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