# Searching for a declaration (using matchers)

This example shows how to search for a specific declaration using different criteria.

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

    namespace ns{
        int a = 1;
        int b = 2;
        double c = 3.0;

        int func1(int a) {
            int b = a + 2;
            return b;
        }

        double func2(double a) {
            double b = a + 2.0;
            return b;
        }

         double func3(double a) {
            double b = a + 3.0;
            return b;
        }
    }

The following code will show you how to search for functions and variables

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

    # Find the location of the xml generator (castxml or gccxml)
    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"

    # Parse the c++ file
    decls = parser.parse([filename], xml_generator_config)

    global_namespace = declarations.get_global_namespace(decls)

    ns_namespace = global_namespace.namespace("ns")

    int_type = declarations.cpptypes.int_t()
    double_type = declarations.cpptypes.double_t()

    # Search for the function by name
    criteria = declarations.calldef_matcher(name="func1")
    func1 = declarations.matcher.get_single(criteria, ns_namespace)

    # Search for functions which return an int
    criteria = declarations.calldef_matcher(return_type="int")
    func2 = declarations.matcher.get_single(criteria, ns_namespace)

    # Search for functions which return an int, using the cpptypes class
    criteria = declarations.calldef_matcher(return_type=int_type)
    func3 = declarations.matcher.get_single(criteria, ns_namespace)

    print(func1)
    print(func2)
    print(func3)

    # This prints:
    # int ns::func1(int a) [free function]
    # int ns::func1(int a) [free function]
    # int ns::func1(int a) [free function]

    # Search for functions which return a double. Two functions will be found
    criteria = declarations.calldef_matcher(return_type=double_type)
    func4 = declarations.matcher.find(criteria, ns_namespace)

    print(len(func4))
    print(func4[0])
    print(func4[1])

    # This prints:
    # 2
    # double ns::func2(double a) [free function]
    # double ns::func3(double a) [free function]

    # Finally, look for variables by name and by type
    criteria = declarations.variable_matcher(name="a")
    var_a1 = declarations.matcher.find(criteria, ns_namespace)

    criteria = declarations.variable_matcher(decl_type=int_type)
    var_a2 = declarations.matcher.find(criteria, ns_namespace)

    print(var_a1[0])
    print(var_a2[0])
    print(var_a2[1])

    # This prints:
    # ns::a [variable]
    # ns::a [variable]
    # ns::b [variable]