map -- r7rs Definition

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Kind

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functor;

Implemented by

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• map (from vonuvoli);

Procedure signature

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Procedure variants:

• ((map-procedure list |1...|) -> (list-proper))
  • inputs:
    • a value of type map-procedure;
    • a value of type list;
    • ... -- at least one time;
  • output: a value of type list-proper;

Exports

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• scheme:base -- (scheme base);

Exports recursive

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• scheme -- (scheme);

Description

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(map proc list_1 list_2 ...)

Domain: It is an error if proc does not accept as many arguments as there are lists and return a single value.

The map procedure applies proc element-wise to the elements of the lists and returns a list of the results, in order. If more than one list is given and not all lists have the same length, map terminates when the shortest list runs out. The lists can be circular, but it is an error if all of them are circular. It is an error for proc to mutate any of the lists. The dynamic order in which proc is applied to the elements of the lists is unspecified. If multiple returns occur from map, the values returned by earlier returns are not mutated.

(map cadr '((a b) (d e) (g h)))   ===>  (b e h)

(map (lambda (n) (expt n n))
     '(1 2 3 4 5))                ===>  (1 4 27 256 3125)

(map + '(1 2 3) '(4 5 6 7))         ===>  (5 7 9)

(let ((count 0))
  (map (lambda (ignored)
         (set! count (+ count 1))
         count)
       '(a b)))                 ===>  (1 2) or (2 1)

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The text herein was sourced and adapted as described in the "R7RS attribution of various text snippets" appendix.

Referenced-types

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• map-procedure;
• list;
• list-proper;