draconisplusplus/include/rfl/replace.hpp

#ifndef RFL_REPLACE_HPP_
#define RFL_REPLACE_HPP_

#include <type_traits>

#include "from_named_tuple.hpp"

namespace rfl {

  /// Replaces one or several fields, returning a new version
  /// with the non-replaced fields left unchanged.
  template <class T, class RField, class... OtherRFields>
  auto replace(T&& _t, RField&& _field, OtherRFields&&... _other_fields) {
    if constexpr (internal::is_named_tuple_v<T>) {
      return std::forward<T>(_t).replace(
          to_named_tuple(std::forward<RField>(_field)),
          to_named_tuple(std::forward<OtherRFields>(_other_fields))...);
    } else {
      return from_named_tuple<T>(
          to_named_tuple(std::forward<T>(_t))
              .replace(to_named_tuple(std::forward<RField>(_field)),
                       to_named_tuple(
                           std::forward<OtherRFields>(_other_fields))...));
    }
  }

  /// Replaces one or several fields, returning a new version
  /// with the non-replaced fields left unchanged.
  template <class T, class RField, class... OtherRFields>
  auto replace(const T& _t, RField&& _field, OtherRFields&&... _other_fields) {
    if constexpr (internal::is_named_tuple_v<T>) {
      return _t.replace(
          to_named_tuple(std::forward<RField>(_field)),
          to_named_tuple(std::forward<OtherRFields>(_other_fields))...);
    } else {
      return from_named_tuple<T>(to_named_tuple(_t).replace(
          to_named_tuple(std::forward<RField>(_field)),
          to_named_tuple(std::forward<OtherRFields>(_other_fields))...));
    }
  }

} // namespace rfl

#endif