implementation module MatchStrings import StdEnv head :: String -> Char head "" = abort "Empty String" head s = s.[0] tail :: String -> String tail "" = abort "Empty String" tail s = s % (1, size s - 1) is_gelijk :: String String -> Bool is_gelijk "" "" = True is_gelijk a b = (size a == size b) && (head a == head b) && is_gelijk (tail a) (tail b) is_deelstring :: String String -> Bool is_deelstring _ "" = False is_deelstring a b = is_begin a b || is_deelstring a (tail b) is_begin :: String String -> Bool is_begin "" _ = True is_begin _ "" = False is_begin a b = head a == head b && is_begin (tail a) (tail b) is_deel :: String String -> Bool is_deel "" _ = True is_deel _ "" = False is_deel a b = head a == head b && is_deel (tail a) (tail b) || is_deel a (tail b) is_match :: String String -> Bool is_match a b = is_begin_match a b || size b > 0 && is_begin_match a (tail b) is_begin_match :: String String -> Bool is_begin_match "" _ = True is_begin_match a "" = head a == '*' && size a == 1 is_begin_match a b | head a == '.' || head a == head b = is_begin_match (tail a) (tail b) | head a == '*' = is_begin_match a (tail b) || is_begin_match (tail a) b | otherwise = False //Start= (head pink_floyd, tail pink_floyd) //Start= is_gelijk "" " " //Start= is_deelstring "there" pink_floyd //Start= is_deelstring "there" marillion //Start= is_deel "there" marillion //Start= is_deel "she and her" pink_floyd //Start= is_deel radiohead pink_floyd //Start= is_match "*.here*.here*." pink_floyd //Start= is_match ".here.here." pink_floyd pink_floyd= "Is there anybody in there?" marillion= "Just for the record" radiohead= "There there"