Hello Julian,

Prelude> let f g = g . g
Prelude> let sum x y = x + y
Prelude> f sum

If you are trying to call 'f' and see the result, args are missing.

If you are trying to create new type, use 'let'.

Prelude> (\x y -> x + y) . (\x y -> x + y)

Similar story. Let or args

;)