Mikhail said:
Eric Sosman wrote:
Give me an example, of trickery, that YOU consider really cool, that is also
portable...
Straying from topicality, hence the change in Subject ...
Once upon a time, in my rambunctious youth, I would have had
no trouble answering your question. It was cool to use `x&(x-1)'
to zero the lowest-order one-bit, it was cool to use "horizontal
addition" to count the one-bits or compute parity, it was cool to
use `POP PC' instead of `RETURN' (yes! it was faster!), it was
cool to use a computed GOTO instead of an IF (as you may deduce,
my R.Y. was some time ago ...)
But a funny thing happened: Progress.
The first computer I used had forty thousand decimal digits
of memory, of which one hundred locations were reserved for the
table that allowed it to add and subtract integers. All other
arithmetic -- integer multiplication and division, all kinds of
floating-point -- were done via subroutines. I no longer recall
the instruction timings for that machine, but I do remember that
when it was replaced by a newer system that could execute some
kinds of instructions in LESS THAN TWO MICROSECONDS it seemed
like an onrush of unthinkable speed.
On that machine, in my R.Y., "cool tricks" were a necessity,
a staple of daily existence. They were the difference between
a program that ran and a program that failed (sorry: your code
is twenty digits bigger than memory). Moving a few instructions
out of an inner loop was a big deal -- and the compilers of the
day were not very good at such things. After all, they had only
the resources of the same slow small machine at their disposal,
and were already stressed simply to get the translations done.
(It was not unusual for a compiler to be a program of five or
so sequential "passes" communicating intermediate results via
temporary files, sometimes on reels of magnetic tape or even on
decks of punched cards.) In my R.Y. the compilers needed all the
help we could give them.
Ah, but there's been Progress.
Not quite twenty years ago I bought my first x386 machine,
and it wasn't long before I had a sort of magical realization:
My very modest 640x480 display was being driven by a bare-bones
low-end video card with SIXTEEN TIMES THE MEMORY CAPACITY OF MY
ENTIRE COLLEGE CAMPUS! In a PERIPHERAL, for Crissakes!
It sort of brought home to me the degree to which progress
had changed my world -- and the sobering fact that the cool tricks
I once employed to squeeze three more instructions into the size
of one disk sector were simply no longer relevant. The economic
facts that once ruled my profession no longer held; a different
dynamic was loose in the world.
The world's finest maker of buggy whips goes to the poorhouse
when the automobile comes along. The careful choice of leathers
for different parts of the whip, the judicious use of oak for
stiffness and ash for springiness that gives the handle its
inimitable feel, the consummate craftsmanship in the double-looped
stitching to prevent water and snow from penetrating and rotting
the interior ... Irrelevant. Useless. Outmoded. Inane.
As one can admire the skills of the buggy whip makers and the
inordinate amount of labor they would expend on a single whip, so
one can admire the "cool tricks" of the programmer-craftsmen and
their perseverance at desk-checking to avoid messing up even one
of their couple of compiles per day. (I remember once poring over
a core dump trying to see whether a failed program had at least
computed the right intermediate results before dying, doing pencil-
and-paper long division IN HEXADECIMAL to check the results.) As
I say, one can admire the ingenuity, cleverness, sneakiness, and
sweat -- but the proper venue for such admiration is the same as
for admiring buggy whips: In a museum of antiquities, not in code
written for the present day.
Can you make a fire by rubbing two sticks together? It's
doable -- I've seen it done -- but do you feel any less "able"
if you cannot do it yourself?
Do you know how to flake flint to make a knife edge? If not,
do you find your daily life impeded by the loss of that cool trick?
What kind of sapling will make a good bow? What animal's
entrails will you wind to make a good bowstring, and how do you
get them out of the carcase intact, and how do you prevent them
from rotting -- how, for that matter, do you catch and kill the
animal?
All these once-essential skills are now become irrelevant.
Interesting to antiquarians, perhaps, and in that limited sense
still cool -- but of no serious consequence any more. You could
be the world's greatest fire-maker, the best flint-flaker ever
to "Ouch!" his thumb, and the best bowyer who ever bent birch,
and you would be ... what? Not chatting on Usenet, I imagine.
I have (figuratively) lived in caves and eaten tasty nematodes
scrabbled from the dirt (there's a trick to finding the good ones,
I'll show ya how it's done). Nowadays I live in a house and get my
food from a supermarket -- and y'know? I really don't miss the
nematodes all that much.
And *that's* cool.
