C++: Default initialize an integral type in a template function

Question

For educational purposes I am wrting my own C++ numerical vector template class. I want to be able to write (v, w) for the dot product of two vectors and consequently overload operator,() as follows:

template<class T>
const T Vector<T>::operator,(const Vector<T>& v) const
{
    assertEqualSize(v);

    T t;
    for(size_t i=0; i<numElements; i++) {
        t += elements[i] * v[i];
    }
    return t;
}

My question now is: how do I properly initialize t with a sensible value (e.g. 0.0 for Vector<double>)? I tried T t(); but then g++ tells me, e.g., that "double(*)()" cannot be converted to "const double" at the return statement and that operator+=() would not be defined for "(double(), double)".

Thank you very much!

Answer 1

What you need is termed value initialization, which has the effect of zero-initializing built-in types:

T t{};     // C++11
T t = T(); // C++03 and C++11

The reason this doesn't work

T t();

is that it is a declaration of a parameterless function called t, returning a T.