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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// <iterator>
// template <InputIterator Iter>
// Iter prev(Iter x, Iter::difference_type n = 1); // constexpr in C++17
#include <iterator>
#include <cassert>
#include <type_traits>
#include "test_macros.h"
#include "test_iterators.h"
template <class It>
TEST_CONSTEXPR_CXX17 void
check_prev_n(It it, typename std::iterator_traits<It>::difference_type n, It result)
{
static_assert(std::is_same<decltype(std::prev(it, n)), It>::value, "");
assert(std::prev(it, n) == result);
It (*prev_ptr)(It, typename std::iterator_traits<It>::difference_type) = std::prev;
assert(prev_ptr(it, n) == result);
}
template <class It>
TEST_CONSTEXPR_CXX17 void
check_prev_1(It it, It result)
{
static_assert(std::is_same<decltype(std::prev(it)), It>::value, "");
assert(std::prev(it) == result);
}
TEST_CONSTEXPR_CXX17 bool tests()
{
const char* s = "1234567890";
check_prev_n(forward_iterator <const char*>(s), -10, forward_iterator <const char*>(s+10));
check_prev_n(bidirectional_iterator<const char*>(s+10), 10, bidirectional_iterator<const char*>(s));
check_prev_n(bidirectional_iterator<const char*>(s), -10, bidirectional_iterator<const char*>(s+10));
check_prev_n(random_access_iterator<const char*>(s+10), 10, random_access_iterator<const char*>(s));
check_prev_n(random_access_iterator<const char*>(s), -10, random_access_iterator<const char*>(s+10));
check_prev_n(s+10, 10, s);
check_prev_1(bidirectional_iterator<const char*>(s+1), bidirectional_iterator<const char*>(s));
check_prev_1(random_access_iterator<const char*>(s+1), random_access_iterator<const char*>(s));
check_prev_1(s+1, s);
return true;
}
int main(int, char**)
{
tests();
#if TEST_STD_VER >= 17
static_assert(tests(), "");
#endif
return 0;
}
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