Am Dienstag, 7. Oktober 2008 23:38 schrieb David Menendez: > 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.
I think you're right, I was being stupid. Oh, well, it's late here _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
