private static Tuple<Operator, string> findComparator(string value)
{
Operator comparison = Operator.EQ;
if (value.StartsWith(">=") && value.Length > 2)
{ comparison = Operator.GTE; value = value.Substring(2); }
else if (value.StartsWith(">"))
{ comparison = Operator.GT; value = value.Substring(1); }
else if (value.StartsWith("<=") && value.Length > 2)
{ comparison = Operator.LTE; value = value.Substring(2); }
else if (value.StartsWith("<"))
{ comparison = Operator.LT; value = value.Substring(1); }
else if (value.StartsWith("~"))
{ comparison = Operator.APPROX; value = value.Substring(1); }
return Tuple.Create(comparison,value);
}