Hi, I think you want to use 'indexed' from clojure.contrib with your tri-nums to get a lazy indexed sequence.
Tobias On Wed, Mar 24, 2010 at 2:21 PM, Glen Rubin <rubing...@gmail.com> wrote: > I wrote the following code to produce a lazy sequence of the triangle > numbers. (triangle numbers are the series of numbers: 1, 1+2, 1+2+3, > etc...) > > (defn tri-nums [] > "prduce a lazy sequence of triangle numbers" > (let [triangles (map #(range 1 %) (iterate inc 2))] > (map #(reduce + %) triangles))) > > However, I now have produced a large triangle number (76576500) and > want to know which triangle number it is (e.g. the first, second, > third, etc...) > > So, I wrote the following code which should accept a triangle number > as input and tell you which one it is in the series: > > (defn which-tri [z] > (loop [x 1 y (first (tri-nums))] > (cond > (= y z) > x > (< y z) > (recur (inc x) (first (rest (tri-nums)))) > true > (println "no such tri-num")))) > > > The problem is that this function works for the first two triangle > numbers (1, 3), but then just sits there doing nothing on any higher > (6, 10, etc...). > > Any thoughts? > > thanks! > > -- > 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<clojure%2bunsubscr...@googlegroups.com> > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > > To unsubscribe from this group, send email to clojure+ > unsubscribegooglegroups.com or reply to this email with the words "REMOVE > ME" as the subject. > -- 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 To unsubscribe from this group, send email to clojure+unsubscribegooglegroups.com or reply to this email with the words "REMOVE ME" as the subject.
