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122 lines
4.7 KiB
Racket
122 lines
4.7 KiB
Racket
#lang racket/base
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(require (for-syntax racket/base syntax/parse racket/syntax syntax/datum syntax/strip-context))
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(provide (all-defined-out))
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(define-syntax-rule (br:debug-define (syntax (id pat-arg ... . rest-arg)) body-exp)
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(br:define #'(id pat-arg ... . rest-arg)
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#`(begin
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(for-each displayln
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(list
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(format "input pattern = #'~a" '#,'(id pat-arg ... . rest-arg))
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(format "output pattern = #'~a" (cadr '#,'body-exp))
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(format "invoked as = ~a" (syntax->datum #'(id pat-arg ... . rest-arg)))
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(format "expanded as = ~a" '#,(syntax->datum body-exp))
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(format "evaluated as = ~a" #,body-exp)))
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#,body-exp)))
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(module+ test
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(require rackunit racket/port)
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(parameterize ([current-output-port (open-output-nowhere)])
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(check-equal? (let ()
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(br:debug-define #'(foo <x> <y> <z>)
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#'(apply + (list <x> <y> <z>)))
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(foo 1 2 3)) 6)
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(check-equal? (let ()
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(br:debug-define #'(foo <x> ...) #'(apply * (list <x> ...)))
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(foo 10 11 12)) 1320)))
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(define-syntax (br:define stx)
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(define-syntax-class syntaxed-id
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#:literals (syntax)
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#:description "id in syntaxed form"
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(pattern (syntax name:id)))
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(define-syntax-class syntaxed-thing
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#:literals (syntax)
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#:description "some datum in syntaxed form"
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(pattern (syntax thing:expr)))
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(syntax-parse stx
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#:literals (syntax)
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[(_ (syntax (id pat-arg ... . rest-arg)) body ...) ; (define #'(foo arg) #'(+ arg arg))
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#'(define-syntax id (λ (stx)
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(define result
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(syntax-case stx ()
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[(_ pat-arg ... . rest-arg) body ...]))
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(if (not (syntax? result))
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(datum->syntax stx result)
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result)))]
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[(_ sid:syntaxed-id sid2:syntaxed-id) ; (define #'f1 #'f2)
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#'(define-syntax sid.name (make-rename-transformer sid2))]
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[(_ sid:syntaxed-id sid2:syntaxed-thing) ; (define #'f1 #'42)
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#'(define-syntax sid.name (λ (stx) sid2))]
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[(_ (sid:syntaxed-id stx-arg ...) expr ...) ; (define (#'f1 stx) expr ...)
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(raise-syntax-error 'define "definition of a syntax transformer must use lambda notation, because otherwise it's too easy to confuse the compile-time shape and the run-time shape" (syntax->datum #'sid.name))]
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[(_ sid:syntaxed-id (λ (stx-arg ...) expr ...)) ; (define #'f1 (λ(stx) expr ...)
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#:fail-when (not (= (length (syntax->datum #'(stx-arg ...))) 1))
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(raise-syntax-error 'define "did not get exactly one argument for macro" (syntax->datum #'(stx-arg ...)))
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#'(define-syntax (sid.name stx-arg ...) expr ...)]
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[(_ args ...) #'(define args ...)]))
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(module+ test
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(require rackunit)
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(br:define #'plus (λ(stx) #'+))
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(br:define #'plusser #'plus)
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(br:define #'(times arg) #'(* arg arg))
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(br:define #'timeser #'times)
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(br:define #'fortytwo #'42)
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(check-equal? (plus 42) +)
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(check-equal? plusser +)
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(check-equal? (plusser 42) +)
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(check-equal? (times 10) 100)
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(check-equal? (timeser 12) 144)
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(check-equal? (let ()
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(br:define #'(foo x)
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(with-syntax ([zam +])
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#'(zam x x))) (foo 42)) 84)
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;; todo: error from define not trapped by check-exn
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#;(check-exn exn:fail:syntax? (λ _ (br:define (#'times stx stx2) #'*)))
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(check-equal? fortytwo 42))
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;; todo: support `else` case
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(define-syntax (br:define-cases stx)
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(syntax-parse stx
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#:literals (syntax)
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; (define-cases #'foo [#'(_ arg) #'(+ arg arg)] [#'(_ 42 bar) #'42] ...)
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[(_ (syntax top-id) [(syntax (_ pat-arg ... . rest-arg)) body ...] ...)
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#'(define-syntax top-id (λ (stx)
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(define result
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(syntax-case stx ()
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[(_ pat-arg ... . rest-arg) body ...] ...))
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(if (not (syntax? result))
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(datum->syntax stx result)
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result)))]
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[(_ top-id [(_ pat-arg ... . rest-arg) body ...] ...)
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#'(define top-id
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(case-lambda
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[(pat-arg ... . rest-arg) body ...] ...))]))
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(module+ test
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(br:define-cases #'op
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[#'(_ "+") #''got-plus]
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[#'(_ arg) #''got-something-else])
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(check-equal? (op "+") 'got-plus)
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(check-equal? (op 42) 'got-something-else)
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(br:define-cases f
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[(_ arg) (add1 arg)]
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[(_ arg1 arg2) (+ arg1 arg2)])
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(check-equal? (f 42) 43)
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(check-equal? (f 42 5) 47)) |