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)
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 #include <deque>
17 #include <cassert>
18 
19 template <typename C>
20 void del_at_start(C c)
21 {
22     typename C::iterator first = c.begin();
23     typename C::iterator it1 = first + 1;
24     typename C::iterator it2 = c.end() - 1;
25 
26     c.erase (first);
27 
28     typename C::iterator it3 = c.begin();
29     typename C::iterator it4 = c.end() - 1;
30     assert(  it1 ==   it3);
31     assert( *it1 ==  *it3);
32     assert(&*it1 == &*it3);
33     assert(  it2 ==   it4);
34     assert( *it2 ==  *it4);
35     assert(&*it2 == &*it4);
36 }
37 
38 template <typename C>
39 void del_at_end(C c)
40 {
41     typename C::iterator first = c.end() - 1;
42     typename C::iterator it1 = c.begin();
43     typename C::iterator it2 = first - 1;
44 
45     c.erase (first);
46 
47     typename C::iterator it3 = c.begin();
48     typename C::iterator it4 = c.end() - 1;
49     assert(  it1 ==   it3);
50     assert( *it1 ==  *it3);
51     assert(&*it1 == &*it3);
52     assert(  it2 ==   it4);
53     assert( *it2 ==  *it4);
54     assert(&*it2 == &*it4);
55 }
56 
57 int main(int, char**)
58 {
59     std::deque<int> queue;
60     for (int i = 0; i < 20; ++i)
61         queue.push_back(i);
62 
63     while (queue.size() > 1)
64     {
65         del_at_start(queue);
66         del_at_end(queue);
67         queue.pop_back();
68     }
69 
70   return 0;
71 }
72