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beautiful-racket/beautiful-racket-lib/br/syntax.rkt

149 lines
5.4 KiB
Racket

#lang racket/base
(require (for-syntax racket/base syntax/parse racket/syntax syntax/strip-context)
syntax/strip-context racket/function)
(provide (all-defined-out) (all-from-out syntax/strip-context))
(define-syntax (syntax-match stx)
(syntax-case stx (syntax)
[(_ stx-arg [(syntax pattern) body ...] ...)
#'(syntax-case stx-arg ()
[pattern body ...] ...)]))
(define-syntax (add-syntax stx)
;; todo: permit mixing of two-arg and one-arg binding forms
;; one-arg form allows you to inject an existing syntax object using its current name
(syntax-case stx (syntax)
[(_ ([(syntax sid) sid-stx] ...) body ...)
#'(with-syntax ([sid sid-stx] ...) body ...)]
;; todo: limit `sid` to be an identifier
[(_ ([sid] ...) body ...)
#'(with-syntax ([sid sid] ...) body ...)]))
(define-syntax syntax-let (make-rename-transformer #'add-syntax))
(define-syntax inject-syntax (make-rename-transformer #'add-syntax))
(define-syntax (map-syntax stx)
(syntax-case stx ()
[(_ _proc _args)
#'(let ([args _args])
(datum->syntax args
(if (and (syntax? args) (list? (syntax-e args)))
(for/list ([arg (in-list (syntax->list args))])
(datum->syntax arg (_proc (syntax->datum arg))))
(error 'not-syntax-list))))]))
(define-syntax (filter-syntax stx)
(syntax-case stx ()
[(_ _proc _args)
#'(let ([args _args])
(datum->syntax args
(if (and (syntax? args) (list? (syntax-e args)))
(for*/list ([arg (in-list (syntax->list args))]
[result (in-value (_proc (syntax->datum arg)))]
#:when result)
arg)
(error 'not-syntax-list))))]))
#;(define-syntax syntax-variable (make-rename-transformer #'format-id))
(define (context stx)
(hash-ref (syntax-debug-info stx) 'context))
(define-syntax-rule (scopes stx)
(format "~a = ~a" 'stx
(cons (syntax->datum stx)
(for/list ([scope (in-list (context stx))])
scope))))
(define (->syntax x)
(if (syntax? x) x (datum->syntax #f x)))
(define-syntax (define-scope stx)
(syntax-case stx ()
[(_ id)
#'(define-scope id ())]
[(_ id scope-ids)
(with-syntax ([id-sis (format-id #'id "~a-sis" #'id)]
[add-id (format-id #'id "add-~a" #'id)]
[flip-id (format-id #'id "flip-~a" #'id)]
[remove-id (format-id #'id "remove-~a" #'id)]
[id? (format-id #'id "~a?" #'id)]
[id* (format-id #'id "~a*" #'id)]
[(scope-id-sis ...) (map (λ(sid) (format-id sid "~a-sis" sid)) (syntax->list #'scope-ids))])
#'(begin
(define id-sis
(let ([sis-in (list scope-id-sis ...)])
(if (pair? sis-in)
(apply append sis-in)
(list
(let ([si (make-syntax-introducer 'use-site)])
(list (procedure-rename (curryr si 'add) 'add-id)
(procedure-rename (curryr si 'flip) 'flip-id)
(procedure-rename (curryr si 'remove) 'remove-id)))))))
(define add-id (λ(x) ((apply compose1 (map car id-sis)) (->syntax x))))
(define flip-id (λ(x) ((apply compose1 (map cadr id-sis)) (->syntax x))))
(define remove-id (λ(x) ((apply compose1 (map caddr id-sis)) (->syntax x))))
(define (id x) (add-id (datum->syntax #f (syntax-e (->syntax x)))))
(define (id* x) (replace-context (add-id (datum->syntax #f '_)) (->syntax x)))
(define (id? x)
(and
(member (car (context (add-id (datum->syntax #f '_))))
(context (->syntax x)))
#t))))]))
(define (scopes-equal? stxl stxr)
;; "A bound-identifier=? comparison checks that two identifiers have exactly the same scope sets"
(bound-identifier=? (datum->syntax stxl '_) (datum->syntax stxr '_)))
(module+ test
(require rackunit)
(define-scope red)
(define stx (datum->syntax #f 'x))
(define red-stx (add-red stx))
(define double-red-stx (add-red (add-red stx)))
(check-false (red? stx))
(check-true (red? red-stx))
(check-true (red? double-red-stx))
(check-false (scopes-equal? stx red-stx))
(check-true (scopes-equal? red-stx double-red-stx))
(check-false (scopes-equal? red-stx (remove-red double-red-stx)))
(define-scope blue) ; scope addition is commutative
(define blue-stx (blue stx))
(check-true (scopes-equal? (add-blue red-stx) (add-red blue-stx)))
(check-true (scopes-equal? (remove-red (add-blue red-stx)) (remove-red (add-red blue-stx))))
(define-scope green) ; replace scopes at outer layer
(check-true (scopes-equal? (green red-stx) (green blue-stx)))
;; replace scopes everywhere
(check-true (scopes-equal? (car (syntax->list (green* #`(#,blue-stx #,red-stx))))
(car (syntax->list (green* #`(#,red-stx #,blue-stx))))))
;; todo: test flipping
(define-scope purple (red blue))
(check-true (purple? (add-purple stx)))
(check-true (scopes-equal? (purple (green stx)) (add-blue (remove-green (add-red (add-green (add-blue stx))))))))
(define-syntax (with-scopes stx)
(syntax-case stx (syntax)
[(_ (scope-id) (syntax expr))
#'(scope-id expr)]))