LogicalExpression e = parser.parse().e;
RecordPointer r = new UnbackedRecord();
r.addField(new SchemaPath("a", ExpressionPosition.UNKNOWN), new IntegerScalar(3));
SimpleEvaluationVisitor builder = new SimpleEvaluationVisitor(r);
BasicEvaluator eval = e.accept(builder, null);
DataValue v = eval.eval();
System.out.println(v);
}
}