private RPNExpression ParseToRPN(string expression)
{
RPNExpression rpnExpression = new RPNExpression(_FunctionEvaluator, _FunctionCallPrecedence);
rpnExpression.DoWork(delegate
{
Token token = null;
MatchCollection matches = this.Regex.Matches(expression);
foreach (Match match in matches)
{
int groupIndex = -1;
for (int index = 0; index < _TokenDefinitions.Count; index++)
{
if (match.Groups[index + 1].Success)
{
groupIndex = index;
break;
}
}
token = new Token(_TokenDefinitions[groupIndex], match.Value);
rpnExpression.ApplyToken(token);
}
});
return(rpnExpression);
}
public IExpression Parse(string expression)
{
lock (_CacheLock)
{
if (_ExpressionCache.ContainsKey(expression))
{
return(_ExpressionCache[expression]);
}
else
{
//1. parse to reverse polish notation expression
RPNExpression rpn = ParseToRPN(expression);
//2.
IExpression iexpression = rpn.Compile();
//3. into cache
_ExpressionCache[expression] = iexpression;
return(iexpression);
}
}
}