Problem with trick to overcome the absence of template typedefs

[gumbers]

Hi there,

Can anyone see the problem with this code? http://codepad.org/ODBfNNW2

Thanks a lot,
Ricardo Abreu

[Codeplug]

Put all relevant information here in this thread. Do you think that link will work in 5 years?

#include <utility>
#include <iostream>

namespace Testing
{
    template<typename T>
    struct CmdArg
    {
        typedef std::pair<T, bool> type;
    };
    
    template<typename T>
    typename CmdArg<T>::type f(const T& t)
    {
        return CmdArg<T>::type(t, false);
    }
}

int main()
{
    Testing::CmdArg<int>::type arg = Testing::f(11);
    
    std::cout << arg.first << " " << arg.second << std::endl;
    return 0;
}

Fixes are in red.

gg

[gumbers]

OK, its solved. I actually had to add another 'typename' for it to work:

#include <utility>
#include <iostream>

namespace Testing
{
    template<typename T>
    struct CmdArg
    {
        typedef std::pair<T, bool> type;
    };
    
    template<typename T>
    typename CmdArg<T>::type f(const T& t)
    {
        return typename CmdArg<T>::type(t, false);
    }
}

int main()
{
    Testing::CmdArg<int>::type arg = Testing::f(11);
    
    std::cout << arg.first << " " << arg.second << std::endl;
    return 0;
}

Thank you and sorry for not posting the code here before - I assumed IRC rules. Also, hopefully in 5 years C++ will already have template typedefs

Again, many thanks,
gumbers

[laserlight]

Also, hopefully in 5 years C++ will already have template typedefs

C++0x (which might be finalised this year) will have template typedefs via a template "using" statement. Now, whether or not compilers have implemented or will soon implement it is another matter, but hopefully they will take less than 5 years to get it done

(Incidentally, if you read the recent C++0x "slow chat" forum, template typedefs will not be supported by the up and coming MSVC10.)

[Graham]

C++0x (which might be finalised this year) [...]

If it isn't, they'll have to start calling it "C++1x".

[TheCPUWizard]

If it isn't, they'll have to start calling it "C++1x".

Nahhh. we will just call the coming years 200A,200B,200C....