boost::histogram::axis::traits::is_inclusive — Meta-function to detect whether an axis is inclusive.
Doxygen does not render this well. This is a meta-function (template alias), it accepts an axis type and represents compile-time boolean which is true or false, depending on whether the axis is inclusive or not.
An inclusive axis has a bin for every possible input value. In other words, all possible input values always end up in a valid cell and there is no need to keep track of input tuples that need to be discarded. A histogram which consists entirely of inclusive axes can be filled more efficiently, which can be a factor 2 faster.
An axis with underflow and overflow bins is always inclusive, but an axis may be inclusive under other conditions. The meta-function checks for the method
constexpr static bool inclusive(), and uses the result. If this method is not present, it uses get_options<Axis> and checks whether the underflow and overflow bits are present.