I have read that Scala&#39;s type system is weakened by Java interoperability and therefore cannot perform some of the same powers as Haskell&#39;s type system.  Is this true?  Is the weakness because of type erasure, or am I wrong in every way?  Is this difference the reason that Scala has no typeclasses?


Disadvantages of Scala type system versus Haskell?

This question may be naive, but:

 - is there `const` keyword in C?
 - since which version?
 - are there any semantic and/or syntactic differences between `const` in C and C++?    




Is there const in C?

In Bash I can easily do something like

    command1 &amp;&amp; command2 || command3

which means to run command1 and if command1 succeeds to run command2 and if command1 fails to run command3.

What&#39;s the equivalent in PowerShell?


What are the PowerShell equivalents of Bash&#39;s &amp;&amp; and || operators?

I have a to do this:

    AccountList.Split(vbCrLf)

In c# AccountList is a string.
How can i do?

thanks

equivalent of vbCrLf in c#

What are the main differences among them? And in which typical scenarios is it better to use each language?


What are the differences between Perl, Python, AWK and sed?

I&#39;ve been programming in Java for a while and just got thrown onto a project that&#39;s written entirely in C#.  I&#39;m trying to come up to speed in C#, and noticed enums used in several places in my new project, but at first glance, C#&#39;s enums seem to be more simplistic than the Java 1.5+ implementation.  Can anyone enumerate the differences between C# and Java enums, and how to overcome the differences?  (I don&#39;t want to start a language flame war, I just want to know how to do some things in C# that I used to do in Java).  For example, could someone post a C# counterpart to Sun&#39;s famous Planet enum example?

    public enum Planet {
      MERCURY (3.303e+23, 2.4397e6),
      VENUS   (4.869e+24, 6.0518e6),
      EARTH   (5.976e+24, 6.37814e6),
      MARS    (6.421e+23, 3.3972e6),
      JUPITER (1.9e+27,   7.1492e7),
      SATURN  (5.688e+26, 6.0268e7),
      URANUS  (8.686e+25, 2.5559e7),
      NEPTUNE (1.024e+26, 2.4746e7),
      PLUTO   (1.27e+22,  1.137e6);

      private final double mass;   // in kilograms
      private final double radius; // in meters
      Planet(double mass, double radius) {
          this.mass = mass;
          this.radius = radius;
      }
      public double mass()   { return mass; }
      public double radius() { return radius; }

      // universal gravitational constant  (m3 kg-1 s-2)
      public static final double G = 6.67300E-11;

      public double surfaceGravity() {
          return G * mass / (radius * radius);
      }
      public double surfaceWeight(double otherMass) {
          return otherMass * surfaceGravity();
      }
    }

    // Example usage (slight modification of Sun&#39;s example):
    public static void main(String[] args) {
        Planet pEarth = Planet.EARTH;
        double earthRadius = pEarth.radius(); // Just threw it in to show usage

        // Argument passed in is earth Weight.  Calculate weight on each planet:
        double earthWeight = Double.parseDouble(args[0]);
        double mass = earthWeight/pEarth.surfaceGravity();
        for (Planet p : Planet.values())
           System.out.printf(&quot;Your weight on %s is %f%n&quot;,
                             p, p.surfaceWeight(mass));
    }

    // Example output:
    $ java Planet 175
    Your weight on MERCURY is 66.107583
    Your weight on VENUS is 158.374842
    [etc ...]

C# vs Java Enum (for those new to C#)

I&#39;ve searched the wiki modules page, but I can&#39;t find anything similar to virtualenv (python) or rvm. 

Anyone here separates node.js in their own env? I really don&#39;t like to install npm system-wide.

Is there a virtual environment for node.js?

Can someone please explain the major differences between Scala, Groovy and Clojure. I know each of these compiles to run on the JVM but I&#39;d like a simple comparison between them.

Scala vs. Groovy vs. Clojure

I&#39;ve searched on the Internet for comparisons between [F#][1] and [Haskell][2] but haven&#39;t found anything really definitive. What are the primary differences and why would I want to choose one over the other?


  [1]: http://en.wikipedia.org/wiki/F_Sharp_%28programming_language%29
  [2]: http://en.wikipedia.org/wiki/Haskell_%28programming_language%29

What are the primary differences between Haskell and F#?

Is there a Bash equivalent to the Python&#39;s `pass` statement?


What is the Bash equivalent of Python&#39;s pass statement

For those of you experienced in both Haskell and some flavor of Lisp, I&#39;m curious how &quot;pleasant&quot; (to use a horrid term) it is to write code in Haskell vs. Lisp.

Some background: I&#39;m learning Haskell now, having earlier worked with Scheme and CL (and a little foray into Clojure). Traditionally, you could consider me a fan of dynamic languages for the succinctness and rapidity they provide. I quickly fell in love with Lisp macros, as it gave me yet another way to avoid verbosity and boilerplate.

I&#39;m finding Haskell **incredibly** interesting, as it&#39;s introducing me to ways of coding I didn&#39;t know existed. It definitely has some aspects that seem like they would aid in achieving agility, like ease of writing partial functions. However, I&#39;m a bit concerned about losing Lisp macros (I assume I lose them; truth be told I may have just not learned about them yet?) and the static typing system.

Would anyone who has done a decent amount of coding in both worlds mind commenting on how the experiences differ, which you prefer, and if said preference is situational?

Haskell, Lisp, and verbosity

Is there an [XSLT][1] equivalent for JSON? Something to allow me to do transformations on JSON like XSLT does to XML.


  [1]: http://www.w3.org/TR/xslt

XSLT equivalent for JSON

Python has syntactically sweet list comprehensions:

    S = [x**2 for x in range(10)]
    print S;
    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

In PHP I would need to do some looping:

    $output = array();
    $Nums = range(0,9);
    
    foreach ($Nums as $num) 
    {
        $out[] = $num*=$num;
    }
    print_r($out);

to get:

Array
(
    [0] =&gt; 0
    [1] =&gt; 1
    [2] =&gt; 4
    [3] =&gt; 9
    [4] =&gt; 16
    [5] =&gt; 25
    [6] =&gt; 36
    [7] =&gt; 49
    [8] =&gt; 64
    [9] =&gt; 81
)

Is there anyway to get a similar list comprehension syntax in PHP? Is there anyway to do it with any of the new features in PHP 5.3?

Thanks!

Does PHP have an equivalent to Python&#39;s list comprehension syntax?

Is there a Python equivalent to Ruby symbols? 

 - If so then what is it?

 - If not then are we stuck with using **strings** as our **keys** in dictionaries only?

Is there a Python equivalent to Ruby symbols?

I know this is a [duplicate][1], however, the Grails world has moved on considerably since that question was asked more than a year ago, as has the IDE support in Eclipse, so please don&#39;t just blindly close it.  

I thought the answer was yes and have embarked on a new project with [Grails 1.2.0][2] and have flirted with the Groovy/Grails bits of the [STS Eclipse Integration][3].

I think the question deserves revisiting after a year of Grails evolution, when the answer was definitely mixed.

So, as an experienced Java web developer I have these questions and would appreciate *my assumptions* being challenged:

 - Is Grails now worth it vs. Ruby or roll your own?
 - Has it overcome its buggy start?  
 - Does it really confer rapid development benefits?  *(I admit I am struggling now I am past the extensive baseline configuration to make my bespoke app which is not list and page oriented)*
 - Does it perform for real world production apps?  *(It feels heavy)*
 - Is the Eclipse plug-in better than it was and fit for purpose? *(I think not yet)*

Thanks

**EDIT:**
I am learning as I go and I have a couple of significant gripes to make about living with the framework - rather than framework capabilities themselves.  I am adding these because I think they should be considerations and are based on my experience and opinion, and may help someone who is trying to decide whether to go grails.  I may also be showing my lack of experience with the framework, so none of this is meant as out and out criticisms.  I am an experienced developer and this is what I have found:  

**Debugging is really hard**.  In fact it is almost impossible, especially as a beginner in the framework, which is when you need your trusty debugger friend the most.  I have spent way more time than I ought to tracking down problems of syntactical errors in some part of the code to do with referring to domain fields which cause silent failures somewhere in the stack.

**Logging is frankly awful**.  You have two modes, &quot;nothing useful&quot; and &quot;an inordinate amount of useless stuff&quot;. My debug log was 128Mb after a single page request and contains nothing about my error.  The whole issue of logging needs reconsideration in the framework in my opinion.

**The STS Eclipse IDE is of marginal value**.  Other than syntax hilighting it is not much use.  You can&#39;t debug the code so it is a glorified editor.  The code hints are patchy and there is no GSP support at all as far as I can see.  It also is the slowest Eclipse plug-in I have on my desktop - by about 2 minutes to start up.  It is shockingly slow.  I have reverted to a text editor (which you&#39;ll notice all the online tutorial videos do too) and some custom syntax hilighting.

**I have some serious concerns about performance**.  A bit too early to say, but I am already finding myself tweaking the database because of hibernate.  Perhaps that&#39;s to be expected, but I am really having to keep my domain model simple for the conventions to yield performant queries.

And one last one, the convention that your logical domain model and your physical database model should be identical is not a smart default and unlikely ever to be the case in the real world.  I know you can separate the two, but it creates a degree of complexity which I think could be avoided if the conventions were extended.  There is inadequate documentation about composition and [what you need to do to make it work in practice][4].  


  [1]: https://stackoverflow.com/questions/397228/is-grails-worth-it
  [2]: http://www.grails.org/1.2+Release+Notes
  [3]: http://www.grails.org/STS+Integration
  [4]: https://stackoverflow.com/questions/2123871/how-do-i-save-a-composite-field-value-in-grails-gsp/

Is Grails (now) worth it?

I read on another Stack Overflow question that Python was just like Ruby, as it relates to &quot;everything&#39;s an object,&quot; and everything in Python was an object, just like Ruby. 

Is this true? Is everything an object in Python like Ruby?

How are the two different in this respect or are they really the same? For example, can you take a number and do the Ruby stuff I&#39;ve seen like:

    y = 5.plus 6

Can that be done the same way in Python?

Is everything an object in Python like Ruby?

I am a RoR programmer new to Python. I am trying to find the syntax that will allow me to set a variable to a specific value only if it wasn&#39;t previously assigned. Basically I want:

    # only if var1 has not been previously assigned
    
    var1 = 4

Python: Assign Value if None Exists

Ruby example:

    name = &quot;Spongebob Squarepants&quot;
    puts &quot;Who lives in a Pineapple under the sea? \n#{name}.&quot;
The successful Python string concatenation is seemingly verbose to me.


  [1]: http://stackoverflow.com/questions/4450592/string-interpolation-in-python/4450610#4450610
  [2]: http://stackoverflow.com/users/279627/sven-marnach
  [3]: http://stackoverflow.com/users/543475/einlama

Is there a Python equivalent to Ruby&#39;s string interpolation?

I have defined a class myComplex. I need to map it to integers. In C++ I would have created a map as 
`map&lt;myComplex,int&gt;` first;

How to do such thing in C#?

What is C# equivalent of &lt;map&gt; in C++?

What is the cleanest way to make Javascript do something _like_ Python&#39;s list comprehension?

In Python if I have a list of objects whose name&#39;s I want to &#39;pull out&#39; I would do this...

    list_of_names = [x.name for x in list_of_objects]

In javascript I don&#39;t really see a more &#39;beautiful&#39; way of doing that other than just using a for loop construct.


FYI: I&#39;m using jQuery; maybe it has some nifty feature that makes this possible? 

More specifically, say I use a jQuery selector like `$(&#39;input&#39;)` to get all `input` elements, how would I _most cleanly_ create an array of all the `name` attributes for each of these `input` elements--i.e., all of the `$(&#39;input&#39;).attr(&#39;name&#39;)` strings in an array?

Make Javascript do List Comprehension

I&#39;m trying to convert some Python code into Ruby. Is there an equivalent in Ruby to the `try` statement in Python?

Ruby equivalent for Python&#39;s &quot;try&quot;?

Powershell&#39;s array notation has rather bizarre, albeit documented, behavior for slicing the end of arrays.  This section from [the official documentation](https://technet.microsoft.com/en-us/library/hh847882.aspx) sums up the bizarreness rather well:

&gt; Negative numbers count from the end of the array. For example, &quot;-1&quot; 
&gt; refers to the last element of the array. To display the last three
&gt; elements of the array, type:
&gt; 
&gt;     $a[-3..-1]
&gt; 
&gt; However, be cautious when using this notation.
&gt; 
&gt;     $a[0..-2]
&gt; 
&gt; This command does not refer to all the elements of the array, except
&gt; for  the last one. It refers to the first, last, and second-to-last
&gt; elements in the array.

The following code confirms the bizarreness:

    $a = 0,1,2,3
    $a[1..-1]

Which indeed outputs this bizarre result:

    1
    0
    3

So, the question is, what _is_ the idiomatic way to slice with one index relative the start and another relative the end of the array?  

Please tell me it&#39;s something better than this ugly mess:

    $a[1..($a.Count-1)]

------------

Edit:

Another way to describe what I&#39;m looking for is this: The idiomatic Powershell equivalent of this python expression:

    a=1,2,3,4
    a[1:-1]

Which, of course, evaluates to `(2,3)`

What is the idiomatic way to slice an array relative to both of its ends?

I read that after years yaml will be used instead of xml. Please compare the relative advantages and disadvantages of each specification.

YAML compared to XML

Is there something in [PHP][1] equivalent to [LINQ][2] in C#?

  [1]: http://en.wikipedia.org/wiki/PHP
  [2]: http://en.wikipedia.org/wiki/Language_Integrated_Query


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