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.)
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