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?

--
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