apply.h

/*
 * Copyright (c) 2008-2018 the MRtrix3 contributors.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, you can obtain one at http://mozilla.org/MPL/2.0/
 *
 * MRtrix3 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.
 *
 * For more details, see http://www.mrtrix.org/
 */


#ifndef __apply_h__
#define __apply_h__

#include <tuple>
#include <type_traits>

#include "types.h" // For FORCE_INLINE

namespace MR {
  namespace {

    template<size_t N>
      struct Apply { NOMEMALIGN
        template<typename F, typename T>
          static FORCE_INLINE void apply (F && f, T && t)
          {
            Apply<N-1>::apply (::std::forward<F>(f), ::std::forward<T>(t));
            ::std::forward<F>(f) (::std::get<N> (::std::forward<T>(t)));
          }
      };

    template<>
      struct Apply<0> { NOMEMALIGN
        template<typename F, typename T>
          static FORCE_INLINE void apply (F && f, T && t)
          {
            ::std::forward<F>(f) (::std::get<0> (::std::forward<T>(t)));
          }
      };




    template<size_t N>
      struct Unpack { NOMEMALIGN
        template<typename F, typename T, typename... A>
          static FORCE_INLINE auto unpack (F && f, T && t, A &&... a)
          -> decltype(Unpack<N-1>::unpack (
                ::std::forward<F>(f), ::std::forward<T>(t),
                ::std::get<N-1>(::std::forward<T>(t)), ::std::forward<A>(a)...
                ))
          {
            return Unpack<N-1>::unpack (::std::forward<F>(f), ::std::forward<T>(t),
                ::std::get<N-1>(::std::forward<T>(t)), ::std::forward<A>(a)...
                );
          }
      };

    template<>
      struct Unpack<0> { NOMEMALIGN
        template<typename F, typename T, typename... A>
          static FORCE_INLINE auto unpack (F && f, T &&, A &&... a)
          -> decltype(::std::forward<F>(f)(::std::forward<A>(a)...))
          {
            return ::std::forward<F>(f)(::std::forward<A>(a)...);
          }
      };

  }




  //! invoke \c f(x) for each entry in \c t
  template <class F, class T>
    FORCE_INLINE void apply (F && f, T && t) 
    {
      Apply< ::std::tuple_size<
        typename ::std::decay<T>::type
        >::value-1>::apply (::std::forward<F>(f), ::std::forward<T>(t));
    }

  //! if \c t is a tuple of elements \c a..., invoke \c f(a...)
  template<typename F, typename T>
    FORCE_INLINE auto unpack (F && f, T && t)
    -> decltype(Unpack< ::std::tuple_size<
        typename ::std::decay<T>::type
        >::value>::unpack (::std::forward<F>(f), ::std::forward<T>(t)))
    {
      return Unpack< ::std::tuple_size<
        typename ::std::decay<T>::type
        >::value>::unpack (::std::forward<F>(f), ::std::forward<T>(t));
    }
}

#endif