[Haskell-cafe] Pattern match failure

I'm trying to write a function to recognize a context free grammar, but I keep getting pattern match failure errors. This is what I have: data Grammar c = Brule c c c | Rule c c gez = [(Brule 'S' 'p' 'D'),(Brule 'D' 't' 'E'),(Rule 'E' 'j')] recog :: String -> String -> [Grammar Char] -> Bool recog a b list = case list of [Brule x y z] -> if a == [x] then recog [z] b list else recog a b list [Rule x y] -> True how can I solve this pattern matching error? -- View this message in context: http://www.nabble.com/Pattern-match-failure-tp16600643p16600643.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.