#daimonscala 19-1 "JSON parser"

gistfile1.scala

// obj ::= "{" [members] "}".
// arr ::= "[" [values] "]".
// value ::= obj | arr | stringLiteral | floatingPointNumber | "null" | "true" | "false".
// values ::= value { "," value }.
// members ::= member { "," member }.
// member ::= stringLiteral ":" value.

object Main {
  import util.parsing.combinator._

  object JSONParser extends JavaTokenParsers {
    def obj: Parser[Map[String,Any]] = "{" ~ members ~ "}" ^^ {
      case "{" ~ members ~ "}" => members.toMap
    }
    def arr: Parser[List[Any]] = "[" ~ values ~ "]" ^^ { case "[" ~ values ~ "]" => values.toList }
    def value: Parser[Any] = obj | arr | stringLiteral | floatingPointNumber | "null" | "true" | "false"
    def values: Parser[List[Any]] = repsep(value, ",")
    def member: Parser[Pair[String,Any]] = stringLiteral ~ ":" ~ value ^^ { 
      case key ~ ":" ~ value => (key -> value)
    }
    def members: Parser[Seq[Pair[String,Any]]] = repsep(member, ",")
   
    def parse(json: String): ParseResult[Map[String,Any]] = parseAll(obj, json)

  }

  def main(args: Array[String]) {
    val json = """
{"menu": {
  "id": "file",
  "value": "File",
  "popup": {
    "menuitem": [
      {"value": "New", "onclick": "CreateNewDoc()"},
      {"value": "Open", "onclick": "OpenDoc()"},
      {"value": "Close", "onclick": "CloseDoc()"}
    ]
  }
}}
"""
    val result = JSONParser.parse(json)
    println(result.get)
       // Map("menu" -> Map("id" -> "file", "value" -> "File", "popup" -> Map("menuitem" -> List(Map("value" -> "New", "onclick" -> "CreateNewDoc()"), Map("value" -> "Open", "onclick" -> "OpenDoc()"), Map("value" -> "Close", "onclick" -> "CloseDoc()")))))  }  
}