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document relation order for current-typecheck-relation; closes #48

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Stephen Chang 2017-01-24 15:57:50 -05:00
parent b23ee8fc3f
commit 896ec53151
1 changed files with 16 additions and 10 deletions
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turnstile/scribblings/reference.scrbl
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@ -327,22 +327,28 @@ immediately before attacing a type to a syntax object, i.e., by
One should extend @racket[current-type-eval] if canonicalization of types
depends on combinations of different types, e.g., type lambdas and type application in F-omega. }}
@; current-typecheck-relation -------------------------------------------------
@item{@defparam[current-typecheck-relation type-pred type-pred]{
A phase 1 parameter for controlling type checking, used by @racket[define-type-syntax].
A @racket[type-pred] function consumes
two types and returns true if they "type check". It defaults to @racket[type=?] though it does not have to be a symmetric relation.
Useful for reusing rules that differ only in the type check operation, e.g.,
equality vs subtyping.}}
@item{@defproc[(typecheck? [τ1 type?] [τ2 type?]) boolean?]{A phase 1 function that calls
@racket[current-typecheck-relation].}}
A phase 1 parameter for controlling type checking, used by
@racket[define-typed-syntax]. A @racket[type-pred] function consumes two
types---the first is the given type and the second is the expected type---and
returns true if they "type check". It defaults to @racket[type=?] though it
does not have to be a symmetric relation. Useful for reusing rules that differ
only in the type check operation, e.g., equality vs subtyping.}}
@item{@defproc[(typecheck? [τ1 type?] [τ2 type?]) boolean?]{
A phase 1 function that calls @racket[current-typecheck-relation]. The first
argument is the given type and the second is the expected type.}}
@item{@defproc[(typechecks? [τs1 (or/c (list/c type?) (stx-list/c type?))]
[τs2 (or/c (list/c type?) (stx-list/c type?))]) boolean?]{
Phase 1 function mapping @racket[typecheck?] over lists of types, pairwise. @racket[τs1] and @racket[τs2]
must have the same length.}}
Phase 1 function mapping @racket[typecheck?] over lists of types,
pairwise. @racket[τs1] and @racket[τs2] must have the same length. The first
list contains the given types and the second list contains the expected
types.}}
@item{@defproc[(type=? [τ1 type?] [τ2 type?]) boolean?]{A phase 1 equality
@item{@defproc[(type=? [τ1 type?] [τ2 type?]) boolean?]{A phase 1 equality
predicate for types that computes structural, @racket[free-identifier=?]
equality, but includes alpha-equivalence.