docs: private Expression plusMinusOp(Data data) throws TemplateException {
  	Expression expr = modOp(data);
  
  	while (!data.srcCode.isLast()) {
  
  	    // Plus Operation
  	    if (data.srcCode.forwardIfCurrent('+')) expr = _plusMinusOp(data, expr, Factory.OP_DBL_PLUS);
  	    // Minus Operation
  	    else if (data.srcCode.forwardIfCurrent('-')) expr = _plusMinusOp(data, expr, Factory.OP_DBL_MINUS);
  	    else break;
  	}
  	return expr;
      }