How can I resolve the occuring ambiguity when using clog for computing the natural logarithm with complex numbers?

Question

I have a complex double array eigenvalues of which I want to get the natural logarithm of each entry by using clog.

for (int i = 0; i < n; ++i)
{
    qq[i] = clog(eigenvalues[i]);
}

I already dropped the using namespace std; but am still getting error: reference to 'clog' is ambiguous.

How can I make it clear that I want to use the clog from complex.h and not from iostream?

Answer 1

I haven't been able to reproduce this with gcc 7.3 without using namespace std but in general all functions from C headers reside in the global namespace. Therefore you should be able to resolve the ambiguity by prefixing clog with :::

for (int i = 0; i < n; ++i)
{
    qq[i] = ::clog(eigenvalues[i]);
}