Lambda Expression in Powershell

Question

I have a code in C# which uses lambda expressions for delegate passing to a method. How can I achieve this in PowerShell. For example the following is a C# code:

string input = "(,)(;)(:)(!)"; string pattern = @"\((?<val>[\,\!\;\:])\)"; var r = new Regex(pattern); string result = r.Replace(input, m =>     {         if (m.Groups["val"].Value == ";") return "[1]";         else return "[0]";     }); Console.WriteLine(result); 

And this is the PowerShell script without the lambda-expression in place:

$input = "(,)(;)(:)(!)"; $pattern = "\((?<val>[\,\!\;\:])\)"; $r = New-Object System.Text.RegularExpressions.Regex $pattern $result = $r.Replace($input, "WHAT HERE?") Write-Host $result 

Note: my question is not about solving this regular-expression problem. I just want to know how to pass a lambda expression to a method that receives delegates in PowerShell.

Answer 1

In PowerShell 2.0 you can use a script block ({ some code here }) as delegate:

$MatchEvaluator =  {     param($m)     if ($m.Groups["val"].Value -eq ";")    {      #...    } }  $result = $r.Replace($input, $MatchEvaluator) 

Or directly in the method call:

$result = $r.Replace($input, { param ($m) bla }) 

Tip:

You can use [regex] to convert a string to a regular expression:

$r = [regex]"\((?<val>[\,\!\;\:])\)" $r.Matches(...) 

Answer 2

Sometimes you just want something like this:

{$args[0]*2}.invoke(21) 

(which will declare an anonymous 'function' and call it immediately.)