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Rework the docs so that we're explicit about how the variables in contract

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expressions are bound.

svn: r13563
This commit is contained in:
Stevie Strickland 2009-02-13 23:18:26 +00:00
parent 387c8b210f
commit dc78217029
1 changed files with 15 additions and 10 deletions
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25
collects/scribblings/reference/units.scrbl
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@ -160,9 +160,9 @@ the corresponding import. Each @scheme[tagged-sig-id] in an
[sig-elem [sig-elem
id id
(contracted [id contract] ...)
(define-syntaxes (id ...) expr) (define-syntaxes (id ...) expr)
(define-values (value-id ...) expr) (define-values (value-id ...) expr)
(contracted [id contract] ...)
(open sig-spec) (open sig-spec)
(sig-form-id . datum)])]{ (sig-form-id . datum)])]{
@ -177,15 +177,6 @@ of bindings for import or export:
importing the signature, and @scheme[id] must be defined by units importing the signature, and @scheme[id] must be defined by units
exporting the signature.} exporting the signature.}
@item{Each @scheme[contracted] form in a signature declaration means
that a unit exporting the signature must supply a variable definition
for each @scheme[id] in that form. If the signature is imported, then
uses of @scheme[id] inside the unit are protected by the appropriate
contracts using the unit as the negative blame. If the signature is
exported, then the exported values are protected by the appropriate
contracts which use the unit as the positive blame, but internal uses
of the exported identifiers are not protected.}
@item{Each @scheme[define-syntaxes] form in a signature declaration @item{Each @scheme[define-syntaxes] form in a signature declaration
introduces a macro to that is available for use in any unit that introduces a macro to that is available for use in any unit that
imports the signature. Free variables in the definition's imports the signature. Free variables in the definition's
@ -198,6 +189,17 @@ of bindings for import or export:
signature. Free variables in the definition's @scheme[expr] are signature. Free variables in the definition's @scheme[expr] are
treated the same as for @scheme[define-syntaxes].} treated the same as for @scheme[define-syntaxes].}
@item{Each @scheme[contracted] form in a signature declaration means
that a unit exporting the signature must supply a variable definition
for each @scheme[id] in that form. If the signature is imported, then
uses of @scheme[id] inside the unit are protected by the appropriate
contracts using the unit as the negative blame. If the signature is
exported, then the exported values are protected by the appropriate
contracts which use the unit as the positive blame, but internal uses
of the exported identifiers are not protected. Variables in the
@scheme[contract] expressions are treated the same as for
@scheme[define-syntaxes].}
@item{Each @scheme[(open sig-spec)] adds to the signature everything @item{Each @scheme[(open sig-spec)] adds to the signature everything
specified by @scheme[sig-spec].} specified by @scheme[sig-spec].}
@ -644,6 +646,9 @@ without adding contracts to the imported and exported signatures.
The unit value must import a subset of the import signatures and export a The unit value must import a subset of the import signatures and export a
superset of the export signatures listed in the unit contract. Any superset of the export signatures listed in the unit contract. Any
identifier which is not listed for a given signature is left alone. identifier which is not listed for a given signature is left alone.
Variables used in a given @scheme[ctc] expression first refer to other
variables in the same signature, and then to the context of the
@scheme[unit/c] expression.
Here is an example use of @scheme[unit/c]: Here is an example use of @scheme[unit/c]: