Put#include "LargeInt.h"

void Add(SpecializedList first, SpecializedList second, 
     SpecializedList& result)
// Post:  result = first + second.
{
  int carry = 0;
  bool finished1 = false;
  bool finished2 = false;
  int temp;
  int digit1;
  int digit2;

  first.ResetBackward();
  second.ResetBackward();

  while  ( !finished1 && !finished2)
  {
    first.GetPriorItem(digit1, finished1);
    second.GetPriorItem(digit2, finished2);
    temp = digit1 + digit2 + carry;
    carry = temp / 10;
    result.PutFront(temp % 10);
  }
  while ( !finished1)
  {// Adds remaining digits (if any) in first to the sum.
    first.GetPriorItem(digit1, finished1);
    temp = digit1 + carry;
    carry = temp / 10;
    result.PutFront(temp % 10);
  }
  while ( !finished2)
  {// Adds remaining digits (if any) in second to the sum.
    second.GetPriorItem(digit2, finished2);
    temp = digit2 + carry;
    carry = temp / 10;
    result.PutFront(temp % 10);
  }
  if (carry != 0)		// Adds in carry (if any)
    result.PutFront(carry);
}

LargeInt LargeInt::operator+(LargeInt second)
// self is first operand
{
  SignType selfSign;
  SignType secondSign;
  LargeInt result;

  if (sign == second.sign)
  {
    Add(number, second.number, result.number);
    result.sign = sign;
  }
  else  
  {
    selfSign = sign;
    secondSign = second.sign;
    sign = PLUS;
    second.sign = PLUS;
    if (*this < second)
    {
      Sub(second.number, number, result.number);
      result.sign = secondSign;
    }
    else if (second < *this)
    {
      Sub(number, second.number, result.number);
      result.sign = selfSign;
    }
    sign = selfSign;
  }
  return result;
}

enum RelationType  {LESS, GREATER, EQUAL};
RelationType CompareDigits(SpecializedList first, 
     SpecializedList second);

bool LargeInt::operator<(LargeInt second)
{
  RelationType relation;
  
  if (sign == MINUS && second.sign == PLUS)
    return true;
  else if (sign == PLUS && second.sign == MINUS)
    return false;
  else if (sign == PLUS && numDigits < second.numDigits)
    return true;
  else if (sign == PLUS && numDigits > second.numDigits)
    return false;
  else if (sign == MINUS && numDigits > second.numDigits)
    return true;
  else if (sign == MINUS && numDigits < second.numDigits)
    return false;
  else // Must compare digit by digit
  {
    relation = CompareDigits(number, second.number);
    if (sign == PLUS && relation == LESS)
      return true;
    else if (sign == PLUS && relation == GREATER)
      return false;
    else if (sign == MINUS && relation == GREATER)
      return true;
    else return false;
  }
}

RelationType CompareDigits(SpecializedList first, 
     SpecializedList second)
{
  bool same = true;
  bool finished = false;
  int digit1;
  int digit2;

  first.ResetForward();
  second.ResetForward();
  while ( !finished)
  {
    first.GetNextItem(digit1, finished);  
    second.GetNextItem(digit2, finished);
    if (digit1 < digit2)
      return LESS;
    if (digit1 > digit2)
      return GREATER;
  }
  return EQUAL;
}