learning-haskell/17-applicative/17.9-chapter-excercises.md

Chapter Excercises

fill in the types

1. pure :: a -> [a], (<*>) :: [(a -> b)] -> [a] -> [b]
2. pure :: a -> IO a, (<*>) :: IO (a -> b) -> IO a -> IO b
3. pure :: a -> (b,a), (<*>) :: (c, (a -> b)) -> (c, a) -> (c, b)
4. pure :: a -> (e -> a), (<*>) :: (e -> (a -> b))) -> (e -> a) -> (e -> b)

Write instances

see src/instances.hs

Combinations

see src/combinations.hs