Constexpr

Constexpr is a keyword in C++ that allows the compiler to generate some code at compiler time and inject it into the static part of your executable.

It transparently allows code that is not constexpr to still compile — it would generate that code at runtime, however.

It can also be used in branches with if constexpr, where it only compiles a branch for the code that can be verified at compile time to take one branch.