- COFF - www.tuhs.org

by G. Branden Robinson

At 2024-10-02T16:42:59-0400, Dan Cross wrote: > On Wed, Oct 2, 2024 at 2:27 AM <arnold(a)skeeve.com> wrote: > > Also true. In the late 80s I was a sysadmin at Emory U. We had a Vax > > connected to BITNET with funky hardware and UREP, the Unix RSCS > > Emulation Program, from the University of Pennsylvania. Every time I > > had to dive into that code, I felt like I needed a shower > > afterwards. :-) > > Uh oh, lest the UPenn alumni among us get angry (high, Ron!) I feel I > must point out that UREP wasn't from the University of Pennsylvania, > but rather, from The Pennsylvania State University (yes, "The" is part > of the name). UPenn (upenn.edu) is an Ivy in Philly; Penn State > (psu.edu) is a state school in University Park, which is next to State > College (really, that's the name of the town) with satellite campuses > scattered around the state. There's another method of distinguishing UPenn from Penn State. Permit me to share my favorite joke on the subject, from ten years ago. "STATE COLLEGE, Pa. -- Construction workers tore down Penn State's iconic Joe Paterno statue on campus two years ago -- but this town might not be without one for much longer. Two alumni already have received the OK from the borough to install a projected $300,000 life-sized bronze sculpture downtown, about two miles from the original site." -- ESPN ([1]) "The key difference is that the new statue will look the other way." -- Chris Lawrence Regards, Branden [1] https://www.espn.com/college-football/story/_/id/10828351/joe-paterno-honor…

6 months, 2 weeks

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Re: [TUHS] Re: Minimum Array Sizes in 16 bit C (was Maximum)

by Paul Winalski

On Tue, Oct 1, 2024 at 9:13 AM <arnold(a)skeeve.com> wrote: > This goes back to the evolution thing. At the time, C was a huge > step up from FORTRAN and assembly. > Certainly it's a step up (and a BIG step up) from assembly. But I'd say C is a step sidewise from Fortran. An awful lot of HPTC programming involves throwing multidimensional arrays around and C is not suitable for that. -Paul W.

6 months, 2 weeks

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Re: [TUHS] Re: Minimum Array Sizes in 16 bit C (was Maximum)

by Paul Winalski

On Tue, Oct 1, 2024 at 10:07 AM <arnold(a)skeeve.com> wrote: [regarding writing an Ada compiler as a class project] > Did you do generics? That and the run time, which had some real-time > bits to it (*IIRC*, it's been a long time), as well as the cross > object code type checking, would have been real bears. > > Like many things, the first 90% is easy, the second 90% is hard. :-) > > I was in DEC's compiler group when they were implementing Ada for VAX/VMS. It gets very tricky when routine libraries are involved. Just figuring out the compilation order can be a real bear (part of this is the cross object code type checking you mention). From my viewpoint Ada suffered two problems. First, it was such a large language and very tricky to implement--even more so than PL/I. Second, it had US Government cooties. -Paul W.

6 months, 2 weeks

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Re: [TUHS] Re: Minimum Array Sizes in 16 bit C (was Maximum)

by Stuff Received

[-->COFF] On 2024-10-01 10:56, Dan Cross wrote (in part): > I've found a grounding in mathematics useful for programming, but > beyond some knowledge of the physical constraints that the universe > places on us and a very healthy appreciation for the scientific > method, I'm having a hard time understanding how the hard sciences > would help out too much. Electrical engineering seems like it would be > more useful, than, say, chemistry or geology. I see this as related to the old question about whether it is easier to teach domain experts to program or teach programmers about the domain. (I worked for a company that wrote/sold scientific libraries for embedded systems.) We had a mixture but the former was often easier. S. > > I talk to a lot of academics, and I think they see the situation > differently than is presented here. In a nutshell, the way a lot of > them look at it, the amount of computer science in the world increases > constantly while the amount of time they have to teach that to > undergraduates remains fixed. As a result, they have to pick and > choose what they teach very, very carefully, balancing a number of > criteria as they do so. What this translates to in the real world > isn't that the bar is lowered, but that the bar is different. > > - Dan C.

6 months, 2 weeks

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Shadowing variables in Go.

by Ralph Corderoy

Taken to COFF... Hi Arnold, > In main(), I *think* I'm assigning to the global clientSet so that > I can use it later. But because of the 'err' and the :=, I've > actually created a local variable that shadows the global one, and in > otherfunc(), the global clientSet is still nil. Kaboom! > > The correct way to write the code is: > > var err error > clientSet, err = cluster.MakeClient() // or whatever I think this is a common problem when learning Go, like assigning getchar()'s value to a char in C. It was back in ’14 anyway, when I saw https://www.qureet.com/blog/golang-beartrap/ which has an ‘err’ at an outer scope be unwritten by the ‘:=’ with the new, assigned-to ‘err’ going un-checked. The author mentions ‘go vet’ highlights these cases with -shadow, which is off by default. https://pkg.go.dev/github.com/golangci/govet#hdr-Shadowed_variables suggests that's still the case. -- Cheers, Ralph.

6 months, 2 weeks

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Re: [TUHS] Re: Minimum Array Sizes in 16 bit C (was Maximum)

by Paul Winalski

[moving to COFF as this has drifted away from Unix] On Sat, Sep 28, 2024 at 2:06 PM Larry McVoy <lm(a)mcvoy.com> wrote: > I have a somewhat different view. I have a son who is learning to program > and he asked me about C. I said "C is like driving a sports car on a > twisty mountain road that has cliffs and no guard rails. If you want to > check your phone while you are driving, it's not for you. It requires > your full, focussed attention. So that sounds bad, right? Well, if > you are someone who enjoys driving a sports car, and are good at it, > perhaps C is for you." > > If you really want a language with no guard rails, try programming in BLISS. Regarding C and C++ having dangerous language features--of course they do. Every higher-level language I've ever seen has its set of toxic language features that should be avoided if you want reliability and maintainability for your programs. And a set of things to avoid if you want portability. Regarding managed dynamic memory allocation schemes that use garbage collection vs. malloc()/free(), there are some applications where they are not suitable. I'm thinking about real-time programs. You can't have your missle defense software pause to do garbage collection when you're trying to shoot down an incoming ballistic missile. -Paul W.

6 months, 2 weeks

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Fwd: Re: Trove of CSTR's

by Warren Toomey

Poul-Henning also suggests this link as well ... Warren ----- Forwarded message from Poul-Henning Kamp ----- There is also 3B stuff in various other subdirectories on that site, for instance: https://www.telecomarchive.com/six-digit.html ----- End forwarded message -----

6 months, 2 weeks

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Re: [TUHS] Re: Minimum Array Sizes in 16 bit C (was Maximum)

by Jim Capp

Moving to COFF ,.. From: "Rich Salz" <rich.salz(a)gmail.com> To: "TUHS main list" <tuhs(a)tuhs.org> Cc: "Douglas McIlroy" <douglas.mcilroy(a)dartmouth.edu> Sent: Monday, September 30, 2024 4:03:15 PM Subject: [TUHS] Re: Minimum Array Sizes in 16 bit C (was Maximum) On Mon, Sep 30, 2024 at 3:12 PM Steffen Nurpmeso < steffen(a)sdaoden.eu > wrote noone ever told them that even the eldest C can be used in a safe way; Perhaps we have different meanings of the word safe. void foo(char *p) { /* interesting stuff here */ ; free(p); } void bar() { char *p = malloc(20); foo(p); printf("foo is %s\n", p); foo(p); } Why should I have to think about this code when the language already knows what is wrong. No one would make the claim that programming in machine "language" is safe. No one would make the claim that programming in assembly "language" is safe. I've always viewed C as a portable assembler. I think the real issue has nothing to do with the "safety" of C, but rather the "safety" of your-choice-of-C-libraries-and-methods. My $.02 Jim

6 months, 2 weeks

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Re: Maximum Array Sizes in 16 bit C

by Aron Insinga

FWIW, I just saw this in code generated by bison: (yyvsp[-4].string_val), (yyvsp[-2].string_val), (yyvsp[0].string_val) (IIUC) referencing the addresses under the top of the stack when passing $2, $4, $6 into a function from an action (skipping a couple of tokens). So the sign just depends on which way the stack is growing. As for range checking of pointers into a malloc'd block of memory, the pointer could have just 2 things: the address at the start of the block and the pointer itself, some moving address in the block; and then before the start of the block malloc could stash the address of the end of the block (where it could be referenced by all pointers into the block). So instead of a triple word, the pointer is a double word, and the malloc'd block has an extra word before it. This must have been done before by someone, somewhere. I don't think of pointers and arrays in C as the same thing, but rather array references as an alternate syntax for pointer arithmetic (or vice versa). - Aron

6 months, 3 weeks

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Re: [TUHS] Maximum Array Sizes in 16 bit C

by Douglas McIlroy

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

6 months, 3 weeks

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