CIS 194 Week 4

Prelude.hs

-- Prelude functions which are defined in terms of foldr
-- http://www.cis.upenn.edu/~cis194/spring13/lectures/04-higher-order.html

length' :: [a] -> Int
length' = foldr (\_ acc -> 1 + acc) 0

sum' :: Num a => [a] -> a
sum' = foldr (*) 1

product' :: Num a => [a] -> a
product' = foldr (*) 1

and' :: [Bool] -> Bool
and' = foldr (\e acc -> e && acc) True

or' :: [Bool] -> Bool
or' = foldr (\e acc -> e || acc) False

any :: (a -> Bool) -> [a] -> Bool
any' p = foldr(\e acc -> p e || acc) False

all' :: (a -> Bool) -> [a] -> Bool
all' p = foldr(\e acc -> p e && acc) True