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Advantages of using forward
Could someone please explain to me what perfect forwarding is about?
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What is Perfect Forwarding. Perfect forwarding allows a template function that accepts a set of arguments to forward these arguments to another function whilst retaining the lvalue or rvalue nature of the original function arguments.
When t is a forwarding reference (a function argument that is declared as an rvalue reference to a cv-unqualified function template parameter), this overload forwards the argument to another function with the value category it had when passed to the calling function.
The std::forward function as the std::move function aims at implementing move semantics in C++. The function takes a forwarding reference. According to the T template parameter, std::forward identifies whether an lvalue or an rvalue reference has been passed to it and returns a corresponding kind of reference.
In a type declaration, “ && ” indicates either an rvalue reference or a universal reference – a reference that may resolve to either an lvalue reference or an rvalue reference. Universal references always have the form T&& for some deduced type T .
http://www.justsoftwaresolutions.co.uk/cplusplus/rvalue_references_and_perfect_forwarding.html
Why is this useful? Well, it means that a function template can pass its arguments through to another function whilst retaining the lvalue/rvalue nature of the function arguments by using std::forward. This is called "perfect forwarding", avoids excessive copying, and avoids the template author having to write multiple overloads for lvalue and rvalue references.
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