Is this matching from Scala is available in C#?

Question

I found nice little one example of Scala today. Something like:

(1 to 100) map { x =>   
  (x % 2, x % 6) match {  
    case (0,0) => "First"
    case (0,_) => "Second"    
    case (_,0) => "Third"    
    case _ => x toString    
  }
} foreach println

And i wonder if I could do something similar in C#. I tried to search on my own but it's hard since I don't know name of this expression. It seems pretty useful. So can I do this in C#?

Very similar: http://stackoverflow.com/questions/2320919/how-can-i-duplicate-the-f-discriminated-union-type-in-c — ChaosPandion, Apr 03 '11 at 06:48

score 5 · Answer 1 · answered Apr 03 '11 at 07:52

Pattern matching is not available in C#.

But you can use Nemerle .Net language which supports Pattern Matching and many other great stuff which C# doesn't support.

foreach (x in $[1 .. 100])
{
   Console.WriteLine(
     match((x % 2, x % 6))
     {
       | (0, 0) => "First"
       | (0, _) => "Second"
       | (_, 0) => "Third"
       | _      => x.ToString()
     })
}

score 3 · Accepted Answer · answered Apr 03 '11 at 06:51

It's called (functional) pattern matching, and is a hallmark of functional programming languages such as Scala, F#, and Haskell. http://codebetter.com/matthewpodwysocki/2008/09/16/functional-c-pattern-matching/ discusses how to simulate F#'s version of it in C#.

Alex · Answer 3 · 2011-04-03T08:15:30.457

2

Since I don't know Scala, I can't verify that this does the same thing, but you can probably base your code off this.

Enumerable.Range(1, 100)
    .Select(x => new {original = x, two = x % 2, six = x % 6})
    .Select(x =>
    {
        if (x.two == 0 && x.six == 0)
            return "First";
        else if (x.two == 0)
            return "Second";
        else if (x.six == 0)
            return "Third";
        else
            return x.original.ToString();
    }).ToList().ForEach(s => Console.WriteLine(s));

Outputs:

1
Second
3
Second
5
First
7
Second
9
Second
...

edited Apr 03 '11 at 08:15

answered Apr 03 '11 at 07:05

Alex

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Is that what the Scala code actually does? I don't get the Scala code, but I'm pretty sure you're code can never print "Third". (Quick check - it doesn't - http://ideone.com/redmN ) – Kobi Apr 03 '11 at 08:05
Nice feature. I'll change my code to reflect the Scala output. – Alex Apr 03 '11 at 08:12

Is this matching from Scala is available in C#?

3 Answers3