OK, cartesian_product it is.
Two comments on your version. First, unlike mine (and the current
"combinations"), it takes a single argument, a seq of seqs (rather
than multiple seq arguments); which of these ways is preferred?
Second, I had the clauses of my for loop backwards, which was slowing
things down. I think this version:
(defn combinations "Take a seq of seqs and return a lazy list of
ordered combinations (pick 1 from each seq)"
[seqs]
(if (empty? seqs) '(())
(for [rst (combinations (rest seqs))
item (first seqs)]
(cons item rest))))
is actually significantly faster than the iterative one you posted
(and also much simpler); do your benchmarks agree?
On Jan 24, 12:47 am, Mark Engelberg <mark.engelb...@gmail.com> wrote:
> On Fri, Jan 23, 2009 at 11:43 PM, <jawo...@berkeley.edu> wrote:
> > I think the usual mathematical name is be cartesian-product (or maybe
> > cross-product), although selections is OK with me too.
>
> Yes, now that you've reminded me, I agree that cartesian-product is
> the usual mathematical name, and that would probably be my first
> choice.
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