Re: [suse-programming-e] C++ technicality

Hello Jerry, I tried this and It worked for me on g++ (3.4.4). #include<list> using namespace std; std::list P; /*I tried for list template, it should work for pair also*/ typedef class P* Y; typdef std::list<Y> P_new; /*P_new is the class what u are expecting.*/ HTH, Vamsi kundeti On 8/24/05, John D Lamb wrote:

Jerry Feldman wrote:

...

On Sunday 21 August 2005 3:51 pm, John D Lamb wrote:

...

Here's a puzzle: I'd like to define something like

typedef std::pair P;

I can obviously do

class P : public std::pair{};

or

typedef std::pair P; In this case, you have not yet defined P. You could use a forward declaration, such as: class P; Then, typedef std::pair P; should work. I have not tried your example specifically.

Sadly it doesn't work though I actually had to try this to see. It does confirm that I'm not being totally stupid in thinking that C++ might reasonably allow this sort of thing.

The C++ standard doesn't allow you to use typedef for a name already declared in the same scope.

I think C++ won't allow you to do something like:

class X x;

i.e. create a template class whose template parameter is a pointer to an object of this class. It will allow

class Y : public class X {} x;

which is nearly the same.

For my own problem, I've worked out I can use static_cast rather than reinterpret_cast, which is a bit of an improvement.

-- JDL

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