private EquationGrammarParser getParser(final String equation) {
final ANTLRInputStream input = new ANTLRInputStream(equation);
final EquationGrammarLexer lexer = new EquationGrammarLexer(input);
final TokenStream tokenStream = new CommonTokenStream(lexer);
final EquationGrammarParser parser = new EquationGrammarParser(tokenStream);
final ANTLRErrorStrategy handler = new BailErrorStrategy();
parser.setErrorHandler(handler);
final ParseTreeListener listener = new EquationGrammerListener();
parser.addParseListener(listener);
return parser;
}