What is if constexpr in C++17?

Can you explain what if constexpr is in C++17?

Sure! The if constexpr statement in C++17 allows for compile-time conditional branching. It enables you to write code that can be evaluated at compile time, which can help optimize performance and reduce code bloat.

How does it differ from regular if statements?

Unlike regular if statements, which are evaluated at runtime, if constexpr is evaluated at compile time. This means that the compiler can eliminate branches of code that are not taken, leading to more efficient binaries.

Can you give me a simple example?

Certainly! Here's a simple example:

template<typename T>
void checkType(T value) {
    if constexpr (std::is_integral_v<T>) {
        std::cout << "It's an integer!";
    } else {
        std::cout << "It's not an integer!";
    }
}

In this example, the message printed depends on whether the type T is an integral type.

What are the benefits of using if constexpr?

The benefits include improved performance by eliminating unnecessary code paths, better type safety, and cleaner code by allowing more expressive templates.