/usr/lib/help/fold-left is in scheme9 2013.11.26-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | S9fES (fold-left procedure object list ...) ==> object
Fold a series of lists by combining the result so far with adjacent
members of the given LISTs by PROCEDURE. PROCEDURE must by a K-ary
procedure where K is the number of lists passed to FOLD-LEFT plus
one. OBJECT is the base element that is used in the place of the
intermediate result in the first application of PROCEDURE. FOLD-LEFT
folds lists by grouping applications of PROCEDURE to the left.
Applications of FOLD-LEFT can be rewritten as follows:
(fold-left p2 0 (a b)) == (p2 (p2 0 a) b)
(fold-left p3 0 (a b) (c d)) == (p3 (p3 0 a c) b d)
(fold-left p4 0 (a b) (c d) (e f)) == (p4 (p4 0 a c e) b d f)
(fold-left cons 0 '(1 2 3)) ==> (((0 . 1) . 2) . 3)
(fold-left list 0 '(1 2) '(3 4) '(5 6)) ==> ((0 1 3 5) 2 4 6)
(fold-left + 0 '(1 2 3)) ==> 6
(fold-left - 0 '(1 2 3)) ==> -6
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