tchrist@convex.COM (Tom Christiansen) (01/28/91)
I didn't realize it at first, but I seem to have stumbled upon a possible
religious issue. It has to do with two different approaches to problems.
I really think this software engineering issue -- hence, the cross-posting.
One of these involves taking an input stream and performing repeated mungings
on the stream using various UNIX filters. The alternative is to re-order
the algorithm to place the locus of control at the center of a loop within
some kind of script.
I've come to believe that the first approach is, for many problems that
people try to use it on, simply too slow, awkward, and difficult to under-
stand when compared with the other approach.
One correspondent believes that these two methodologies are completely
interchangeable. Others believe one or the other to be superior. I'm
interested in some non-inflammatory, theoretical discussions on this. In
a way, it reminds me of functional programming versus other styles.
Here was the task that got this all started: write a ``which'' that
displays each possible path rather than just the first one. My version
(well, the shell one at least :-) was this:
for dir in `echo $PATH | tr : ' ' `; do
test -x $dir/$1 && echo $dir/$1
done
Another poster, who now lives in my global kill file because I got fed up
with abusive rhetoric when what I really wanted was some discussion on the
relative merits of the two methodologies, proposed essentially this:
ls -dFL `echo "$PATH" | tr : '\012' | sed -e "s:\$:/$1:"` | sed -ne 's/*$//p'
(but you have to throw away stderr)
I'm willing to be convinced otherwise by reasonable persuasion, but to me,
the 2nd method seems to me more complex and hard to maintain. While it
does run slower than the first way, but that's not the real point. I'm
looking at maintainability and complexity. If you were grading on style,
what would you look for?
My gut feel is that solutions like #2 are good for job security, but bad
for convincing people that you don't have to be a wizard use UNIX. I
think some problems are simple enough for approach #2, but for more
complex ones, while you *can* hammer #2 into working for you, #1 is better
for the reasons stated.
--tom
--
"Hey, did you hear Stallman has replaced /vmunix with /vmunix.el? Now
he can finally have the whole O/S built-in to his editor like he
always wanted!" --me (Tom Christiansen <tchrist@convex.com>)