Full specialization of a member function template of a class template

[Dave]

Hello all,

I am trying to create a full specialization of a member function template of
a class template. I get the following errors:

Line 29: 'foo<T1>::bar' : illegal use of explicit template arguments
Line 29: 'bar' : unable to match function definition to an existing
declaration

What am I doing wrong?

Thanks,
Dave


#include <iostream>

using namespace std;

template <typename T1>
class foo
{
public:
template <typename T2>
void bar(const T2 &param);
};

template <typename T1>
template <typename T2>
void foo<T1>::bar(const T2 &param)
{
static_cast<void>(param);

cout << "Point 1" << endl;
}

template <typename T1>
template <>
void foo<T1>::bar<double>(const double &param)
{
static_cast<void>(param);

cout << "Point 2" << endl;
}

int main()
{
foo<int> var;

var.bar(4.5);
}

 

[Victor Bazarov]

Hello all,

I am trying to create a full specialization of a member function template of
a class template. I get the following errors:

Line 29: 'foo<T1>::bar' : illegal use of explicit template arguments
Line 29: 'bar' : unable to match function definition to an existing
declaration

What am I doing wrong?

It is expressly prohibited. If you want to explicitly specialise
a member template, the enclosing class has to be specialised as well.

See 14.7.3/17.

 

[John Carson]

It is expressly prohibited. If you want to explicitly specialise
a member template, the enclosing class has to be specialised as well.

See 14.7.3/17.

In this case a workaround is to add the specialised member function to the
class declaration:

template <typename T1>
class foo
{
public:
template <typename T2>
void bar(const T2 &param);

void bar(const double &param);
};

template <typename T1>
void foo<T1>::bar(const double &param)
{
static_cast<void>(param);
cout << "Point 2" << endl;
}

 

[Buster]

Hello all,

I am trying to create a full specialization of a member function template of
a class template.

From the standard (towards the end of 14.7.3),

"In an explicit specialization declaration for a member of a class
template or a member template that appears in namespace scope, the
member template and some of its enclosing class templates may remain
unspecialized, except that the declaration shall not explicitly
specialize a class member template if its enclosing class templates
are not explicitly specialized as well."

Crystal clear?

You can't explicitly specialize a member template of a class template,
but you can explicitly specialize a member template of an explicit
specialization of a class template.

I get the following errors:
Line 29: 'foo<T1>::bar' : illegal use of explicit template arguments
Line 29: 'bar' : unable to match function definition to an existing
declaration

That's pretty crap. G++ 3.3.1 gives "enclosing class templates are not
explicitly specialized".

 

[pdixtl]

would you know how to explicitly specialize a member template when template argument for the member is different than template argument of the class?