json

file: grammer.rkt


#lang ragg

json: number | string

    | array  | object

number: NUMBER

string: STRING

array: "[" [json ("," json)*] "]"

object: "{" [kvpair ("," kvpair)*] "}"

kvpair: STRING ":" json



-----------------------------------------------------------
file: lex.rkt

#lang racket

(require ragg/support
         parser-tools/lex
         "grammer.rkt"
         (prefix-in : parser-tools/lex-sre))

(provide lex read-data)

(define-lex-abbrevs
  [punctuator
   (:or "{" "}" "[" "]" "," ":")])

(define-lex-abbrevs
  [string-literal
   (:: #\" (:* char-literal) #\")]
  [char-literal1
   (:or (:: #\\ any-char) (char-complement #\"))]
  [char-literal
   (:or any-char #\1)])

(define-lex-abbrevs
  [number-literal
   (:: int-literal
       (:? frac-literal)
       (:? exp-literal))]
  [int-literal (:: (:? #\-) digits)]
  [frac-literal (:: #\. digits)]
  [exp-literal (:: e-literal digits)]
  [digits (repetition 1 +inf.0 numeric)]
  [e-literal (:: (:or #\e #\E) (:? (:or #\- #\+)))])


(define lex
  (lexer-src-pos
   [number-literal (token 'NUMBER lexeme)]
   [string-literal (token 'STRING lexeme)]
   [punctuator lexeme]
   [(:+ whitespace) (void)]
   [(eof) (void)]))


(define (read-data in)
  (syntax->datum
   (parse (λ ()
            (lex in)))))


--------------------------------------------------
run this:

(require "lex.rkt")


(define (get-jd str)
  (let ([in (open-input-string str)])
    (read-data in)))


(define obj (get-jd "{\"a\":1,\"b\":2}"))

get:
>obj
'(json
  (object
   "{"
   (kvpair
    "\"a\":1,\"b\""
    ":"
    (json (number "2")))
   "}"))