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clarify effective-constant nature of `list?'

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Closes PR 11525
This commit is contained in:
Matthew Flatt 2010-12-10 12:45:18 -07:00
parent 335e679ec7
commit f6f6facd9e
1 changed files with 4 additions and 1 deletions
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collects/scribblings/reference/pairs.scrbl
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@ -153,7 +153,10 @@ null
@defproc[(list? [v any/c]) boolean?]{Returns @scheme[#t] if @scheme[v] @defproc[(list? [v any/c]) boolean?]{Returns @scheme[#t] if @scheme[v]
is a list: either the empty list, or a pair whose second element is a is a list: either the empty list, or a pair whose second element is a
list. This procedure takes amortized constant time. list. This procedure effectively takes constant time due to internal caching
(so that any necessary traversals of pairs can in principle count as an
extra cost of allocating the pairs).
@mz-examples[ @mz-examples[
(list? '(1 2)) (list? '(1 2))
(list? (cons 1 (cons 2 '()))) (list? (cons 1 (cons 2 '())))