functional/overloaded_function/test/identity.cpp

// Copyright (C) 2009-2012 Lorenzo Caminiti
// Distributed under the Boost Software License, Version 1.0
// (see accompanying file LICENSE_1_0.txt or a copy at
// http://www.boost.org/LICENSE_1_0.txt)
// Home at http://www.boost.org/libs/functional/overloaded_function

#include <boost/functional/overloaded_function.hpp>
#include <boost/function.hpp>
#define BOOST_TEST_MODULE TestIdentity
#include <boost/test/unit_test.hpp>
#include <string>

//[identity_make_checks
template<typename F>
void check(F identity) {
    BOOST_CHECK( identity("abc") == "abc" );
    BOOST_CHECK( identity(123) == 123 );
    BOOST_CHECK( identity(1.23) == 1.23 );
}
//]

//[identity_decls
const std::string& identity_s(const std::string& x) { return x; } // As pointer.

int identity_i_impl(int x) { return x; }
int (&identity_i)(int) = identity_i_impl; // Function reference.

double identity_d_impl(double x) { return x; }
boost::function<double (double)> identity_d = identity_d_impl; // Functor.
//]

BOOST_AUTO_TEST_CASE( test_identity ) {
    //[identity_calls
    BOOST_CHECK( identity_s("abc") == "abc" );
    BOOST_CHECK( identity_i(123) == 123 );
    BOOST_CHECK( identity_d(1.23) == 1.23 );
    //]

    {
        //[identity
        boost::overloaded_function<
              const std::string& (const std::string&)
            , int (int)
            , double (double)
        > identity(identity_s, identity_i, identity_d);

        // All calls via single `identity` function.
        BOOST_CHECK( identity("abc") == "abc" );
        BOOST_CHECK( identity(123) == 123 );
        BOOST_CHECK( identity(1.23) == 1.23 );
        //]
    }
    
    {
        //[identity_make
        BOOST_AUTO(identity, boost::make_overloaded_function(
                identity_s, identity_i, identity_d));

        BOOST_CHECK( identity("abc") == "abc" );
        BOOST_CHECK( identity(123) == 123 );
        BOOST_CHECK( identity(1.23) == 1.23 );
        //]
    }

    //[identity_make_call
    check(boost::make_overloaded_function(identity_s, identity_i, identity_d));
    //]
}