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128 lines
5.0 KiB
Racket
128 lines
5.0 KiB
Racket
#lang racket/base
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(require (for-syntax racket/base br/syntax racket/syntax) syntax/strip-context racket/function)
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(provide (all-defined-out))
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(define (->syntax x)
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(if (syntax? x) x (datum->syntax #f x)))
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(define (context stx)
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(hash-ref (syntax-debug-info stx) 'context))
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(define-syntax-rule (scopes stx)
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(format "~a = ~a" 'stx
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(cons (syntax->datum stx)
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(for/list ([scope (in-list (context stx))])
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scope))))
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(define (syntax-find stx stx-or-datum)
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(unless (syntax? stx)
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(raise-argument-error 'syntax-find "not given syntax object as first argument" stx))
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(define datum
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(cond [(syntax? stx-or-datum) (syntax->datum stx-or-datum)]
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[(symbol? stx-or-datum) stx-or-datum]
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[else (raise-argument-error 'syntax-find "not given syntax or datum as second argument" stx-or-datum)]))
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(let/ec exit
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(let loop ([so stx])
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(cond
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[(eq? (syntax->datum so) datum) (exit so)]
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[(syntax->list so) => (curry map loop)]))))
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(define-syntax (define-scope stx)
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(syntax-case stx ()
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[(_ id)
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#'(define-scope id ())]
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[(_ id scope-ids)
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(with-syntax ([id-sis (suffix-id #'id "-sis")]
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[add-id (prefix-id "add-" #'id)]
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[flip-id (prefix-id "flip-" #'id)]
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[id-binding-form (suffix-id #'id "-binding-form")]
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[define-id (prefix-id "define-" #'id)]
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[with-id-identifiers (infix-id "with-" #'id "-identifiers")]
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[let-id-syntax (infix-id "let-" #'id "-syntax")]
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[with-id-binding-form (infix-id "with-" #'id "-binding-form")]
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[remove-id (prefix-id "remove-" #'id)]
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[id? (suffix-id #'id "?")]
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[id* (suffix-id #'id "*")]
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[(scope-id-sis ...) (suffix-ids #'scope-ids "-sis")])
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#'(begin
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(define id-sis
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(let ([sis-in (list scope-id-sis ...)])
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(if (pair? sis-in)
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(apply append sis-in)
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(list
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(let ([si (make-syntax-introducer #t)])
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(list (procedure-rename (curryr si 'add) 'add-id)
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(procedure-rename (curryr si 'flip) 'flip-id)
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(procedure-rename (curryr si 'remove) 'remove-id)))))))
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(define add-id (λ(x) ((apply compose1 (map car id-sis)) (->syntax x))))
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(define flip-id (λ(x) ((apply compose1 (map cadr id-sis)) (->syntax x))))
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(define remove-id (λ(x) ((apply compose1 (map caddr id-sis)) (->syntax x))))
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(define (id x) (add-id (datum->syntax #f (syntax-e (->syntax x)))))
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(define (id-binding-form x) (syntax-local-introduce (id x)))
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(define (id* x) (replace-context (add-id (datum->syntax #f '_)) (->syntax x)))
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(define (id? x)
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(and
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(member (car (context (add-id (datum->syntax #f '_))))
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(context (->syntax x)))
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#t))
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(define-syntax-rule (with-id-identifiers (name (... ...)) . body)
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(with-syntax ([name (id* 'name)] (... ...)) . body))
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(define-syntax-rule (with-id-binding-form (name (... ...)) . body)
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(with-syntax ([name (id-binding-form 'name)] (... ...)) . body))
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(define-syntax-rule (let-id-syntax ([pat val] (... ...)) . body)
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(let-syntax ([pat (id* val)] (... ...)) . body))))]))
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(define (scopes-equal? stxl stxr)
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;; "A bound-identifier=? comparison checks that two identifiers have exactly the same scope sets"
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(bound-identifier=? (datum->syntax stxl '_) (datum->syntax stxr '_)))
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(module+ test
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(require rackunit)
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(define-scope red)
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(define stx (datum->syntax #f 'x))
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(define red-stx (add-red stx))
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(define double-red-stx (add-red (add-red stx)))
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(check-false (red? stx))
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(check-true (red? red-stx))
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(check-true (red? double-red-stx))
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(check-false (scopes-equal? stx red-stx))
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(check-true (scopes-equal? red-stx double-red-stx))
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(check-false (scopes-equal? red-stx (remove-red double-red-stx)))
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(define-scope blue) ; scope addition is commutative
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(define blue-stx (blue stx))
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(check-true (scopes-equal? (add-blue red-stx) (add-red blue-stx)))
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(check-true (scopes-equal? (remove-red (add-blue red-stx)) (remove-red (add-red blue-stx))))
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(define-scope green) ; replace scopes at outer layer
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(check-true (scopes-equal? (green red-stx) (green blue-stx)))
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;; replace scopes everywhere
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(check-true (scopes-equal? (car (syntax->list (green* #`(#,blue-stx #,red-stx))))
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(car (syntax->list (green* #`(#,red-stx #,blue-stx))))))
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;; todo: test flipping
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(define-scope purple (red blue))
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(check-true (purple? (add-purple stx)))
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(check-true (scopes-equal? (purple (green stx)) (add-blue (remove-green (add-red (add-green (add-blue stx))))))))
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(define-syntax (with-scopes stx)
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(syntax-case stx (syntax)
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[(_ (scope-id) (syntax expr))
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(with-syntax ([add-scope-id (format-id #'scope-id "add-~a" #'scope-id)])
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#'(add-scope-id expr))]))
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