View Compilation Error

0_0_11459560_20301.cpp:9: error: non-lvalue in assignment
0_0_11459560_20301.cpp: In function `int flow()':
0_0_11459560_20301.cpp:15: error: `visit' undeclared (first use this function)
0_0_11459560_20301.cpp:15: error: (Each undeclared identifier is reported only once for each function it appears in.)