narrow.h

/***************************************************************************
 * LehrFEM++ - A simple C++ finite element libray for teaching
 * Developed from 2018 at the Seminar of Applied Mathematics of ETH Zurich,
 * lead developers Dr. R. Casagrande and Prof. R. Hiptmair
 ***************************************************************************/
 
#ifndef INCG_1944399668484015bcf9f347522a68c3
#define INCG_1944399668484015bcf9f347522a68c3
#include <type_traits>
 
namespace lf::base {
 
template <class TO, class FROM>
auto narrow(FROM from) noexcept -> TO {
  static_assert(std::is_arithmetic_v<TO>, "TO must be an arithmetic type");
  const TO to = static_cast<TO>(std::forward<FROM>(from));
  if constexpr (std::is_arithmetic_v<TO>) {
    LF_ASSERT_MSG(static_cast<FROM>(to) == from &&
                      (std::is_signed_v<FROM> == std::is_signed_v<TO> ||
                       ((to < TO{}) == (from < FROM{}))),
                  "Narrowing error.");
  } else {
    LF_ASSERT_MSG(static_cast<FROM>(to) == from, "Narrowing error.");
  }
  return to;
}
 
}  // namespace lf::base
 
#endif  // INCG_1944399668484015bcf9f347522a68c3