fromFutureImport.h

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/**
 * @file   larcorealg/CoreUtils/fromFutureImport.h
 * @brief  Code that might appear as standard C++ in the future.
 * @author Gianluca Petrillo (petrillo@slac.stanford.edu)
 * @date   April 25, 2019
 * 
 * This is currently a header-only library.
 */

#ifndef LARCOREALG_COREUTILS_FROMFUTUREIMPORT_H
#define LARCOREALG_COREUTILS_FROMFUTUREIMPORT_H


#include <utility> // std::forward()

/**
 * @defgroup FutureStandards Future C++ features
 * @brief Features expected to be provided by future C++ standards.
 */


/**
 * Namespace anticipating some simple features of C++ standards not yet adopted.
 *
 * It is recommended that whenever all supported compilers support each single
 * feature, that be removed from here, and the standard one immediately adopted.
 * 
 * The aim is that the interface and behaviour here are as similar as possible,
 * so that the update should boil down to a different header inclusion and a
 * different namespace.
 *
 * @addtogroup FutureStandards
 */ 
namespace util::pre_std {
  
#if (__cplusplus < 202000L) // still to be defined, should be C++20
  
  /// Transparent functor that returns its argument just as passed.
  struct identity {
    
    struct is_transparent {}; // STL algorithms will be happy to find this
    
    template <typename T>
    constexpr T&& operator() (T&& t) const noexcept
      { return std::forward<T>(t); }
    
  }; // identity<>

#endif // (__cplusplus < 202000L)
  
} // namespace pre_std


  
#endif // LARCOREALG_COREUTILS_FROMFUTUREIMPORT_H