Thread: Pointers to objects -- passing and returning pointers

I'm writing a large numbers class just for fun and currently use no pointers. I basically have objects with functions for performing operations and these functions return the answer as another LargeNumber. So

Code:

(LargeNumber)c = (LargeNumber)a.add((LargeNumber)b);

will return another (LargeNumber)c that equals a + b. What I want to do is define it to take and return pointers because this would be (supposedly) faster. I was working with it earlier and got a couple errors about scope and pointers so I figure I was doing it wrong.

Here's my multiply function, it's short because it uses add() and other routines, I added a couple comments.

Code:

LargeNumber LargeNumber::mul(LargeNumber x)
{
  LargeNumber muls[2] = LargeNumber(0,0,0);
  muls[0] = simplemul(x.getDigit(x.getLength()));//simplemul multiples the entire number by a single digit
  muls[0].setSign(1);//sign figured out latter, all positive for addition
  bool yy = 1;
  for(int i = x.getLength() - 1; i > 0; i--)//elementary arithmetic, multiply top by each digit in the bottom...
  {
    muls[yy] = simplemul(x.getDigit(i));
    muls[yy].setSign(1);
    muls[yy].mul10(x.getLength() - i); //adds a zero to the right
    muls[yy] = muls[yy].add(muls[!yy]);
    yy = !yy;
  }
  muls[!yy].setDec(getDec() + x.getDec());//finds the decimal
  if(getSign() == 0 && x.getSign() == 0)
    muls[!yy].setSign(1);
  else
    muls[!yy].setSign(getSign() && x.getSign());
  return muls[!yy];
}

I want to turn this into a function that takes a pointer of a LargeNumber and returns a pointer to another LargeNumber.


Just for simplicity I don't need you to rewrite the entire function. Just pointify this and/or explain something

Code:

LargeNumber* LargeNumber::mul(LargeNumber* x)
{
  LargeNumber muls[2] = LargeNumber(0,0,0); //Define muls[2] somehow...
  muls[0] = simplemul(x.getDigit(x.getLength()));
  //do stuff (I understand x->function()??)
  return muls[yy];
}

Code:

LargeNumber* a = &LargeNumber(...);
LargeNumber* b = &LargeNumber(...)
LargeNumber* c = a->mul(b);

//Alternatively I assume this would work??

LargeNumber a = LargeNumber(...);
LargeNumber b = LargeNumber(...);
LargeNumber* c = a.mul(&b);