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clarify test argument to make-contract, make-chaperone-contract, and make-flat-contract

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closes #1313
This commit is contained in:
Robby Findler 2016-04-30 20:39:32 -05:00
parent bb03281308
commit 9acd36724d
1 changed files with 8 additions and 4 deletions
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12
pkgs/racket-doc/scribblings/reference/contracts.scrbl
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@ -2035,9 +2035,8 @@ higher-order contracts is @racketresult[anonymous-contract], for
@tech{chaperone contracts} is @racketresult[anonymous-chaperone-contract], and for @tech{chaperone contracts} is @racketresult[anonymous-chaperone-contract], and for
@tech{flat contracts} is @racketresult[anonymous-flat-contract]. @tech{flat contracts} is @racketresult[anonymous-flat-contract].
The first-order predicate @racket[test] can be used to determine which values The first-order predicate @racket[test] is used to determine which values
the contract applies to; this must be the set of values for which the the contract applies to. This test is used
contract fails immediately without any higher-order wrapping. This test is used
by @racket[contract-first-order-passes?], and indirectly by @racket[or/c] by @racket[contract-first-order-passes?], and indirectly by @racket[or/c]
and @racket[from-or/c] to determine which higher-order contract to wrap a and @racket[from-or/c] to determine which higher-order contract to wrap a
value with when there are multiple higher-order contracts to choose from. value with when there are multiple higher-order contracts to choose from.
@ -2071,7 +2070,12 @@ At least one of the @racket[late-neg-proj], @racket[proj],
The projection arguments (@racket[late-neg-proj], @racket[proj], and The projection arguments (@racket[late-neg-proj], @racket[proj], and
@racket[val-first-proj]) must be in sync with the @racket[test] argument. @racket[val-first-proj]) must be in sync with the @racket[test] argument.
In particular, if the test argument returns @racket[#f] for some value, In particular, if the test argument returns @racket[#f] for some value,
then the projections must raise a blame error for that value. then the projections must raise a blame error for that value and if the
test argument returns @racket[#t] for some value, then the projection must
not signal any blame for this value, unless there are higher-order interactions
later. In other words, for @tech{flat contracts}, the @racket[test] and
@racket[projection] arguments must check the same predicate (which is
why thee default projection uses the @racket[test] argument directly).
Projections for @tech{chaperone contracts} must produce a value that passes Projections for @tech{chaperone contracts} must produce a value that passes
@racket[chaperone-of?] when compared with the original, uncontracted value. @racket[chaperone-of?] when compared with the original, uncontracted value.