What is enable_if in C++?

Can you explain what enable_if is in C++?

Sure! enable_if is a template metaprogramming utility that allows you to conditionally enable or disable function templates based on certain conditions.

How does it work with template specialization?

It works by using SFINAE (Substitution Failure Is Not An Error). If the condition in enable_if is false, the template is ignored during overload resolution.

Can you give me a simple code example?

Absolutely! Here's a basic example:

#include <type_traits>

template<typename T>
typename std::enable_if<std::is_integral<T>::value, T>::type
add(T a, T b) {
    return a + b;
}

int main() {
    int result = add(5, 10); // Works
    // add(5.5, 10.5); // This would cause a compile error
}

What are some common use cases for enable_if?

Common use cases include creating type-safe APIs, enabling/disabling functions based on type traits, and implementing SFINAE-based overloads.