bigint.cpp

//Venix Cador
//Cs23001
//02/10/2013

#include"bigint.h"

bigint::bigint()
{
  zero();
}

void bigint::zero()
{
  for(int i=0; i <MaxValue; i++)// to search each value in the integer to zero
    {
      big[i]= 0;
    }
  size = 0;

}

bigint::bigint(int d)
{
  zero();
  for (int i = 0; d != 0; i++, ++size) // To set the values in the integer array
     {
      big[i] = d % 10;
      d /=10;
     }
}

bigint::bigint(const char d[]) //declaring the character array here.
{
  zero();
  int y = 0;

  do //to initialize each character array value y to the integer value

    {
      ++y;

    }while (d[y] != '\0');

  --y;

  for (int i = 0; d[i] != '\0'; i++, y--, ++size) //setting each array value = to the integer array value.
    {
      big[y] = (int(d[i]) - int('0')); //Casting the big(bigint array) array to an integer value when assigning it to the character array.
    }
}

bool bigint::operator ==(const bigint& y) // using y to compare two bigints.
{
  for(int i = 0; i < MaxValue; i++)
    {
      if(y.big[i] != big[i])
	{
	  return false;
	}
    }
  return true;
}

bool bigint::operator ==(int d)
{
  for (int i = 0; d != 0; ++i)
    {
      if (big[i] != d % 10)
	{
	  return false;
	}
      d /= 10;
    }
  return true;
}

bool bigint::operator ==(const char d[])
{
  int y = 0;

  do
    {
      ++y;
    }while (d[y] != '\0');
  --y;

  for (int i = 0; d[i] != '\0'; i++, y--)
    if (big[y] != (int(d[i]) - int('0'))) return false;

  return true;

}

void bigint::output(std::ostream& out) const
{
  int a = MaxValue;
  int outi = 0;

  do
    {
      --a;
    }while (big[a] == 0);
  do
    {
      if(a & 80)
	{
	  out << big[a];
	}
      else
	out << std::endl << big[a];

      --a;
      ++outi;
    }while (a >= 0);


}
bigint bigint::operator +(bigint rhs)const
{
  int i = 0;
  int remainder = 0;
  int temp = 0; //Need temp to hold the remainder values.


  while (i < MaxValue)
    {
      remainder = rhs.big[i] + big[i] +remainder;
      temp = remainder % 10;
      remainder /= 10;
      rhs.big[i] = temp;
      ++i;
    }

  return rhs;
}


int bigint::operator [](int i)
{
  if ((i < 0)||(i >= size))
    return 0;
  return big[i];
}

int bigint::operator [](int i) const
{
  if((i < 0) || (i >= size))
    return 0;
  return big[i];

}

std::istream& operator >>(std::istream& iput, bigint& rhs)
{
  int tempi = 0;
  char intry;
  char temp[MaxValue];

  iput >> intry;

  while(intry != ';' && !iput.eof())//.eof means end o file
                                  // to set the char array temp to the user's input
    {
      temp[tempi] = intry;
      iput >> intry;
      ++tempi;
    }
  temp[tempi] = 0; //To set the final value of the temp array to 0.
  rhs = bigint(temp);
  return iput;

}

std::ostream& operator <<(std::ostream& out, const bigint& rhs) //calling rhs from std::istream&.
//This time it will display the input.

{
  rhs.output(out);
  return out;
}
//Multiply bigint by powers of 10

void bigint::times10(const int x){ //Shift all elements in the array x number of spaces

  for(int i = ( MaxValue - 1); i >= 0; i--){
    big[i]= big[i - x];

    }
  for(int i = (x -1); i >= 0; --i){ //when previous loop ends, fill remaining x elements with 0.
    big[i] = 0;
  }
}
void bigint::times_single_digit(int x){ //multiply a bigint and a single digit

 int temp = 0;
 int carry = 0;

  for(int i = 0; i < MaxValue; i++){

    temp = ((big[i] * x) + carry) % 10;
    carry = ((big[i] * x) + carry) / 10;
    big[i]= temp;
  }

}
bigint bigint::operator*(const bigint& rhs)
{
  bigint part, result;

  for( int i = 0; i <MaxValue; i++){

    part = * this; //copy the value of the left handside to part

    part.times_single_digit(rhs.big[i]); //Multiply left handside by the spot in rhs
    part.times10(i);// shift the left by i
    result = result + part;
  }
  return result;
}
bigint bigint::factorial() const{

      bigint result(1);

      if (bigint(0) == *this) {
          return result;
      }

      for (bigint i = 1; i != *this + 1; i = i + 1){
              result = result * i;
      }

      return result;
}