prog.cpp: In function 'double foobar()':
prog.cpp:7:2: error: 'cout' was not declared in this scope
cout << "hello";
^
prog.cpp:7:2: note: suggested alternative:
In file included from prog.cpp:4:0:
/usr/include/c++/4.9/iostream:61:18: note: 'std::cout'
extern ostream cout; /// Linked to standard output
^