noop.h

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/*
 *  This file is a part of TiledArray.
 *  Copyright (C) 2013  Virginia Tech
 *
 *  This program 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.
 *
 *  This program 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/>.
 *
 *  Justus Calvin
 *  Department of Chemistry, Virginia Tech
 *
 *  noop.h
 *  June 27, 2013
 *
 */

#ifndef TILEDARRAY_TILE_OP_NOOP_H__INCLUDED
#define TILEDARRAY_TILE_OP_NOOP_H__INCLUDED

#include "../tile_interface/permute.h"
#include "../tile_interface/clone.h"

namespace TiledArray {
  namespace detail {


    template <typename Result, typename Arg, bool Consumable>
    class Noop {
    public:
      typedef Noop<Result, Arg, Consumable> Noop_; 
      typedef Arg argument_type; 
      typedef Result result_type; 

      static constexpr bool is_consumable = Consumable;

    private:

      // Permuting tile evaluation function
      // These operations cannot consume the argument tile since this operation
      // requires temporary storage space.

      result_type eval(const Arg& arg, const Permutation& perm) const {
        TiledArray::Permute<Result, Arg> permute;
        return permute(arg, perm);
      }

      // Non-permuting tile evaluation functions
      // The compiler will select the correct functions based on the
      // consumability of the arguments.

      template <bool C, typename std::enable_if<!C>::type* = nullptr>
      result_type eval(const Arg& arg) const {
        TiledArray::Clone<Result, Arg> clone;
        return clone(arg);
      }

      template <bool C, typename std::enable_if<C>::type* = nullptr>
      result_type eval(Arg& arg) const { return arg; }

    public:


      result_type
      operator()(const argument_type& arg, const Permutation& perm) const {
        return eval(arg, perm);
      }


      template <typename A>
      result_type operator()(A&& arg) const {
        return Noop_::template eval<is_consumable>(arg);
      }


      result_type consume(argument_type& arg) const {
        constexpr bool can_consume = is_consumable_tile<argument_type>::value &&
            std::is_same<result_type, argument_type>::value;
        return Noop_::template eval<can_consume>(arg);
      }

    }; // class Noop

  } // namespace detail
} // namespace TiledArray

#endif // TILEDARRAY_TILE_OP_NOOP_H__INCLUDED