Why is it that clojure maps aren't lazy though? Wouldn't that be just as useful an abstraction as lazy sequences? Aren't map really just lists of pairs in the end anyway?
--Robert McIntyre On Mon, Sep 6, 2010 at 1:19 PM, Michał Marczyk <michal.marc...@gmail.com> wrote: > On 6 September 2010 18:49, Robert McIntyre <r...@mit.edu> wrote: >> I thought that since into uses reduce, it would be lazy, but I was wrong. >> reduce just plows through everything with a non-lazy recursion. > > Well, there's another reason in that the concept of a lazy map is > problematic. In Clojure, at any rate, either you have a map or you > don't -- it's always strict. > >> Why is reduce not lazy? > > The tail call in reduce is a call to itself, so it's pretty hard to > imagine a meaningful way for it to be lazy -- it only has anything to > return other than a result to a further call to reduce upon reaching > the end of the sequence being reduced. Thus, it's purpose is > fundamentally to go through the entire seq producing a single "end > product". > > In contrast, a right fold's tail is a call to the reduction function > with one of the arguments being a further call to foldr, so that can > be made lazy in a sufficiently lazy language; but in Clojure, only > seqs can be lazy, so that wouldn't really work either. > > Sincerely, > Michał > > -- > 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 -- 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
