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## Struct template is_inclusive

boost::histogram::axis::traits::is_inclusive — Meta-function to detect whether an axis is inclusive.

## Synopsis

    // In header: <boost/histogram/axis/traits.hpp>

    template<typename Axis>
    struct is_inclusive {
    };

## Description

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 usesget_options<Axis> and checks whether the underflow and overflow bits are present.

### Template Parameters

1.     typename Axis

   axis type