C++ template specialization rvalue

Question

I'm learning C++ and have a little problem with template specialization. I need to call Variable.Set() a lot so, I made the function take in references so it doesn't spend a lot of time copying the string. But then the problem I have is Variable.Set<int>(5); causes error because the parameter is an rvalue and I don't know the solution for this.

error C2664: 'void Variable::Set(int &)': cannot convert argument 1 from 'int' to 'int &'

void main()
{
    Variable var;
    var.Set<int>(5);
}

struct Variable
{
    int integer;
    float floating;
    std::string string;

    template<typename T> void   Set(T& v);
    template<> void             Set<int> (int& v) { integer = v; }
    template<> void             Set<float> (float& v) { floating = v; }
    template<> void             Set<std::string> (std::string& v) { string = v; }
};

`void main` should be `int main`. And make the parameter type `const&` — Praetorian, May 04 '16 at 20:49
praetorian, post as answer, it works. Also could you explain why? const is supposed to mean you won't change the value so what does it have to do with rvalue and conversion from int to int&? — Budskii, May 04 '16 at 20:52
Possible duplicate of [How come a non-const reference cannot bind to a temporary object?](http://stackoverflow.com/questions/1565600/how-come-a-non-const-reference-cannot-bind-to-a-temporary-object) — LogicStuff, May 04 '16 at 20:54

score 1 · Accepted Answer · answered May 04 '16 at 21:00

You need to change your parameters to constant references (const& as mentioned in Praetorian's comment)

From this link: http://www.codesynthesis.com/~boris/blog/2012/07/24/const-rvalue-references/

while a const lvalue reference can bind to an rvalue, a const rvalue reference cannot bind to an lvalue

C++ template specialization rvalue

1 Answers1