I just came across this example in "Clojure Programming", chapt 4:
(def ^:dynamic *max-value* 255) (defn valid-value? [v] (<= v *max-value*)) (binding [*max-value* 500] (map valid-value? [299])) ;= (false) It's not really explained in the text. I'm guessing this happens because when the (binding...) expression is evaluated, it merely returns the head of the seq. The values of the seq aren't evaluated until the repl implicitly realizes the return value. (I can see the point of this repl behavior, but it has often misled me by giving me different results than I get when running code outside the repl). The workaround in the book is to move the "binding" into the map function, though I would think "doall" would be a better solution. (binding [*max-value* 500] (doall (map valid-value? [299]))) ;= (true) This seems like the same issue that comes up with libraries that implement a with-<blah> API: with-db, and so-forth. You have to walk any seqs within the binding form if the binding is to have any affect on the values in the seqs. -- -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
