Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> bart <bc@freeuk.com> writes:
>> On 19/04/2024 16:26, Tim Rentsch wrote:
> ...
>>> ... Certainly C has some
>>> similarities to Algol 68, but I wouldn't say C and Algol 68
>>> are similar languages, only that they have a few similarities.
>>
>> I can't see any connection between Algol68 and C; I'm surprised at people
>> who say they do.
>
> "Connection" is vague, but Dennis Ritchie has written about the
> influence of Algol 68 on C.

See <https://www.bell-labs.com/usr/dmr/www/chist.pdf, which has multiple
references to Algol 68.

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */

scott@slp53.sl.home (Scott Lurndal) writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>
>> Michael S <already5chosen@yahoo.com> writes:
>>
>>> On Mon, 15 Apr 2024 20:36:58 +0200
>>> Janis Papanagnou <janis_papanagnou+ng@hotmail.com> wrote:
>>>
>>>> Algol 68 and C are so different that mutual understanding might be
>>>> difficult depending on personal background, focus, and fantasy. :-)
>>>
>>> Interesting take.
>>> I never learned Algol-68, but from pieces of info that I occasionally
>>> got I was always thinking of it as rather similar to 'C'.
>>> Both languages originated from common ancestor (Algol-60) and changed
>>> it in similar directions, e.g. blurring the line between operators and
>>> expression, making function pointers first class citizen, allowing
>>> declaration of variables at block scope.
>>> I think, in the past, when I remembered more about Algol-68, I had seen
>>> more similarities.
>>
>> Algol 60 already had block scope declarations.
>>
>> Algol 60 may not have had (pointer to) function/procedure variables,
>> but it did allow procedure identifiers as arguments to a procedure
>> call, and procedure variables are an obvious generalization.
>
> Call-by-name.

Algol 60 also had call by name (already mentioned in my previous
post), but that is unrelated to allowing procedure identifiers
as arguments.

Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
> [...]
>
>> * Algol is "strict" whereas C is "lax" - for example, in Algol
>> the controlling expression of an 'if' statement must be a
>> 'Boolean expression', whereas in C it's just any expression
>
> Small quibble: the controlling expression in C must be of scalar type.

Yes but my comment was only about syntax. In Algol 60 a
'Boolean expression' is a syntactic category unrelated
to any semantic analysis. In C there is no separate
syntactic catgory for "boolean" expressions; there is
only 'expression'.

On 2024-04-20, Ben Bacarisse <ben.usenet@bsb.me.uk> wrote:
> bart <bc@freeuk.com> writes:
>
>> On 19/04/2024 16:26, Tim Rentsch wrote:
> ...
>>> ... Certainly C has some
>>> similarities to Algol 68, but I wouldn't say C and Algol 68
>>> are similar languages, only that they have a few similarities.
>>
>> I can't see any connection between Algol68 and C; I'm surprised at people
>> who say they do.
>
> "Connection" is vague, but Dennis Ritchie has written about the
> influence of Algol 68 on C.

I was looking at both Algols recently; they have a go to statement
with local statement labels, very similar to C.

>> C was put together together as a systems language to do a job, not to
>> implemement some esoteric concept of a language that few could understand.
>>
>> I understood it was based on languages like B and BCPL.
>
> BCPL had assignment statements but B followed Algol 68 and made
> assignment an expression operator (along with the +=, -= etc versions).
> This, of course, fed directly into C.

Algol 60 included a selection operator, suggested by John MacCarthy
of Lisp. That's likely how C ended up with the A ? B : C syntax.

That's actually funny because MacCarthy first invented a three-operand
IF operator, which he simulated via a function in Fortran. He used
that to simplify his chess program and other programs. (This account
is given in his History of Lisp article). His Fortran XIF, being
a function, didn't have the evaluation semantics he wanted such that
XIF(A, B, C) would evaluate only one of A and B. He somehow evolved this
three-way if into the multi-branch conditional which he then favored; it
became the Lisp cond with the M-expression surface syntax, and that
being similar to what he proposed for Algol. Eventually Lisp people
also went full circle, providing a two/three argument if operator or
macro, alongside cond.

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

On 16.04.2024 00:32, Lawrence D'Oliveiro wrote:
> On Mon, 15 Apr 2024 20:36:58 +0200, Janis Papanagnou wrote:
>
>> I usually don't think about whether there's a -1, 0, 42, value used to
>> represent 'EMPTY' in memory. This may stem from the CS education where
>> I've learned not to assume a physical von Neumann architecture with
>> registers etc. ...
>
> The concept of “bits” comes from information theory. It has nothing to do
> with von Neumann or Paul Newman or Gary Oldman or anything else. If you
> have zero information to convey, then the number of bits of information is
> zero.

Thanks for trying to teach me CS.

I'm not speaking about "concepts" I'm speaking either about "units"
or about "[physical] representations"; here about the latter.

Concerning language - and I cannot speak for English, but suppose
there's something similar there as in my native language - we
differentiate between entities and units; we have the unit "bit"
(not "bits"; e.g. "8 bit") and the concrete physical or whatever
entity that hereabouts you refer to as "Bit". In cases where I
speak about memory _representations_ the word to choose is "Bit",
like "Bytes", "Octets", etc.

>
>> Other such values like 'EMPTY' are also known from other languages; like
>> the Algol 68 terms 'NIL' ('null', 'NULL', 'nil'), and 'SKIP'.
>
> Those are all entirely different concepts in Algol 68.

Yes, sure. That's why I wrote "like". - Not sure why you make
so many meaningless posts.

Janis

On 16.04.2024 22:11, Michael S wrote:
> On Mon, 15 Apr 2024 20:36:58 +0200
> Janis Papanagnou <janis_papanagnou+ng@hotmail.com> wrote:
>>
>> Algol 68 and C are so different that mutual understanding might be
>> difficult depending on personal background, focus, and fantasy. :-)
>>
>
> Interesting take.
> I never learned Algol-68, but from pieces of info that I occasionally
> got I was always thinking of it as rather similar to 'C'.

Well, they're from the same language family. But there's some
fundamental differences, also fundamental different approaches,
and different design principles.

At some abstraction point we can say that, say, Fortran and C
or Algol 68, have all for-loops and run on von Neumann systems
but from a design perspective all three sample languages here
are very different.

> [...]
> I think, in the past, when I remembered more about Algol-68, I had seen
> more similarities.

It's the criterons you choose that make us see differences or
similarities (or even equalities). And the set of criterions
is typically chosen from the specific point of view (personal
or analytical or requirements or...).

Janis

On 18.04.2024 00:12, Lawrence D'Oliveiro wrote:
> On Wed, 17 Apr 2024 18:09:06 +0100, Ben Bacarisse wrote:
>
>> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>>
>>> On Mon, 15 Apr 2024 17:50:45 +0100, Ben Bacarisse wrote:
>>>
>>>> Algol 68 has no denotation for the empty value.
>>>
>>> Section 8.1.5.1 of the Revised Report:
>>>
>>> void denotation : empty symbol.
>>
>> Thanks. If I had ever known that, I had forgotten. It's almost never
>> used because values are coerced to void all the contexts where it might
>> be otherwise required. I'm pretty sure I've never written it.
>
> I also did a quick test in a68g that “BEGIN EMPTY END” is a valid program
> (at least compiles without errors). But the last time I posted such a
> thing, someone claimed that a68g was not necessarily a fully conforming
> Algol 68 implementation ...

I don't see why it shouldn't be valid program; I mean you can write
programs like "BEGIN END", "BEGIN EMPTY END", "BEGIN SKIP END",
"BEGIN NIL END", "BEGIN 3.14 END", or, "BEGIN 42 END".
I wouldn't expect that these do anything; only in the latter cases
I'd at least see a point in returning that value to the environment
(which isn't done, though, with the Genie compiler).

Janis