Curried Functions

are functions that take multiple arguments one at a time instead of as tuples.

Using the fact that functions can return other functions we can define curried functions in two ways:

• a function of multiple arguments that returns a non-function output.
• a function of a single (the leftmost) argument that returns a functions that takes the remaining arguments as arguments. The returned function can itself be defined in these two ways.

Examples

A function that adds two numbers a and b can be defined as

• a function that takes both a and b as arguments

  add :: (Int -> Int) -> Int
  add a b = a + b

• a function that takes a as single argument and returns a function that takes b as argument, has a body where a is defined, and returns an int

  add :: Int -> (Int -> Int)
  add a b = a + b