7.19 Curried Definitions

The macros in this section are provided by

(use-modules (ice-9 curried-definitions))

and replace those provided by default.

Prior to Guile 2.0, Guile provided a type of definition known colloquially as a “curried definition”. The idea is to extend the syntax of define so that you can conveniently define procedures that return procedures, up to any desired depth.

For example,

(define ((foo x) y)
  (list x y))

is a convenience form of

(define foo
  (lambda (x)
    (lambda (y)
      (list x y))))

Scheme Syntax: define (… (name args …) …) body …

Scheme Syntax: define* (… (name args …) …) body …

Scheme Syntax: define-public (… (name args …) …) body …

Create a top level variable name bound to the procedure with parameter list args. If name is itself a formal parameter list, then a higher order procedure is created using that formal-parameter list, and returning a procedure that has parameter list args. This nesting may occur to arbitrary depth.

define* is similar but the formal parameter lists take additional options as described in lambda* and define*. For example,

(define* ((foo #:keys (bar 'baz) (quux 'zot)) frotz #:rest rest)
  (list bar quux frotz rest))

((foo #:quux 'foo) 1 2 3 4 5)
⇒ (baz foo 1 (2 3 4 5))

define-public is similar to define but it also adds name to the list of exported bindings of the current module.