Entries from 2013-12-18 to 1 day
sum :: Num a => [a] -> a sum [] = 0 sum (x : xs) = (+) x (sum xs) sum = foldr (+) 0 --よって foldr :: (a -> b -> b) -> a -> [a] -> b --sumの場合はb=aだけど、b /= aのときってどんなとき? --そうだlengthを考えてみよう length :: [a] -> Int leng…
sum :: Num a => [a] -> a sum [] = 0 sum (x : xs) = (+) x (sum xs) sum = foldr (+) 0 --よって foldr :: (a -> b -> b) -> a -> [a] -> b --sumの場合はb=aだけど、b /= aのときってどんなとき? --そうだlengthを考えてみよう length :: [a] -> Int leng…