<<
But David and Larry ("There's no extra checking. In David's method,the WHILE
loop becomes an
infinite loop"), doesn't the WHILE loop always have to check the
condition,whether it's a moving target like SQLCODE <> 100 or an infinite
looplike WHILE 1 = 1.
>>
I think we're getting confused on the difference between the processing of the
WHILE condition, and the programming logic.
Yes, the WHILE loop condition may need to get processed at each iteration. A
compiled language would optimize out an always-true condition. R:Base probably
does not, but that's okay, the processing time is insignificant.
The more important issues to my mind are that the code be clear and
maintainable and, to the extent possible, the same logic is NEVER duplicated in
the code. The first issue mandates for a WHILE loop instead of GOTO / LABEL
processing, the second condition mandates that both the FETCH logic and
end-of-loop logic appear only once in the program. When I said "there's no
extra checking" what I should have said is "the checking logic for ending the
WHILE loop appears only once."
There was a time when I think a lot of R:Base programmers ripped out all their
WHILE loops in favor of GOTO / LABEL structures because of perceived memory
leaks and other problems with this programming structure. For my part, I never
observed the problem with WHILE loops in any stable version of R:Base -- any
problems I did encounter always turned out to have any solution, usually
correcting some problem with my code.
There is a saying in programming -- "Premature optimization is the root of all
evil". In other words, algorithms should be implemented clearly and cleanly
first, and only then optimized if they are not sufficiently fast. In that
vein, I prefer David's method because it is the clearest (at least to me) and
also the easiest to maintain and is always fast enough to get the job done.
--
Larry
