On Wed, Nov 23, 2011 at 3:33 PM, James Reeves <jree...@weavejester.com> wrote: > Hi folks, > > I've just noticed that the evaluation order for reduce differs slight > between Clojure 1.2.1 and 1.3.0. > > If you have a lazy seq xs, (b c d ...) and an expression (reduce f a > xs), then the initial evaluation order in 1.2.1 is what you'd expect: > > a, b, (f a b) > > But in 1.3.0, it's slightly different: > > a, b, c, (f a b) > > For reasons that I can't quite work out, reduce in 1.3.0 evaluates the > first two items of a seq before evaluating the first accumulator (f a > b), even when reduce is supplied with an initial value. > > Technically I shouldn't have code that relies on the evaluation order > of lazy seqs, but I just thought I'd post this just in case anyone ran > into a similar problem. I'm now rearranging my code so that any > side-effects are pulled out of the Java iterator before I turn it into > a seq. > > - James
the change to the internal reduce protocol required moving the seq argument to the first argument position, so in the recur you have to do something like (recur (next the-seq) (f accum (first the-seq))) so natural the call to next happens first > -- > 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 -- And what is good, Phaedrus, And what is not good— Need we ask anyone to tell us these things? -- 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
