lambda

lambda Macro

Syntax:

lambda lambda-list [[ {declaration}* | documentation ]] {form}* → function

Arguments and Values:

lambda-list—an ordinary lambda list.

declaration—a declare expression; not evaluated.

documentation—a string; not evaluated.

form—a form.

function—a function.

Description:

Provides a shorthand notation for a function special form involving a lambda expression such that:

(lambda lambda-list [[ {declaration}* | documentation ]] {form}*)

≡ (function (lambda lambda-list [[ {declaration}* | documentation ]] {form}*))

≡ #’(lambda lambda-list [[ {declaration}* | documentation ]] {form}*)

Examples:

(funcall (lambda (x) (+ x 3)) 4) → 7 

See Also:

lambda (symbol)

Notes:

This macro could be implemented by:

(defmacro lambda (&whole form &rest bvl-decls-and-body)

(declare (ignore bvl-decls-and-body))

‘#’,form)

Expanded Reference: lambda (Macro)

The lambda macro provides convenient shorthand so that (lambda ...) is equivalent to #'(lambda ...) or (function (lambda ...)).

(funcall (lambda (x) (+ x 1)) 10)
=> 11

Because the macro makes (lambda ...) evaluate to a function, it can be passed directly to higher-order functions.

(mapcar (lambda (x) (* x x)) '(1 2 3 4 5))
=> (1 4 9 16 25)

(remove-if (lambda (x) (evenp x)) '(1 2 3 4 5))
=> (1 3 5)

These three forms are equivalent:

(lambda (x) (+ x 1))
;; is the same as:
#'(lambda (x) (+ x 1))
;; is the same as:
(function (lambda (x) (+ x 1)))

Lambda expressions close over their lexical environment.

(let ((offset 10))
  (mapcar (lambda (x) (+ x offset)) '(1 2 3)))
=> (11 12 13)