Invoking templatized base class constructor from templatized derived class constructor
 

Ok, I've got code that looks something like this:

==================================================

template<typename T1, typename T2>
class Base
{
public:
explicit Base(const T1 & t1) { /* ... */ }
};

template<typename T1, typename T2, typename T3>
class Derived : public Base<T1, T2>
{
public:
Derived() : Base(my_t3) { /* ... */ }

private:
T3 my_t3;
};

================================================== ==

GCC 3.3.1 reports the following error:

In constructor `Derived<T1, T2, T3>::Derived()':
error: class `Derived<T1, T2, T3>' does not have any field named
`template<class T1, T2> class Base'

It would seem that GCC interprets my initialization of Base in
Derived's constructor as a field assignment. Is my syntax wrong? Is
there some way to more directly indicate that I'm invoking Base's
constructor?

Thanks,
--Steve (mrstephengross@hotmail.com)

Re: Invoking templatized base class constructor from templatizedderived class constructor
 

mrstephengross wrote:
> Ok, I've got code that looks something like this:
>
> ==================================================
>
> template<typename T1, typename T2>
> class Base
> {
> public:
> explicit Base(const T1 & t1) { /* ... */ }
> };
>
> template<typename T1, typename T2, typename T3>
> class Derived : public Base<T1, T2>
> {
> public:
> Derived() : Base(my_t3) { /* ... */ }

Has to be

Derived() : Base<T1,T2>(my_t3) { }

or you need to typedef 'Base<T1,T2>' as "Base" before.

>
> private:
> T3 my_t3;
> };
>
> ================================================== ==
>
> GCC 3.3.1 reports the following error:
>
> In constructor `Derived<T1, T2, T3>::Derived()':
> error: class `Derived<T1, T2, T3>' does not have any field named
> `template<class T1, T2> class Base'
>
> It would seem that GCC interprets my initialization of Base in
> Derived's constructor as a field assignment. Is my syntax wrong?

Yes.

> Is
> there some way to more directly indicate that I'm invoking Base's
> constructor?

See above.

V

Re: Invoking templatized base class constructor from templatized derived class constructor
 

Thanks!

--Steve

Re: Invoking templatized base class constructor from templatizedderived class constructor
 

Victor Bazarov wrote:
> mrstephengross wrote:
>> Ok, I've got code that looks something like this:
>>
>> ==================================================
>>
>> template<typename T1, typename T2>
>> class Base
>> {
>> public:
>> explicit Base(const T1 & t1) { /* ... */ }
>> };
>>
>> template<typename T1, typename T2, typename T3>
>> class Derived : public Base<T1, T2>
>> {
>> public:
>> Derived() : Base(my_t3) { /* ... */ }
>
> Has to be
>
> Derived() : Base<T1,T2>(my_t3) { }

That's the correct syntax, but isn't there a logic flaw
in the Base() call? The Base() constructor expects a
'T1' parameter, rather than a 'T3' parameter.

[snip]

Regards,
Larry

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Re: Invoking templatized base class constructor from templatized derived class constructor
 

>That's the correct syntax, but isn't there a logic flaw
in the Base() call? The Base() constructor expects a
'T1' parameter, rather than a 'T3' parameter.

Yeah, you're right... I didn't paste in my example correctly. But the
main issue has been resolved: apparently C++ requires that you
explicitly specify the constructor's template arguments. I had been
using a compiler (KCC) that was more forgiving...

--Steve

Re: Invoking templatized base class constructor from templatizedderived class constructor
 

mrstephengross wrote:
>>That's the correct syntax, but isn't there a logic flaw
> in the Base() call? The Base() constructor expects a
> 'T1' parameter, rather than a 'T3' parameter.
>
> Yeah, you're right... I didn't paste in my example correctly. But the
> main issue has been resolved: apparently C++ requires that you
> explicitly specify the constructor's template arguments. I had been
> using a compiler (KCC) that was more forgiving...
>
> --Steve
>

"Base<T1, T2>" IS the class name. "Base" is something
entirely different. g++ is merely enforcing the standard.

BTW, you do know that you compile/link C++ code with the GCC
command "g++", NOT with the command "gcc"???

Regards,
Larry

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