Moved to Coff, because it's about programming style, not history.
> Perhaps I'm missing something? Clever arithmetic in the index
> calculation aside, this is semantically different than using an actual
> negative integer to index into an array? Moreover, if the intent is to
> start the sequence with 0, why set `fib(0)` to 1? How is this
> substantially different from the usual way of writing this:
I said the Fibonacci example was silly. Maybe you'll be more convinced by
the binomial-coefficient program below.
The array of interest is fib. base is simply scaffolding and doesn't appear
in the working code. You won't find the ith Fibonacci in base[i]; it's in
fib(i). But fib(-1) exists. What's important is that the C convention of
array indexes beginning at 0 has been circumvented.
I could be accused of subterfuge in depending on the semantics of static
storage to initialize fib(-1) to zero. Subterfuge or not, it's customary C
usage. The binomial-coefficient program relies on "out-of-bounds" zeros
abutting two sides of a triangle.
int base[N][N+2];
#define binom(n,i) base[n][(i)+1]
void fill() {
binom(0,0) = 1;
for(n=1; n<N; n++)
for(i=0; i<=n; i++)
binom(n,i) = binom(n-1,i) + binom(n,i-1);
}
I think the offset algorithm above looks better than the more typical one
below.
The two programs happen to have identical character counts.
int binom[N][N+1];
void fill() {
for(n=0; n<N; n++) {
binom[n][0] = 1;
for(i=1; i<n; i++)
binom[n][i] = binom[n-1][i] + binom[n][i-1];
binom[n][n] = 1;
}
}
Doug
A summary of a couple of longer posts.
Ralph Corderoy and I used different C syntax than to access an MxN array A,
whose subscripts begin at M0 and N0 in the respective dimensions. Here's a
somewhat simplified version of both. In our examples, M0 and M0 were
negative.
Mine:
int base[M][N];
#define A(i,j) base[i-M0][j-N0]
Ralph's
int base[M][N];
int (*A)[N] = (int(*)[N])&base[-M0][-N0];
In my scheme element references must be written A(i,j). Ralph retains C
array syntax, A[i][j].
Doug
Mea culpa.
I thought I could offer a simple example, but my binomial-coefficient
program is wrong, and loses its force when corrected. For a convincing
example, see the program in
https://digitalcommons.dartmouth.edu/cs_tr/385/
Unfortunately you have to read a couple of pages of explanation to see what
this program is up to. It's a fun problem, though.
Doug
Moved to COFF.
On 2024-09-20 11:07, Dave Horsfall wrote (in part):
>
> Giggle... In a device driver I wrote for V6, I used the expression
>
> "0123"[n]
>
> and the two programmers whom I thought were better than me had to ask me
> what it did...
>
> -- Dave, brought up on PDP-11 Unix[*]
>
> [*]
> I still remember the days of BOS/PICK/etc, and I staked my career on Unix.
Working on embedded systems, we often used constructs such as a[-4] to
either read or modify stuff on the stack (for that particular
compiler+processor only).
S.
> I you have historical resources on Plan 9 or Inferno, or are reminded of
> any interesting tidbits, you can also share them here, as this list is
> already recognized by historians as a legitimate source.
Can someone tell me where the original "here" of the quoted message is?
Thanks,
Doug
Hi all, Edouard asked me to pass this e-mail on to both TUHS and COFF lists.
Cheers, Warren
----- Forwarded message from Edouard Klein <edouardklein(a)gmail.com> -----
Subject: History tract during the next IWMP9 in Paris next May
Date: Thu, 29 Aug 2024 22:46:30 +0200 (1 week, 4 days, 19 hours ago)
Dear Unix history enthusiasts,
The 11th International Workshop on Plan 9 will be held in Paris on May
22-24 2025.
One of the focus area this year will be Plan 9's history and its
influence on later computer science and industry trends.
The history team at the CNAM (where the conference will be held) has
agreed to help us prepare for the event and stands ready to record oral
histories, or any other format that would make the participants happy.
They had organized in 2017 a "colloque" at which Clem spoke (and I
listened somewhere in the audience) on UNIX:
https://technique-societe.cnam.fr/colloque-international-unix-en-europe-ent…
I will keep the list posted as our efforts pan out, but I thought I'd
get the word out as soon as possible.
I you have historical resources on Plan 9 or Inferno, or are reminded of
any interesting tidbits, you can also share them here, as this list is
already recognized by historians as a legitimate source.
The program committee members, many (if not all) of whom roam this very
list, would welcome any proposal or contributions in this area :)
The CfP is at:
http://iwp9.org/
Looking forward to read what you care to share, or to seeing you in
person in Paris,
Cheers,
Edouard.
----- End forwarded message -----
I just noticed this:
Sep 2018: The Multics History Project Archives were donated to the Living
Computer Museum in Seattle. This included 11 boxes of tapes, and 58 boxes of
Multics and CTSS documentation and listings. What will happen to these items
is unknown.
https://multicians.org/multics-news.html#events
That last sentence is ironic; I _assume_ it was written before the recent news.
I wonder what will happen to all such material at the LCM. Anyone know?
Noel
That's where it all began for Unix in Oz (the Dept of Power Systems paid
for the Ed5 tape, as I recall). I'm told that the campus has changed so
much it's now unrecognisable...
https://www.openday.unsw.edu.au/planner
-- Dave
I'm cleaning out my desk as retirement looms (a few more months) and
found my Sun coffee mug!
https://udel.edu/~mm/sun/
The back of the mug says such good things, yet...
Mike Markowski
> From: Larry McVoy
{Moving this to COFF, as it's not UNIX-related. I'll have another reply there
as well, about the social media point.}
> The amazing thing, to me, is I was a CS student in very early 1980's
> and I had no idea of the history behind the arpanet.
I don't think that was that uncommon; at MIT (slightly earlier, I think -
-'74-'77 for me) the undergrad's weren't learning anything about networking
there either, then.
I think the reason is that there wasn't much to teach - in part because we
did not then know much about networking, and in part because it was not yet
crystal clear how important it would become (more below on that).
There was research going on in the area, but even at MIT one doesn't teach
(or didn't then; I don't know about now) on-going research subjects to
undergrads. MIT _did_ have, even then, a formal UROP ('undergrad research
opportunities') program, which allowed undergrads to be part of research
groups - a sheer genius idea - which in some fast-moving fields, like CS, was
an inestimable benefit to more forward undergrads in those fields.
I joined the CSR group at LCS in '77 because I had some operating system
ideas I wanted to work on; I had no idea at that point that they were doing
anything with networks. They took me on as the result of the sheerest chance;
they had just gotten some money from DARPA to build a LAN, and the interface
was going to be built for a UNIBUS PDP-11, and they needed diagnostics, etc
written; and they were all Multicians. I, by chance, knew PDP-11 assembler -
which none of them did - the MIT CS introductory course at that point taught
it. So the deal was that I'd help them with that, and I could use the machine
to explore my OS ideas in return.
Which never really happened; it fairly became clear to me that data
networking was going to have an enormous impact on the world, and at that
point it was also technically interesting, so I quickly got sucked into that
stuff. (I actually have a written document hiding in a file drawer somewhere
from 1978 or so, which makes it plain that that I'm not suffering 20-20
hindsight here, in talking about foreseeing the impact; I should dig it up.)
The future impact actually wasn't hard to foresee: looking at what printed
books had done to the world, and then telgraphs/telephones, and what
computers had already started to do at that point, it was clear that
combining them all was going to have an incredible impact (and we're still
adapting to it).
Learning about networking at the time was tricky. The ARPANET - well, NCP and
below - was pretty well documented in a couple of AFIPS papers (linked to at
the bottom here:
https://gunkies.org/wiki/ARPANET
which I have a very vague memory I photocopied at the time out of the bound
AFIPS proceedings in the LCS library). The applications were only documented
in the RFC's.
(Speaking of which, at that level, the difference between the ARPANET and the
Internet was not very significant - it was only the internals, invisible to
the people who did 'application' protocols, that were completely different.
HTTP would probably run just fine on top of NCP, for instance.)
Anything past that, the start of the internet work, that, I picked up by i)
direct osmosis from other people in CSR who were starting to think about
networks - principally Dave Clark and Dave Reed - and then ii) from documents
prepared as part of the TCP/IP effort, which were distributed electronically.
Which is an interesting point; the ARPANET was a key tool in the internet
work. The most important aspect was email; non-stop discussion between the
widely separated groups who were part of the project. It also made document
distribution really easy (which had also been true of the latter stages of
the ARPANET project, with the RFC's). And of course it was also a long-haul
network that we used to tie the small internets at all the various sites
(BBN, SRI, ISI - and eventually MIT) into the larger Internet.
I hate to think about trying to do all that work on internets, and the
Internet, without the ARPANE there, as a tool.
Noel
