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svn: r9132

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This commit is contained in:
Eli Barzilay 2008-04-02 07:47:38 +00:00
parent fb392dd331
commit 3ab57fbe50
1 changed files with 6 additions and 5 deletions
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11
collects/scribblings/reference/pairs.scrbl
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@ -346,10 +346,10 @@ The sort is stable; if two elements of @scheme[lst] are ``equal''
The @scheme[#:key] argument @scheme[extract-key] is used to extract a
key value for comparison from each list element. That is, the full
comparison procedure is essentially
comparison procedure is essentially
@schemeblock[
(lambda (x y)
(lambda (x y)
(less-than? (extract-key x) (extract-key y)))
]
@ -360,9 +360,10 @@ By default, @scheme[extract-key] is applied to two list elements for
@scheme[extract-key] is an expensive operation; for example, if
@scheme[file-or-directory-modify-seconds] is used to extract a
timestamp for every file in a list, then @scheme[cache-keys?] should
be @scheme[#t], but if @scheme[extract-key] is @scheme[car], then
@scheme[cache-keys?] should be @scheme[#f]. As another example,
providing @scheme[extract-key] as @scheme[(lambda (x) (random))] and
be @scheme[#t] to minimize file-system calls, but if
@scheme[extract-key] is @scheme[car], then @scheme[cache-keys?]
should be @scheme[#f]. As another example, providing
@scheme[extract-key] as @scheme[(lambda (x) (random))] and
@scheme[#t] for @scheme[cache-keys?] effectively shuffles the list.}
@examples[