As of C++20, yes, but only if the std::string is destroyed by the end of constant evaluation. So while your example will still not compile, something like this will: constexpr std::size_t n = std::string(“hello, world”).size(); However, as of C++17, you can use string_view: constexpr std::string_view sv = “hello, world”; A string_view is a string-like object … Read more
Suppose it does something a little more complicated. constexpr int MeaningOfLife ( int a, int b ) { return a * b; } const int meaningOfLife = MeaningOfLife( 6, 7 ); Now you have something that can be evaluated down to a constant while maintaining good readability and allowing slightly more complex processing than just … Read more
I believe there is a difference. Let’s rename them so that we can talk about them more easily: const double PI1 = 3.141592653589793; constexpr double PI2 = 3.141592653589793; Both PI1 and PI2 are constant, meaning you can not modify them. However only PI2 is a compile-time constant. It shall be initialized at compile time. PI1 … Read more
Basic meaning and syntax Both keywords can be used in the declaration of objects as well as functions. The basic difference when applied to objects is this: const declares an object as constant. This implies a guarantee that once initialized, the value of that object won’t change, and the compiler can make use of this … Read more