Simplifying template code

[helios]

I have the following function:

template <bool V>
struct conditional_assignment{};

template <>
struct conditional_assignment<false>{
    template <typename T1, typename T2>
    static void func(T1 &dst, const T2& src){
    }
};

template <>
struct conditional_assignment<true>{
    template <typename T1, typename T2>
    static void func(T1 &dst, const T2& src){
        dst = src;
    }
};

template <typename T>
void f(const T &ip){
    constexpr bool is_ip4 = IpAddress_to_protocol<T>::value == AF_INET;
    constexpr bool is_ip6 = IpAddress_to_protocol<T>::value == AF_INET6;
    if (is_ip4){
        SomeType4 hop;
        //...
        conditional_assignment<is_ip4>::func(hop, ip);
        //...
    }else if (is_ip6){
        SomeType6 hop;
        //...
        conditional_assignment<is_ip6>::func(hop, ip);
        //...
    }
}

I'd like to get rid of conditional_assignment, in favor of something a bit more legible. What could I do here?

PS: To be clear, T may be equal to IpAddress4 or IpAddress6, which have, respectively, implicit conversions to SomeType4 and SomeType6, but not to SomeType6 and SomeType4.

[coder777]

Consider using enable_if. See:

http://www.cplusplus.com/reference/type_traits/enable_if/?kw=enable_if

[helios]

I would still need two conditional_assignment overloads. I don't want to call a function just to maybe do an assignment.

[coder777]

Maybe conditional:

http://www.cplusplus.com/reference/type_traits/conditional/

is what you want?