Currying

Currying is a functional programming language operation performed on functions of more than one argument, named after the logician Haskell Curry. Currying a function f of two arguments produces a function g of one argument that returns a function of one argument such that f(x, y) equals (g(x))(y), or in Lisp notation (f x y) equals ((g x) y). By extension, fully currying a function f of three arguments produces g such that f(x, y, z) equals ((g(x))(y))(z), or in Lisp notation (f x y z) equals (((g x) y) z).

To do currying in the Scheme programming language:

 (define curry2
   (lambda (f)
     (lambda (x)    ; take the first argument
       (lambda y    ; and the rest of the args as a list
         (f x . y)))))

If g equals (curry2 f), then (f x y) equals ((g x) y), and (f x y z) equals ((g x) y z).

These languages automatically fully curry functions called with too few arguments:

• ML
• Haskell

See also:

• lazy evaluation