How to declare the values calculated at compile time in C++ using constexpr

This article introduces the knowledge of "how to declare the values calculated in C++ at compile time using constexpr". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Con.5: use constexpr to declare values that can be calculated at compile time

Reason (reason)

Better performance, better compile-time checking, guaranteed compile-time evaluation, no possibility of race conditions.

Better performance, better compilation checking, to ensure compile-time computing, there are no competition conditions.

Example (sample)

Double x = f (2); / / possible run-time evaluation

Const double y = f (2); / / possible run-time evaluation

Constexpr double z = f (2); / / error unless f (2) can be evaluated at compile time

Enforcement (implementation recommendations)

Flag const definitions with constant expression initializers.

Tag uses a constant definition initialized by a constant expression.

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