12 Jan
2009
12 Jan
'09
4:48 p.m.
On Mon, 12 Jan 2009 21:04:35 +0100 (CET)
Henning Thielemann
On Mon, 12 Jan 2009, Andrew Coppin wrote:
Off the top of my head, try this:
convert b 0 = [] convert b n = n `mod` b : convert b (n `div` b)
(Takes a number and yields the radix-B representation of it. Backwards.)
convert b = unfoldr (\n -> if n > 0 then Just (n `mod` b, n `div` b) else Nothing)
I have the nice function 'toMaybe' which simplifies this to: unfoldr (\n -> toMaybe (n>0) (n `mod` b, n `div` b))
I would use the more general idiom: unfoldr (\n -> guard (n > 0) >> return (n `mod` b, n `div` b)) -- Robin