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Invoking templatized base class constructor from templatized derived class constructor

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

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

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

template<typena me 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 (mr************ @hotmail.com)

Jul 23 '05 #1
5 7346
mrstephengross wrote:
Ok, I've got code that looks something like this:

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

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

template<typena me 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
Jul 23 '05 #2
Thanks!

--Steve

Jul 23 '05 #3
Victor Bazarov wrote:
mrstephengross wrote:
Ok, I've got code that looks something like this:

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

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

template<typena me 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

--
Anti-spam address, change each 'X' to '.' to reply directly.
Jul 23 '05 #4
>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

Jul 23 '05 #5
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

--
Anti-spam address, change each 'X' to '.' to reply directly.
Jul 23 '05 #6

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