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beautiful-racket/beautiful-racket-lib/br/define.rkt

227 lines
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Racket

#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 ...))
(define-for-syntax (expand-macro mac)
(syntax-disarm (local-expand mac 'expression #f) #f))
(br:define #'(define-inverting (syntax (_id . _patargs)) _syntaxexpr)
#'(br:define (syntax (_id . 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)))