[Haskell-cafe] A simple beginner question

[Luke Palmer]

On Tue, Jun 3, 2008 at 6:48 PM, Ronald Guida <oddron at gmail.com> wrote:
> filter (\x -> case x of A -> True; otherwise -> False) sampleTypes
>  ==> [A]
>
> filter (\x -> case x of B _ -> True; otherwise -> False) sampleTypes
>  ==> [B 5]

There's a neat little mini-trick for these types of pattern matches:

filter (\x -> case x of B {} -> True; otherwise -> False) sampleTypes

Does the same thing, but works no matter how many arguments the
constructor B takes.

Luke