Good question. Also, I wonder if there are any existing realize type functions? i.e. (realize (filter ...))
or how would I realize without printing? Tim On Oct 25, 10:12 am, "Marshall T. Vandegrift" <llas...@gmail.com> wrote: > Tim Robinson <tim.blacks...@gmail.com> writes: > > => (defn oops! [] > > (let [x1 (atom (hash-map)) > > v1 (filter > > #(let [xv1 (@data %)] > > (if (= xv1 "v1") > > (swap! x1 assoc :k1 "other"))) > > (keys @data)) > > rxv (reset! flag @x1)] > > (println v1))) > > So why didn't the first version with deref work? > > Because `filter' produces a lazy list, which isn't realized (and the > side effects generated) until your call to `println'. > > Furthermore, the documentation for `filter' explicitly notes that "pred > must be free of side-effects." Looking at the implementation, I'm not > sure why function-argument purity matters more for `filter' than any > other sequence-generating higher-order function. Does anyone else know > the reason? > > -Marshall -- 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
