public override Num multi(Num num, bool haveNegative)
{
if (num is IntegerNum)
{
int n;
if ((isPlus == 2 && num.isPlus == 1) || (isPlus == 1 && num.isPlus == 2)) //-a * b, a * -b
n = 0 - integer * ((IntegerNum)num).integer;
else //a * b, -a * -b, 还有无符号的情况
n = integer * ((IntegerNum)num).integer;
if (!haveNegative)
return new IntegerNum(n, 0);
else if (n >= 0)
return new IntegerNum(n, 1);
else return new IntegerNum(0 - n, 2);
}
else return null;
}
public override Num add(Num num, bool haveNegative)
{
if (num is IntegerNum)
{
int n;
if (isPlus == 2 && num.isPlus == 2) //-a + -b
n = 0 - integer - ((IntegerNum)num).integer;
else if (isPlus == 1 && num.isPlus == 2)//a + -b
n = integer - ((IntegerNum)num).integer;
else if (isPlus == 2 && num.isPlus == 1)//-a + b
n = ((IntegerNum)num).integer - integer;
else //a + b
n = integer + ((IntegerNum)num).integer;
if (!haveNegative)
return new IntegerNum(n, 0);
else if (n >= 0)
return new IntegerNum(n, 1);
else return new IntegerNum(0 - n, 2);
}
else return null;
}
public override Num div(Num num, bool haveNegative)
{
if (num is IntegerNum)
{
int n;
if (((IntegerNum)num).integer == 0)
return null;
int remainder = integer % ((IntegerNum)num).integer;
if (remainder != 0)
return null;
if ((isPlus == 2 && num.isPlus == 1) || (isPlus == 1 && num.isPlus == 2)) //-a / b, a / -b
n = 0 - integer / ((IntegerNum)num).integer;
else //a / b, -a / -b, 还有无符号的情况
n = integer / ((IntegerNum)num).integer;
if (!haveNegative)
return new IntegerNum(n, 0);
else if (n >= 0)
return new IntegerNum(n, 1);
else return new IntegerNum(0 - n, 2);
}
else return null;
}
public override Num sub(Num num, bool haveNegative)
{
if (num is IntegerNum)
{
int n;
if (isPlus == 2 && num.isPlus == 2) //(-a) - (-b)
n = ((IntegerNum)num).integer - integer;
else if (isPlus == 1 && num.isPlus == 2)//a - (-b)
n = integer + ((IntegerNum)num).integer;
else if (isPlus == 2 && num.isPlus == 1)//-a - b
n = 0 - integer - ((IntegerNum)num).integer;
else//a - b
n = integer - ((IntegerNum)num).integer;
if (!haveNegative)
{
if(n < 0)//要求不能有负数，但是出现了负数
return null;
return new IntegerNum(n, 0);
}
else if (n >= 0)
return new IntegerNum(n, 1);
else return new IntegerNum(0 - n, 2);
}
else return null;
}
public override bool isEqual(Num num)
{
if (base.isEqual(num) && integer == ((IntegerNum)num).integer)
return true;
else return false;
}
public NumNode(Num num)
{
content = num;
}
public virtual Num sub(Num num, bool haveNegative)
{
return null;
}
public virtual bool isEqual(Num n)
{
if (isPlus == n.isPlus)
return true;
else return false;
}
private Num compute(Num n1, Num n2, string op)
{
if (op == "+")
return n1.add(n2, true);
else if (op == "-")
return n1.sub(n2, true);
else if (op == "×")
return n1.multi(n2, true);
else
return n1.div(n2, true);
}