Iterator library
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friend constexpr decltype(auto) iter_move( const std::common_iterator& i )

    noexcept(noexcept(ranges::iter_move(std::declval<const I&>()))

        requires std::input_iterator<I>;
(since C++20)

Casts the result of dereferencing the underlying iterator to its associated rvalue reference type.

The function body is equivalent to: return std::ranges::iter_move(std::get<I>(i.var));.

This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::common_iterator<I, S> is an associated class of the arguments.

If i.var does not hold an I object (i.e. an iterator), the behavior is undefined.


[edit] Parameters

i - a source iterator adaptor

[edit] Return value

An rvalue reference or a prvalue temporary.

[edit] Complexity


[edit] Example

#include <iomanip>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
void print(auto const& rem, auto const& v)
    std::cout << rem << '[' << size(v) << "] { ";
    for (int o{}; auto const& s : v)
        std::cout << (o++ ? ", " : "") << std::quoted(s);
    std::cout << " }\n";
int main()
    std::vector<std::string> p{"Andromeda", "Cassiopeia", "Phoenix"}, q;
    print("p", p);
    print("q", q);
    using CTI = std::counted_iterator<std::vector<std::string>::iterator>;
    using CI = std::common_iterator<CTI, std::default_sentinel_t>;
    CI last{std::default_sentinel};
    for (CI first{{p.begin(), 2}}; first != last; ++first)
        q.emplace_back(/* ADL */ iter_move(first));
    print("p", p);
    print("q", q);

Possible output:

p[3] { "Andromeda", "Cassiopeia", "Phoenix" }
q[0] {  }
p[3] { "", "", "Phoenix" }
q[2] { "Andromeda", "Cassiopeia" }

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 3953 C++20 the return type was std::iter_rvalue_reference_t<I> changed to decltype(auto)

[edit] See also

casts the result of dereferencing an object to its associated rvalue reference type
(customization point object)[edit]
casts the result of dereferencing the underlying iterator to its associated rvalue reference type
(function) [edit]
obtains an rvalue reference
(function template) [edit]
obtains an rvalue reference if the move constructor does not throw
(function template) [edit]
forwards a function argument
(function template) [edit]
moves a range of elements to a new location
moves a range of elements to a new location in backwards order