09/08/03 21:18:14
>>606
-- Haskell で．foldl1 は末尾再帰だから許して
comb n r | r == 0 = 1
| n == r = 1
| otherwise = comb (n-1) r + comb (n-1) (r-1)
fact n = foldl1 (*) [1..n]
comb' n r = fact n `div` (fact r * fact (n-r))
main = print $ comb' 4 2
09/08/03 21:18:14
>>606
-- Haskell で．foldl1 は末尾再帰だから許して
comb n r | r == 0 = 1
| n == r = 1
| otherwise = comb (n-1) r + comb (n-1) (r-1)
fact n = foldl1 (*) [1..n]
comb' n r = fact n `div` (fact r * fact (n-r))
main = print $ comb' 4 2