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Procedure must be a procedure taking as many arguments as there
are lists. If more than one list is given, then they must
all be the same length. map applies procedure element-wise
to the elements of the lists and returns a list of the results, in
order from left to right. The dynamic order in which procedure is
applied to the elements of the lists is unspecified; use
for-each to sequence side effects.
(map cadr '((a b) (d e) (g h))) ⇒ (b e h)
(map (lambda (n) (expt n n)) '(1 2 3 4)) ⇒ (1 4 27 256)
(map + '(1 2 3) '(4 5 6)) ⇒ (5 7 9)
(let ((count 0))
(map (lambda (ignored)
(set! count (+ count 1))
count)
'(a b c))) ⇒ unspecified
Similar to map, except that the resulting list is terminated by
initial-value rather than the empty list. The following are
equivalent:
(map procedure list list …) (map* '() procedure list list …)
Similar to map and map*, respectively, except that the
results of applying procedure to the elements of lists are
concatenated together by append rather than by cons. The
following are equivalent, except that the former is more efficient:
(append-map procedure list list …) (apply append (map procedure list list …))
Similar to map and map*, respectively, except that the
results of applying procedure to the elements of lists are
concatenated together by append! rather than by cons. The
following are equivalent, except that the former is more efficient:
(append-map! procedure list list …) (apply append! (map procedure list list …))
The arguments to for-each are like the arguments to map,
but for-each calls procedure for its side effects rather
than for its values. Unlike map, for-each is guaranteed
to call procedure on the elements of the lists in order from
the first element 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)
Next: Reduction of Lists, Previous: Searching Lists, Up: Lists [Contents][Index]