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br-parser-tools/collects/parser-tools/private-lex/stx.rkt

211 lines
9.1 KiB
Racket

(module stx mzscheme
(require "util.rkt"
syntax/id-table)
(provide parse)
(define (bad-args stx num)
(raise-syntax-error
#f
(format "incorrect number of arguments (should have ~a)" num)
stx))
;; char-range-arg: syntax-object syntax-object -> nat
;; If c contains is a character or length 1 string, returns the integer
;; for the character. Otherwise raises a syntax error.
(define (char-range-arg stx containing-stx)
(let ((c (syntax-e stx)))
(cond
((char? c) (char->integer c))
((and (string? c) (= (string-length c) 1))
(char->integer (string-ref c 0)))
(else
(raise-syntax-error
#f
"not a char or single-char string"
containing-stx stx)))))
(test-block ()
((char-range-arg #'#\1 #'here) (char->integer #\1))
((char-range-arg #'"1" #'here) (char->integer #\1)))
(define orig-insp (variable-reference->module-declaration-inspector
(#%variable-reference)))
(define (disarm stx)
(syntax-disarm stx orig-insp))
;; parse : syntax-object (box (list-of syntax-object)) -> s-re (see re.rkt)
;; checks for errors and generates the plain s-exp form for s
;; Expands lex-abbrevs and applies lex-trans.
(define (parse stx disappeared-uses)
(let loop ([stx stx]
[disappeared-uses disappeared-uses]
;; seen-lex-abbrevs: id-table
[seen-lex-abbrevs (make-immutable-free-id-table)])
(let ([recur (lambda (s)
(loop (syntax-rearm s stx)
disappeared-uses
seen-lex-abbrevs))]
[recur/abbrev (lambda (s id)
(loop (syntax-rearm s stx)
disappeared-uses
(free-id-table-set seen-lex-abbrevs id id)))])
(syntax-case (disarm stx) (repetition union intersection complement concatenation
char-range char-complement)
(_
(identifier? stx)
(let ((expansion (syntax-local-value stx (lambda () #f))))
(unless (lex-abbrev? expansion)
(raise-syntax-error 'regular-expression
"undefined abbreviation"
stx))
;; Check for cycles.
(when (free-id-table-ref seen-lex-abbrevs stx (lambda () #f))
(raise-syntax-error 'regular-expression
"illegal lex-abbrev cycle detected"
stx
#f
(list (free-id-table-ref seen-lex-abbrevs stx))))
(set-box! disappeared-uses (cons stx (unbox disappeared-uses)))
(recur/abbrev ((lex-abbrev-get-abbrev expansion)) stx)))
(_
(or (char? (syntax-e stx)) (string? (syntax-e stx)))
(syntax-e stx))
((repetition arg ...)
(let ((arg-list (syntax->list (syntax (arg ...)))))
(unless (= 3 (length arg-list))
(bad-args stx 2))
(let ((low (syntax-e (car arg-list)))
(high (syntax-e (cadr arg-list)))
(re (caddr arg-list)))
(unless (and (number? low) (exact? low) (integer? low) (>= low 0))
(raise-syntax-error #f
"not a non-negative exact integer"
stx
(car arg-list)))
(unless (or (and (number? high) (exact? high) (integer? high) (>= high 0))
(eq? high +inf.0))
(raise-syntax-error #f
"not a non-negative exact integer or +inf.0"
stx
(cadr arg-list)))
(unless (<= low high)
(raise-syntax-error
#f
"the first argument is not less than or equal to the second argument"
stx))
`(repetition ,low ,high ,(recur re)))))
((union re ...)
`(union ,@(map recur (syntax->list (syntax (re ...))))))
((intersection re ...)
`(intersection ,@(map recur (syntax->list (syntax (re ...))))))
((complement re ...)
(let ((re-list (syntax->list (syntax (re ...)))))
(unless (= 1 (length re-list))
(bad-args stx 1))
`(complement ,(recur (car re-list)))))
((concatenation re ...)
`(concatenation ,@(map recur (syntax->list (syntax (re ...))))))
((char-range arg ...)
(let ((arg-list (syntax->list (syntax (arg ...)))))
(unless (= 2 (length arg-list))
(bad-args stx 2))
(let ((i1 (char-range-arg (car arg-list) stx))
(i2 (char-range-arg (cadr arg-list) stx)))
(if (<= i1 i2)
`(char-range ,(integer->char i1) ,(integer->char i2))
(raise-syntax-error
#f
"the first argument does not precede or equal second argument"
stx)))))
((char-complement arg ...)
(let ((arg-list (syntax->list (syntax (arg ...)))))
(unless (= 1 (length arg-list))
(bad-args stx 1))
(let ((parsed (recur (car arg-list))))
(unless (char-set? parsed)
(raise-syntax-error #f
"not a character set"
stx
(car arg-list)))
`(char-complement ,parsed))))
((op form ...)
(identifier? (syntax op))
(let* ((o (syntax op))
(expansion (syntax-local-value o (lambda () #f))))
(set-box! disappeared-uses (cons o (unbox disappeared-uses)))
(cond
((lex-trans? expansion)
(recur ((lex-trans-f expansion) (disarm stx))))
(expansion
(raise-syntax-error 'regular-expression
"not a lex-trans"
stx))
(else
(raise-syntax-error 'regular-expression
"undefined operator"
stx)))))
(_
(raise-syntax-error
'regular-expression
"not a char, string, identifier, or (op args ...)"
stx))))))
;; char-set? : s-re -> bool
;; A char-set is an re that matches only strings of length 1.
;; char-set? is conservative.
(define (char-set? s-re)
(cond
((char? s-re) #t)
((string? s-re) (= (string-length s-re) 1))
((list? s-re)
(let ((op (car s-re)))
(case op
((union intersection) (andmap char-set? (cdr s-re)))
((char-range char-complement) #t)
((repetition)
(and (= (cadr s-re) (caddr s-re)) (char-set? (cadddr s-re))))
((concatenation)
(and (= 2 (length s-re)) (char-set? (cadr s-re))))
(else #f))))
(else #f)))
(test-block ()
((char-set? #\a) #t)
((char-set? "12") #f)
((char-set? "1") #t)
((char-set? '(repetition 1 2 #\1)) #f)
((char-set? '(repetition 1 1 "12")) #f)
((char-set? '(repetition 1 1 "1")) #t)
((char-set? '(union "1" "2" "3")) #t)
((char-set? '(union "1" "" "3")) #f)
((char-set? '(intersection "1" "2" (union "3" "4"))) #t)
((char-set? '(intersection "1" "")) #f)
((char-set? '(complement "1")) #f)
((char-set? '(concatenation "1" "2")) #f)
((char-set? '(concatenation "" "2")) #f)
((char-set? '(concatenation "1")) #t)
((char-set? '(concatenation "12")) #f)
((char-set? '(char-range #\1 #\2)) #t)
((char-set? '(char-complement #\1)) #t))
(test-block ()
((parse #'#\a) #\a)
((parse #'"1") "1")
((parse #'(repetition 1 1 #\1)) '(repetition 1 1 #\1))
((parse #'(repetition 0 +inf.0 #\1)) '(repetition 0 +inf.0 #\1))
((parse #'(union #\1 (union "2") (union)))
'(union #\1 (union "2") (union)))
((parse #'(intersection #\1 (intersection "2") (intersection)))
'(intersection #\1 (intersection "2") (intersection)))
((parse #'(complement (union #\1 #\2)))
'(complement (union #\1 #\2)))
((parse #'(concatenation "1" "2" (concatenation)))
'(concatenation "1" "2" (concatenation)))
((parse #'(char-range "1" #\1)) '(char-range #\1 #\1))
((parse #'(char-range #\1 "1")) '(char-range #\1 #\1))
((parse #'(char-range "1" "3")) '(char-range #\1 #\3))
((parse #'(char-complement (union "1" "2")))
'(char-complement (union "1" "2"))))
)