Hi Mike, If I understood your aim correctly, and if you accept changing the output of (combinations [[1 2]]) to ((1) (2)) instead of (1 2), which I think makes more sense,then the reduce function does the job in one line for you.
(defn combinations [items] (reduce #(for [l % i %2] (conj l i)) [[]] items)) the same, wordier and maybe clearer: (defn combinations [items] (reduce (fn [output item] (for [o output i item] (conj o i))) [[]] items)) and if you really need the output to be a list of lists instead of a list of vectors, maybe something like: (defn combinations [items] (map seq (reduce #(for [o % i %2] (conj o i)) [[]] items))) Btw, I learned an awful lot about compact ways of doing stuff in Clojure by doing the exercises (and checking others' solutions) on 4clojure.com, which I warmly recommend. Nico On Feb 27, 3:45 am, Mike Ledoux <mike.led...@gmail.com> wrote: > So I recently decided to start learning Clojure. I installed Clojure > box and wrote this little method to compute all possible combinations > of input: > > (defn combinations [items] > (if (== (count items) 1) > (flatten items) > (for [frstitems (flatten (first items)) > tlitm (combinations (rest items))] > (flatten (list frstitems tlitm))))) > > so (combinations [[1 2] [1 2]]) > > returns > > ((1 1) (1 2) (2 1) (2 2)) > > Is there a way I can get rid of the if form? Having the if statement > duplicates what the for loop does when it creates frstitems. I tried > removing the if statement so the function looks like: > > (defn combinations [items] > (for [frstitems (flatten (first items)) > tlitm (combinations (rest items))] > (flatten (list frstitems tlitm)))) > > but when I do this the function just returns an empty list. I tried > to figure out why using the REPL but did not discover the problem. > > Is what I'm asking possible and if so what would the function look > like? Thank you. > > So far Clojure is pretty cool! > > Mike -- 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
