Re: Variadic templates and passing by reference

From:

Frank Birbacher <bloodymir.crap@gmx.net>

Newsgroups:

comp.lang.c++.moderated

Date:

Sun, 11 Mar 2012 18:55:34 -0700 (PDT)

Message-ID:

<9s4et9F198U1@mid.dfncis.de>

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Hi!

Am 11.03.12 08:01, schrieb Thomas Richter:

To be specific, consider declarations as follows:

class A;

template<class ...U> void Launch(A &t,U&... other);

template<class ...U> void Launch(int x,U&... other);

Now I get a problem because, when I want to call "Launch" with int
arguments as in

class A a,b; Launch(a,5,b);

Would the following do the trick?

template<class ...U>
void Launch(A &t,U&&... other);
templateh<class ...U>
void Launch(int x,U&&... other);

Functions called would be:
Launch(a,5,b);
=> Launch<int, A&>(A &t, int&&, A&);
=> Launch<A&>(int x, A&);
=> Launch<>(A &t);

So I guess this solves your problem. Can, BTW, anyone tell me the
necessary syntax for forwarding inside Launch?

template<class ...U>
void Launch(A &t,U&&... other)
{
    t = A(); // modify t somehow

    // is this the syntax for forwarding?
    Launch(std::forward<U...>(other...));
}

And does the declaration of the Launch(int, U&&) overload need to be
visible before the definition of Launch(A&, U&&)? There were some
lookup rules for templates regarding built in types (like int here)
that relate to declarations visible at the point of template
definition. Does this apply here?

Frank
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