On Sun, Dec 28, 2008 at 6:01 PM, Craig Marshall <cra...@gmail.com> wrote: > > Hi, > > I'm trying to learn lisp and Clojure and so I'm trying some excercises > suggested here on the group a while ago. > > I'm not doing too well, I had to cheat on excercise one (make a series > of integers) by looking at the source code to the range function, and > I'm now having to ask for help with excercise two! > > I know I could just find a different implementation online, but I > would prefer to understand why my method doesn't work. If anyone can > point to my mistake(s), I'd be very grateful.. > > (defn fib-helper [a b] > (fib-helper b (+ a b)))
This defines an infinitely recursive function. It never actually returns anything, so it quickly exhausts the stack. Were you trying for a lazy infinite sequence of fibonacci numbers? > (defn fib (fib-helper 0 1)) ; This doesn't work either: (defn fib (fib- > helper '(0 1))) > > (println (take 5 fib)) It looks like you want to use (def fib ...) instead of (defn fib ...), but because of the infinitely recursive fib-helper this will not get you much further :) For exercise two, perhaps you should try for the traditional recursive definition of fib? i.e. if I want to calculate the nth fibonacci number, I have to first calculate the (n-1)th and (n-2)th fibonacci numbers and then add them together and return the result. At some point this has to terminate, so you need to make sure that there is a way out of the recursion. (You're probably already familiar with recursion, in which case, sorry for stating the obvious :) clojure.contrib.lazy-seqs has a lazy infinite sequence implementation. -- Michael Wood <esiot...@gmail.com> --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
