When retrieving an element from a temporary built-in array or temporary
STL container (for example by operator[]), shouldn't it be an rvalue
reference?  In the following example, shouldn't str1 and str2 be
move-constructed, rather than copy-constructed?

    //////////////////////////////////////////////////////////////////////
    #include <vector>
    #include <string>
    using namespace std;

    struct array_holder { string c_array[42]; };
    array_holder get_array();
    vector<string> get_vector();

    int main()
    {
      // Move semantics?
      string str1 = get_vector().at(1);
      string str2 = get_array().c_array[2];  // temporary built-in array
    }
    //////////////////////////////////////////////////////////////////////

As C++0x will provide a means to overload member functions for rvalue
objects, using ref-qualifiers, I would expect a function like
std::vector::at to be overloaded as follows:

    const value_type& at(size_type n) const &;
    value_type& at(size_type n) &;
    value_type&& at(size_type n) &&;

And I would also expect that an element of an rvalue array would itself
be an rvalue.  Does that sound reasonable?  Or has it been considered
before?

Kind regards,

    Niels
--
Niels Dekker
http://www.xs4all.nl/~nd/dekkerware
Scientific programmer at LKEB, Leiden University Medical Center

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