#lang racket/base (require (for-syntax racket/list racket/base syntax/parse br/syntax racket/syntax syntax/datum racket/string)) (provide (all-defined-out) (for-syntax with-shared-id with-calling-site-id)) (module+ test (require rackunit)) (define-for-syntax (upcased? str) (equal? (string-upcase str) str)) (define-for-syntax (generate-literals pats) ;; generate literals for any symbols that are not ... or _ or _underscore-prefixed (define pattern-arg-prefixer "_") (for/list ([pat-arg (in-list (syntax-flatten pats))] #:when (let ([pat-datum (syntax->datum pat-arg)]) (and (symbol? pat-datum) (not (member pat-datum '(... _ else))) ; exempted from literality (not (string-prefix? (symbol->string pat-datum) pattern-arg-prefixer)) (not (upcased? (symbol->string pat-datum)))))) pat-arg)) ;; expose the caller context within br:define macros with syntax parameter (begin-for-syntax (require (for-syntax racket/base) racket/stxparam) (provide caller-stx shared-syntax) (define-syntax-parameter caller-stx (λ(stx) (error 'caller-stx-not-parameterized))) (define-syntax-parameter shared-syntax (λ(stx) (error 'shared-syntax-not-parameterized)))) (define-syntax (define-cases stx) (define-syntax-class syntaxed-id #:literals (syntax) #:description "id in syntaxed form" (pattern (syntax name:id))) (define-syntax-class syntaxed-thing #:literals (syntax) #:description "some datum in syntaxed form" (pattern (syntax thing:expr))) (syntax-parse stx #:literals (syntax) ;; defective for function [(_ top-id) (raise-syntax-error 'define-cases "no cases given" (syntax->datum #'top-id))] ;; function matcher [(_ top-id:id [(_ . pat-args) . body] ...) #'(define top-id (case-lambda [pat-args . body] ... [else (raise-syntax-error 'define-cases "no matching case for argument pattern" (object-name top-id))]))])) (module+ test (define-cases f [(_ arg) (add1 arg)] [(_ arg1 arg2) (+ arg1 arg2)]) (check-equal? (f 42) 43) (check-equal? (f 42 5) 47)) (define-syntax-rule (debug-define-macro (id . pat-args) body-exp) (define-macro (id . pat-args) #`(begin (for-each displayln (list (format "input pattern = #'~a" '#,'(id . pat-args)) (format "output pattern = #'~a" (cadr '#,'body-exp)) (format "invoked as = ~a" (syntax->datum #'(id . pat-args))) (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 () (debug-define-macro (foo _X _Y _Z) #'(apply + (list _X _Y _Z))) (foo 1 2 3)) 6) (check-equal? (let () (debug-define-macro (foo _X ...) #'(apply * (list _X ...))) (foo 10 11 12)) 1320))) (begin-for-syntax (begin-for-syntax (require (for-syntax racket/base)) (define-syntax-rule (make-shared-syntax-macro caller-stx) #'(syntax-rules stx [(_ form) #'(datum->syntax caller-stx (if (syntax? form) (syntax-e form) form))])))) (begin-for-syntax (define-syntax-rule (with-shared-id (id ...) . body) (with-syntax ([id (shared-syntax 'id)] ...) . body)) (define-syntax with-calling-site-id (make-rename-transformer #'with-shared-id))) (define-syntax (define-macro stx) (define-syntax-class syntaxed-id #:literals (syntax) #:description "id in syntaxed form" (pattern (syntax name:id))) (define-syntax-class syntaxed-thing #:literals (syntax) #:description "some datum in syntaxed form" (pattern (syntax thing:expr))) (define-syntax-class transformer-func #:literals (lambda λ) (pattern ([~or lambda λ] (arg:id) . body:expr))) (syntax-parse stx #:literals (syntax) [(_ id:id sid:syntaxed-id) #'(define-syntax id (make-rename-transformer sid))] [(_ id:id func:transformer-func) #'(define-syntax id func)] [(_ id:id thing:syntaxed-thing) #'(define-syntax id (λ(stx) thing))] [(_ (id:id . patargs) . body:expr) #'(define-macro-cases id [(id . patargs) (begin . body)])])) (define-syntax (define-macro-cases stx) (define-syntax-class syntaxed-id #:literals (syntax) #:description "id in syntaxed form" (pattern (syntax name:id))) (define-syntax-class syntaxed-thing #:literals (syntax) #:description "some datum in syntaxed form" (pattern (syntax thing:expr))) (syntax-parse stx #:literals (syntax) [(_ id:id) ; defective for syntax (raise-syntax-error 'define-macro-cases "no cases given" (syntax->datum #'id))] [(_ id:id . patexprs) ;; todo: rephrase this check as a syntax-parse pattern above (let ([all-but-last-pat-datums (map syntax->datum (syntax->list (syntax-case #'patexprs () [((pat result) ... last-one) #'(pat ...)])))]) (when (member 'else all-but-last-pat-datums) (raise-syntax-error 'define-cases "else case must be last" (syntax->datum #'id)))) (with-syntax* ([((pat . result-exprs) ... else-result-exprs) (syntax-parse #'patexprs #:literals (syntax else) ;; syntax notation on pattern is optional [(((~or (syntax pat) pat) result-expr) ... (else . else-result-exprs)) #'((pat result-expr) ... else-result-exprs)] [(((~or (syntax pat) pat) result-expr) ...) #'((pat result-expr) ... (list (raise-syntax-error 'define-cases (format "no matching case for syntax pattern ~v" (syntax->datum stx)) (syntax->datum #'id))))])] [LITERALS (generate-literals #'(pat ...))]) #'(define-syntax id (λ (stx) (define result (syntax-case stx LITERALS [pat (syntax-parameterize ([caller-stx (make-rename-transformer #'stx)]) (syntax-parameterize ([shared-syntax (make-shared-syntax-macro caller-stx)]) . result-exprs))] ... [else . else-result-exprs])) (if (syntax? result) result (datum->syntax #'id result)))))])) (module+ test (define-macro plus (λ(stx) #'+)) (check-equal? (plus 42) +) (define-macro plusser #'plus) (check-equal? (plusser 42) +) (check-equal? plusser +) (define-macro (times [nested ARG]) #'(* ARG ARG)) (check-equal? (times [nested 10]) 100) (define-macro timeser #'times) (check-equal? (timeser [nested 12]) 144) (define-macro fortytwo #'42) (check-equal? fortytwo 42) (check-equal? (let () (define-macro (foo X) (with-syntax ([zam +]) #'(zam X X))) (foo 42)) 84) (begin (define-macro (redefine ID) #'(define ID 42)) (redefine zoombar) (check-equal? zoombar 42)) ;; use caller-stx parameter to introduce identifier unhygienically (define-macro (zam ARG1 ARG2 ARG3) (with-syntax ([dz (datum->syntax caller-stx 'dirty-zam)]) #`(define dz 'got-dirty-zam))) (zam 'this 'that 42) (check-equal? dirty-zam 'got-dirty-zam) (define-macro (add _x) #'(+ _x _x)) (check-equal? (add 5) 10) (define-macro-cases add-again [(_ X) #'(+ X X)]) (check-equal? (add-again 5) 10) (define-macro-cases add-3rd [(_ X) #'(+ X X)]) (check-equal? (add-3rd 5) 10) (define-macro add-4th #'add-3rd) (check-equal? (add-4th 5) 10) (define foo-val 'got-foo-val) (define (foo-func) 'got-foo-func) (define-macro-cases op [(_ "+") #''got-plus] [(_ _ARG) #''got-something-else] [(_) #'(foo-func)] [_ #'foo-val]) (check-equal? (op "+") 'got-plus) (check-equal? (op 42) 'got-something-else) (check-equal? (op) 'got-foo-func) (check-equal? op 'got-foo-val) (define-macro-cases elseop [(_ _arg) #''got-arg] [else #''got-else]) (check-equal? (elseop "+") 'got-arg) (check-equal? (elseop "+" 42) 'got-else) (check-exn exn:fail:syntax? (λ _ (expand-once #'(define-macro-cases no-cases)))) (check-exn exn:fail:syntax? (λ _ (expand-once #'(define-macro-cases badelseop [else #''got-else] [(_ _arg) #''got-arg])))))