public static double Evaluate(string expression)
{
var lexer = new CalculatorLexer(new AntlrInputStream(expression));
lexer.RemoveErrorListeners();
lexer.AddErrorListener(new ThrowExceptionErrorListener());
var tokens = new CommonTokenStream(lexer);
var parser = new CalculatorParser(tokens);
var tree = parser.compileUnit();
var visitor = new ExcelVisitor();
return(visitor.Visit(tree));
}