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clarify has-contract? and prop:contracted relationship

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Robby Findler 2012-06-18 11:25:24 -05:00
parent ac8a4f23e5
commit 2d8f41bfb9
1 changed files with 8 additions and 1 deletions
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9
collects/scribblings/reference/contracts.scrbl
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@ -1778,7 +1778,8 @@ constructed by @racket[build-flat-contract-property].
These properties attach a contract value to the protected structure,
chaperone, or impersonator value. The function @racket[has-contract?]
returns @racket[#t] for values that have one of these properties, and
@racket[value-contract] extracts the contract value.
@racket[value-contract] extracts the value from the property (which
is expected to be the contract on the value).
}
@deftogether[(
@ -2095,11 +2096,17 @@ Produces the name used to describe the contract in error messages.
@defproc[(value-contract [v has-contract?]) contract?]{
Returns the contract attached to @racket[v], if recorded.
Otherwise it returns @racket[#f].
To support @racket[value-contract] and @racket[has-contract?]
in your own contract combinators, use @racket[prop:contracted] or
@racket[impersonator-prop:contracted].
}
@defproc[(has-contract? [v any/c]) boolean?]{
Returns @racket[#t] if @racket[v] is a value that
has a recorded contract attached to it.
See also @racket[value-contract].
}