RE: Regular Expressions

Just to clarify: I did not ask for performance data. I asked only whether
performance had been tested and compared. We can probably infer the answer,
so no response is needed. Sorry if I confused things.

On a side note: I see (but do not select) these random taglines prior to
typing my message. I don't know why my computer's in a Douglas Adams mood.
It's not me. Honest. :)

Dennis Lovelady
http://www.linkedin.com/in/dennislovelady
--
"There is a theory which states that if ever anyone discovers exactly what
the Universe is for and why it is here, it will instantly disappear and be
replaced by something even more bizarrely inexplicable.

There is another theory which states that this has already happened."
-- The Hitchhiker's Guide to the Galaxy

I am not going to provide performance comparisons, Dennis. These and
other
measures would be part of on-site acceptance-testing and as such would
provide figures more relevant than any I might generate.


Regards,
Joihn McKay mba

----- Original Message -----
From: "Dennis Lovelady" <iseries@xxxxxxxxxxxx>
To: "'RPG programming on the IBM i / System i'" <rpg400-l@xxxxxxxxxxxx>
Sent: Friday, August 13, 2010 2:10 PM
Subject: RE: Regular Expressions

Thank you for your responses, John. While I don't see the benefit of
using
one individual's API under the conception that another's API is

difficult

to
learn/use, I salute you making this available. I am not some other
person,
and this may exactly fit that other person's needs!

But I did notice that you avoided the performance question. I'm just
saying. :)

Dennis Lovelady
http://www.linkedin.com/in/dennislovelady
--
"For a moment, nothing happened. Then, after a second or so, nothing
continued to happen."
-- The Hitchhiker's Guide to the Galaxy

I had three objectives for producing this implementation.

The first objective was to use a single call instead of REGCOMP,
REGEXEC
and REGFREE.. This is closer to the "standard" implementation found

in

other
languages and scripts. It also makes regular expressions more
accessible to
those who are unfamiliar with the IBM api's.

My second objective was to remove the confusion / ambiguity

caused

by
differing character sets / ccsid's. While I cannot guarantee that

my

implementation will work successfully across all the character sets

/

ccsid's, it is more robust than the IBM-supplied api's.

My third objective was to widen the range of regular expressions
available here. Allied to this was the need to improve the
documentation
for RPG developers.

Two of the examples illustrate a return position rather than 1
(alpha, h
and alp25a, \d, both of which return position 4).

Messages which can be of help in determining whether a regular
expression is valid or not can be obtained from the return code. A
negative
return code (range -1 to -18) will indicate the message based on the
IBM
documentation. These return codes are in the readme, which can be
viewed on
line.

I agree with you in that "the hard part is in coming up with the
right
expression". This is the case in all implementations of regular
expressions. Different implementations use different (albeit very
similar)
syntaxes and there is a set of standard escape characters and
punctuation
characters.

I had considered an implementation of REGEXEC on its own, but

this

cannot be done without a related implementation of REGCOMP. If you
think
this to be useful, I will look at it again.


Regards,
John McKay mba

----- Original Message -----
From: "Dennis Lovelady" <iseries@xxxxxxxxxxxx>
To: "'RPG programming on the IBM i / System i'" <rpg400-

l@xxxxxxxxxxxx>

Sent: Friday, August 13, 2010 10:03 AM
Subject: RE: Regular Expressions

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?