9 Feb
2007
9 Feb
'07
9:42 a.m.
If you look at the definition of 'powers' you'll note it's infinite. So there's no easy way to take the product of this list, if I don't know how many items to take from it.
So you need finite lists.
-- how many of the prime p are in the unique factorisation -- of the integer n? f 0 _ = 0 f n p | n `mod` p == 0 = 1 + f (n `div` p) p | otherwise = 0
powers n = map (f n) primes
Extremely high-level hint: Move from div to divMod (i.e., let f return a pair), and add List.unfoldr (or takeWhile) capacities to map. ;-) Wolfram