Templated member function help

[mattjgalloway]

I'm having some problems with a templated member function of a templated class. Unfortunately I can't replicate it with a simple example so I know something odd must be going on!!!

Basically it's like this...

I have a few classes all templated by one type. Inside one of the classes is a templated member function. When I try to use this templated function in another class, the compiler complains with:

error: expected primary-expression before 'int'
error: expected ',' or ';' before 'int'

The odd thing is that if I remove the <int> from the call to the function it compiles fine. Currently this part of the code isn't actually used as I never create an instance of the class, it's just there in my code for later. So I am thinking this might be something to do with it.

It's confusing I know and I'll try to get a simple example working.

I think basically the compiler isn't noticing that the function I am calling is a template and so it's wondering why I am putting in the <int>. How can I force it to know it's going to be a template?

[mattjgalloway]

Ok here's an example:

#include <iostream>
using namespace std;
 
template <typename T>
class One {
    public:
        One() {;}
        ~One() {;}
 
        template <typename TT>
        TT doSomething(TT var1);
    private:
};
 
template <typename T>
template <typename TT>
TT One<T>::doSomething(TT var1) {
    return var1;
}
 
template <typename T>
class Two {
    public:
        Two(One<T> *a);
        ~Two() {;}
    private:
        One<T> *_one;
};
 
template <typename T>
Two<T>::Two(One<T> *a) {
    _one = a;
    int ret = _one->doSomething<int>(5);
}
 
int main() {
    return 0;
}

The output from the compiler is:

memfunc.cpp: In constructor 'Two<T>::Two(One<T>*)':
memfunc.cpp:33: error: expected primary-expression before 'int'
memfunc.cpp:33: error: expected ',' or ';' before 'int'

It's annoying... basically inside the compiler for Two, it's not noticing that doSomething is a template and so it complains about the <int> part of that line...

What am I doing wrong?

[mattjgalloway]

Ok, WHAT! If I remove the <int> it works, compiles fine. And then if I change it slightly to actually use the template (I made the doSomething function save to a public int inside class Two and then cout'ed that value to check it saved it).

It seemed to work out the <int> itself. This is really wierd because it shouldn't do that, should it!?

Like for instance if I did:

template <typename T>
T doSomething(T var1) {
   return var1;
}

(i.e. a templated function, not member function)
Then it'd be WRONG to do:

int ret = doSomething(5)

I would have to do:

int ret = doSomething<int>(5)

I am mega confused...