public static CommonFunction operator +(CommonFunction f1, CommonFunction f2)
{
Sum result = new Sum();
if (f1 is Sum)
{
result.operands = ((Sum)f1).operands;
result.signs = ((Sum)f1).signs;
}
else
{
result.operands.Add(f1);
result.signs.Add(true);
}
if (f2 is Sum)
{
result.operands.AddRange(((Sum)f2).operands);
result.signs.AddRange(((Sum)f2).signs);
}
else
{
result.operands.Add(f2);
result.signs.Add(true);
}
return result;
}
public static CommonFunction operator -(CommonFunction f1)
{
Sum result = new Sum();
if (f1 is Sum)
{
result = (Sum)f1;
for (int i = 0; i < result.signs.Count; i++)
{
result.signs[i] = !result.signs[i];
}
}
else
{
result.operands.Add(f1);
result.signs.Add(false);
}
return result;
}
private CommonFunction Expression()
{
Sum sum = new Sum();
if (!IsAddop(look))
{
sum.operands.Add(Term());
sum.signs.Add(true);
}
while (IsAddop(look))
{
switch (look)
{
case '+':
Match('+');
sum.operands.Add(Term());
sum.signs.Add(true);
break;
case '-':
Match('-');
sum.operands.Add(Term());
sum.signs.Add(false);
break;
default:
throw new Exception();
}
}
return sum;
}
