On Tue, Sep 4, 2012 at 2:23 PM, Stephen Compall <stephen.comp...@gmail.com> wrote: > On Tue, 2012-09-04 at 09:48 -0700, Sean Corfield wrote: >> Stephen, could you elaborate on this? > > Requiring pred to be free of side effects provides many invariants about > it to the `take-while' implementation; the legality of out-of-order > calling is just one of them.
But that is a hypothetical, yes? You're not suggesting that take-while actually does that, right? > It might mean something somewhere in between. I am basing > this only on what the docstring says. [1] That commit also added "pred must be free of side-effects" to `filter` and replaced lazy-cons with lazy-seq (which suggests lazy-seq changed its semantics along the way since (lazy-seq :a [:b]) just yields (:b) these days but clearly needed to behave more like cons back then?). I think calling `pred` out of linear order is a far less likely intended freedom than those of calling `pred` more than once on a given element or calling `pred` on more elements that strictly needed. Either way, it's all a bit of a moot point: the docstring says - for take-while and filter - that the predicate should be free of side-effects and I think that makes it clear that using a predicate with side-effects can legally lead to "undesirable" behavior (such as being called more times than you might expect). So the OP should consider that possibility in their code. -- Sean A Corfield -- (904) 302-SEAN An Architect's View -- http://corfield.org/ World Singles, LLC. -- http://worldsingles.com/ "Perfection is the enemy of the good." -- Gustave Flaubert, French realist novelist (1821-1880) -- 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
