Re: Regular Expressions

Dennis,

It would seem to me that your concerns could be simply addressed by
keeping track of the last expression REGCOMP'd and not doing the
REGFREE until the expression changes or the activation group ends.

In fact, if it we're me, I'd consider keeping a lookup table of
expressions and either the DS or pointers to dynamically allocated DSs
that REGCOMP uses.

That way you could have more than one regex "active" as it were.

Charles

On Fri, Aug 13, 2010 at 5:03 AM, Dennis Lovelady <iseries@xxxxxxxxxxxx> wrote:

Thanks, John.  I've seen implementations like this before (but not public
domain).  I cannot download and restore a save file to the systems I access,
so there is conjecture here.  That conjecture can be solved by having a FAQ
for the product.  I presume that you're doing REGCOMP, REGEXP, REGFREE with
each operation.  Have you measured the performance of this against the
alternative (REGCOMP at the beginning of a process, REGEXP for each of x
million rows/columns/whatevers, REGFREE at the end?

My studies on this (which I unfortunately cannot share) suggest that one
would be much better off using REGCOMP and REGFREE themselves, rather than
taking such a generic approach.  After all, the hard part isn't in calling
those expressions or evaluating their results; the hard part is in coming up
with the right expression, and that remains a hurdle with your approach.

In other words, what is the value-add that may be traded for performance?

Your examples, when they find a match, find them in position 1, and return a
1.  What happens if a match is found in position n?

When one makes a mistake with a regular expression, what help (optional or
otherwise) does the function return?

Dennis Lovelady
http://www.linkedin.com/in/dennislovelady
--
"Better to remain silent and be thought a fool than to speak out and remove
all doubt."
       -- Abraham Lincoln

Single function regular expressions  - regexp - now available for free
at www.rpglanguage.com/regexp

Regards,
John McKay  mba
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