What is constexpr and how does it relate to template metaprogramming?

What is constexpr and how does it relate to template metaprogramming?

constexpr is a keyword in C++ that allows you to evaluate functions and variables at compile time. It enhances template metaprogramming by enabling more complex computations during compilation, leading to optimized code.

Can you give me an example of using constexpr in a template?

Sure! Here's a simple example:

template<int N>
constexpr int factorial() {
    return N <= 1 ? 1 : N * factorial<N - 1>();
}

constexpr int result = factorial<5>(); // result is 120 at compile time

What are the benefits of using constexpr in templates?

Using constexpr in templates allows for compile-time evaluation, which can lead to faster execution, reduced runtime overhead, and improved type safety. It also enables more expressive and flexible template metaprogramming.

Are there any limitations to using constexpr?

Yes, there are some limitations. For instance, constexpr functions must have a single return statement, and they cannot contain certain constructs like dynamic memory allocation or exceptions.