View Compilation Error

0_0_7630327_22943.cpp: In member function `bool BigNum::operator<(const int&) const':
0_0_7630327_22943.cpp:321: error: `thi' undeclared (first use this function)
0_0_7630327_22943.cpp:321: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_7630327_22943.cpp:321: error: expected `)' at end of input
0_0_7630327_22943.cpp:321: error: expected `;' at end of input
0_0_7630327_22943.cpp:321: error: expected `}' at end of input