suzanne.soy/type-expander
1
0
Fork 0
Code Issues 8 Pull Requests Actions Packages Projects Releases Wiki Activity

Support functions of two arguments as type expanders (so that they can access the prop:type-expander? struct instance itself). Provided prop:type-expander? and prop-type-expander-ref

Browse Source
This commit is contained in:
Georges Dupéron 2017-05-06 18:03:41 +02:00
parent f4ed90dd26
commit 8ff2ab2530
2 changed files with 53 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
scribblings/type-expander.scrbl
View File

@ -320,17 +320,26 @@ arguments. More than two levels of nesting are possible.
assignment transformer} macros with the syntax
@racket[(set! macro-name arg …)] as an argument).}
@defthing[prop:type-expander struct-type-property?]{
@deftogether[
(@defthing[prop:type-expander
(struct-type-property/c
(or/c exact-positive-integer?
(→ prop:type-expander? any/c any/c)
(→ any/c any/c)))]
@defproc[(prop:type-expander? [v any/c]) boolean?]
@defproc[(prop:type-expander-ref [v prop:type-expander?]) any/c])]{
A
@tech[#:doc '(lib "scribblings/reference/reference.scrbl")]{
structure type property} to identify structure types that
act as @tech[#:key "type expander"]{type expanders} like
the ones created by @racket[define-type-expander].
The property value must be a procedure of arity 1 or an
@racket[exact-nonnegative-integer?] designating a field
index within the structure which contains such a
procedure.
The property value must be a procedure of arity 1 or 2, or an
@racket[exact-nonnegative-integer?] designating a field index within the
structure which contains such a procedure. If the procedure's arity includes
2, then the first argument is the structure itself (which satisfies
@racket[prop:type-expander?]), and the second argument is the syntax object to
transform. Otherwise, the single argument is the syntax object to transform.
The procedure serves as a syntax transformer when
expanding the use of a type expander. If the type expander

57
type-expander.hl.rkt
View File

@ -426,8 +426,8 @@ identifier would have to implement the @tc[prop:rename-transformer],
(make-struct-type-property 'type-expander prop-guard))]
The value of the @tc[prop:type-expander] property should either be a
transformer procedure which will be called when expanding the type, or the
index of a field containing such a procedure.
transformer procedure of one or two arguments which will be called when
expanding the type, or the index of a field containing such a procedure.
@chunk[<prop-guard>
(define (prop-guard val struct-type-info-list)
@ -453,13 +453,19 @@ corresponding to the use of the expander. If the property's value is a
procedure, we therefore check that its arity includes 1.
@chunk[<prop-guard-field-value>
(if (and (procedure? type-expander)
(arity-includes? (procedure-arity type-expander) 1))
type-expander
(raise-argument-error 'prop:type-expander-guard
(~a "the value of the " val "-th field should"
" be a procedure whose arity includes 1")
type-expander))]
(cond
[(and (procedure? type-expander)
(arity-includes? (procedure-arity type-expander) 2))
(curry type-expander instance)]
[(and (procedure? type-expander)
(arity-includes? (procedure-arity type-expander) 1))
type-expander]
[else
(raise-argument-error 'prop:type-expander-guard
(~a "the value of the " val "-th field should"
" be a procedure whose arity includes 1 or"
" 2")
type-expander)])]
In the first case, when the property value is a field index, we return an
accessor function. The accessor function expects a struct instance, performs
@ -472,11 +478,15 @@ argument).
@chunk[<prop-guard-procedure>
[(procedure? val)
(if (arity-includes? (procedure-arity val) 1)
(λ (_) val)
(raise-argument-error 'prop:type-expander-guard
"a procedure whose arity includes 1"
val))]]
(cond
[(arity-includes? (procedure-arity val) 2)
(λ (s) (curry val s))]
[(arity-includes? (procedure-arity val) 1)
(λ (_) val)]
[else
(raise-argument-error 'prop:type-expander-guard
"a procedure whose arity includes 1 or 2"
val)])]]
When the value of the @racket[prop:type-expander] property is neither a
positive field index nor a procedure, an error is raised:
@ -485,10 +495,10 @@ positive field index nor a procedure, an error is raised:
[else
(raise-argument-error
'prop:type-expander-guard
(~a "a procedure whose arity includes 1, or an exact "
(~a "a procedure whose arity includes 1 or 2, or an exact "
"non-negative integer designating a field index within "
"the structure that should contain a procedure whose "
"arity includes 1.")
"arity includes 1 or 2.")
val)]]
@subsection{The @racket[type-expander] struct}
@ -1823,10 +1833,19 @@ will be written in @tc[racket], not @tc[typed/racket]).
syntax/stx
auto-syntax-e
"parameterize-lexical-context.rkt"
debug-scopes)
debug-scopes
racket/contract/base)
;; TODO: move this in a separate chunk and explain it
(provide prop:type-expander
(contract-out
(rename has-prop:type-expander?
prop:type-expander?
(-> any/c boolean?))
(rename get-prop:type-expander-value
prop:type-expander-ref
(-> has-prop:type-expander?
any/c)))
type-expander
apply-type-expander
;bind-type-vars
@ -1877,8 +1896,10 @@ We can finally define the overloaded forms, as well as the
(require (submod ".." expander))
(require (for-syntax (submod ".." expander)))
(require (for-syntax typed-racket/base-env/annotate-classes))
(provide prop:type-expander
prop:type-expander?
prop:type-expander-ref
expand-type
define-type-expander
patch-type-expander