On Friday, January 2, 2015 8:13:41 PM UTC-5, novato wrote: > > I choose clojure as my first programming language after some research. I > am learning by doing Clojure Koans <http://clojurekoans.com/> exercises. > I reached to the functions "lesson" and I have a doubt on the following > code: > ((fn [x] (* 5 x)) 5) > > Why is that the last 5 is outside the fn parentheses? Why this doesn't > work? > (fn [x] (* 5 x) 5) > > Thanks in advice for the clarification and excuse my poor english. >
The (fn ...) form evaluates to a function. In the first case, there is a (fn ...) form that evaluates to a function that quintuples its argument, inside a form that calls this function with 5 and should itself evaulate to 25. The second line will evaluate to a function that quintuples its argument, throws this result away, and then returns 5, without calling that function. (constantly 5) would be equivalent, and more efficient (at least prior to JIT optimization). Everything inside the (fn ...) parentheses is part of the function definition. It might help to break the first one into its components. This is equivalent: (let [f (fn [x] (* 5 x))] (f 5)) First we create (fn [x] (* 5 x)) and call it f. Then we call f with 5. Replacing the symbol f with what f gets bound to by the let should produce the same results; and such a replacement produces the first line of code from your post. -- 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/d/optout.
