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.
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