On Jun 14, 5:31 am, Max Suica <max.su...@gmail.com> wrote: > > A lazy right fold[1] allows short-circuiting, so here's one attempt: > > Wow, that made my head explode. > > Some points: > > 1) That's not exatly foldr, as (foldr + 0 [range 100]) ought to work
Agreed, having to write that as (foldr (fn [x f-rest] (+ x (f-rest))) 0 (range 100)) shows that deficiency rather quickly. > 2) Foldr is not tail recursive nor can you really call an anamorphism > lazy The function I posted wasn't tail recursive either. It called the passed in f on the (delayed) result of the recursion before returning. It's certainly lazy on the spine of the list, in that evaluation is deferred until the caller needs a value, just like foldr should be. It's the inability to delay evaluation of arbitrary args (the recursion, here) that keeps us from being able to write, say, (foldr + 0 [1..10]) and have it work. > 3) Never the less you did it, through some mind twisting continuation > passing style > 4) That's fn awesome :D where did you learn it? There're three ways to defer evaluation that I know of in Clojure: delayed macro evaluation, force/delay, and what you see. The macro approach doesn't really work, the force/delay looks even worse, so ... -Sudish --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
