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beautiful-racket/beautiful-racket-demo/regexcellent-demo/main.rkt

66 lines
2.0 KiB
Racket

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