How does cin evaluate to true when inside an if statement?

Question

I thought that:

if (true) 
{execute this statement}

So how does if (std::cin >> X) execute as true when there is nothing

Answer 1

std::cin is of type std::basic_istream which inherits from std::basic_ios, which has an operator : std::basic_ios::operator bool which is called when used in if statement.