Re: Parse

[Harry Binswanger hb@xxxxxxxx]

Re parse, Robert wrote:
You only need to null out the prospective results if 1) the result S/Gs
already
are initialized and have content going into the parse, and 2) there's a chance
that the parse itself will bomb, e.g. if S/G 01 is empty -- in that case, you
could emerge on the far side of the parse with erroneous results in 03 and
05.
Could you say a little more about error conditions in parsing--or point me
to the relevant docs (nothing is in "XPL User's Guide")? I get from above
that if XS fails, due to nothing in s/g 01, then what was already in 03 and
05, if anything, might still be in them. And later, you indicate that 03
and 05 may not get flushed when they should be giving a null. That's an
eye-opener. Could explain some strange results I've been getting. Any other
strange error conditions?

E.g., is it kosher to use the same s/g twice as in:
 or ?
I think that in Xy 3+ that used to put an ascii 01 or 02 somewhere on
screen, so I've been avoiding it, but it would be convenient to do that in
some looped parses.
Your example above should at least be checking that S/G 05
has content ( greater than 0) before rewinding.

Good idea. Thanks.



Harry Binswanger
hb@xxxxxxxx