hugeint.cpp

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// Fig. 11.23: Hugeint.cpp 
// HugeInt member-function and friend-function definitions.
#include <cctype> // isdigit function prototype
using std::isdigit;

#include <cstring> // strlen function prototype
using std::strlen;

#include "Hugeint.h" // HugeInt class definition

// default constructor; conversion constructor that converts
// a long integer into a HugeInt object
HugeInt::HugeInt( long value )
{
   // initialize array to zero
   for ( int i = 0; i <= 29; i++ )
      integer[ i ] = 0;   

   // place digits of argument into array 
   for ( int j = 29; value != 0 && j >= 0; j-- )
   {
      integer[ j ] = value % 10;
      value /= 10;
   } // end for
} // end HugeInt default/conversion constructor

// conversion constructor that converts a character string 
// representing a large integer into a HugeInt object
HugeInt::HugeInt( const char *string )
{
   // initialize array to zero
   for ( int i = 0; i <= 29; i++ )
      integer[ i ] = 0;

   // place digits of argument into array
   int length = strlen( string );

   for ( int j = 30 - length, k = 0; j <= 29; j++, k++ )

      if ( isdigit( string[ k ] ) )
         integer[ j ] = string[ k ] - '0';
} // end HugeInt conversion constructor

// addition operator; HugeInt + HugeInt
HugeInt HugeInt::operator+( const HugeInt &op2 ) const
{
   HugeInt temp; // temporary result
   int carry = 0;

   for ( int i = 29; i >= 0; i-- )
   {
      temp.integer[ i ] = 
         integer[ i ] + op2.integer[ i ] + carry;

      // determine whether to carry a 1
      if ( temp.integer[ i ] > 9 )
      {
         temp.integer[ i ] %= 10;  // reduce to 0-9
         carry = 1;
      } // end if
      else // no carry 
         carry = 0;
   } // end for

   return temp; // return copy of temporary object
} // end function operator+

// addition operator; HugeInt + int
HugeInt HugeInt::operator+( int op2 ) const
{ 
   // convert op2 to a HugeInt, then invoke 
   // operator+ for two HugeInt objects
   return *this + HugeInt( op2 ); 
} // end function operator+

// addition operator;
// HugeInt + string that represents large integer value
HugeInt HugeInt::operator+( const char *op2 ) const 
{ 
   // convert op2 to a HugeInt, then invoke 
   // operator+ for two HugeInt objects
   return *this + HugeInt( op2 ); 
} // end operator+

// overloaded output operator
ostream& operator<<( ostream &output, const HugeInt &num )
{
   int i;

   for ( i = 0; ( num.integer[ i ] == 0 ) && ( i <= 29 ); i++ )
      ; // skip leading zeros

   if ( i == 30 )
      output << 0;
   else

      for ( ; i <= 29; i++ )
         output << num.integer[ i ];

   return output;
} // end function operator<<

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