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

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

In C++, both constexpr and const are used to define constants, but they have different purposes. Const is used to declare a variable that cannot be modified after its initialization, while constexpr is used to declare that a variable or function can be evaluated at compile time.

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

Sure! You would use constexpr when you want to define a constant expression that can be evaluated at compile time, such as in template parameters or array sizes. For example:

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

This function can be used in contexts that require compile-time evaluation.

Are there any limitations to using constexpr?

Yes, there are some limitations. For instance, constexpr functions must have a return type and cannot contain any statements that would cause side effects, like modifying global variables or performing I/O operations.

Can I use constexpr with classes?

Absolutely! You can use constexpr with class member functions, allowing them to be evaluated at compile time as well. Just ensure that the function meets the constexpr requirements.