language-comparisons

I have read that Scala's type system is weakened by Java interoperability and therefore cannot perform some of the same powers as Haskell'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? The big difference is that Scala doesn't have Hindley-Milner global type inference and instead uses a form of local type inference, requiring you to specify types for method parameters and the return type for overloaded or recursive functions. This isn't driven by type erasure or by other requirements

I've searched the wiki modules page, but I can't find anything similar to virtualenv (python) or rvm. Anyone here separates node.js in their own env? I really don't like to install npm system-wide. bxjx If having system wide npm packages is your main issue, then maybe consider using the very cool 'bundle' command with npm. This is closer to freezing gems or using bundler in rails, rather than rvm. It's super easy. Just create a package.json file: { "name": "yourapp", "version": "0.0.1", "dependencies": {"jade": "0.4.1"}} and then run: npm bundle vendor or if your npm version is >= 1.0 run: npm

My first F# day. If I have this: let cat = Animal() Now how do I check at later stage if cat is Animal ? In C# bool b = cat is Animal; In F#? @ildjarn deserves the credit here for answering first, but I'm submitting the answer here so it can be accepted. The F# equivalent of the C# is keyword is :? . For example: let cat = Animal() if cat :? Animal then printfn "cat is an animal." else printfn "cat is not an animal." For demonstration only (don't define an is function): let is<'T> (x: obj) = x :? 'T type Animal() = class end type Cat() = inherit Animal() let cat = Cat() cat |> is<Animal> /

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] => 0 [1] => 1 [2] => 4 [3] => 9 [4] => 16 [5] => 25 [6] => 36 [7] => 49 [8] => 64 [9] => 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! Maybe something like this? $out=array_map(function($x) {return $x*$x;},

In Bash I can easily do something like command1 && command2 || command3 which means to run command1 and if command1 succeeds to run command2 and if command1 fails to run command3. What's the equivalent in PowerShell? What Bash must be doing is implicitly casting the exit code of the commands to a Boolean when passed to the logical operators. PowerShell doesn't do this - but a function can be made to wrap the command and create the same behavior: > function Get-ExitBoolean($cmd) { & $cmd | Out-Null; $? } ( $? is a bool containing the success of the last exit code ) Given two batch files: #pass

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++? There are no syntactic differences between C and C++ with regard to const keyword, besides a rather obscure one: in C (since C99) you can declare function parameters as void foo(int a[const]); which is equivalent to void foo(int *const a); declaration. C++ does not support such syntax. Semantic differences exist as well. As @Ben Voigt already noted, in C const declarations do not produce constant expressions, i.e. in C you can't use