mbutterick
/
br-parser-tools
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

*** empty log message ***

Browse Source 
original commit: e2f00fe1953094ae8e76f7846e95809887c2e451
tokens
Scott Owens 23 years ago
parent 8111e35427
commit 67313d8a93
1 changed files with 8 additions and 123 deletions
Show Stats Download Patch File Download Diff File

127
collects/parser-tools/lex.ss
Unescape Escape View File

@ -3,11 +3,13 @@
;; Provides the syntax used to create lexers and the functions needed to ;; Provides the syntax used to create lexers and the functions needed to
;; create and use the buffer that the lexer reads from. See doc.txt. ;; create and use the buffer that the lexer reads from. See doc.txt.
(require-for-syntax "private-lex/generate-code.ss") (require-for-syntax "private-lex/generate-code.ss"
(require-for-syntax "private-lex/structs.ss") "private-lex/structs.ss")
(require (lib "list.ss") (require (lib "list.ss")
(lib "readerr.ss" "syntax") (lib "readerr.ss" "syntax")
"private-lex/token.ss") "private-lex/token.ss")
(provide lexer lexer-src-loc define-lex-abbrev define-lex-abbrevs (provide lexer lexer-src-loc define-lex-abbrev define-lex-abbrevs
make-lex-buf make-lex-buf
get-position position-offset position-line position-col position? get-position position-offset position-line position-col position?
@ -15,126 +17,9 @@
(define-syntaxes (lexer lexer-src-loc) (define-syntaxes (lexer lexer-src-loc)
(let ((code
(lambda (wrap)
`(letrec ((match
(lambda (lb first-pos longest-match-length longest-match-action length)
(let ((match
(push-back lb (- length longest-match-length)))
(end-pos (get-position lb)))
(if (not longest-match-action)
(raise-read-error
(format "lexer: No match found in input starting with: ~a"
(list->string (filter char? (lex-buffer-from lb))))
#f
(position-line first-pos)
(position-col first-pos)
(position-offset first-pos)
(- (position-offset end-pos) (position-offset first-pos))))
(,wrap
(longest-match-action
(lambda ()
first-pos)
(lambda ()
end-pos)
(lambda ()
(if (char? (car match))
(list->string (reverse match))
(list->string (reverse (cdr match)))))
lb))))))
(lambda (lb)
(unless (lex-buffer? lb)
(raise-type-error
'lexer
"lex-buf"
0
lb))
(let ((first-pos (get-position lb)))
(let lexer-loop (
;; current-state
(state start-state)
;; the character to transition on
(char (next-char lb))
;; action for the longest match seen thus far
;; including a match at the current state
(longest-match-action
(vector-ref actions start-state))
;; how many characters have been read
;; including the one just read
(length 1)
;; how many characters are in the longest match
(longest-match-length 0))
(let ((next-state
(cond
((eof-object? char)
(vector-ref eof-table state))
(else
(vector-ref
trans-table
(bitwise-ior (char->integer char)
(arithmetic-shift state 8)))))))
(cond
((not next-state) (match lb
first-pos
longest-match-length
longest-match-action
length))
(else
(let ((act (vector-ref actions next-state)))
(lexer-loop next-state
(next-char lb)
(if act
act
longest-match-action)
(add1 length)
(if act
length
longest-match-length)))))))))))))
(values (values
(lambda (stx) (build-lexer #'here `(lambda (x) x))
(syntax-case stx () (build-lexer #'here `(lambda (x) (list x first-pos end-pos)))))
((_)
(raise-syntax-error #f "empty lexer is not allowed" stx))
((_ re-act ...)
(begin
(for-each
(lambda (x)
(syntax-case x ()
((re act) (void))
(_ (raise-syntax-error 'lexer
"expects regular expression / action pairs"
x))))
(syntax->list (syntax (re-act ...))))
(let* ((table (generate-table (syntax (re-act ...)) stx))
(code
`(let ((start-state ,(table-start table))
(trans-table ,(table-trans table))
(eof-table ,(table-eof table))
(actions (vector ,@(vector->list (table-actions table)))))
,(code `(lambda (x) x)))))
(datum->syntax-object #'here code #f))))))
(lambda (stx)
(syntax-case stx ()
((_)
(raise-syntax-error #f "empty lexer is not allowed" stx))
((_ re-act ...)
(begin
(for-each
(lambda (x)
(syntax-case x ()
((re act) (void))
(_ (raise-syntax-error 'lexer
"expects regular expression / action pairs"
x))))
(syntax->list (syntax (re-act ...))))
(let* ((table (generate-table (syntax (re-act ...)) stx))
(code
`(let ((start-state ,(table-start table))
(trans-table ,(table-trans table))
(eof-table ,(table-eof table))
(actions (vector ,@(vector->list (table-actions table)))))
,(code `(lambda (x) (list x first-pos end-pos))))))
(datum->syntax-object #'here code #f)))))))))
(define-syntax (define-lex-abbrev stx) (define-syntax (define-lex-abbrev stx)

Write Preview
Loading…
Cancel
Save