Hi, Am Mittwoch, 13. Juli 2011 11:02:40 UTC+2 schrieb bsmith.occs: > > On Wed, Jul 13, 2011 at 08:43, Meikel Brandmeyer <m...@kotka.de> wrote: > > Hi, > > > > I think the culprit is here: > > > https://github.com/clojure/clojure/blob/5f9d6a02c530a02251197e1b844af37440a6b569/src/clj/clojure/core/protocols.clj#L64 > > > > The line "(recur cls (next s) f (f val (first s)))" must be written as > > > > (let [v (f val (first s))] > > (recur cls (next s) f v)) > > > > for your scenario to work. > > I'm probably being a little dense this morning, but... > > I've stared at both examples for some time now and still don't see why > the first should behave differently than the second. > > Can you give me a hint? > Because - although not guaranteed - clojure evaluates function arguments from the left to the right. So the next element in the sequence is realised before the function f is called. In the second snippet f will be called always before the next element is realised. If f is pure, there won't be a difference. If f is not pure, it will be a difference. Especially if next relies on side-effects of f (or vice versa) as in the scenario described by the OP.
Sincerely Meikel -- 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
