View Compilation Error

0_0_11798241_18067.cpp: In member function `void TwoSat::add_clause_or(int, bool, int, bool)':
0_0_11798241_18067.cpp:178: error: `x' undeclared (first use this function)
0_0_11798241_18067.cpp:178: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_11798241_18067.cpp:178: error: `xval' undeclared (first use this function)
0_0_11798241_18067.cpp:179: error: `y' undeclared (first use this function)
0_0_11798241_18067.cpp:179: error: `yval' undeclared (first use this function)