View Compilation Error

0_0_8652786_1697.cpp: In function `int main()':
0_0_8652786_1697.cpp:6: error: `f' undeclared (first use this function)
0_0_8652786_1697.cpp:6: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_8652786_1697.cpp: In function `int f(int)':
0_0_8652786_1697.cpp:13: error: `int f(int)' used prior to declaration
0_0_8652786_1697.cpp:16: error: non-lvalue in assignment