Re: [Haskell-beginners] Using symbolic values in the case expression

11 Nov 2010

      On Thursday 11 November 2010 18:45:43, C K Kashyap wrote:
...
Is there a way out?
What I need to do is implement a protocol - so it would be nice to
write a case expression with patters being symbolic.
Guards?

case expr of
  res | res == v1 -> "One"
      | res == v2 -> "Two"
  _ -> error "Three"

Or perhaps a little preprocessor abuse might help.

{-# LANGUAGE CPP #-}

#define V1 1
#define V2 2

case expr of
  V1 -> "One"
  V2 -> "Two"
  _  -> error "Three"

Re: [Haskell-beginners] Using symbolic values in the case expression

Daniel Fischer