I think this is indeed the best way to do this- On closer examination, although there's some overhead in using "reductions" it appears to be slower by only a constant factor- So with larger data sets it'll retain a reasonable performance, same ball park as my tail-call optimized versions.
On Dec 27, 8:52 pm, David Cabana <drcab...@gmail.com> wrote: > Try this: > > (use '[clojure.contrib.seq-utils :only (reductions)]) > > (defn left-total [lst] > (map vector lst > (reductions + (cons 0 lst)))) > > > > On Sun, Dec 27, 2009 at 8:36 PM, Conrad <drc...@gmail.com> wrote: > > I've been writing Clojure code today and have noticed the same pattern > > show up multiple times, but can't find an elegant way to code it in > > idiomatic Clojure. I feel like I'm missing an obvious solution... > > anyone else see something I don't? Thanks in advance! > > > The problem boils down to the following minimal example: Suppose you > > want to write a function "left-total" which takes a list of number and > > returns pairs of said numbers, along with the total of numbers to the > > left: > > > => (left-total [3 5 10 1 2 7]) > > ([3 0] [5 3] [10 8] [1 18] [2 19] [7 21]) > > > I can think of several ways to write this function. Three acceptable > > versions of this function are written below, but all of them are > > hideous looking. Is there a better solution? (Note that any solution > > should avoid thrashing the stack or performing more than the minimum > > number of additions.) -- 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
