Groups | Search | Server Info | Login | Register

Groups > comp.lang.misc > #11709

Re: Algol 68 - to be or not to be a Local Range

Show all headers | View raw

On 2025-12-22 18:35, Andy Walker wrote:
> On 20/12/2025 16:39, Janis Papanagnou wrote:
> [re "LOC" inside loops:]
>> Re "A68G"; actually (AFAICT) that's not a Genie issue. I found that
>> property explicitly described and with a similar example in
>> Lindsey, van der Meulen: "Informal Introduction to ALGOL 68" [*]
> 
>      Hmm.  You seem to be correct.  "FOR i ..." seems to be a local
> definition of "i", but technically not a declaration, so that a few
> weasel words later, you get the effect you describe.  So in deeply nested
> loops you can have arbitrarily many copies of values with the same
> identifier.  This is pretty yucky, IMO, and also breaks the equivalence
> of loops with "the same" code written out using jumps and explicit tests
> [as described in the RR].

I also don't like it. Moreover, I think it muddies the clean language
design. - On the other hand, if I hadn't read that paper I probably
wouldn't ever have noticed it in practice.

> 
>> (If I understand correctly that's an informal amendment to the RR?)
>
>      No, it's supposed to be an informal description of A68, readable
> by people who don't understand two-level grammars.  [...]

I thought to have read somewhere that the committee members would have
"accepted" it [informally] as clarifying document. (But okay, I may be
just mistaken with my reading or interpretation of some statements.)

BTW, I think the explanation level of that paper is quite good. (I'm
generally not an advocate of using formal standard documents for plain
programmers.) This paper fills the gap quite well between a textbook
and all the formal details (and peculiar language) you typically find
in standards.

Janis

Back to comp.lang.misc | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

Algol 68 - to be or not to be a Local Range Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-20 13:28 +0100
  Re: Algol 68 - to be or not to be a Local Range Andy Walker <anw@cuboid.co.uk> - 2025-12-20 14:01 +0000
    Re: Algol 68 - to be or not to be a Local Range Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-20 17:39 +0100
      Re: Algol 68 - to be or not to be a Local Range Andy Walker <anw@cuboid.co.uk> - 2025-12-22 17:35 +0000
        Re: Algol 68 - to be or not to be a Local Range Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-22 19:10 +0100
        Re: Algol 68 - to be or not to be a Local Range Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-22 21:17 +0000
    Re: Algol 68 - to be or not to be a Local Range Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-21 01:59 +0000
      Re: Algol 68 - to be or not to be a Local Range Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-21 05:47 +0100

csiph-web