Bignum Bignum::operator*(const Bignum & bn) const {
Bignum tmp; short symbol = 0, bit;
const Bignum & self = *this;
Bignum::Info info = Bignum::Info(self, bn);
if (self[info.a_index] < 0) { symbol ^= 1; }
if (bn[info.b_index] < 0) { symbol ^= 1; }
self[info.a_index] = llabs(self[info.a_index]);
bn[info.b_index] = llabs(bn[info.b_index]);
for (int i = bignum_len - 1; i >= info.a_index; i--) {
for (int j = bignum_len - 1; j >= info.b_index; j--) {
bit = i - ( (bignum_len - 1) - j);
tmp[bit] += (self[i] * bn[j]);
tmp.carry(bit);
}
}
if (symbol) {
tmp[-tmp.bignum_used_len()] *= -1;
}
return tmp;
}
/////////////////////////////////////
//
// Operator Computing
//
////////////////////////////////////
Bignum Bignum::operator+(const Bignum & bn) const {
Bignum tmp;
const Bignum & self = *this;
Bignum::Info info = Bignum::Info(self, bn);
if (bn[info.b_index] < 0) {
tmp = bn;
tmp[info.b_index] = llabs(tmp[info.b_index]);
return self - bn;
} else if (self[info.a_index] < 0) {
tmp = self;
tmp[info.a_index] = llabs(tmp[info.a_index]);
return bn - tmp;
}
for (int i = bignum_len - 1; i >= 0; i--) {
tmp[i] += self[i] + bn[i];
tmp.carry(i);
}
return tmp;
}