Am Montag 08 Februar 2010 22:58:03 schrieb Matthew Phillips: > P.S. > > > Daniel: > > > > [*] classic example: why will > > > > average xs = sum / len > > where > > (sum,len) = foldl' accum (0,0) xs > > accum (sm,ln) x = (sm+x,ln+1) > > > > cause a stack overflow for long lists? > > You gave a strong hint before this, so I'd guess it's due to the lazy > tuple creation in "accum"?
Well, the tuples are forced, so in that sense, tuple creation is not lazy. But the components of the tuple are *not* forced, so they become large thunks and in that sense, tuple creation is lazy and that's indeed the cause of the stack overflow. I think you get full marks for this :) _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
