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: ?]
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