is_output_iterator.h

/*  This file is part of the Vc library. {{{
Copyright © 2015 Matthias Kretz <kretz@kde.org>

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the names of contributing organizations nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
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}}}*/

#ifndef VC_TRAITS_IS_OUTPUT_ITERATOR_H_
#define VC_TRAITS_IS_OUTPUT_ITERATOR_H_

#include <iterator>

namespace Vc_VERSIONED_NAMESPACE
{
namespace Traits
{
namespace is_output_iterator_impl
{
template <typename T, typename ValueType = typename std::iterator_traits<T>::value_type,
          typename = decltype(*std::declval<T &>() = std::declval<
                                  ValueType>())  // tests that assignment to a
                                                 // dereferenced iterator is possible, if
                                                 // yes, T is an OutputIterator
          >
std::true_type test(int);
template <typename T> std::false_type test(...);
}  // namespace is_output_iterator_impl

template <typename T>
struct is_output_iterator
    : public std::conditional<
          std::is_void<typename std::iterator_traits<T>::value_type>::value,
          std::true_type, decltype(is_output_iterator_impl::test<T>(int()))>::type
{
};

static_assert(!std::is_void<std::iterator_traits<int *>::value_type>::value, "");
static_assert(is_output_iterator<int *>::value, "");
static_assert(!is_output_iterator<const int *>::value, "");

}  // namespace Traits
}  // namespace Vc

#endif  // VC_TRAITS_IS_OUTPUT_ITERATOR_H_

// vim: foldmethod=marker