#lang racket/base (require (for-syntax racket/base syntax/parse racket/syntax syntax/datum syntax/strip-context)) (provide (all-defined-out)) (define-syntax-rule (br:debug-define (syntax (id pat-arg ... . rest-arg)) body-exp) (br:define #'(id pat-arg ... . rest-arg) #`(begin (for-each displayln (list (format "input pattern = #'~a" '#,'(id pat-arg ... . rest-arg)) (format "output pattern = #'~a" (cadr '#,'body-exp)) (format "invoked as = ~a" (syntax->datum #'(id pat-arg ... . rest-arg))) (format "expanded as = ~a" '#,(syntax->datum body-exp)) (format "evaluated as = ~a" #,body-exp))) #,body-exp))) (module+ test (require rackunit racket/port) (parameterize ([current-output-port (open-output-nowhere)]) (check-equal? (let () (br:debug-define #'(foo ) #'(apply + (list ))) (foo 1 2 3)) 6) (check-equal? (let () (br:debug-define #'(foo ...) #'(apply * (list ...))) (foo 10 11 12)) 1320))) (define-syntax (br:define stx) (define-syntax-class syntaxed-id #:literals (syntax) #:description "id in syntaxed form" (pattern (syntax name:id))) (syntax-parse stx #:literals (syntax) [(_ (syntax (id pat-arg ... . rest-arg)) body ...) ; (define #'(foo arg) #'(+ arg arg)) #'(define-syntax id (λ (stx) (define result (syntax-case stx () [(_ pat-arg ... . rest-arg) body ...])) (if (not (syntax? result)) (datum->syntax stx result) result)))] [(_ sid:syntaxed-id sid2:syntaxed-id) ; (define #'f1 #'f2) #'(define-syntax sid.name (make-rename-transformer sid2))] [(_ (sid:syntaxed-id stx-arg ...) expr ...) ; (define (#'f1 stx) expr ...) (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))] [(_ sid:syntaxed-id (λ (stx-arg ...) expr ...)) ; (define #'f1 (λ(stx) expr ...) #:fail-when (not (= (length (syntax->datum #'(stx-arg ...))) 1)) (raise-syntax-error 'define "did not get exactly one argument for macro" (syntax->datum #'(stx-arg ...))) #'(define-syntax (sid.name stx-arg ...) expr ...)] [(_ args ...) #'(define args ...)])) (module+ test (require rackunit) (br:define #'plus (λ(stx) #'+)) (br:define #'plusser #'plus) (br:define #'(times arg) #'(* arg arg)) (br:define #'timeser #'times) (check-equal? (plus 42) +) (check-equal? plusser +) (check-equal? (plusser 42) +) (check-equal? (times 10) 100) (check-equal? (timeser 12) 144) (check-equal? (let () (br:define #'(foo x) (with-syntax ([zam +]) #'(zam x x))) (foo 42)) 84) ;; todo: error from define not trapped by check-exn #;(check-exn exn:fail:syntax? (λ _ (br:define (#'times stx stx2) #'*))))