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#lang scheme/base
;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; PARSEQ.PLT
;; A Parser Combinator library.
;;
;; Bonzai Lab, LLC. All rights reserved.
;;
;; Licensed under LGPL.
;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; json.ss - a parser for the json format
;; yc 1/5/2010 - first version
;; yc 7/76/2010 - updated json-string to handle single quotes.
(require "../main.ss"
)
(define hex-digit (seq d <- (choice digit #\a #\b #\c #\d #\e #\f
#\A #\B #\C #\D #\E #\F)
(return (case d
((#\0) 0)
((#\1) 1)
((#\2) 2)
((#\3) 3)
((#\4) 4)
((#\5) 5)
((#\6) 6)
((#\7) 7)
((#\8) 8)
((#\9) 9)
((#\a #\A) 10)
((#\b #\B) 11)
((#\c #\C) 12)
((#\d #\D) 13)
((#\e #\E) 14)
((#\f #\F) 15)))))
(define (hex->char h)
(case h
((0) #\0)
((1) #\1)
((2) #\2)
((3) #\3)
((4) #\4)
((5) #\5)
((6) #\6)
((7) #\7)
((8) #\8)
((9) #\9)
((10) #\a)
((11) #\b)
((12) #\c)
((13) #\d)
((14) #\e)
((15) #\f)))
(define (hexes->char hexes)
(integer->char (hexes->integer hexes)))
(define (char->hexes c)
(integer->hexes (char->integer c)))
(define (char->hex-chars c)
(map hex->char (char->hexes c)))
(define (hexes->integer hexes)
(define (helper rest acc)
(cond ((null? rest) acc)
(else
(helper (cdr rest) (+ (* acc 16) (car rest))))))
(helper hexes 0))
(define (integer->hexes i)
(define (helper q acc)
(if (= q 0)
acc
(let-values (((q r)
(quotient/remainder q 16)))
(helper q (cons r acc)))))
(helper i '()))
(define unicode-char
(seq #\\ #\u
code <- (repeat hex-digit 4 4)
(return (hexes->char code))))
(define (json-string/inner quote)
(zero-many (choice e-newline
e-return
e-tab
e-backslash
(escaped-char #\\ quote)
(escaped-char #\\ #\/)
(escaped-char #\\ #\\)
(escaped-char #\\ #\b #\backspace)
(escaped-char #\\ #\f #\page)
unicode-char
(char-not-in (list quote
#\newline
#\return
#\tab
#\\
#\backspace
#\page))
)))
(define json-string
(choice (seq #\' atoms <- (json-string/inner #\') #\'
(return (list->string atoms)))
(seq #\" atoms <- (json-string/inner #\") #\"
(return (list->string atoms)))))
(define json-array (tokens v <- (bracket/delimited #\[ json-value #\, #\])
(return (list->vector v))))
(define json-object (tokens v <- (bracket/delimited #\{ json-pair #\, #\})
(return (make-immutable-hash v))))
(define json-pair (tokens key <- (choice json-string
(seq c <- alpha
lst <- (zero-many alphanumeric)
(return (list->string (cons c lst)))))
#\:
value <- json-value
(return (cons key value))))
(define json-literal (choice (tokens "true" (return #t))
(tokens "false" (return #f))
(tokens "null" (return '()))
))
(define json-value (choice json-literal json-array json-object real-number json-string))
(define read-json (make-reader json-value))
(provide read-json)
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