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66 lines
1.9 KiB
Racket
66 lines
1.9 KiB
Racket
7 years ago
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#lang br/quicklang
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(require brag/support "grammar.rkt")
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(provide (all-from-out br/quicklang) (all-defined-out))
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(module+ reader
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(provide read-syntax))
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(define-lex-abbrev regex-chars (char-set "()*+?.^$|<!=[]"))
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(define lex
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(lexer
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[(:+ "\n") (token 'NEWLINE lexeme)]
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[(from/stop-before ";" "\n") (token 'COMMENT #:skip? #t)]
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[(:+ whitespace) (token 'SP lexeme #:skip? #t)]
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[regex-chars lexeme]
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[alphabetic (token 'LITERAL lexeme)]))
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(define (read-syntax src ip)
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(define parse-tree (parse (λ () (lex ip))))
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(strip-context
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(with-syntax ([PT parse-tree])
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#'(module regexcellent-mod regexcellent-demo
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(for ([line (in-list PT)])
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(displayln line))))))
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(define-macro (top . LINES) #'(list . LINES))
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(define (line . pieces)
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(format "This pattern matches ~a." (string-join pieces ", followed by ")))
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(define (pat . xs)
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(if (= (length xs) 1)
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(car xs)
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(format "a sequence starting with ~a" (string-join xs ", followed by "))))
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(define (lookbehind pat)
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(format "a lookbehind assertion of ~a" pat))
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(define (lookahead pat)
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(format "a lookahead assertion of ~a" pat))
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(define (choice . pats)
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(format "a choice of ~a" (string-join pats "; or ")))
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(define (repeat thing [quantifier #f] [maybe-non-greedy? #f])
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(string-join
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(filter values
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(list thing
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(case quantifier
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[("*") "repeated zero or more times"]
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[("+") "repeated one or more times"]
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[("?") "zero or once"]
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[else #f])
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(and maybe-non-greedy? "non-greedily")))
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" "))
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(define (group pat)
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(format "the group containing ~a" pat))
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(define (any) "any character")
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(define (start) "the start of the input")
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(define (end) "the end of the input")
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(define (literals . strs)
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(format "the literal string ~v" (string-join strs "")))
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(define (chars . lits)
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(format "any member of the character set {~a}" (string-join (map ~v lits) ", ")))
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