Hello Felipe, Wednesday, October 11, 2006, 4:47:59 AM, you wrote:
Why does this works? "Yet Another Haskell Tutorial" teaches that pattern matching occurs at one stage and guard processing at other, and that there's no back (page 94).
something is definitely wrong - either book or your understanding. it's very widely used feature, i just took a quick scan of Hugs Prelude and found a lot of its uses: (!!) :: [a] -> Int -> a xs !! n | n<0 = error "Prelude.!!: negative index" [] !! _ = error "Prelude.!!: index too large" (x:_) !! 0 = x (_:xs) !! n = xs !! (n-1) lexmatch (x:xs) (y:ys) | x == y = lexmatch xs ys lexmatch xs ys = (xs,ys) showLitChar c | c > '\DEL' = showChar '\\' . protectEsc isDigit (shows (fromEnum c)) showLitChar '\DEL' = showString "\\DEL" x ^ 0 = 1 x ^ n | n > 0 = .... _ ^ _ = error "Prelude.^: negative exponent" i don't even say that i use this feature every day :) -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com