public object Evaluate(string formula)
{
if (string.IsNullOrEmpty(formula))
{
return(0);
}
var inputStream = new AntlrInputStream(formula);
var lexer = new FormulaLexer(inputStream);
var tokens = new CommonTokenStream(lexer);
var parser = new FormulaParser(tokens);
var errorListener = new FormulaErrorListener();
parser.RemoveErrorListeners();
parser.AddErrorListener(errorListener);
var parseTree = parser.main();
if (!errorListener.IsValid)
{
throw new FormulaException(
errorListener.ErrorLocation,
errorListener.ErrorMessage);
}
return(new EvaluationVisitor(Functions).VisitMain(parseTree));
}