libcxx/test/std/iterators/predef.iterators/reverse.iterators/reverse.iter.nonmember/minus.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // <iterator>
  10
  11 // reverse_iterator
  12
  13 // template <RandomAccessIterator Iter1, RandomAccessIterator Iter2>
  14 //   requires HasMinus<Iter2, Iter1>
  15 // auto operator-(const reverse_iterator<Iter1>& x, const reverse_iterator<Iter2>& y) // constexpr in C++17
  16 //  -> decltype(y.base() - x.base());
  17
  18 #include <iterator>
  19 #include <cstddef>
  20 #include <cassert>
  21 #include <type_traits>
  22
  23 #include "test_macros.h"
  24 #include "test_iterators.h"
  25
  26 template <class, class, class = void>
  27 struct HasMinus : std::false_type {};
  28 template <class R1, class R2>
  29 struct HasMinus<R1, R2, decltype((R1() - R2(), void()))> : std::true_type {};
  30
  31 // Test non-subtractable base iterator types
  32 static_assert(HasMinus<std::reverse_iterator<int*>, std::reverse_iterator<int*> >::value, "");
  33 static_assert(HasMinus<std::reverse_iterator<int*>, std::reverse_iterator<const int*> >::value, "");
  34
  35 #if TEST_STD_VER >= 11
  36 static_assert(!HasMinus<std::reverse_iterator<int*>, std::reverse_iterator<char*> >::value, "");
  37 static_assert(!HasMinus<std::reverse_iterator<bidirectional_iterator<int*> >,
  38                         std::reverse_iterator<bidirectional_iterator<int*> > >::value,
  39               "");
  40 #endif
  41
  42 template <class It1, class It2>
  43 TEST_CONSTEXPR_CXX17 void test_one(It1 l, It2 r, std::ptrdiff_t x) {
  44   const std::reverse_iterator<It1> r1(l);
  45   const std::reverse_iterator<It2> r2(r);
  46   assert((r1 - r2) == x);
  47 }
  48
  49 template <class Iter>
  50 TEST_CONSTEXPR_CXX17 void test() {
  51   // Test same base iterator type
  52   char s[3] = {0};
  53
  54   test_one(Iter(s), Iter(s), 0);
  55   test_one(Iter(s), Iter(s + 1), 1);
  56   test_one(Iter(s + 1), Iter(s), -1);
  57 }
  58
  59 TEST_CONSTEXPR_CXX17 bool tests() {
  60   {
  61     test<char*>();
  62     test<random_access_iterator<char*> >();
  63 #if TEST_STD_VER >= 20
  64     test<cpp20_random_access_iterator<char*>>();
  65 #endif
  66   }
  67   {
  68     // Test different (but subtractable) base iterator types
  69     using PC  = const char*;
  70     char s[3] = {0};
  71     test_one(PC(s), s, 0);
  72     test_one(PC(s), s + 1, 1);
  73     test_one(PC(s + 1), s, -1);
  74   }
  75
  76   return true;
  77 }
  78
  79 int main(int, char**) {
  80   tests();
  81 #if TEST_STD_VER > 14
  82   static_assert(tests(), "");
  83 #endif
  84   return 0;
  85 }