Elimination of absurd patterns
Felipe Almeida Lessa
felipe.lessa at gmail.com
Tue May 3 04:03:23 CEST 2011
On Mon, May 2, 2011 at 6:20 PM, C Rodrigues <red5_2 at hotmail.com> wrote:
> I was experimenting with using GADTs for subtyping when I found something
> interesting. Hopefully someone can satisfy my curiosity.
> Here are two equivalent GADTs. My understanding was that GHC would
> translate "Foo" and "Bar" into isomorphic data types. However, GHC 6.12.3
> generates better code for 'fooName' than for 'barName'. In 'fooName', there
> is no pattern match against 'FooExtra'. In 'barName', there is a pattern
> match against 'BarExtra'. What makes these data types different?
IIRC, GHC 6.12.3 had some problems with type equalities. Did you try GHC 7.0.3?
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