(1) | ||
reference operator* () const; | (since C++11) (until C++17) | |
constexpr reference operator* () const; | (since C++17) | |
(2) | ||
pointer operator->() const; | (since C++11) (until C++17) | |
constexpr pointer operator->() const; | (since C++17) (deprecated in C++20) |
Returns an rvalue-reference or pointer to the current element.
static_cast<reference>(*base())
(until C++20)ranges::iter_move(base())
(since C++20).base()
.(none).
->
is directly used.Note that (2) eventually returns a pointer if ->
is directly used. When dereferencing a pointer the returned value is an lvalue. This may lead to unintended behavior.
#include <iomanip> #include <iostream> #include <iterator> #include <string> #include <vector> void print(auto rem, auto const& v) { for (std::cout << rem; auto const& e : v) std::cout << quoted(e) << ' '; std::cout << '\n'; } int main() { std::vector<std::string> p{"alpha", "beta", "gamma", "delta"}, q; print("1) p: ", p); for (std::move_iterator it{p.begin()}, end{p.end()}; it != end; ++it) { it->push_back('!'); // calls -> string::push_back(char) q.emplace_back( *it ); } print("2) p: ", p); print("3) q: ", q); std::vector v{1,2,3}; std::move_iterator it{v.begin()}; // *it = 13; // error: using rvalue as lvalue }
Output:
1) p: "alpha" "beta" "gamma" "delta" 2) p: "" "" "" "" 3) q: "alpha!" "beta!" "gamma!" "delta!"
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 an prvalue | returns the object instead |
(C++11) | accesses an element by index (public member function) |
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