// Copyright (C) 2014 Lorenzo Caminiti.

#include <boost/type_traits/has_equal_to.hpp>
#include <functional>
#include <cassert>
#include <iostream>

namespace aux {

template< bool Condition >
struct static_if_statement {
    template< typename F > void then ( F const& f ) { f(); }
    template< typename F > void else_ ( F const& ) { }
};

template< >
struct static_if_statement<false> {
    template< typename F > void then ( F const& ) { }
    template< typename F > void else_ ( F const& f ) { f(); }
};

} // namespace

template< bool Condition, typename F >
aux::static_if_statement<Condition> static_if ( F const& f ) {
    aux::static_if_statement<Condition> if_;
    if_.then(f);
    return if_;
}

template< typename T >
void assign ( T& x, T const& y ) {
    x = y;

    static_if<boost::has_equal_to<T>::value>(
        std::bind([] ( auto x, auto y ) {
            assert(x == y);
            std::cout << "asserted for: " << typeid(T).name() << std::endl;
        }, x, y)
    ).else_(
        [] ( ) {
            std::cout << "cannot assert for: " << typeid(T).name() << std::endl;
        }
    );
}

int main ( ) {
    int i = 1;
    struct x_t { } x;

    static_assert(boost::has_equal_to<int>::value == 1, "int equal");
    static_assert(boost::has_equal_to<x_t>::value == 0, "x_t not equal");

    assign(i, i);
    assign(x, x);
    
    return 0;
}