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add a case-> contract example

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Robby Findler 2013-08-31 17:37:17 -05:00
parent bf2ebebff6
commit 74de8bd122
1 changed files with 18 additions and 10 deletions
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28
pkgs/racket-pkgs/racket-doc/scribblings/reference/contracts.scrbl
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@ -938,16 +938,24 @@ The @racket[#:pre-cond] and @racket[#:post-cond] keywords are aliases for
}
@defform*/subs[#:literals (any values ->)
[(case-> (-> dom-expr ... rest range) ...)]
([rest (code:line) (code:line #:rest rest-expr)]
[range range-expr (values range-expr ...) any])]{
This contract form is designed to match
@racket[case-lambda]. Each argument to @racket[case->] is a
contract that governs a clause in the
@racket[case-lambda]. If the @racket[#:rest] keyword is
present, the corresponding clause must accept an arbitrary
number of arguments. The @racket[range] specification is
just like that for @racket[->] and @racket[->*].
[(case-> (-> dom-expr ... rest range) ...)]
([rest (code:line) (code:line #:rest rest-expr)]
[range range-expr (values range-expr ...) any])]{
This contract form is designed to match
@racket[case-lambda]. Each argument to @racket[case->] is a
contract that governs a clause in the
@racket[case-lambda]. If the @racket[#:rest] keyword is
present, the corresponding clause must accept an arbitrary
number of arguments. The @racket[range] specification is
just like that for @racket[->] and @racket[->*].
For example, this contract matches a function with two
cases, one that accepts an integer, returning void, and one
that accepts no arguments and returns an integer.
@racketblock[(case-> (-> integer? void?)
(-> integer?))]
Such a contract could be used to guard a function that controls
access to a single shared integer.
}