Why compiler produces an error on template function

Question

Why following code works fine:

template <typename Set, typename Vector> void copySetToVector2(Set &s, Vector &v)
{
    copy(s.begin(), s.end(), inserter(v, v.begin()));
}

int main()
{
    set<int> s1;
    s1.insert(1);
    s1.insert(2);
    s1.insert(3);

    vector<int> v1;

    copySetToVector2(s1, v1);
    return 0;
}

But if I change variables to pointers in template function compiler produces error:

'std::set< int >*' is not a class, struct, or union type

What is wrong here?

You mean when you change `Set &s, Vector &v` to `Set *s, Vector *v` you get this error? — David G, Jan 24 '13 at 19:37
Your compiler says "What is wrong here?" Laziest compiler ever! — Kerrek SB, Jan 24 '13 at 19:37
Works here: template void copySetToVector2(Set* s, Vector* v) { copy(s->begin(), s->end(), inserter(*v, v->begin())); } — Frank Osterfeld, Jan 24 '13 at 19:42

score 4 · Accepted Answer · edited May 23 '17 at 12:27

If you change this:

template <typename Set, typename Vector> void copySetToVector2(Set &s, Vector &v)

to this:

template <typename Set, typename Vector> void copySetToVector2(Set *s, Vector *v)

then the body needs to look like this:

template <typename Set, typename Vector> void copySetToVector2(Set *s, Vector *v)
{
    copy(s->begin(), s->end(), inserter(*v, v->begin()));
}

The dot notation s.begin() does not work for pointers. You need to switch to s->begin(). See This link for more details.

Why compiler produces an error on template function

1 Answers1