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290 lines
12 KiB
Racket
290 lines
12 KiB
Racket
#lang racket/base
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(require (for-syntax racket/list racket/base syntax/parse racket/syntax syntax/datum syntax/strip-context racket/string) sugar/define)
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(provide (all-defined-out))
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;; everything is prefixed br: whether it needs it or not so it can be stripped by #lang br
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(define-for-syntax (syntax-flatten stx)
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(flatten
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(let loop ([stx stx])
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(define maybe-list (syntax->list stx))
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(if maybe-list
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(map loop maybe-list)
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stx))))
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(define-for-syntax (generate-literals pats)
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;; generate literals for any symbols that are not ... or _ or _underscore-prefixed
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(define pattern-arg-prefixer "_")
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(for/list ([pat-arg (in-list (syntax-flatten pats))]
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#:when (let ([pat-datum (syntax->datum pat-arg)])
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(and (symbol? pat-datum)
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(not (member pat-datum '(... _ else))) ; exempted from literality
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(not (string-prefix? (symbol->string pat-datum) pattern-arg-prefixer)))))
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pat-arg))
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;; expose the caller context within br:define macros with syntax parameter
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(begin-for-syntax
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(require (for-syntax racket/base) racket/stxparam)
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(provide caller-stx shared-syntax)
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(define-syntax-parameter caller-stx (λ(stx) (error 'caller-stx-not-parameterized)))
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(define-syntax-parameter shared-syntax (λ(stx) (error 'shared-syntax-not-parameterized))))
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(define-syntax (br:define-cases 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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;; defective for syntax or function
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[(_ top-id)
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(raise-syntax-error 'define-cases "no cases given" (syntax->datum #'top-id))]
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;; defective for syntax
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[(_ (sid:syntaxed-id _ ...) _ ...) ; (define (#'f1 stx) expr ...)
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(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))]
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;; syntax matcher
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[(_ top-id:syntaxed-id . patexprs)
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;; todo: rephrase this check as a syntax-parse pattern above
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(let ([all-but-last-pat-datums (map syntax->datum (syntax->list (syntax-case #'patexprs ()
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[((pat result) ... last-one) #'(pat ...)])))])
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(when (member 'else all-but-last-pat-datums)
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(raise-syntax-error 'define-cases "else case must be last" (syntax->datum #'top-id.name))))
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(with-syntax* ([((pat result-expr) ... else-result-expr)
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(syntax-case #'patexprs (syntax else)
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[(((syntax pat) result-expr) ... (else else-result-expr))
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#'((pat result-expr) ... else-result-expr)]
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[(((syntax pat) result-expr) ...)
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#'((pat result-expr) ... (raise-syntax-error 'define-cases (format "no matching case for syntax pattern ~v" (syntax->datum stx)) (syntax->datum #'top-id.name)))])]
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[LITERALS (generate-literals #'(pat ...))])
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#'(define-syntax top-id.name (λ (stx)
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(define result
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(syntax-case stx LITERALS
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[pat (syntax-parameterize ([caller-stx (make-rename-transformer #'stx)])
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(syntax-parameterize ([shared-syntax (make-shared-syntax-macro caller-stx)])
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result-expr))] ...
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[else else-result-expr]))
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(if (syntax? result)
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result
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(datum->syntax #'top-id.name result)))))]
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;; function matcher
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[(_ top-id:id [(_ . pat-args) . body] ...)
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#'(define top-id
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(case-lambda
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[pat-args . body] ...
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[else (raise-syntax-error 'define-cases "no matching case for argument pattern" (object-name top-id))]))]))
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(module+ test
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(require rackunit)
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(define foo-val 'got-foo-val)
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(define (foo-func) 'got-foo-func)
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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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[#'(_) #'(foo-func)]
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[#'_ #'foo-val])
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(check-equal? (op "+") 'got-plus)
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(check-equal? (op 42) 'got-something-else)
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(check-equal? (op) 'got-foo-func)
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(check-equal? op 'got-foo-val)
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(br:define-cases #'elseop
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[#'(_ _arg) #''got-arg]
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[else #''got-else])
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(check-equal? (elseop "+") 'got-arg)
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(check-equal? (elseop "+" 42) 'got-else)
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;; todo: how to check for syntax error?
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;; `define-cases: else case must be last in: badelseop`
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#;(check-exn exn:fail? (λ _ (br:define-cases #'badelseop
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[else #''got-else]
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[#'(_ _arg) #''got-arg])))
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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)
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;; todo: error from define-cases not trapped by check-exn
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;;(check-exn exn:fail:syntax? (λ _ (define-cases (#'times stx stx2) #'*)))
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)
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(define-syntax (br:define stx)
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;;todo: share syntax classes
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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
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[(_ (syntax (id . pat-args)) . body) ; (define #'(foo arg) #'(+ arg arg))
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#'(br:define-cases (syntax id) [(syntax (_ . pat-args)) . body])]
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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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[(_ (syntax id) (syntax thing)) ; (define #'f1 #'42)
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#'(br:define-cases (syntax id) [#'_ (syntax thing)])]
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[(_ (sid:syntaxed-id stx-arg ...) . exprs) ; (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 ...) . exprs)) ; (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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(with-syntax ([(first-stx-arg other ...) #'(stx-arg ...)])
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#'(define-syntax (sid.name first-stx-arg) . exprs))]
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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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(check-equal? (plus 42) +)
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(br:define #'plusser #'plus)
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(check-equal? (plusser 42) +)
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(check-equal? plusser +)
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(br:define #'(times [nested _ARG]) #'(* _ARG _ARG))
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(check-equal? (times [nested 10]) 100)
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(br:define #'timeser #'times)
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(check-equal? (timeser [nested 12]) 144)
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(br:define #'fortytwo #'42)
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(check-equal? fortytwo 42)
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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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(begin
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(br:define #'(redefine _id) #'(define _id 42))
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(redefine zoombar)
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(check-equal? zoombar 42))
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;; use caller-stx parameter to introduce identifier unhygienically
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(br:define #'(zam _arg1 _arg2 _arg3)
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(with-syntax ([dz (datum->syntax caller-stx 'dirty-zam)])
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#`(define dz 'got-dirty-zam)))
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(zam 'this 'that 42)
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(check-equal? dirty-zam 'got-dirty-zam))
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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-rule (br:define+provide arg ...)
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(define+provide arg ...))
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(define-for-syntax (expand-macro mac)
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(syntax-disarm (local-expand mac 'expression #f) #f))
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(define-syntax (br:define-inverting stx)
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(syntax-case stx (syntax)
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[(_ (syntax (_id _patarg ... . _restarg)) _syntaxexpr ...)
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#'(br:define-cases-inverting (syntax _id)
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[(syntax (_ _patarg ... . _restarg)) _syntaxexpr ...])]))
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(begin-for-syntax
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(begin-for-syntax
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(require (for-syntax racket/base))
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(define-syntax (make-shared-syntax-macro stx)
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(syntax-case stx ()
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[(_ caller-stx)
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#'(λ(stx) (syntax-case stx ()
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[(_ form)
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#'(datum->syntax caller-stx (if (syntax? form)
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(syntax-e form)
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form))]))]))))
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(define-syntax (br:define-cases-inverting stx)
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(syntax-case stx (syntax)
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[(_ (syntax _id) [(syntax _pat) . _bodyexprs] ...)
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(with-syntax ([LITERALS (generate-literals #'(_pat ...))])
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#'(define-syntax (_id stx)
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(syntax-case stx ()
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[(_id . rest)
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(let* ([expanded-macros (map expand-macro (syntax->list #'rest))]
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[fused-stx (with-syntax ([(expanded-macro (... ...)) expanded-macros])
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#`(_id expanded-macro (... ...)))])
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(define result
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(syntax-case fused-stx LITERALS ;; put id back together with args to make whole pattern
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[_pat (syntax-parameterize ([caller-stx (make-rename-transformer #'stx)])
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(syntax-parameterize ([shared-syntax (make-shared-syntax-macro caller-stx)])
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. _bodyexprs))] ...
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[else (raise-syntax-error 'define-cases-inverting (format "no matching case for syntax pattern ~v" (syntax->datum stx)) (syntax->datum #'_id))]))
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(if (syntax? result)
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result
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(datum->syntax #'_id result)))])))]))
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(module+ test
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;; an inverting macro expands its arguments.
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;; so `foo` does not get `(falsy a) (falsy b) (falsy c)` as arguments,
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;; but rather the result of their expansion, namely `((#f a) (#f b) (#f c))`
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;; and `tree` does not get `(foo (#f a) (#f b) (#f c))` as its first argument,
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;; but rather the result of its expansion, namely (a b c).
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(br:define-inverting #'(tree (_id ...) _vals)
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#'(let ()
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(define-values (_id ...) _vals)
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(list _id ...)))
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(br:define-cases-inverting #'foo
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[#'(_ (#f _id) ...) #'(_id ...)])
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(define-syntax-rule (falsy id) (#f id))
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(check-equal? (tree (foo (falsy a) (falsy b) (falsy c)) (values 1 2 3)) '(1 2 3))) |