std::move_iterator
<iterator>
std::move_iterator
is an iterator adaptor which behaves exactly like the underlying iterator (which must be at least a LegacyInputIterator or model input_iterator
(since C++20), or stronger iterator concept(since C++23)), except that dereferencing converts the value returned by the underlying iterator into an rvalue. If this iterator is used as an input iterator, the effect is that the values are moved from, rather than copied from.
iterator_type
Iter
iterator_category
std::iterator_traits <Iter>::iterator_category
value_type
std::iterator_traits <Iter>::value_type
difference_type
std::iterator_traits <Iter>::difference_type
pointer
Iter
reference
iterator_type
Iter
iterator_category
iterator_concept
Iter
models std::random_access_iterator
Iter
only models std::bidirectional_iterator
Iter
only models std::forward_iterator
value_type
difference_type
pointer
Iter
reference
Iter
current
the underlying iterator requires (!std::sized_sentinel_for <Iterator1, Iterator2>)
constexpr bool disable_sized_sentinel_for
This partial specialization of std::disable_sized_sentinel_for
prevents specializations of move_iterator
from satisfying sized_sentinel_for
if their underlying iterators do not satisfy the concept.
Feature-test macro | Value | Std | Feature |
---|---|---|---|
__cpp_lib_move_iterator_concept |
202207L |
(C++23) | Make std::move_iterator<T*> a random access iterator |
#include <algorithm> #include <iomanip> #include <iostream> #include <iterator> #include <ranges> #include <string> #include <string_view> #include <vector> void print(const std::string_view rem, const auto& v) { std::cout << rem; for (const auto& s : v) std::cout << std::quoted (s) << ' '; std::cout << '\n'; }; int main() { std::vector <std::string > v{"this", "_", "is", "_", "an", "_", "example"}; print("Old contents of the vector: ", v); std::string concat; for (auto begin = std::make_move_iterator (v.begin()), end = std::make_move_iterator (v.end()); begin != end; ++begin) { std::string temp{*begin}; // moves the contents of *begin to temp concat += temp; } // Starting from C++17, which introduced class template argument deduction, // the constructor of std::move_iterator can be used directly: // std::string concat = std::accumulate(std::move_iterator(v.begin()), // std::move_iterator(v.end()), // std::string()); print("New contents of the vector: ", v); print("Concatenated as string: ", std::ranges::single_view (concat)); }
Possible output:
Old contents of the vector: "this" "_" "is" "_" "an" "_" "example" New contents of the vector: "" "" "" "" "" "" "" Concatenated as string: "this_is_an_example"
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 2106 | C++11 | dereferencing a move_iterator could return a dangling referenceif the dereferencing the underlying iterator returns a prvalue |
returns the object instead |
LWG 3736 | C++20 | move_iterator was missing disable_sized_sentinel_for specialization
|
added |
P2259R1 | C++20 | member iterator_category was defined even ifstd::iterator_traits <Iter>::iterator_category is not defined |
iterator_category isnot defined in this case |