bartc <b...@freeuk.com> writes: > [repost as original seems to have gone to email; my newsreader has > somehow acquired a 'Reply' button where 'Followup' normally goes.]
[I thought it was intended but my reply bounced.] > On 10/03/2018 14:23, Ben Bacarisse wrote: >> Ben Bacarisse <ben.use...@bsb.me.uk> writes: > >> Off topic: I knocked up this Haskell version as a proof-of-concept: >> >> import Data.List >> >> pn n l = pn' n (map (:[]) l) >> where pn' n lists | n == 1 = lists >> | otherwise = diag (pn' (n-1) lists) lists >> diag l1 l2 = zipWith (++) (concat (inits l1)) >> (concat (map reverse (inits l2))) >> <snip> > What's the output? (And what's the input; how do you invoke pn, if > that's how it's done?) You pass a number and a list which should probably be infinite like [1..]. You'd better take only a few of the resulting elements then: *Main> let triples = pn 3 [1..] *Main> take 20 triples [[1,1,1],[1,1,2],[1,2,1],[1,1,3],[1,2,2],[2,1,1],[1,1,4],[1,2,3],[2,1,2],[1,3,1],[1,1,5],[1,2,4],[2,1,3],[1,3,2],[2,2,1],[1,1,6],[1,2,5],[2,1,4],[1,3,3],[2,2,2]] or you can index the list to look at particular elements: *Main> triples !! 10000000 [70,6,1628] but, as I've said, the order of the results is not the usual one (except for pairs). -- Ben. -- https://mail.python.org/mailman/listinfo/python-list
