Hi, On 12 Okt., 07:05, Aravindh Johendran <ajohend...@gmail.com> wrote:
> (def *cont* identity) > (defmacro =values [& retvals] > `(*cont* ~...@retvals)) > > why would the following two expressions throw errors??? > (binding [*cont* (fn [m n] (=values (list m n)))] (*cont* 'a 'b)) So what happens here: The macro =values in the anonymous fn expands into a call to *cont*. So it is equivalent to: (binding [*cont* (fn [m n] (*cont* (list m n)))] (*cont* :a :b)). So when you call *cont* in the binding you actually call the anonymous function which calls again *cont*, ie. itself. But this time you only pass one argument (the list) while the function expects two. Hence the error. > However, these two expression work without a problem! > ((binding [*cont* (fn [m n] (=values (list m n)))] *cont*) 'a 'b) Here your basically return the anonymous function and call it passing :a and :b. Since the we already left the binding body the original root value (identity) of *cont* is restored. So calling it with one argument does not cause the error. > (binding [*cont* (fn [m n] (list m n))] (*cont* 'a 'b)) I think it should be clear by now, why this one works: you have no recursive call to *cont*. Hence problem here. Hope that helps. 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
