SimpleCharStream scs = new SimpleCharStream(
new StringReader("(" + s + ")"), caller.getBeginLine(),
caller.getBeginColumn(), s.length() + 2);
// FMLexer token_source = new FMLexer(scs);
FMLexer token_source = new FMLexer(scs);
token_source.SwitchTo(FMConstants.EXPRESSION);
FMParser parser = new FMParser(token_source);
parser.setTemplate(caller.getTemplate());
Expression exp = null;
try {
exp = parser.Exp();