On Feb 4, 2006, at 1:31 PM, Jon Fairbairn wrote:
...
There ought to be a list_product somewhere (I mean [1..]
`list_product` [4..] ==
[(1,4),(2,4),(1,5),(3,4),(2,5),(1,6),...]). Is there?
Not that I know of, but here's one which handles finite lists
correctly; it'd be a nice addition to Data.List:
dzip :: [a] -> [b] -> [(a,b)]
dzip = dzipWith (,)
dzipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
dzipWith f [] ys = []
dzipWith f as [] = []
dzipWith f as (y:ys) = dzipK ys [y]
where dzipK (b:bs) rbs =
zipWith f as rbs ++ dzipK bs (b : rbs)
dzipK [] rbs = dzipT as
where dzipT ys@(_:yt) = zipWith f ys rbs ++ dzipT yt
dzipT [] = []
-Jan-Willem Maessen
Jón
--
Jón Fairbairn Jon.Fairbairn at
cl.cam.ac.uk
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