[c++11][NOTE] Perfect Forwarding

Perfect Forwarding:

• Applicable only to function templates.
• Preserves arguments’ lvalueness/rvalueness/constness when
  forwarding them to other functions.
• Implemented via std::forward.

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Perfect forwarding isn’t really perfect. There are several kinds of arguments that cannot be

perfectly forwarded, including (but not necessarily limited to):

• 0 as a null pointer constant.
• Names of function templates (e.g., std::endl and other manipulators).
• Braced initializer lists.
• In-class initialized const static data members lacking an out-of-class definition.
• Bit fields.

For details consult the comp.std.c++ discussion, "Perfect Forwarding Failure Cases"

referenced in the Further Information section of the course.

• unnamed lvalue references are lvalues, and unnamed rvalue references are rvalues.
• named lvalue references and named rvalue references are lvalues.

This is how std::forward works when this function return T&&!!


References:
Rvalue Reference Declarator: && [MSDN]
Forward template [MSDN]
How to: Write a Move Constructor [MSDN]
Rvalue References and Perfect Forwarding in C++0x [Just software]