boost_1_45_0/libs/property_tree/doc/json_parser.qbk

[/
 / Copyright (c) 2008 Marcin Kalicinski (kalita <at> poczta dot onet dot pl)
 / Copyright (c) 2009 Sebastian Redl (sebastian dot redl <at> getdesigned dot at)
 /
 / Distributed under the Boost Software License, Version 1.0. (See accompanying
 / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 /]
[section JSON Parser]
[def __json__ [@http://en.wikipedia.org/wiki/JSON JSON format]]
The __json__ is a data interchange format derived from the object literal
notation of JavaScript. (JSON stands for JavaScript Object Notation.)
JSON is a simple, compact format for loosely structured node trees of any depth,
very similar to the property tree dataset. It is less stuctured than XML and has
no schema support, but has the advantage of being simpler, smaller and typed
without the need for a complex schema.

The property tree dataset is not typed, and does not support arrays as such.
Thus, the following JSON / property tree mapping is used:

* JSON objects are mapped to nodes. Each property is a child node.
* JSON arrays are mapped to nodes. Each element is a child node with an empty
  name. If a node has both named and unnamed child nodes, it cannot be mapped
  to a JSON representation.
* JSON values are mapped to nodes containing the value. However, all type
  information is lost; numbers, as well as the literals "null", "true" and
  "false" are simply mapped to their string form.
* Property tree nodes containing both child nodes and data cannot be mapped.

JSON round-trips, except for the type information loss.

For example this JSON:

 {
    "menu": 
    {
       "foo": true,
       "bar": "true",
       "value": 102.3E+06,
       "popup": 
       [
          {"value": "New", "onclick": "CreateNewDoc()"},
          {"value": "Open", "onclick": "OpenDoc()"},
       ]
    }
 }

will be translated into the following property tree:

 menu
 {
    foo true
    bar true
    value 102.3E+06
    popup
    {
       ""
       {
          value New
          onclick CreateNewDoc()
       }
       ""
       {
          value Open
          onclick OpenDoc()
       }
    }
 }

[endsect] [/json_parser]