> Compiling the following with ghc-4.06 produces an erroneous
> error message:
>
> module O where
>
> a :: Int
> a = 1
>
> b :: Int
> b = 2
>
> c :: Int
> c = 3
>
> f :: Int -> Bool
> f i = case i of
> a -> True
> b -> True
> c -> True
>
>
> The compiler complains:
>
> o.hs:14: Pattern match(es) are overlapped in a group of case
> alternatives
> beginning
> a:
> b -> ...
> c -> ...
You're not an Erlang programmer by any chance are you? :-)
As Kevin pointed out, the warning is correct. In Haskell, a variable name
in a pattern is always a new binding, and shadows any existing bindings of
the same name.
Cheers,
Simon
