On Tue, Aug 11, 2009 at 11:40 AM, John Harrop<jharrop...@gmail.com> wrote: > On Tue, Aug 11, 2009 at 6:39 AM, Krukow <karl.kru...@gmail.com> wrote: >> >> I was browsing through core when I noticed something I didn't >> understand in 'into' (from core.clj): >> >> ;redef into with batch support >> (defn into >> "Returns a new coll consisting of to-coll with all of the items of >> from-coll conjoined." >> [to from] >> (if (instance? clojure.lang.IEditableCollection to) >> (#(loop [ret (transient to) items (seq from)] >> (if items >> (recur (conj! ret (first items)) (next items)) >> (persistent! ret)))) >> (#(loop [ret to items (seq from)] >> (if items >> (recur (conj ret (first items)) (next items)) >> ret))))) >> >> I am wondering about the construct #(loop ...). As far as I can see >> you might as well just use (loop). I.e., >> >> (defn into2 >> "Returns a new coll consisting of to-coll with all of the items of >> from-coll conjoined." >> [to from] >> (if (instance? clojure.lang.IEditableCollection to) >> (loop [ret (transient to) items (seq from)] >> (if items >> (recur (conj! ret (first items)) (next items)) >> (persistent! ret))) >> (loop [ret to items (seq from)] >> (if items >> (recur (conj ret (first items)) (next items)) >> ret)))) >> >> I suspect that I am missing some point. Could someone clarify? > > I don't know. Perhaps at this point during bootstrap loop doesn't create > recur points and so the anonymous lambdas are necessary? But then recur > would rebind the (nonexistent) lambda parameters I'd have thought.
I don't know either. 'loop' is a macro that expands to 'loop*', which is in turn a special form. At that most basic level, loop* still creates a recur point, so I don't think that's the point. I wonder if it has to do with clearing locals for tail calls or perhaps avoiding holding the head of 'from'. --Chouser --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
