/// <summary>
///
/// </summary>
/// <param name="number1"></param>
/// <param name="number2"></param>
/// <param name="setValueIndicated">this is true if the return value is a clone and not the
/// same instance as number1</param>
/// <returns></returns>
private static INumeric Add(INumeric number1, INumeric number2, out bool isReplace)
{
//the default value is false, as most cases don't need a clone operation
isReplace = false;
if (number1 == null)
{
isReplace = true;
return number2;
}
if (number2 == null)
return number1;
INumeric rv = null;
//determine the longer number
bool? num1IsLonger = Numeric.AbsoluteValueCompare(number1.As<Numeric>(),
number2.As<Numeric>());
//note: below we clone the 2nd arg if it is being modified as part of the operation
//we don't clone the 1st arg as it is
if (number1.IsPositive && number2.IsPositive)
{
rv = Increment(number1, number2);
}
else if (number1.IsPositive && number2.IsPositive == false)
{
switch (num1IsLonger)
{
case null:
rv = Decrement(number1, number2);
break;
case true:
rv = Decrement(number1, number2);
break;
case false:
isReplace = true;
var cloneNum2 = number2.Clone();
rv = Decrement(cloneNum2, number1);
rv.As<Numeric>().IsPositive = false;
break;
}
}
else if (number1.IsPositive == false && number2.IsPositive)
{
switch (num1IsLonger)
{
case null:
rv = Decrement(number1, number2);
break;
case true:
rv = Decrement(number1, number2);
break;
case false:
isReplace = true;
rv = Decrement(number2.Clone(), number1);
rv.As<Numeric>().IsPositive = true;
break;
}
}
else if (number1.IsPositive == false && number2.IsPositive == false)
{
rv = Increment(number1, number2);
rv.As<Numeric>().IsPositive = false;
}
return rv;
}
public void Subtract(INumeric numeric)
{
if (numeric == null)
return;
//if (!this.HasCompatibleNumberSystem(numeric))
// throw new InvalidOperationException("incompatible number system");
numeric.As<Numeric>().SwitchSign();
bool isClone = false;
var val = Add(this, numeric, out isClone);
numeric.As<Numeric>().SwitchSign(); //we don't want to return a modified arg
if (isClone)
this.As<Numeric>().SetValue(val);
}