23.8.9 Producing side effects

Function: for-each* proc circ0 circ ...

Syntax: for-each*/stx proc circ0 circ ...

This procedure extends the R6RS specification for for-each to allow the arguments to be of unequal length; it terminates when the shortest list runs out of elements.

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.

(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)

At least one of the list arguments must be a finite list.

Function: pair-for-each f ell0 ell ...

Syntax: pair-for-each/stx f ell0 ell ...

Like for-each, but f is applied to successive sublists of the argument lists. That is, f is applied to the cons cells of the lists, rather than the lists’ elements. These applications occur in left–to–right order.

The f procedure may reliably apply set-cdr! to the pairs it is given without altering the sequence of execution.

(pair-for-each
    (lambda (pair)
      (display pair)
      (newline))
  '(a b c))
-| (a b c)
-| (b c)
-| (c)

The list arguments must have equal length.

Function: pair-for-each* f circ0 circ ...

Syntax: pair-for-each*/stx f circ0 circ ...

Like for-each*, but f is applied to successive sublists of the argument lists. That is, f is applied to the cons cells of the lists, rather than the lists’ elements. These applications occur in left–to–right order.

The f procedure may reliably apply set-cdr! to the pairs it is given without altering the sequence of execution.

(pair-for-each*
    (lambda (pair)
      (display pair)
      (newline))
  '(a b c))
-| (a b c)
-| (b c)
-| (c)

At least one of the list arguments must be a finite list.