asked on

Cannot invoke a template member function?

I define a template function in a class called CTestClass, as follows:

class CTestClass
{
public:
CTestClass();
virtual ~CTestClass();

public:
template<class T> void f() {
...
do something
...
};
};

Then I need to invoke the template function f, as follows:

CTestClass TestClass;

TestClass.f<int>();
^^^^^^^^^^^^

But the above statement always get a compile error:

error C2062: type 'int' unexpected.

However, if I define the template function f as a global function intead in a class, like this,

template<class T> void f() {
...
do something
...
};

then the compile will be correct.

What's wrong with this?

AlexFM

class CTestClass
{
public:
CTestClass(){};
virtual ~CTestClass(){};

public:
template<class T> void f()
{
};
};

int _tmain(int argc, _TCHAR* argv[])
{
CTestClass TestClass;
TestClass.f<int>();

return 0;
}

This is compiled in VC++ 8.0. What version do you use?

chcw

ASKER

I'm using Visual C++ 6.0

ASKER CERTIFIED SOLUTION

AlexFM

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bastibartel

Hi there,

I have had trouble with explicite instantiation too (VC6++).
And my workaround was a dummy argument to the template function to specifiy the template type

class A
{
public:
A() {;}
template <class T> void Func(T* pT)
{
}
};

//** then this implicite instant. will work.

A a;
double d
a.Func(&d);

Cheers,
Sebastian

SOLUTION

bastibartel

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bastibartel

AlexFM noted correctly.
>Your code is correct according to C++ standard, but VC++ 6.0 developed in 1998 doesn't support it.

I explained that
> explicit specialization for (template) member functions does not work in VC++6, but implicite specialization can be used instead in VC++6.
(the whole class does not neccessarily have to be templated)

That solves the problem for the Asker.
Either that or switching to VC++8.

Sebastian