// Subtraction
char* Sub(char* s1, char* s2, char* result)
{
BigInt a, b, c;
StrToBigInt(s1, &a);
StrToBigInt(s2, &b);
DoSub(&a, &b, &c);
return BigIntToStr(&c, result);
}
double DoOperation(char operation, double op1, double op2, int* isErr)
{
switch (operation)
{
case '+':
return DoAdd(op1, op2);
break;
case '-':
return DoSub(op1, op2);
break;
case '*':
return DoMul(op1, op2);
break;
case '/':
return DoDiv(op1, op2, isErr);
break;
}
return op2;
//return WinCalculator->DoOperation(operation, op1, op2, isErr);
}
// implement of division by using binary search
// result = a / b
BigInt* DoDiv(BigInt* a, BigInt* b, BigInt* result, BigInt* remainder)
{
int low, high, mid;
BigInt c, d, e, t;
low = 0; // the min of left shift
high = GetMaxLeftShiftLen(b); // the max of left shift
memset(t.bit, 0, BIG_INT_BIT_LEN); // init 0
CopyBigInt(a, &c); // c = a
// if a sign == b sign, do subtraction
if (a->bit[SIGN_BIT] == b->bit[SIGN_BIT])
{
t.bit[SIGN_BIT] = POSITIVE;
while (1)
{
while (low <= high)
{
mid = (low + high) / 2;
ShiftArithmeticLeft(b, mid, &d);
DoSub(&c, &d, &e); // e = c - d
// e >= 0
if (d.bit[SIGN_BIT] == e.bit[SIGN_BIT] || IsZero(&e))
low = mid + 1;
else
high = mid - 1;
}
// high == -1 means c - b < 0
if (high != -1)
{
t.bit[high] = 1;
// here unified the operation
// it can improve i think
ShiftArithmeticLeft(b, high, &d);
// c = c - d, let c be the next dividend
DoSub(&c, &d, &c);
low = 0;
high--;
}
else
{
// now the dividend c is the remainder
CopyBigInt(&c, remainder);
break;
}
}
}
// if a sign != b sign, do addition
else
{
t.bit[SIGN_BIT] = NEGATIVE;
while (1)
{
while (low <= high)
{
mid = (low + high) / 2;
ShiftArithmeticLeft(b, mid, &d);
DoAdd(&c, &d, &e); // e = c + d
// e >= 0
if (d.bit[SIGN_BIT] != e.bit[SIGN_BIT] || IsZero(&e))
low = mid + 1;
else
high = mid - 1;
}
// high == -1 means c - b < 0
if (high != -1)
{
t.bit[high] = 1;
// here unified the operation
// it can improve i think
ShiftArithmeticLeft(b, high, &d);
// c = c + d, let c be the next dividend
DoAdd(&c, &d, &c);
low = 0;
high--;
}
else
{
// now the dividend c is the remainder
CopyBigInt(&c, remainder);
break;
}
}
}
return ToComplement(&t, result);
}
