for-each -- r7rs Definition

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Kind

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functor;

Extended by

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• for-each (from vonuvoli);

Procedure signature

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Procedure variants:

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

Exports

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• scheme:base -- (scheme base);

Exports recursive

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• scheme -- (scheme);

Description

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(for-each proc list_1 list_2 ...)

Domain: It is an error if proc does not accept as many arguments as there are lists.

The arguments to for-each are like the arguments to map, but for-each calls proc for its side effects rather than for its values. Unlike map, for-each is guaranteed to call proc on the elements of the lists in order from the first element(s) to the last, and the value returned by for-each is unspecified. If more than one list is given and not all lists have the same length, for-each 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.

(let ((v (make-vector 5)))
  (for-each (lambda (i)
              (vector-set! v i (* i i)))
            '(0 1 2 3 4))
  v)                                ===>  #(0 1 4 9 16)

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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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• for-each-procedure;
• list;
• undefined;