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 // <deque>
10 
11 // iterator erase(const_iterator f, const_iterator l)
12 
13 //  Erasing items from the beginning or the end of a deque shall not invalidate iterators
14 //  to items that were not erased.
15 
16 
17 #include <deque>
18 #include <cstdint>
19 #include <cassert>
20 
21 template <typename C>
22 void del_at_start(C c, size_t num)
23 {
24     typename C::iterator first = c.begin();
25     typename C::iterator last  = first + num;
26     typename C::iterator it1 = last;
27     typename C::iterator it2 = c.end() - 1;
28 
29     c.erase (first, last);
30 
31     typename C::iterator it3 = c.begin();
32     typename C::iterator it4 = c.end() - 1;
33     assert(  it1 ==   it3);
34     assert( *it1 ==  *it3);
35     assert(&*it1 == &*it3);
36     assert(  it2 ==   it4);
37     assert( *it2 ==  *it4);
38     assert(&*it2 == &*it4);
39 }
40 
41 template <typename C>
42 void del_at_end(C c, size_t num)
43 {
44     typename C::iterator last  = c.end();
45     typename C::iterator first = last - num;
46     typename C::iterator it1 = c.begin();
47     typename C::iterator it2 = first - 1;
48 
49     c.erase (first, last);
50 
51     typename C::iterator it3 = c.begin();
52     typename C::iterator it4 = c.end() - 1;
53     assert(  it1 ==   it3);
54     assert( *it1 ==  *it3);
55     assert(&*it1 == &*it3);
56     assert(  it2 ==   it4);
57     assert( *it2 ==  *it4);
58     assert(&*it2 == &*it4);
59 }
60 
61 
62 int main(int, char**)
63 {
64     std::deque<int> queue;
65     for (int i = 0; i < 20; ++i)
66         queue.push_back(i);
67 
68     while (queue.size() > 1)
69     {
70         for (size_t i = 1; i < queue.size(); ++i)
71         {
72             del_at_start(queue, i);
73             del_at_end  (queue, i);
74         }
75         queue.pop_back();
76     }
77 
78   return 0;
79 }
80