gnubol: X-WHEN revisited

[RKRayhawk@aol.com]

In a message dated 12/26/99 5:11:41 PM EST, tej@melbpc.org.au writes:

<<  quoting some one else
 > Concerning the nesting of EVALUATES and SEARCHES, I would offer this
 > expression to you: really, honestly, and sincerely, ... we need to get all 
of
 > it to nest before we deploy any cardinal verb.
 
 The problem is with evaluate and search I don't actually know how
 to do it because some of the clauses are almost valid in the
 other verb, but not quite - and this can depend on the symbol
 table.
  >>

I would certainly like to hear more about this, you have looked at it closer 
than perhaps anyone.

As a minor aside I would mention that the ALSO particle is intriguing as a 
resource that can be used to pop the X-WHEN stack in a emergency fashion. I 
think ALSO can not appear in a SORT WHEN clause, so when we encounter it 
there we could draw certain conclusions.

It would be too late for the current WHEN clause, which is going to get 
pretty munged, but any ALSO in a SEARCH WHEN could be used to pop S-WHEN off 
the stack (atleast if there is hope that that would possibly help some: that 
is, if we are in a SEARCH nested inside of
an EVALUATE) this is the least handsome of the X-WHEN ideas but it could 
definitely help.

If we studied this, we probably could find ways to minimize damage whilst in 
the SEARCH WHEN that is trashing its way through the E-WHEN.  I know that 
ALSO can also occur in VALUE clauses, but I think its only role in the 
procedure division is in the two aspects of the EVALUATE.

But this is a very small part of the picture.

I think that the problem will look less dramatic when we fully address the 
fact that the EVALUATE WHENs have dynamic syntax projected by the EVALUATE 
header. We have to deal with that in the actions (or else in semantics), so 
the rules will have to be very flexible; more harvestors then editors.  In 
that sense it could be even easier to plug them in optionally to SEARCH (as 
incongruous as that may seem) we just need to include them as error 
productions in SEARCH and positive logic for EVALUATE.

Best Wishes,
Bob Rayhawk
RKRayhawk@aol.com

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