draconisplusplus/include/rfl/internal/VisitTree.hpp

#ifndef RFL_INTERNAL_VISITTREE_HPP_
#define RFL_INTERNAL_VISITTREE_HPP_

namespace rfl {
  namespace internal {

    struct VisitTree {
      /// Evaluates a visitor pattern using a tree-like structure.
      template <int _begin, int _end, class Visitor, class... Args>
      static inline auto
      visit(const auto& _v, const int _i, const Args&... _args) {
        static_assert(_end > _begin, "_end needs to be greater than _begin.");
        if constexpr (_end - _begin == 1) {
          return _v.template visit<_begin>(_args...);
        } else {
          constexpr int middle = (_begin + _end) / 2;
          if (_i < middle) {
            return visit<_begin, middle, Visitor>(_v, _i, _args...);
          } else {
            return visit<middle, _end, Visitor>(_v, _i, _args...);
          }
        }
      }
    };

  } // namespace internal
} // namespace rfl

#endif