Luke, Thanks for the nice answer. So maybe I'll give mapM3 the name mapM' and put it in my personal library.
But I'm still a bit curious about the performance profile of mapM. The profiler is telling me they're allocating around the same amount of memory, so I am not clear what is making it slow. I am guessing it has something to do with extra thunks due to laziness, but a 10x slowdown? Thanks again, B On Thu, Apr 24, 2008 at 4:45 PM, Luke Palmer <[EMAIL PROTECTED]> wrote: > On Thu, Apr 24, 2008 at 11:28 PM, Ben <[EMAIL PROTECTED]> wrote: > > 2) Is there a reason to not use mapM3 above? > > Yes, there certainly is. mapM3 is not equivalent to mapM; it is too strict: > > *Main> take 3 $ head $ mapM return [1,2,3,4,undefined] > [1,2,3] > *Main> take 3 $ head $ mapM3 return [1,2,3,4,undefined] > [*** Exception: Prelude.undefined > > So, like foldl', mapM3 seems a viable alternative for mapM, but not a > replacement. > > Luke > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
