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Documented define-pvars; Add the identifiers in reverse order as noted in the documentation.

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This commit is contained in:
Georges Dupéron 2017-01-23 18:54:23 +01:00
parent 41634ba262
commit 9db3ca62f8
2 changed files with 40 additions and 4 deletions
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4
current-pvars.rkt
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@ -125,7 +125,7 @@
(raise-syntax-error 'with-pvars "bad syntax" stx)
(void))
(let* ([pvars (syntax->list (stx-car (stx-cdr stx)))]
[quoted-pvars (map (λ (v) `(quote-syntax ,v)) pvars)]
[quoted-pvars (reverse (map (λ (v) `(quote-syntax ,v)) pvars))]
[body (stx-cdr (stx-cdr stx))]
[old-pvars-index (find-last-current-pvars)]
[old-pvars (try-nth-current-pvars old-pvars-index)]
@ -154,7 +154,7 @@
(raise-syntax-error 'with-pvars "bad syntax" stx)
(void))
(let* ([pvars (syntax->list (stx-cdr stx))]
[quoted-pvars (map (λ (v) `(quote-syntax ,v)) pvars)]
[quoted-pvars (reverse (map (λ (v) `(quote-syntax ,v)) pvars))]
[old-pvars-index (find-last-current-pvars)]
[old-pvars (try-nth-current-pvars old-pvars-index)]
[binding (syntax-local-identifier-as-binding

40
scribblings/stxparse-info.scrbl
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@ -1,7 +1,11 @@
#lang scribble/manual
@require[@for-label[stxparse-info/parse
stxparse-info/current-pvars
racket/base]]
racket/syntax
racket/base]
scribble/example]
@(define ev ((make-eval-factory '(racket))))
@title{stxparse-info : tracking bound syntax pattern variables with
@racketmodname[syntax/parse]}
@ -64,4 +68,36 @@ know which syntax pattern variables are within scope.
(with-pvars (v₁ v₂)
(let-syntax ([v₁ (make-syntax-mapping depth (quote-syntax valvar))]
[v₂ (make-syntax-mapping depth (quote-syntax valvar))])
code))]}
code))]}
@defform[(define-pvars (pvar ...))
#:contracts ([pvar identifier?])]{
Prepends the given @racket[pvar ...] to the list of pattern variables which
are known to be bound, in the same way as @racket[with-pvars]. Whereas
@racket[with-pvars] makes the modified list visible in the @racket[_body],
@racket[define-pvars] makes the modified list visible in the statements
following @racket[define-pvars]. @racket[define-pvars] can be used multiple
times within the same @racket[let] or equivalent.
This can be used to implement macros which work similarly to
@racket[define/syntax-parse] or @racket[define/with-syntax], and have them
record the syntax pattern variables which they bind.
@examples[#:eval ev
#:hidden
(require stxparse-info/parse
stxparse-info/current-pvars
racket/syntax
(for-syntax racket/base))]
@examples[#:eval ev
#:escape UNSYNTAX
(let ()
(code:comment "Alternate version of define/syntax-parse which")
(code:comment "contains (define-pvars (x)) in its expanded form.")
(define/syntax-parse x #'1)
(define/syntax-parse y #'2)
(define-syntax (get-pvars stx)
#`'#,(current-pvars))
(get-pvars))]}