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Re: Callback



fixed

The easiest example I use - the almost-only-one, actually, is when I use the qsort API - when you call qsort, you tell it what data is to be sorted, how long each element is, and a pointer to a procedure that will compare 2 elements and return either that they are the same or that one or the other is larger. That procedure is the callback - maybe we can think of it as a CALL BACK to the caller of qsort. qsort walks through the elements and passes pairs of them to the callback procedure.

I'm probably stepping out on a limb - maybe one can look at it as a kind of exit program. That's a user-defined program called at some point in a system or application process. Close enough definition, I hope!

HTH
Vern

On 10/15/2012 4:11 PM, Porterfield, Sean wrote:
http://en.wikipedia.org/wiki/Callback_%28computer_programming%29

I can read the example and think it's pretty neat, but I'd be hard pressed to explain it... I know callbacks are used in HTTPAPI and/or WSDL2RPG. Hopefully Scott Klement can explain it so that mere mortals can understand. :)
--
Sean Porterfield


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Richard Reeve
Sent: Monday, October 15, 2012 17:09
To: midrange-l@xxxxxxxxxxxx
Subject: Re: Callback


No, he specifically said callback. I thought it strange that I've been on this platform for 20 plus years and have never heard of it.
------------------------------
On Mon, Oct 15, 2012 3:54 PM CDT Daniel T. Rowan wrote:

>Are you sure they weren't referring to a rollback? I've never heard of a >callback either.
>
>On Mon, Oct 15, 2012 at 3:50 PM, Richard Reeve <richreeve@xxxxxxxxx> wrote:
>
>> Has anyone ever heard of a callback as it is related to the IBM i? I was >> asked to explain a callback during an interview and I'd never even heard of >> it. Can any of you explain to me what a callback is and how it is used?
>> I tried google but didn't get a good explanation.
>>
>> Thanks.
>>
>> Warmest Regards,
>>
>> Richard Reeve
>> --
>> This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list >> To post a message email: MIDRANGE-L@xxxxxxxxxxxx >> To subscribe, unsubscribe, or change list options, >> visit: http://lists.midrange.com/mailman/listinfo/midrange-l
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>>
>>
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