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A variable declared constexpr is implicitly const and its value may be used as a constant expression. Comparison with #define A constexpr is type-safe replacement for #define based compile-time expressions. With constexpr the compile-time evaluated expression is replaced with the result. For examp...

A function that is declared constexpr is implicitly inline and calls to such a function potentially yield constant expressions. For example, the following function, if called with constant expression arguments, yields a constant expression too: C++11 constexpr int Sum(int a, int b) { return ...

C++17 The if constexpr statement can be used to conditionally compile code. The condition must be a constant expression. The branch not selected is discarded. A discarded statement inside a template is not instantiated. For example: template<class T, class ... Rest> void g(T &&p, Re...