What is the difference between const and constexpr in C++?

What is the difference between const and constexpr in C++?

In C++, const is used to declare variables whose values cannot be changed after initialization, while constexpr is used to declare variables that can be evaluated at compile time. This means constexpr can be used in contexts where constant expressions are required.

Can you give me an example of when to use constexpr?

Sure! You can use constexpr for functions that can be evaluated at compile time. For example:

constexpr int square(int x) {
    return x * x;
}

This function can be used in constant expressions, like array sizes.

Are there any limitations to using constexpr?

Yes, constexpr functions must have a single return statement and cannot contain any side effects. They also cannot modify any global or static variables.

How does constexpr improve performance?

constexpr can improve performance by allowing computations to be done at compile time rather than runtime, reducing the overhead during execution.