public override Double Compute()
{
if (String.IsNullOrWhiteSpace(this.Expression))
{
return(Double.NaN);
}
if (Helper.IsNumericValue(this.Expression))
{
return(this.ApplyFunction(Double.Parse(this.Expression)));
}
var _operatorList = new List <String>();
var _unitList = new List <IComputeUnit>();
try
{
// prepare
int i = 0;
while (i < Expression.Length)
{
var strExpression = Expression.Substring(i);
var nextMatch = Regex.Match(strExpression, @"[\+\-*/%([{]");
if (!nextMatch.Success) // must be numeric number
{
_unitList.Add(new NumericUnit(strExpression));
break;
}
if (nextMatch.Index == 0)
{
if (Regex.IsMatch(nextMatch.Value, @"[([{]"))
{
var subExpression = Helper.GetSubExpression(strExpression);
var unit = ExpressionHandler.Parse(subExpression);
if (unit == null)
{
return(Double.NaN);
}
_unitList.Add(unit);
i += subExpression.Length;
}
else if (Regex.IsMatch(nextMatch.Value, @"[\+\-*/%]"))
{
Debug.Assert(nextMatch.Index == 0 && nextMatch.Length == 1);
_operatorList.Add(strExpression[0].ToString());
i++;
}
}
else
{
if (Regex.IsMatch(strExpression, @"^[0-9]")) // start with number, it must be a numeric unit
{
_unitList.Add(new NumericUnit(strExpression.Substring(0, nextMatch.Index)));
i += nextMatch.Index;
}
else // must be a complex unit
{
var subExpression = Helper.GetSubExpression(strExpression);
var unit = ExpressionHandler.Parse(subExpression);
if (unit == null)
{
return(Double.NaN);
}
_unitList.Add(unit);
i += subExpression.Length;
}
}
}
// calculate
Debug.Assert(_operatorList.Count == _unitList.Count - 1);
var operators = new List <String>();
var values = new List <Double>();
Double value = Double.NaN;
for (i = 0; i < _operatorList.Count; i++)
{
if (Double.IsNaN(value))
{
value = _unitList[i].Compute();
}
if (Double.IsNaN(value))
{
return(Double.NaN);
}
if (_operatorList[i] == "*" || _operatorList[i] == "/" || _operatorList[i] == "%")
{
if (_operatorList[i] == "*")
{
value *= _unitList[i + 1].Compute();
}
else
{
var temp = _unitList[i + 1].Compute();
if (temp == 0)
{
return(Double.NaN);
}
if (_operatorList[i] == "/")
{
value /= temp;
}
else
{
value %= temp;
}
}
continue;
}
if (Double.IsNaN(value))
{
return(Double.NaN);
}
if (operators.Any() && operators.Last() == "-")
{
value *= -1;
}
values.Add(value);
operators.Add(_operatorList[i]);
value = Double.NaN;
}
if (Double.IsNaN(value) && (!_operatorList.Any() || _operatorList.Last() == "+" || _operatorList.Last() == "-"))
{
value = _unitList.Last().Compute();
}
if (!Double.IsNaN(value))
{
if (operators.Any() && operators.Last() == "-")
{
value *= -1;
}
values.Add(value);
}
// apply function
return(this.ApplyFunction(values.Sum()));
}
catch
{
return(Double.NaN);
}
finally
{
_operatorList.Clear();
_unitList.Clear();
}
}