C++ 唯一PTR的STL旋转常量迭代器

我在使用常量迭代器上的std:：rotate时遇到问题，该迭代器位于唯一的\u ptr中间

我试过：

std::vector<std::unique_ptr<Object> >::const_iterator middle;
// middle is pointing at somewhere within vec defined elsewhere.
std::rotate(vec.begin(), middle, vec.end());

这导致调用rotate…iterator，…const_iterator&，…iterator时没有匹配的函数

因此我试着这样做： std:：vector>：：const_iterator first=vec.begin； std:：vector>：：const_iterator last=vec.end； 标准：旋转第一、中间、最后

然后它给出了一系列错误消息，如下所示。 这是一个错误还是我犯了一些错误

In file included from /usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/algorithm:63:0,
             from file.cpp:8:
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/unique_ptr.h: In function ‘void std::__rotate(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’:
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1677:7:   instantiated from ‘void std::rotate(_FIter, _FIter, _FIter) [with _FIter = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
file.cpp:76:35:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/unique_ptr.h:207:7: error: deleted function ‘std::unique_ptr<_Tp, _Tp_Deleter>::unique_ptr(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1601:22: error: used here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1677:7:   instantiated from ‘void std::rotate(_FIter, _FIter, _FIter) [with _FIter = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
file.cpp:76:35:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1603:5: error: passing ‘const std::unique_ptr<Object>’ as ‘this’ argument of ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(std::unique_ptr<_Tp, _Tp_Deleter>&&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’ discards qualifiers
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1677:7:   instantiated from ‘void std::rotate(_FIter, _FIter, _FIter) [with _FIter = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
file.cpp:76:35:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/unique_ptr.h:207:7: error: deleted function ‘std::unique_ptr<_Tp, _Tp_Deleter>::unique_ptr(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1624:22: error: used here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1677:7:   instantiated from ‘void std::rotate(_FIter, _FIter, _FIter) [with _FIter = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
file.cpp:76:35:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1626:5: error: passing ‘const std::unique_ptr<Object>’ as ‘this’ argument of ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(std::unique_ptr<_Tp, _Tp_Deleter>&&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’ discards qualifiers
In file included from /usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_tree.h:62:0,
             from /usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/map:60,
             from dir/file3.hpp:4,
             from dir/file2.hpp:3,
             from file.hpp:3,
             from file.cpp:1:
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/unique_ptr.h: In static member function ‘static void std::__iter_swap<_BoolType>::iter_swap(_ForwardIterator1, _ForwardIterator2) [with _ForwardIterator1 = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >, _ForwardIterator2 = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >, bool _BoolType = false]’:
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:138:7:   instantiated from ‘void std::iter_swap(_ForwardIterator1, _ForwardIterator2) [with _ForwardIterator1 = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >, _ForwardIterator2 = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1609:5:   instantiated from ‘void std::__rotate(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1677:7:   instantiated from ‘void std::rotate(_FIter, _FIter, _FIter) [with _FIter = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
file.cpp:76:35:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/unique_ptr.h:207:7: error: deleted function ‘std::unique_ptr<_Tp, _Tp_Deleter>::unique_ptr(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:88:31: error: used here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:89:11: error: passing ‘const std::unique_ptr<Object>’ as ‘this’ argument of ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’ discards qualifiers
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/unique_ptr.h:208:19: error: deleted function ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:89:11: error: used here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:90:11: error: passing ‘const std::unique_ptr<Object>’ as ‘this’ argument of ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(std::unique_ptr<_Tp, _Tp_Deleter>&&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’ discards qualifiers
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h: In static member function ‘static _OI std::__copy_move<true, false, std::random_access_iterator_tag>::__copy_m(_II, _II, _OI) [with _II = const std::unique_ptr<Object>*, _OI = const std::unique_ptr<Object>*]’:
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:404:70:   instantiated from ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = true, _II = const std::unique_ptr<Object>*, _OI = const std::unique_ptr<Object>*]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:442:39:   instantiated from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = true, _II = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >, _OI = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:506:47:   instantiated from ‘_OI std::move(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >, _OI = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1602:5:   instantiated from ‘void std::__rotate(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1677:7:   instantiated from ‘void std::rotate(_FIter, _FIter, _FIter) [with _FIter = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
file.cpp:76:35:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:368:8: error: passing ‘const std::unique_ptr<Object>’ as ‘this’ argument of ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’ discards qualifiers
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/unique_ptr.h:208:19: error: deleted function ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:368:8: error: used here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h: In static member function ‘static _BI2 std::__copy_move_backward<true, false, std::random_access_iterator_tag>::__copy_move_b(_BI1, _BI1, _BI2) [with _BI1 = const std::unique_ptr<Object>*, _BI2 = const std::unique_ptr<Object>*]’:
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:601:18:   instantiated from ‘_BI2 std::__copy_move_backward_a(_BI1, _BI1, _BI2) [with bool _IsMove = true, _BI1 = const std::unique_ptr<Object>*, _BI2 = const std::unique_ptr<Object>*]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:610:34:   instantiated from ‘_BI2 std::__copy_move_backward_a2(_BI1, _BI1, _BI2) [with bool _IsMove = true, _BI1 = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >, _BI2 = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:681:15:   instantiated from ‘_BI2 std::move_backward(_BI1, _BI1, _BI2) [with _BI1 = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >, _BI2 = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1625:5:   instantiated from ‘void std::__rotate(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1677:7:   instantiated from ‘void std::rotate(_FIter, _FIter, _FIter) [with _FIter = __gnu_cxx::__normal_iterator<const std::unique_ptr<Object>*, std::vector<std::unique_ptr<Object> > >]’
file.cpp:76:35:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:566:6: error: passing ‘const std::unique_ptr<Object>’ as ‘this’ argument of ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’ discards qualifiers
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/unique_ptr.h:208:19: error: deleted function ‘std::unique_ptr<_Tp, _Tp_Deleter>& std::unique_ptr<_Tp, _Tp_Deleter>::operator=(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = Object, _Tp_Deleter = std::default_delete<Object>, std::unique_ptr<_Tp, _Tp_Deleter> = std::unique_ptr<Object>]’
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c++/4.5.1/bits/stl_algobase.h:566:6: error: used here
make: *** [file.o] Error 1

不能将rotate与const_迭代器一起使用，因为rotate会更改指定范围内的元素。相反，您必须使用迭代器。

不能将rotate与常量迭代器一起使用，因为rotate会更改指定范围内的元素。相反，您必须使用迭代器。

如果要使用，则rotate本质上调用swapT&，T&，因此您不能使用const_迭代器

我想有人可能会要求在const_迭代器上运行一个专门版本的rotate for list。不过，我认为您可以相当容易地构建一个。如果要实现，则rotate本质上调用swapT&，T&，因此您不能使用const_迭代器

---

我想有人可能会要求在const_迭代器上运行一个专门版本的rotate for list。不过，我认为您可以相当轻松地构建一个对象。

但是对象本身没有更改，只是移动了，对吗？@chemelnucfin：迭代器没有更改，但它们指向的内容是更改的。注意const迭代器和const_迭代器之间的区别，要旋转的迭代器实际上是通过复制来传递的。@tomasz，我已经尝试过使用swap和上面的项，但这似乎对const_迭代器有效？唯一一个没有做到的是混合常数iter和iter。swapplayers.begin，middle没有，但是const_iter i=vec.begin=>swapi，middle起作用了。我没有测试实际结果，但它至少已编译。@chemelnucfin:swap不使用迭代器作为参数，而是使用要交换的对象的引用。您刚刚交换了两个迭代器，内容保持不变。这就像常数tmp=i；i=中间；中间=tmp；。可能不是你想要的。如果你需要交换内容，你必须调用swap*i，*middle，但是它们不能是const\u iterator类型。@chemelnucfin可能你可以使用rotate\u copy。但是对象本身没有改变，只是被移动了，对吗？@chemelnucfin:迭代器没有改变，但它们指向的内容是。注意const迭代器和const_迭代器之间的区别，要旋转的迭代器实际上是通过复制来传递的。@tomasz，我已经尝试过使用swap和上面的项，但这似乎对const_迭代器有效？唯一一个没有做到的是混合常数iter和iter。swapplayers.begin，middle没有，但是const_iter i=vec.begin=>swapi，middle起作用了。我没有测试实际结果，但它至少已编译。@chemelnucfin:swap不使用迭代器作为参数，而是使用要交换的对象的引用。您刚刚交换了两个迭代器，内容保持不变。这就像常数tmp=i；i=中间；中间=tmp；。可能不是你想要的。如果需要交换内容，必须调用swap*i、*middle，但它们不能是const\u iterator类型。@chemelnucfin您可能可以使用rotate\u copy。