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generate-regular-expressions.rkt
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generate-regular-expressions.rkt
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#lang racket
(module+ test (require rackunit))
(define (wrap s) (~a #\( s #\)))
(define (emit-re re)
(define e emit-re)
(define (e* res) (map e res))
(match re
[(list '? re) (~a (wrap (e re)) "?")]
[(list '* re) (~a (wrap (e re)) "*")]
[(list '+ re) (~a (wrap (e re)) "+")]
[(list 'seq re* ...) (apply ~a (e* re*))]
[(list 'union re* ...) (wrap (apply ~a (add-between (map wrap (e* re*)) "|")))]
[(list 'ahead re) (~a "(?=" (wrap (e re)) ")")]
[(list 'not-ahead re) (~a "(?!" (wrap (e re)) ")")]
[(list 'sub re) (~a (wrap (e re)))]
[(list 'between from to re) (wrap (~a (wrap (e re)) "{" from "," to "}"))]
[(list 'bracket name) (~a "[[:" name ":]]")]
[(list 'ignore-case re) (~a "((?i)" (e re) "(?-i))")]
[(? number? n) (~a n)]
[(? char? c) (~a (ch c))]
[(? string? s) (~a s)]
[_ (error 'emit-re "got ~a" re)]))
(define-syntax (define-builder stx)
(syntax-case stx ()
[(_ name (var ...) prefix)
(syntax/loc stx
(define (name var ...) (cons prefix (list var ...))))]
[(_ name var prefix)
(syntax/loc stx
(define (name . var) (cons prefix var)))]))
(define-builder union res 'union)
(define-builder seq res 'seq)
(define-builder optional (re) '?)
(define-builder one-or-more (re) '+)
(define-builder zero-or-more (re) '*)
(define-builder sub (re) 'sub)
(define-builder between (from to re) 'between)
(define-builder not-ahead (re) 'not-ahead)
(define-builder bracket (name) 'bracket)
(define-builder ignore-case (re) 'ignore-case)
; ch : char -> string
; escapes characters
(define (ch c)
(define escapes '(#\? #\* #\+ #\^ #\$ #\\ #\# #\. #\- #\/))
(cond
[(and (string? c) (= (string-length c) 1))
(ch (string-ref c 0))]
[(char? c)
(if (member c escapes)
(~a #\\ c)
c)]
[(symbol? c)
(ch (symbol->string c))]
[else
(error 'char "got: ~a" c)]))
; str : string -> string
; escape characters if needed
(define (str s)
(apply ~a (map ch (string->list s))))
(define <sign> (union (ch '+) (ch '-)))
(define <digit2> "[0-1]")
(define <digit8> "[0-7]")
(define <digit10> "[0-9]")
(define <digit16> "[0-9abcdefABCDEF]")
(define (digit n)
(case n
[(2) <digit2>]
[(8) <digit8>]
[(10) <digit10>]
[(16) <digit16>]
[else (error)]))
(define <exp-mark16> "[sl]")
(define <exp-mark10> "[sldef]")
(define <exp-mark8> <exp-mark10>)
(define <exp-mark2> <exp-mark10>)
(define (exp-mark n)
(cond
[(extflonum?) "[tT]"]
[else (case n
[(2) <exp-mark2>]
[(8) <exp-mark8>]
[(10) <exp-mark10>]
[(16) <exp-mark16>]
[else (error)])]))
(define <exactness> (seq #\# "[ei]"))
(define (general-number n)
(seq (optional <exactness>) (number n)))
(define (number n)
(union (exact n) (inexact n)))
(define (exact n)
(union (exact-rational n) (exact-complex n)))
(define (exact-rational n)
(seq (optional <sign>) (unsigned-rational n)))
(define (unsigned-rational n)
(union (unsigned-integer n)
(seq (unsigned-integer n) #\/ (unsigned-integer n))))
(define (exact-integer n)
(seq (optional <sign>) (unsigned-integer n)))
(define (unsigned-integer n)
(one-or-more (digit n)))
(define (exact-complex n)
(seq (optional (exact-rational n)) <sign> (optional (unsigned-rational n)) "i"))
(define (inexact n)
(union (inexact-real n) (inexact-complex n)))
(define (inexact-real n)
(union (seq (optional <sign>) (inexact-normal n))
(seq <sign> (inexact-special n))))
(define (inexact-unsigned n)
(union (inexact-normal n) (inexact-special n)))
(define (inexact-normal n)
(seq (inexact-simple n) (optional (sub (seq (exp-mark n) (exact-integer n))))))
(define (inexact-simple n)
(union (seq (digits# n) (optional #\.) (zero-or-more #\#))
(seq (optional (unsigned-integer n)) #\. (digits# n))
(seq (digits# n) #\/ (digits# n))))
(define (inexact-special n)
(sub (seq (union (str "inf.") (str "nan.")) "[0ftT]")))
(define (digits# n)
(seq (one-or-more (digit n)) (zero-or-more #\#)))
(define (inexact-complex n)
(union (seq (optional (inexact-real n)) <sign> (optional (inexact-unsigned n)) #\i)
(seq (inexact-real n) #\@ (inexact-real n))))
(define <delimiter-ahead> "(?=[()\\[\\]{}\",'`;\\ \\s])")
(define (extflonum)
(parameterize ([extflonum? #t])
(seq (sub (union (seq #\# "[bB]" (inexact-real 2))
(seq #\# "[oO]" (inexact-real 8))
(seq #\# "[xX]" (inexact-real 16))
(seq (optional (seq #\# "[bB]")) (inexact-real 10))))
<delimiter-ahead>)))
(define extflonum? (make-parameter #f))
(define (binary-numbers)
(seq (sub (seq #\# (zero-or-more (seq "[bBeEiI]"))
(general-number 2)))
<delimiter-ahead>))
(define (decimal-numbers)
(seq (sub (seq #\# (zero-or-more (seq "[dDeEiI]"))
(general-number 10)))
<delimiter-ahead>))
(define (octal-numbers)
(seq (sub (seq #\# (zero-or-more (seq "[oOeEiI]"))
(general-number 8)))
<delimiter-ahead>))
(define (hexadecimal-numbers)
(seq (sub (seq #\# (zero-or-more (seq "[xXeEiI]"))
(general-number 16)))
<delimiter-ahead>))
'binary
(displayln (emit-re (binary-numbers)))
(newline)
'octal
(displayln (emit-re (octal-numbers)))
(newline)
'decimal
(displayln (emit-re (decimal-numbers)))
(newline)
'hexadecimal
(displayln (emit-re (hexadecimal-numbers)))
'extflonum
(displayln (emit-re (extflonum)))
(define <characters>
(let ()
(define names '("null" "nul" "backspace" "tab" "newline" "linefeed"
"vtab" "page" "return" "space" "rubout"))
(union
; named characters
(ignore-case (apply union (for/list ([n names]) (~a (str "#\\") n))))
; unicode octal
(seq #\# #\\ (between 1 3 (digit 8)))
; unicode hexadecimal
(seq #\# #\\ #\u (between 1 4 (digit 16)))
(seq #\# #\\ #\U (between 1 8 (digit 16)))
(seq #\# #\\ "." "(?=[^[:alpha:]])"))))
'characters
(displayln (emit-re <characters>))