Boost Extensions
================

There are three extensions to the Boost Property Tree library:

* Assign
* Conversion
* Lua parser
* Python API

This code is part of another library called Golld, but complete and useful for
itself. Because of that, the namespace used in this code is golld.


Assign
------

This extension provides a more concise and elegant alternative to create a
boost::property_tree::basic_ptree. For instance, a property_tree like:

    key1 value1
    key2
    {
        key3 12345
        {
            key4 "value4 with spaces"
        }
        key5 value5
        "" 10
        "" 11
        "" 12
    }

Can be created:

    ptree pt =
        tree()
        ("key1", "value1")
        ("key2", tree()
            ("key3", 12345)
            (tree()
                ("key4", "value4 with spaces"))
            ("key5", "value5")
            (10)(11)(12));

That code is cleaner that:

    ptree pt;
    pt.add("key1", "value1");

    ptree tmpPt1;
    tmpPt1.add("key3", 12345);

    ptree tmpPt2;
    tmpPt2.add("key4", "value4 with spaces");

    tmpPt1.push_back(std::make_pair("", tmpPt2));
    tmpPt1.add("key5", "value5");

    ptree tmpPt3;
    tmpPt3.put_value(10);
    tmpPt1.push_back(std::make_pair("", tmpPt3));

    ptree tmpPt4;
    tmpPt4.put_value(11);
    tmpPt1.push_back(std::make_pair("", tmpPt4));

    ptree tmpPt5;
    tmpPt5.put_value(12);
    tmpPt1.push_back(std::make_pair("", tmpPt5));

    pt.add_child("key2", tmpPt1);


Conversion
----------

This is only functions to convert a boost::ptree to a C++ sequence, a Boost
Array, or build a ptree from the union of other two ptrees.


Lua parser
----------

This is a Lua parser, as the XML or JSON parsers. It will run the Lua script
whose name was passed to read_lua function, and will build a boost::ptree from a
resulting Lua table.

Or, it will output a Lua script from a boos::ptree.


Python API
----------

This extension is a Python wrapper in the Boost Property Tree library. Its
intent is easily the exposing to Python of C++ code using the Boost Property
Tree library.

If you is using the SWIG to expose your classes, the ptree.i module will make transparent
the Python -> C++ ptree translation. To this, only include a %include "ptree.i" in your .i
file. Else, the binding code don't uses the SWIG anyway and a ptree can be created and
used in Python just as:

    pt1 = (tree()
             ('key1', 1)
             ('key2', 2)
             ('subtree', tree()(1)(2)(3))
         ).ptree
    pt2 = read_json('tree.json')
    pt1.add('aaa', 'bbb')
    print pt1