[Haskell-cafe] unary pattern matching

John Meacham john at repetae.net
Thu Jan 26 20:14:26 EST 2006

I have often wanted a shorthand syntax for testing if a value matches a
given pattern. I want to implement such an extension for jhc but can't
decide an appropriate syntax so I thought I'd ask the group. basically I
want something like

/Left (Just _)/   expands to 

\x -> case x of
        Left (Just _) -> True
        _ -> False

so you can do things like

when (/Just _/ x) $ putStrLn "x is something"

map /Left (Foo _ 'x')/ xs

to get a list of booleans saying whether the xs match or not.

however, the '/' syntax clearly doesn't work, nor would anything that
conflicts with normal haskell syntax. does anyone have any better ideas?


John Meacham - ⑆repetae.net⑆john⑈ 

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