Good old `push` still works.

    x = []
    x.push &#39;a&#39;

Far better is to use list comprehensions.

For instance rather than this:

    things = []
    for x in list
      things.push x.color

do this instead:

    things = (x.color for x in list)


If you are chaining calls then you want the append to return the array rather than it&#39;s length.
In this case you can use .concat([newElement])

Has to be [newElement] as concat is expecting an array like the one its concatenating to.
Not efficient but looks cool in the right setting.


I&#39;m making an app where I add a subview to a view using `addSubview:` on an `IBAction`. In the same way, when the button with that `IBAction` is touched again should call `removeFromSuperview` on that subview added on that `IBAction`: 

**PSEUDO CODE**

    -(IBAction)showPopup:(id)sender 
    {
        System_monitorAppDelegate *delegate = (System_monitorAppDelegate *)[[UIApplication sharedApplication] delegate];
        UIView *rootView = delegate.window.rootViewController.view;

	    if([self popoverView] is not on rootView) 
        { 
		    [rootView addSubview:[self popoverView]];
	    } 
        else 
        {
		    [[self popoverView] removeFromSuperview];
        }
 
    }

Check if a subview is in a view

I am trying to list time complexities of operations of common data structures like Arrays, Binary Search Tree, Heap, Linked List, etc. and especially I am referring to Java. They are very common, but I guess some of us are not 100% confident about the exact answer. Any help, especially references, is greatly appreciated.

E.g. For singly linked list: Changing an internal element is O(1). How can you do it? You *HAVE* to search the element before changing it. Also, for the Vector, adding an internal element is given as O(n). But why can&#39;t we do it in amortized constant time using the index? Please correct me if I am missing something.

I am posting my findings/guesses as the first answer. 


  [1]: http://essays.hexapodia.net/datastructures/

What are the time complexities of various data structures?

What is the prescribed way to append a value to an Array in CoffeeScript?  I&#39;ve checked the PragProg CoffeeScript book but it only discusses creating, slicing and splicing, and iterating, but not appending.


In CoffeeScript how do you append a value to an Array?

<p>What is the prescribed way to append a value to an Array in CoffeeScript?  I've checked the PragProg CoffeeScript book but it only discusses creating, slicing and splicing, and iterating, but not appending.</p>


I have tried below code

    String s[]={&quot;1&quot;,&quot;2&quot;,&quot;3&quot;,&quot;4&quot;};  
    Collection c=Arrays.asList(s);  
    System.out.println(c.remove(&quot;1&quot;) +&quot;  remove flag&quot;);  
  
    System.out.println(&quot; collcetion &quot;+c);  

I was getting

    Exception in thread &quot;main&quot; java.lang.UnsupportedOperationException  
    at java.util.AbstractList.remove(Unknown Source)  
    at java.util.AbstractList$Itr.remove(Unknown Source)  
    at java.util.AbstractCollection.remove(Unknown Source)  
    at test.main(test.java:26)  

Can anyone help me to solve this issue?

java.lang.UnsupportedOperationException at java.util.AbstractList.remove(Unknown Source)

I have an array in Bash, for example:

&lt;!-- language: none --&gt;

    array=(a c b f 3 5)

I need to sort the array. Not just displaying the content in a sorted way, but to get a new array with the sorted elements. The new sorted array can be a completely new one or the old one.

How to sort an array in Bash

Apparently, we can pass complex class instances to functions, but why can&#39;t we pass arrays to functions?

Why can&#39;t we pass arrays to function by value?

The DOM method `document.querySelectorAll()` (and a few others) return a `NodeList`.

To operate on the list, e.g. using `forEach()`, the `NodeList` must first be converted to an `Array`.

What&#39;s the best way to convert the `NodeList` to an `Array`?

In JavaScript, what is the best way to convert a NodeList to an array?

I want to have an array of Lists.
In c++ I do like:

    List&lt;int&gt; a[100];

which is an array of 100 Lists. each list can contain many elements.
I don&#39;t know how to do this in c#. Can anyone help me?

An array of List in c#

Say I have an `Array[Int]` like

    val array = Array( 1, 2, 3 )

Now I would like to append an element to the array, say the value `4`, as in the following example: 

    val array2 = array + 4     // will not compile

I can of course use `System.arraycopy()` and do this on my own, but there must be a Scala library function for this, which I simply could not find. Thanks for any pointers!

Notes:

1. I am aware that I can append another Array of elements, like in the following line, but that seems too round-about:

        val array2b = array ++ Array( 4 )     // this works
 
2. I am aware of the advantages and drawbacks of List vs Array and here I am for various reasons specifically interested in extending an Array. 

### Edit 1

Thanks for the answers pointing to the `:+` operator method. This is what I was looking for. Unfortunately, it is rather slower than a custom append() method implementation using `arraycopy` -- about two to three times slower. Looking at the implementation in `SeqLike[]`, a builder is created, then the array is added to it, then the append is done via the builder, then the builder is rendered. Not a good implementation for arrays. I did a quick benchmark comparing the two methods, looking at the fastest time out of ten cycles. Doing 10 million repetitions of a single-item append to an 8-element array instance of some class `Foo` takes 3.1 sec with `:+` and 1.7 sec with a simple `append()` method that uses `System.arraycopy();` doing 10 million single-item append repetitions on 8-element arrays of Long takes 2.1 sec with `:+` and 0.78 sec with the simple `append()` method. Wonder if this couldn&#39;t be fixed in the library with a custom implementation for `Array`?

### Edit 2

For what it&#39;s worth, I filed a ticket:
https://issues.scala-lang.org/browse/SI-5017
 

 

Scala: what is the best way to append an element to an Array?

I am new to programming. In my latest Python 2.7 project I encountered the following:

&gt; RuntimeWarning: overflow encountered in long_scalars

Could someone please elaborate what this means and what I could do to fix that?

The code runs through, but I&#39;m not sure if it is a good idea to just ignore the warning.

It happens during an append process like:

    SomeList.append(VeryLongFormula)

Python RuntimeWarning: overflow encountered in long scalars

I&#39;m getting mad with list indexes, and can&#39;t explain what I&#39;m doing wrong.

I have this piece of code in which I want to create a list of lists, each one containing values of the same circuit parameter (voltage, current etc..) that I&#39;m reading from a `csv` file that looks like this:

    Sample, V1, I1, V2, I2
    0, 3, 0.01, 3, 0.02
    1, 3, 0.01, 3, 0.03

And so on. What I want is to create a list that for example contains V1 and I1 (but I want to chose interactively) in the form [[V1], [I1]], so:

    [[3,3], [0.01, 0.01]]

The code that I&#39;m using is this:

    plot_data = [[]]*len(positions)    
    for row in reader:
        for place in range(len(positions)):
            value = float(row[positions[place]])
            plot_data[place].append(value)

`plot_data` is the list that contains all the values, while `positions` is a list with the indexes of the columns that I want to copy from the `.csv` file. The problem is that if I try the commands in the shell, seems to work, but if I run the script instead of appending each value to the proper sub-list, it appends all values to all lists, so I obtain 2 (or more) identical lists.

Appending to one list in a list of lists appends to all other lists, too

When I&#39;m adding a div to body, it&#39;s returning the body as the object and then whenever I use that - it&#39;s obviously using body. Bad.

Code:-

    var holdyDiv = $(&#39;body&#39;).append(&#39;div&#39;);
    $(holdyDiv).attr(&#39;id&#39;, &#39;holdy&#39;);

The &#39;id&#39; of holdy is now being added to body... eh? What am I doing wrong.

jQuery - Appending a div to body, the body is the object?

I&#39;m attempting to customize an existing JS library without modifying the original JS code.  This code loads in a few external JS files which I do have access to, and what I&#39;d like to do is change one of the functions contained in the original file without copying and pasting the whole thing into the second JS file.
&lt;br&gt;
So for example, the off limits JS might have a function like this:

    var someFunction = function(){
        alert(&quot;done&quot;);
    }

I&#39;d like to be able to somehow append or prepend some JS code into that function.  The reason is primarily that in the original untouchable JS the function is pretty enormous and if that JS ever gets updated, the function I overwrite it with will be out of date.

I&#39;m not entirely sure this is possible, but I figured I&#39;d check.


Adding code to a javascript function programmatically

Yesterday I did a deep night coding session and created a small node.js/JS (well actually CoffeeScript, but CoffeeScript is just JavaScript so lets say JS) app.

what&#39;s the goal:

 1. client sends a canvas datauri (png) to server (via socket.io)
 2. server uploads image to amazon s3

step 1 is done.

the server now has a string a la 

    data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAMgAAADICAYAAACt...

my question is: **what are my next steps to &quot;stream&quot;/upload this data to Amazon S3 and create an actual image there?**

knox https://github.com/LearnBoost/knox seems like an awesome lib to PUT something to S3, **but what I&#39;m missing is the glue between the base64-encoded-image-string and actual upload action**?

Any ideas, pointers and feedback welcome.

Uploading base64 encoded Image to Amazon S3 via Node.js

I am really torn between two different stacks with which to build a large application. One the one hand there is this option:

- Node.js
    - express
    - coffee script
    - coffeekup
    - mongoose/mongodb
    or
    - presistencejs/mysql

&lt;br/&gt;

- Play Framework w/ Scala
  - Anorm w/ mysql
  - or mongodb

The node.js path is appealing to me because i can write all of the server side code, views and client side code in coffeescript, which i already know. If i go down this road i am still not 100% sure which db path i would take. mongoose makes storing data quick and easy, but the lack of true relationships might be more difficult to work with given the data model i have in mind (very SQLish).

The Play Framework path is also appealing because i know the framework well when using Java, but i don&#39;t know much about Scala, so there would be a hit to productivity as i work through learning that language. The Anorm database access layer is appealing because i can write the SQL by hand which i would prefer, and have the results mapped to objects automatically, which saves a lot of effort.

I keep leaning towards node.js, but i&#39;m not sold on the best db access layer to use. Anyone have any experience with any of this and can share some insight?

NodeJS vs Play Framework for large project

In what ways can you comment in CoffeeScript?

The documentation say you can use three hash symbols to start and close a comment block:

    ###
      Comments
      go
      here
    ###

I&#39;ve found that I can sometimes use the following two formats

    `// backticks allow for straight-JavaScript,
     // but the closing backtick can&#39;t be on a comment line (I think?)
    `

Are there a simpler way to insert short comments in CoffeeScript?

Do NOT use this style**

Since this is getting a lot of views, I want to emphasize that

    /* Comment goes here */

produces a MATH error when the `/*` is on its own line.

As Trevor pointed out in a comment on the question, this is a **regular expression**, **NOT** a comment!


How do I comment in CoffeeScript? &quot;/* this */&quot; doesn&#39;t work

I have a Rails controller in which I am setting a instance variable -

    @user_name = &quot;Some Username&quot;

In my .slim template I am using coffee engine to generate javascript and want to print out the user name from client-sie javascript code -


    coffee:
      $(document).ready -&gt;
        name = &quot;#{@user_name}&quot;
        alert name


But this is the javascript that is being generated??

    $(document).ready(function() {
        var name;
        name = &quot;&quot; + this.my_name;
        alert(name);
    }

**How do I access controller instance variables in my CoffeeScript code??**

I am tagging this as haml since I am guessing haml will have the same issue when using CoffeeScript .



How to access instance variables in CoffeeScript engine inside a Slim template

I&#39;ve got this code that checks for the empty or null string. It&#39;s working in testing. 

    eitherStringEmpty= (email, password) -&gt;
      emailEmpty = not email? or email is &#39;&#39;
      passwordEmpty = not password? or password is &#39;&#39;
      eitherEmpty = emailEmpty || passwordEmpty         
    
    test1 = eitherStringEmpty &quot;A&quot;, &quot;B&quot; # expect false
    test2 = eitherStringEmpty &quot;&quot;, &quot;b&quot; # expect true
    test3 = eitherStringEmpty &quot;&quot;, &quot;&quot; # expect true
    alert &quot;test1: #{test1} test2: #{test2} test3: #{test3}&quot;

What I&#39;m wondering is if there&#39;s a better way than `not email? or email is &#39;&#39;`. Can I do the equivalent of C# `string.IsNullOrEmpty(arg)` in CoffeeScript with a single call? I could always define a function for it (like I did) but I&#39;m wondering if there&#39;s something in the language that I&#39;m missing. 


Content Type	Original Author	Original Content on Stackoverflow
Question	Dave Sag	View Question on Stackoverflow
Solution 1 - Arrays	Thilo	View Answer on Stackoverflow
Solution 2 - Arrays	suranyami	View Answer on Stackoverflow
Solution 3 - Arrays	Paul Schooling	View Answer on Stackoverflow

In CoffeeScript how do you append a value to an Array?

Arrays Problem Overview

Arrays Solutions

Solution 1 - Arrays

Solution 2 - Arrays

Solution 3 - Arrays

What are the time complexities of various data structures?

Check if a subview is in a view

Attributions