?

It is safe to assume that popular handsets are WVGA800 or bigger. Although, there are a good amount of HVGA screens, they are of secondary concern.

List of android screen sizes

http://developer.android.com/guide/practices/screens_support.html

Aspect ratio calculator

http://andrew.hedges.name/experiments/aspect_ratio/

How to use router.navigateByUrl and router.navigate in Angular

navigateByUrl

routerLink directive as used like this:

<a [routerLink]="/inbox/33/messages/44">Open Message 44</a>

is just a wrapper around imperative navigation using router and its navigateByUrl method:

router.navigateByUrl('/inbox/33/messages/44')

as can be seen from the sources:

export class RouterLink {
  ...

  @HostListener('click')
  onClick(): boolean {
    ...
    this.router.navigateByUrl(this.urlTree, extras);
    return true;
  }

So wherever you need to navigate a user to another route, just inject the router and use navigateByUrl method:

class MyComponent {
   constructor(router: Router) {
      this.router.navigateByUrl(...);
   }
}

navigate

There's another method on the router that you can use - navigate:

router.navigate(['/inbox/33/messages/44'])

difference between the two

Using router.navigateByUrl is similar to changing the location bar directly–we are providing the “whole” new URL. Whereas router.navigate creates a new URL by applying an array of passed-in commands, a patch, to the current URL.

To see the difference clearly, imagine that the current URL is '/inbox/11/messages/22(popup:compose)'.

With this URL, calling router.navigateByUrl('/inbox/33/messages/44') will result in '/inbox/33/messages/44'. But calling it with router.navigate(['/inbox/33/messages/44']) will result in '/inbox/33/messages/44(popup:compose)'.

Read more in the official docs.

Customize UITableView header section

You can try this:

 -(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, tableView.frame.size.width, 18)];
    /* Create custom view to display section header... */
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 5, tableView.frame.size.width, 18)];
    [label setFont:[UIFont boldSystemFontOfSize:12]];
     NSString *string =[list objectAtIndex:section];
    /* Section header is in 0th index... */
    [label setText:string];
    [view addSubview:label];
    [view setBackgroundColor:[UIColor colorWithRed:166/255.0 green:177/255.0 blue:186/255.0 alpha:1.0]]; //your background color...
    return view;
}

Selecting multiple classes with jQuery

// Due to this Code ): Syntax problem.    
$('.myClass', '.myOtherClass').removeClass('theclass'); 

According to jQuery documentation: https://api.jquery.com/multiple-selector/

When can select multiple classes in this way:

jQuery(“selector1, selector2, selectorN”) // double Commas. // IS valid.
jQuery('selector1, selector2, selectorN') // single Commas. // Is valid.

by enclosing all the selectors in a single '...' ' or double commas, "..."

So in your case the correct way to call multiple classes is:

$('.myClass', '.myOtherClass').removeClass('theclass'); // your Code // Invalid.
$('.myClass , .myOtherClass').removeClass('theclass');  // Correct Code // Is valid.

How to construct a relative path in Java from two absolute paths (or URLs)?

If you know the second string is part of the first:

String s1 = "/var/data/stuff/xyz.dat";
String s2 = "/var/data";
String s3 = s1.substring(s2.length());

or if you really want the period at the beginning as in your example:

String s3 = ".".concat(s1.substring(s2.length()));

Removing App ID from Developer Connection

App IDs cannot be removed because once allocated they need to stay alive so that another App ID doesn't accidentally collide with a previously existing App ID.

Apple should however support hiding unwanted App IDs (instead of completely deleting them) to reduce clutter.

How do I output lists as a table in Jupyter notebook?

I recently used prettytable for rendering a nice ASCII table. It's similar to the postgres CLI output.

import pandas as pd
from prettytable import PrettyTable

data = [[1,2,3],[4,5,6],[7,8,9]]
df = pd.DataFrame(data, columns=['one', 'two', 'three'])

def generate_ascii_table(df):
    x = PrettyTable()
    x.field_names = df.columns.tolist()
    for row in df.values:
        x.add_row(row)
    print(x)
    return x

generate_ascii_table(df)

Output:

+-----+-----+-------+
| one | two | three |
+-----+-----+-------+
|  1  |  2  |   3   |
|  4  |  5  |   6   |
|  7  |  8  |   9   |
+-----+-----+-------+

Could not instantiate mail function. Why this error occurring

To revisit an old thread, my issue was that one of the "AddressTo" email addresses was not valid. Removing that email address removed the error.

What do these three dots in React do?

This will be compiled into:

React.createElement(Modal, { ...this.props, title: "Modal heading", animation: false }, child0, child1, child2, ...)

where it gives more two properties title & animation beyond the props the host element has.

... is the ES6 operator called Spread.

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax

Returning value from called function in a shell script

You are working way too hard. Your entire script should be:

if mkdir "$lockdir" 2> /dev/null; then 
  echo lock acquired
else
  echo could not acquire lock >&2
fi

but even that is probably too verbose. I would code it:

mkdir "$lockdir" || exit 1

but the resulting error message is a bit obscure.

Change the mouse pointer using JavaScript

With regards to @CrazyJugglerDrummer second method it would be:

elementsToChange.style.cursor = "http://wiki-devel.sugarlabs.org/images/e/e2/Arrow.cur";