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RE: Callback



fixed

I think Vern is trying to differentiate between a callback and an exit. There's really not much point in differentiating, but I'll offer this: Callbacks are usually done by passing a procedure pointer. Exits are usually done by calling a program by name. In the case of the callback the calling program has already loaded the function into memory. An exit is loaded and executed by the operating system at the behest of the calling program.

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of John Yeung
Sent: Thursday, October 18, 2012 9:27 AM
To: Midrange Systems Technical Discussion
Subject: Re: Callback

On Thu, Oct 18, 2012 at 10:21 AM, John Yeung <gallium.arsenide@xxxxxxxxx> wrote:
On Thu, Oct 18, 2012 at 12:58 AM, Vernon Hamberg
<vhamberg@xxxxxxxxxxxxxxx> wrote:
Now another API is readdir() - this one returns a structure for the
NEXT item it finds in the directory - so YOU have to run this in a
loop until no more objects are found. The first API itself contains
the processing loop - that first API seems to fit the idea, again, of
the use of callback functions or programs. Pretty neat!

Neat, yes. Callback? I don't see it. I think you have conflated the
repetitiveness with the callback concept.

Hmm... perhaps I misread you. Maybe you are saying that readdir() indeed does NOT involve callbacks at all, and were specifically trying to highlight the difference between Qp0lProcessSubtree() (which takes a callback, and uses that callback in a loop) and readdir() (which does not, and you have to do the loop yourself).

Sorry if my previous response misconstrued what you were trying to say.

John
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