integral_parameter.hpp

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/*
 * Copyright (C) 2020-2022 The ESPResSo project
 * Copyright (C) 2002,2003,2004,2005,2006,2007,2008,2009,2010
 *   Max-Planck-Institute for Polymer Research, Theory Group
 *
 * This file is part of ESPResSo.
 *
 * ESPResSo is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * ESPResSo is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef ESPRESSO_INTEGRAL_PARAMETER_HPP
#define ESPRESSO_INTEGRAL_PARAMETER_HPP
 
#include <cstddef>
#include <stdexcept>
#include <utility>
 
namespace Utils {
namespace detail {
template <typename T, template <T> class F, T I, T N>
struct integral_parameter_impl {
  template <class... Args> static decltype(auto) eval(T i, Args &&...args) {
    if (i == I)
      return F<I>{}(std::forward<Args>(args)...);
 
    return integral_parameter_impl<T, F, I + T{1}, N>::eval(
        i, std::forward<Args>(args)...);
  }
};
 
template <typename T, template <T> class F, T N>
struct integral_parameter_impl<T, F, N, N> {
  template <class... Args> static decltype(auto) eval(T i, Args &&...args) {
    if (i == N)
      return F<N>{}(std::forward<Args>(args)...);
 
    throw std::runtime_error("Invalid parameter value");
  }
};
} // namespace detail
 
/**
 * @brief Generate a call table for an integral non-type template parameter.
 * Can be used to dynamically create a switch statement for contiguous values.
 */
template <typename T, template <T> class F, T min, T max, class... Args>
decltype(auto) integral_parameter(T i, Args &&...args) {
  return detail::integral_parameter_impl<T, F, min, max>::eval(
      i, std::forward<Args>(args)...);
}
 
} // namespace Utils
 
#endif // ESPRESSO_INTEGRAL_PARAMETER_HPP