On Dec 5, 2007 1:43 PM, Benja Fallenstein <[EMAIL PROTECTED]> wrote: > Hi Paolo, > > On Dec 5, 2007 2:09 PM, Paulo J. Matos <[EMAIL PROTECTED]> wrote: > > I'm glad that my initial post generated such an interesting discussion > > but I'm still not understanding why the first version of findAllPath > > seems to be computing the whole list even when I just request the > > head, while the second one doesn't. > > Because the function starts its work with > > if isNothing lfpaths && isNothing rtpaths > then Nothing > else ... > > which forces the evaluation of 'lfpaths' and 'rtpaths' to see whether > they are Just or Nothing, which recursively forces the evaluation of > findAllPath for the whole tree. >
Oh, but lfpaths is not nothing so that means that isNothing rtpaths shouldn't be evaluated, right? > Hope this helps, > - Benja > > > -- Paulo Jorge Matos - pocm at soton.ac.uk http://www.personal.soton.ac.uk/pocm PhD Student @ ECS University of Southampton, UK _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
