RE: Elimination of absurd patterns
I tried it again using a development version of GHC 7.1 that I downloaded in March. The results are the same, with GHC generating different code for the supposedly equivalent data types. 'barName' has an impossible pattern match against constructor 'BarExtra', whereas 'fooName' does not. Date: Mon, 2 May 2011 23:03:23 -0300 Subject: Re: Elimination of absurd patterns From: felipe.le...@gmail.com To: red...@hotmail.com CC: glasgow-haskell-users@haskell.org On Mon, May 2, 2011 at 6:20 PM, C Rodrigues 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? Cheers, =) -- Felipe. ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Elimination of absurd patterns (reformatted)
On Mon, May 02, 2011 at 09:25:06PM +, C Rodrigues wrote: I'm re-sending this e-mail, hopefully with proper line breaks this time. 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? Not a real answer to your question, but have you tried this with GHC 7.0.3? The type checker changed a lot between 6.12 and 7 and it may now behave more consistently (although I do not know for sure). -Brent ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Elimination of absurd patterns
On Mon, May 2, 2011 at 6:20 PM, C Rodrigues red...@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? Cheers, =) -- Felipe. ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
