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clarify some invariants of make-contract and friends

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Robby Findler 2015-11-08 15:41:03 -06:00
parent 611899764f
commit a8f748abeb
1 changed files with 10 additions and 4 deletions
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14
pkgs/racket-doc/scribblings/reference/contracts.scrbl
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@ -1960,11 +1960,12 @@ contracts is @racketresult[anonymous-chaperone-contract], and for flat
contracts is @racketresult[anonymous-flat-contract].
The first-order predicate @racket[test] can be used to determine which values
the contract applies to; usually, this is the set of values for which the
the contract applies to; this must be the set of values for which the
contract fails immediately without any higher-order wrapping. This test is used
by @racket[contract-first-order-passes?], and indirectly by @racket[or/c] to
determine which of multiple higher-order contracts to wrap a value with. The
default test accepts any value.
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
value with when there are multiple higher-order contracts to choose from.
The default test accepts any value.
The @racket[late-neg-proj] defines the behavior of applying the contract. If it is
supplied, it accepts a blame object that does not have a value for
@ -1986,6 +1987,11 @@ first-order test fails, and produces the value unchanged otherwise.
The @racket[val-first-proj] is like @racket[late-neg-proj], except with
an extra layer of currying.
The projection arguments (@racket[late-neg-proj], @racket[proj], and
@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,
then the projections must raise a blame error for that value.
Projections for chaperone contracts must produce a value that passes
@racket[chaperone-of?] when compared with the original, uncontracted value.
Projections for flat contracts must fail precisely when the first-order test