Method for_each_axis

include/boost/histogram/histogram.hpp:151–153

  /// Apply unary functor/function to each axis
  template <typename Unary>
  void for_each_axis(Unary&& unary) const {
    detail::for_each_axis(axes_, std::forward<Unary>(unary));
  }

  /// Fill histogram with a value tuple
  template <typename... Ts>