BETWEEN SYMMETRIC/ASYMMETRIC

Hi All,

As part of my ongoing quest to understand grammar files, I've been trying to
implement BETWEEN SYMMETRIC/ASYMMETRIC.

I've attached my current work.  Can someone please look and tell me if I'm
on the right track?  With this patch, I get parse errors after BETWEEN if I
go:

SELECT 2 BETWEEN ASYMMETRIC 1 and 3;

or

SELECT 2 BETWEEN SYMMETRIC 1 and 3;

So it doesn't seem to be working - I don't know why!!

Don't look at the NOT BETWEEN stuff - I've not done it yet.

I was forced to put SYMMETRIC and ASYMMETRIC as reserved words - anything
else seemed to give shift/reduce errors.  Is there anything I can do about
that?

Chris