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. regards
On Wed, May 13, 2009 at 7:06 PM, Nico Rolle
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
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.
Pattern matching only works on constructors (and view patterns, but they are a bit more advanced.) I'm not sure what you are trying to accomplish, could you elaborate? Cheers, -- Jochem Berndsen | jochem@functor.nl GPG: 0xE6FABFAB
participants (3)
-
Jochem Berndsen -
Max Rabkin -
Nico Rolle