I miss lots of stuff from when I was a kid. I used to write
elem x (_ ++ x : _) = True elem _ _ = False
and think that was cool. How dumb was I?
Yeah, the Kiel Reduction Language had similarly expressive and fun pattern matching, with subsequence matching and backtracking if the guard failed. Of course, these days, you could use view patterns for the simpler cases, but it doesn't look quite as nice: elem x (break (==x) -> (_, _:_)) = True elem _ _ = False and gets ugly enough to spoil the fun quickly: -- lookup key (_++((key,value):_)) = Just value lookup key (break ((==key).fst) -> (_ , (_,value):_)) = Just value lookup _ _ = Nothing Also, view patterns don't handle match failure by an implicit Monad, let alone MonadPlus, so one often has to insert an explicit Maybe, and there is no backtracking:-( Claus -- Nostalgia isn't what it used to be [source: ?]