//						==================
ExprResult				AddExpression::Add
//						==================
(
	ExprResult&			left,
	ExprResult&			right
) const
{
	// Create a result, and initialise its status as undefined.
	ExprResult result( m_strPrecision );
	result.SetStatus( ExprResult::UNDEF_STATUS );

	// Convert any possible UNSPECIFIED operand.
	left.ConvertFromUnspecified();
	right.ConvertFromUnspecified();

	// Both operands must now have arithmetic types; check if either
	// operand has the type FLOAT.
	if ( left.IsFloat() || right.IsFloat() )
	{
		// Convert both to FLOAT.
		left.ConvertToFloat();
		right.ConvertToFloat();
	}

	// Get the numerical values of the operands.
	double* pNumValLeft  = left.GetNumValue();
	double* pNumValRight = right.GetNumValue();

	// Check if the numerical values exist; i.e. check if no
	// null pointers were returned.
	if ( pNumValLeft != 0 && pNumValRight != 0 )
	{
		// Calculate the numerical value of the result by adding
		// the numerical values of the operands.
		double dlNumVal = (*pNumValLeft) + (*pNumValRight);

		// Since both operands now have the same type, check the type
		// of the left operand to check if both have type INT.
		if ( left.IsInt() )
		{
			// Take as value of the result the conversion of its
			// numerical value to a string; not using exponential
			// notation, and with a precision of 0. Then, set the
			// result type to INT.
			result.SetValue( DoubleAsIntToStr( dlNumVal ) );
			result.SetType( ExprResult::INT );
		}
		else
		{
			// Take as value of the result the conversion of its
			// numerical value to a string, using a precision of
			// ADDPRECISION. Then, set the result type to FLOAT.
			result.SetValue( DoubleToStr( dlNumVal, ADDPRECISION ) );
			result.SetType( ExprResult::FLOAT );
		}

		// Set the result status to OK.
		result.SetStatus( ExprResult::OK );
	}
	else
	{
		// Although the operands were of arithmetic type, no mumerical
		// value could be determined; internal error.
		result.SetStatus( ExprResult::INTERNAL_ERROR );
	}

	return result;
}