Joel-On-Software on the power of a good language

re: Joel-On-Software on the power of a good language

Rupert — Wed, 01 Jul 2009 18:23:16 GMT

I'd prefer a version of map that returned a new array rather than altering the existing one in place. Something like...

function map ($fn, $list)

{

$ret = $null

for ($i = 0; $i -lt $list.length; $i++)

{

$ret += ,(&$fn $list[$i])

}

return $ret

}

re: Joel-On-Software on the power of a good language

James Hugard — Tue, 12 Jun 2007 03:45:31 GMT

Hah, that should be reduced to:

filter map( [ScriptBlock] $fn ) { & $fn $_ }

re: Joel-On-Software on the power of a good language

James Hugard — Fri, 08 Jun 2007 04:45:03 GMT

I prefer this version of "map", because it works with any collection object or scalar:

filter map( [ScriptBlock]$fn )

{

$_ | %{ &$fn $_ }

}

Works like this:

$files = "a

$files = $files.split("`n") | map { $_.Trim() }

re: Joel-On-Software on the power of a good language

Fabio Galuppo — Thu, 05 Oct 2006 02:37:25 GMT

I like the simplicity and "power" of PowerShell... But, check this. Nice work from a strong type-checked language, isn't it? ////////// // C# 2.0 version of "famous" Map/Reduce sample ////////// using con = System.Console; using gen = System.Collections.Generic; namespace DynamicProgram { static class Program { delegate void Function( T arg ); delegate T FunctionWithRet( T arg ); static Function alert = con.WriteLine; static Function alert_i = con.WriteLine; static void SwedishChef( T msg ){ alert( "I'd like some " + msg + "!" ); } static void PutInPot( T ingredient ){ alert( "POT: " + ingredient + " added" ); } static void BoomBoom( T ingredient ){ alert( "BOOM: " + ingredient ); } static void Cook(T i1, T i2, Function f) { alert( "Get the " + i1 ); f(i1); f(i2); } static void map(Function f, gen.IEnumerable a){ foreach (T i in a) f( i ); } static void map(FunctionWithRet f, T[] a){ for( int i = 0; i < a.Length; ++i ) a[i] = f( a[i] ); } delegate T BinaryOperation( T i, T j ); static BinaryOperation add = delegate( int i, int j ){ return i + j; }; static BinaryOperation concat = delegate( string i, string j ){ return i + j; }; static T sum(BinaryOperation binOp, params T[] a) { T t = default(T); foreach (T i in a) t = binOp( t, i ); return t; } static T join( BinaryOperation binOp, params T[] a ) { T t = default(T); foreach (T i in a) t = binOp( t, i ); return t; } static T reduce( BinaryOperation binOp, params T[] a ) { T t = default(T); foreach (T i in a) t = binOp( t, i ); return t; } static T sum_r(BinaryOperation binOp, params T[] a){ return reduce( binOp, a );} static T join_r( BinaryOperation binOp, params T[] a ){ return reduce( binOp, a ); } //extra delegate T reduceHandler( params T[] a ); static reduceHandler reduced_sum = delegate( int[] a ){ return reduce( add, a ); }; static reduceHandler reduced_join = delegate( string[] a ){ return reduce( concat, a ); }; static void Main(string[] args) { alert("I'd like some Spaghetti!"); alert("I'd like some Chocolate Moose!"); SwedishChef("Spagetthi"); SwedishChef("Chocolate Moose"); Cook("Lobster", "Water", PutInPot); Cook("Chicken", "Coconut", BoomBoom); Cook("Lobster", "Water", delegate(string ingredient) { alert("POT: " + ingredient + " added"); }); Cook("Chicken", "Coconut", delegate(string ingredient) { alert("BOOM: " + ingredient); }); int[] a = { 1, 2, 3 }; for( int i = 0; i < a.Length; ++i ) { a[i] *= 2; } foreach ( int i in a ) { alert_i( i ); } a = new int[]{ 1, 2, 3 }; map(delegate(int i) { return i * 2; }, a); map(alert_i, a); alert_i( sum( add, 1, 2, 3 ) ); alert( join( concat, "a", "b", "c" ) ); alert_i( sum_r( add, 1, 2, 3 ) ); alert( join_r( concat, "a", "b", "c" ) ); //extra alert_i( reduced_sum( 1, 2, 3 ) ); alert( reduced_join( "a", "b", "c" ) ); } } } //////////

re: Joel-On-Software on the power of a good language

Lee — Mon, 14 Aug 2006 20:18:36 GMT

lb:

You normally define functions with the parameters listed after the function name, but it is just as correct to provide a param statement. That lets you write:

Function PutInPot {Param($x) Alert "Boom $x"}

Also, all script blocks, functions, and scripts can be written to easily accept pipeline input:

"Hi" | & { begin { "Beginning"} process { write-host "Boom $_" } end { "Ending" } }

function foo { begin { "Beginning"} process { write-host "Boom $_" } end { "Ending" } }
"Hi" | foo

We also support a shortcut for functions act on pipeline input -- called filters. For an example, see the help topic, about_Filter.

re: Joel-On-Software on the power of a good language

Jason Gurtz — Wed, 09 Aug 2006 18:50:15 GMT

I had read the Joel on sw article and it's neat to see this real life example so soon after. :)

re: Joel-On-Software on the power of a good language

lb — Wed, 09 Aug 2006 07:42:18 GMT

Love it!

so this is an anonymous function that accepts a parameter called $x --

{Param($x) Alert "Boom $x"}

while *this* is a named function with a parameter called $x:

Function PutInPot($x) {Alert "Boom $x"}

and am i right trying to compare with ruby and saying that:

{Param($x) Alert "Boom $x"}

is similar to:

{|x| Alert "Boom x"}

---
and next guess: the anonymous function is going to accept piped in variables, where-as the function won't? (in its current form)

lovin the pshell!

re: Joel-On-Software on the power of a good language

PowerShell Team — Thu, 03 Aug 2006 10:32:05 GMT

> How do you bind the Alert alias at definition time and not run-time?

Runtime binding is one of the key features of Shells and other dynamic environments. There are some huge advantages to it but there are some downsides as well. In future releases, we expect to provide users the option to choose more static behaviour. Alias binding is on the top of my list for this.

Jeffrey Snover [MSFT]
Windows PowerShell/Aspen Architect
Visit the Windows PowerShell Team blog at: http://blogs.msdn.com/PowerShell
Visit the Windows PowerShell ScriptCenter at: http://www.microsoft.com/technet/scriptcenter/hubs/msh.mspx

re: Joel-On-Software on the power of a good language

Mike S — Thu, 03 Aug 2006 05:04:54 GMT

PS >Set-Alias Alert Write-Host
PS > function SwedishChef ($food)
>> {
>> Alert "id like some $food"
>> }
PS > SwedishChef spag
id like some spag

Good!

PS > Set-Alias Alert gorb
PS > SwedishChef spag
Alias not resolved because alias 'Alert' referenced command 'gorb', this comman
d is not recognized as a cmdlet, function, operable program, or script file.
At line:3 char:6
+ Alert <<<< "id like some $food"

I personally hate this run-time name binding.

How do you bind the Alert alias at definition time and not run-time?

I dont know power-shell but I would think the syntax of what happened should be
PS > function SwedishChef ($food)
>> {
>> $Alert "id like some $food"
>> }

re: Joel-On-Software on the power of a good language

Gantenbein — Wed, 02 Aug 2006 18:31:55 GMT

Nice to see that the PowerShell scripting language offers functional programming features like LISP or Haskell do.