Typo with “cout < myint”. Why does it work?

Question

I have this code and I searched for hours why it fails to print my income

int const income = 0;
std::cout << \"I\'m sorry, your income is: \" < inco         


        

Answer 1

When I compile this code using GCC 4.3.4, I see a warning:

prog.cpp: In function ‘int main()’:
prog.cpp:6: warning: right-hand operand of comma has no effect

...though why it's a warning rather than an error, I don't know.

EDIT: In fact, I don't know which comma it's referring to either, because this code:

int const income = 0;
std::cout << "I'm sorry your income is: " < income;

...generates the same warning (see here).