View Compilation Error

87448_0_17260.cpp: In member function `BigNum BigNum::operator-(const BigNum&) const':
87448_0_17260.cpp:87: error: no match for 'operator>' in '*(const BigNum*)this > T'
87448_0_17260.cpp: In function `int main()':
87448_0_17260.cpp:140: error: `d' undeclared (first use this function)
87448_0_17260.cpp:140: error: (Each undeclared identifier is reported only once for each function it appears in.)