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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>
// reverse_iterator
// template <RandomAccessIterator Iter1, RandomAccessIterator Iter2>
// requires HasMinus<Iter2, Iter1>
// auto operator-(const reverse_iterator<Iter1>& x, const reverse_iterator<Iter2>& y) // constexpr in C++17
// -> decltype(y.base() - x.base());
#include <iterator>
#include <cstddef>
#include <cassert>
#include <type_traits>
#include "test_macros.h"
#include "test_iterators.h"
template <class, class, class = void>
struct HasMinus : std::false_type {};
template <class R1, class R2>
struct HasMinus<R1, R2, decltype((R1() - R2(), void()))> : std::true_type {};
// Test non-subtractable base iterator types
static_assert(HasMinus<std::reverse_iterator<int*>, std::reverse_iterator<int*> >::value, "");
static_assert(HasMinus<std::reverse_iterator<int*>, std::reverse_iterator<const int*> >::value, "");
#if TEST_STD_VER >= 11
static_assert(!HasMinus<std::reverse_iterator<int*>, std::reverse_iterator<char*> >::value, "");
static_assert(!HasMinus<std::reverse_iterator<bidirectional_iterator<int*> >,
std::reverse_iterator<bidirectional_iterator<int*> > >::value,
"");
#endif
template <class It1, class It2>
TEST_CONSTEXPR_CXX17 void test_one(It1 l, It2 r, std::ptrdiff_t x) {
const std::reverse_iterator<It1> r1(l);
const std::reverse_iterator<It2> r2(r);
assert((r1 - r2) == x);
}
template <class Iter>
TEST_CONSTEXPR_CXX17 void test() {
// Test same base iterator type
char s[3] = {0};
test_one(Iter(s), Iter(s), 0);
test_one(Iter(s), Iter(s + 1), 1);
test_one(Iter(s + 1), Iter(s), -1);
}
TEST_CONSTEXPR_CXX17 bool tests() {
{
test<char*>();
test<random_access_iterator<char*> >();
#if TEST_STD_VER >= 20
test<cpp20_random_access_iterator<char*>>();
#endif
}
{
// Test different (but subtractable) base iterator types
using PC = const char*;
char s[3] = {0};
test_one(PC(s), s, 0);
test_one(PC(s), s + 1, 1);
test_one(PC(s + 1), s, -1);
}
return true;
}
int main(int, char**) {
tests();
#if TEST_STD_VER > 14
static_assert(tests(), "");
#endif
return 0;
}
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