On Tue, 11 Oct 2005 09:36:07 -0600 Steve Comstock <[EMAIL PROTECTED]>
wrote:
:>Art Celestini wrote:
:>> I realize this is more suited for the Assembler List, but as a brief
follow-on
:>> to Steve's parenthetical comment below:
:>>
:>> Many years ago, I had similar disdain for the use of literals. But, as I
wrote
:>> more and more code that I knew would be handed over to others to support
and
:>> maintain, I came to realize that defining my constants "in-line" often
:>> contributed to making that code a little easier for the next guy to
understand.
:>> (While reading the code to get the gist of what it's doing, he won't have
to
:>> interrupt his train of thought to go off somewhere else in the source to
find
:>> the value of some labeled constant.)
:>The point is to use "meaningful labels", so the reader
:>will not need to interrupt their study of the code.
:>> A couple weeks ago, I posted a question regarding CONVTOD, so I happened to
:>> have the snippet below handy, which I'll use as an example. This routine
uses
:>> hex floating point to accommodate the somewhat odd size and structure of
the
:>> STCK(E) clock format, so the instructions used are not typically among
those
:>> that most of us see on a daily basis. I think with the constants being
defined
:>> in-line, it's easier to grasp what the code is doing:
:>>>* When the CONVTOD macro is successful, the difference between ``````
:>>>* the ETOD values (plus one day), converted to seconds, repre- ``````
:>>>* sents the Retention-In-Seconds value: ``````
:>>>* ``````
:>>>CvExp020 DS 0H ``````
:>>> LM R2,R3,CvExpEtodExp Get exp. date's ETOD value ``````
:>>> SRDL R2,8 Make room for exponent ``````
:>>> STM R2,R3,CvExpHfpExp Save in units of micro- ... ``````
:>>> MVI CvExpHfpExp,79 ... seconds in HFP format ``````
:>>> LD FR0,CvExpHfpExp Get difference between ... ``````
:>>> SD FR0,CvExpHfpNow ...expiration & current dates ``````+
:>>> Zero or less? ``````
:>>> BNP CvExp900 Yes ==> Go use zero retention ``````
:>>> DD FR0,=D'1000000' Get difference in secs ``````
:>>> AD FR0,=D'86400.999999' Round up date/second ``````
:>>> AW FR0,=X'4E00000000000000' Align & store for ... ``````
:>>> STD FR0,CvExpRetSecs ... use as fixed point ``````
:>>> MVI CvExpRetSecs,0 Clear HFP exponent byte ``````
:>>> B CvExp900 ==> Go return result to caller ``````
:>I disagree this is easier to grasp the flow
:>with the literals there; I'm not sure of the
:>right labels to choose, but maybe something
:>like:
:> DD FR0,Seconds_Adjuster Get difference in secs
:> AD FR0,Rounder Round up date/second
:> AW FR0,Aligner Align & store for
:>then, if you are checking the details, or debugging, or
:>validating the code, you can look at the values.
Because in the included version, the comment explains the value and one can
see the value in-line and easily confirm that it is correct.
Your version just has the comment - not the true value. Thus one must scan to
find it.
I guess you could use
DD FR0,Seconds_Adjuster Get difference in secs
AD FR0,Rounder Round up date/second
AW FR0,Aligner Align & store for
LITERALS LOCTR ,
Seconds_Adjuster DC D'1000000'
Rounder DC D'86400.999999'
Aligner DC X'4E00000000000000'
main LOCTR ,
but it is a lot messier without providing any real advantage.
--
Binyamin Dissen <[EMAIL PROTECTED]>
http://www.dissensoftware.com
Director, Dissen Software, Bar & Grill - Israel
Should you use the mailblocks package and expect a response from me,
you should preauthorize the dissensoftware.com domain.
I very rarely bother responding to challenge/response systems,
especially those from irresponsible companies.
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