CODEWITHSUNDEEP
c++c++11templatestemplate-specializationenable-if
Jonn Dove
Jonn Dove

Reputation: 487

Can I define templates for different sets of types?

I need to write a templated function, that behaves differently depending on the class of its parameter:

template<class ContainerType>
bool myFunc(ContainerType in){
//do some stuff
}

template<class NotAContainerType>
bool myFunc(NotAContainerType in){
//do something else
}

I am restricted to C++11, so static_if is off the table. Also, the classes of ContainerType and NotAContainerType are really large and might change in the future, so just adding a few exceptions by hand as a template specialization is not sensible either.

I am aware of the std::enable_if workaround, but how do I use it, if I need to apply it to two mutually distinct sets of classes?

Upvotes: 13

Views: 532

Answers (1)

Jarod42
Jarod42

Reputation: 217145

Create a traits for your concept Container, then, you might use SFINAE

template <typename T>
typename std::enable_if<is_container<T>::value, bool>::type
myFunc(T in){
    //do some stuff
}

template <typename T>
typename std::enable_if<!is_container<T>::value, bool>::type
myFunc(T in){
    //do some stuff
}

or tag dispatching

namespace details
{

    template <typename T>
    bool myFunc(T in, std::true_type){
        //do some stuff
    }

    template <typename T>
    bool myFunc(T in, std::false_type){
        //do some stuff
    }

}


template <typename T>
bool myFunc(T in){
    return details::myFunc(in, is_container<T>{});
}

Upvotes: 20

Related Questions