What does a fullstop or period or dot (.) mean in Haskell?

Question

I really wish that Google was better at searching for syntax:

decades         :: (RealFrac a) => a -> a -> [a] -> Array Int Int
decades a b     =         


        

Answer 1

. is a higher order function for function composition.

Prelude> :type (.)
(.) :: (b -> c) -> (a -> b) -> a -> c
Prelude> (*2) . (+1) $ 1
4
Prelude> ((*2) . (+1)) 1
4