On Tue, Oct 7, 2008 at 5:07 PM, Daniel Fischer <[EMAIL PROTECTED]> wrote: > Am Dienstag, 7. Oktober 2008 22:09 schrieb Andrew Coppin: >> Daniel Fischer wrote: >> > Maybe it is as simple as >> > >> > raw_bind (xs:xss) f = do >> > rsYs <- mapM f xs >> > ~rsZ <- raw_bind xss f >> > return (foldr union (cost rsZ) rsYs) >> > >> > then rsZ should only be evaluated when it's needed >> >> Ooo... "lazy pattern matching"? Can somebody explain to me, _very >> slowy_, exactly what that means? <snip> >> If I'm not mistaken, the rsZ variable shouldn't be evaluated until >> needed *anyway*, so what is lazy pattern matching buying me here? > > That depends on how your Monad (and union) is implemented, it may or may not > make a difference. I must admit that I didn't really look at the code you > posted, so I don't know what would be the case here. It was just an easy > thing to try which *might* help.
Unless you're pattern matching against a constructor, which rsZ is not, I think lazy pattern matching is no different from regular pattern matching. -- Dave Menendez <[EMAIL PROTECTED]> <http://www.eyrie.org/~zednenem/> _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
