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ANSI Common Lisp  5 Data and Control Flow 5.3 Dictionary of Data and Control Flow
| 5.3.39 constantly |
Function |
- Syntax:
-
constantly
value
 function
- Arguments and Values:
-
value - an object.
function - a function.
- Description:
-
constantly returns a function that accepts any number of
arguments, that has no side-effects, and that always returns value.
- Examples:
-
(mapcar (constantly 3) '(a b c d)) (3 3 3 3)
(defmacro with-vars (vars &body forms)
`((lambda ,vars ,@forms) ,@(mapcar (constantly nil) vars)))
WITH-VARS
(macroexpand '(with-vars (a b) (setq a 3 b (* a a)) (list a b)))
((LAMBDA (A B) (SETQ A 3 B (* A A)) (LIST A B)) NIL NIL), true
- See Also:
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identity
- Notes:
-
constantly could be defined by:
(defun constantly (object)
#'(lambda (&rest arguments) object))
- Allegro CL Implementation Details:
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None.
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