geniusfat <[EMAIL PROTECTED]> writes:
(snip)
> the order does not matter and each object can be chosen only once.
(snip)
In that case, with the help of Data.List.tails, one can do:
threeOf :: [a] -> [(a,a,a)]
threeOf xs =
[ (p,q,r) | (p:ps) <- tails xs, (q:qs) <- tails ps, r <- qs ]
(the r <- qs is a simpler version of (r:rs) <- tails qs)
or maybe,
nOf :: Int -> [a] -> [[a]]
nOf _ [] = []
nOf 1 xs = map return xs
nOf n (x:xs) = map (x:) (nOf (n-1) xs) ++ nOf n xs
(These are fairly naive versions that just took me a few minutes, but
perhaps they'll do.)
-- Mark
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