Constexpr does not guarantee that a constexpr function can be called at compile time, unfortunately. Only that it can be called at runtime for a subset of all possible parameters.
Except of course the subset of parameters for which it is constexpr callable can't be checked at function definition time (if it exists at all), only at function invocation time.
Which makes the constexpr annotation useless and it is in only because the authors couldn't otherwise get the paper through some committee objections.
Except of course the subset of parameters for which it is constexpr callable can't be checked at function definition time (if it exists at all), only at function invocation time.
Which makes the constexpr annotation useless and it is in only because the authors couldn't otherwise get the paper through some committee objections.