Re: [Haskell-cafe] Data.Map.Map Pattern Matching

On Wed, May 13, 2009 at 7:06 PM, Nico Rolle wrote:

Hi

I tried this but it diddn't work in ghci:

import qualified Data.Map as Map

test :: Map.Map [Int] [[Int]] -> Bool test (fromList[((i:is), (j:js))]) = [i] == j

i get the : "Parse error in pattern Failed." error.

fromList is an ordinary function. Pattern-matching only works on constructors (unless you use view patterns [see http://hackage.haskell.org/trac/ghc/wiki/ViewPatterns]). --Max