# C++ Templates

pygccxml has minimal support for c++ templates, but there is some information that can be extracted from templated declarations.

Let’s consider the following c++ file (example.hpp):

    namespace ns {

    struct B {
      struct D { bool d; };
    };
    struct D {};

    template <typename T1, typename T2>
    struct T {};

    T<B::D, bool> function();

    }

This example show how to extract template parameters from the template declaration.

    from pygccxml import utils
    from pygccxml import declarations
    from pygccxml import parser

    # Find out the c++ parser
    generator_path, generator_name = utils.find_xml_generator()

    # Configure the xml generator
    xml_generator_config = parser.xml_generator_configuration_t(
        xml_generator_path=generator_path,
        xml_generator=generator_name)

    # The c++ file we want to parse
    filename = "example.hpp"

    decls = parser.parse([filename], xml_generator_config)
    global_namespace = declarations.get_global_namespace(decls)
    ns = global_namespace.namespace("ns")

    class_t_decl = []
    for d in ns.declarations:
        if isinstance(d, declarations.class_declaration_t):
            class_declaration_t = d
        if isinstance(d, declarations.class_t):
            class_t_decl.append(d)
        if isinstance(d, declarations.free_function_t):
            free_function_t_decl = d

    print(class_t_decl[0])
    # > ns::B [struct]

    print(class_t_decl[1])
    # > ns::D [struct]

    print(class_declaration_t)
    # > ns::T<ns::B::D, bool> [class declaration]

    print(free_function_t_decl)
    # > ns::T<ns::B::D, bool> ns::function() [free function]

    print(declarations.templates.is_instantiation(class_declaration_t.name))
    # > True

    name, parameter_list = declarations.templates.split(class_declaration_t.name)
    print(name, parameter_list)
    # > 'T', ['ns::B::D', 'bool']