#lang racket/base (require (for-syntax racket/list racket/base syntax/parse racket/syntax syntax/datum syntax/strip-context) sugar/define) (provide (all-defined-out)) ;; everything is prefixed br: whether it needs it or not so it can be stripped by #lang br (define-for-syntax (syntax-flatten stx) (flatten (let loop ([stx stx]) (define maybe-list (syntax->list stx)) (if maybe-list (map loop maybe-list) stx)))) (define-for-syntax (generate-literals pats) ;; generate literals for any symbols that are not ... or _ or _underscore-prefixed (for*/list ([pat-arg (in-list (syntax-flatten pats))] [pat-datum (in-value (syntax->datum pat-arg))] #:when (and (symbol? pat-datum) (not (eq? pat-datum '...)) (not (eq? pat-datum '_)) (not (let ([str (symbol->string pat-datum)]) (regexp-match #rx"^_" str))))) 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) (define-syntax-parameter caller-stx (λ(stx) (error 'not-parameterized)))) ;; todo: support `else` case (define-syntax (br: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 syntax or function [(_ top-id) (raise-syntax-error 'define-cases "no cases given" (syntax->datum #'top-id))] ;; defective for syntax [(_ (sid:syntaxed-id _ ...) _ ...) ; (define (#'f1 stx) expr ...) (raise-syntax-error 'define-cases "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))] ;; syntax matcher [(_ top-id:syntaxed-id [(syntax pat) body ...] ...+) (with-syntax ([(LITERAL ...) (generate-literals #'(pat ...))]) #'(define-syntax top-id.name (λ (stx) (define result (syntax-case stx (LITERAL ...) [pat (syntax-parameterize ([caller-stx (make-rename-transformer #'stx)]) body ...)] ... [else (raise-syntax-error 'define-cases (format "no matching case for syntax pattern ~v" (syntax->datum stx)) (syntax->datum #'top-id.name))])) (if (not (syntax? result)) (datum->syntax stx result) result))))] ;; function matcher [(_ top-id:id [(_ pat-arg ... . rest-arg) body ...] ...) #'(define top-id (case-lambda [(pat-arg ... . rest-arg) body ...] ... [else (raise-syntax-error 'define-cases "no matching case for argument pattern" (object-name top-id))]))])) (module+ test (require rackunit) (define foo-val 'got-foo-val) (define (foo-func) 'got-foo-func) (br:define-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) (br:define-cases f [(_ arg) (add1 arg)] [(_ arg1 arg2) (+ arg1 arg2)]) (check-equal? (f 42) 43) (check-equal? (f 42 5) 47) ;; todo: error from define-cases not trapped by check-exn ;;(check-exn exn:fail:syntax? (λ _ (define-cases (#'times stx stx2) #'*))) ) (define-syntax (br:define stx) ;;todo: share syntax classes (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) ;; syntax [(_ (syntax (id pat-arg ... . rest-arg)) body ...) ; (define #'(foo arg) #'(+ arg arg)) #'(br:define-cases (syntax id) [(syntax (_ pat-arg ... . rest-arg)) body ...])] [(_ sid:syntaxed-id sid2:syntaxed-id) ; (define #'f1 #'f2) #'(define-syntax sid.name (make-rename-transformer sid2))] [(_ (syntax id) (syntax thing)) ; (define #'f1 #'42) #'(br:define-cases (syntax id) [#'_ (syntax thing)])] [(_ (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) #'+)) (check-equal? (plus 42) +) (br:define #'plusser #'plus) (check-equal? (plusser 42) +) (check-equal? plusser +) (br:define #'(times [nested _ARG]) #'(* _ARG _ARG)) (check-equal? (times [nested 10]) 100) (br:define #'timeser #'times) (check-equal? (timeser [nested 12]) 144) (br:define #'fortytwo #'42) (check-equal? fortytwo 42) (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) #'*))) (begin (br:define #'(redefine _id) #'(define _id 42)) (redefine zoombar) (check-equal? zoombar 42)) ;; use caller-stx parameter to introduce identifier unhygienically (br:define #'(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-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 _X _Y _Z) #'(apply + (list _X _Y _Z))) (foo 1 2 3)) 6) (check-equal? (let () (br:debug-define #'(foo _X ...) #'(apply * (list _X ...))) (foo 10 11 12)) 1320))) (define-syntax-rule (br:define+provide arg ...) (define+provide arg ...)) (br:define #'(define-inverting (syntax (_id . _patargs)) _syntaxexpr) #'(define-syntax (_id stx) (let () (define (expand-macro mac) (syntax-disarm (local-expand mac 'expression #f) #f)) (syntax-case stx () [(_ . rest) (with-syntax ([_patargs (map expand-macro (syntax->list #'rest))]) _syntaxexpr)])))) (module+ test ;; an inverting macro expands its arguments. ;; so `foo` does not get `(falsy a) (falsy b) (falsy c)` as arguments, ;; but rather the result of their expansion, namely `((#f a) (#f b) (#f c))` ;; and `tree` does not get `(foo (#f a) (#f b) (#f c))` as its first argument, ;; but rather the result of its expansion, namely (a b c). (define-inverting #'(tree (_id ...) _vals) #'(let () (define-values (_id ...) _vals) (list _id ...))) (define-inverting #'(foo (#f _id) ...) #'(_id ...)) (define-syntax-rule (falsy id) (#f id)) (check-equal? (tree (foo (falsy a) (falsy b) (falsy c)) (values 1 2 3)) '(1 2 3)))