Thread: function template

Originally Posted by laserlight

If T is still double*, then it follows that the * has changed nothing. In other words, using your reasoning, this:

Code:

template <typename T>
void func(T arg);

and this:

Code:

template <typename T>
void func(T**************************************** arg);

still result in T being of type double* if the argument is of type double*. Does that make sense to you? It does not make sense to me.

For that last function declaration, my reasoning would be that, if a double * was passed to it,

T **************************************** arg would now actually be
double * **************************************** arg


But you are telling me that for:

Code:

template <typename T>
void func(T* arg);

double* p;
func(p);

T is of type double. But now what if ones calls func with a double argument, T is still a double?

Originally Posted by Nextstopearth

But now what if ones calls func with a double argument, T is still a double?

The result will be a compilation error. All instantiations of func() accept a pointer to something. A double is not a pointer, so cannot be passed to any functions obtained by instantiating this template.

To spell it out, if you try;

Code:

template <typename T>
void func(T* arg) {};

int main()
{
    double p = 2.0;
    func(p);
}

The compiler will complain bitterly as p is not a pointer type.

Originally Posted by whiteflags

There is a difference between template initialization, which you are talking about mainly in this post and this thread, and template specialization.

I believe what you're referring to as "template initialization" is more commonly known as "template instantiation".