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Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays

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On 2025-12-28 13:53, Andy Walker wrote:
> On 26/12/2025 11:25, Janis Papanagnou wrote:
>> Occasionally I had the demand to create arbitrarily nested arrays of
>> arrays (similar to the question in [*]). This requires something like
>> [][]...[] SOMETYPE and the corresponding nested loops for processing
>>    FOR i ...
>>      ...
>>        FOR j ...
>>          FOR k ...
>> But these are static definitions and don't scale for arbitrary depth.
>> (The dimension/depth of nesting is defined during runtime at start!)
> 
>      See below!
> 
>> In the context of another language I had implemented such logic simply
>> by linearizing the arrays and the associated array index calculation.
>> An alternative approach could be to build the structures recursively
>> (with linked data structures) and with a recursive set of functions.
>> Now pondering what to do in Algol 68...
> 
>      I don't see how anyone can advise without knowing more about
> what the actual, underlying, problem is. 

Sorry. I thought the abstraction would be sufficiently clear. :-/

(Especially since the Stackoverflow link I posted described it as
well. - I admit with a similar abstraction grade, but clear enough
for me at least; I've met that task in the past already, so it's
not new for me. - I seem to recall that I've done something like
that in C++ with template-meta-programming.)

> My personal inclination, from
> a position of complete ignorance about what you're really trying to do,
> would be to go for a recursive solution.

Yes, that's an option. - My own thoughts with recursive functions
were along using them with recursive (linked) data structures. But
that would bloat the simple structure and I was reluctant to take
that path.

> 
>> [...]
>> Or is there some code pattern [in Algol 68] that would simplify the
>> task without muddying the clarity of the algorithms?
> 
>      [This is the "See below"!]  You say that the depth is determined
> at "start".  An alternative could be to construct an A68 program of the
> right depth "on the fly".  A simple program goes through constructing
> the right number of nested "FOR" loops, or whatever.  [...]

Thanks. But Yuck! - I'd prefer static Algol 68 code to introducing
another level of software generation with dynamic creation of code.

Why I was asking - I probably should have mentioned that explicitly,
though I didn't want to restrict possible solutions! - was to get to
know whether there's some, say, functional or meta-programming options
with Algol 68 that I didn't yet have noticed.

Meanwhile I've resorted to the index-linearizing approach, by the way.

> 
>      I should add that my advice is worth no more than you’re paying
> for it, and also that my charges are tripled over the holiday period.

I'm glad that three times 0 is still 0. :-)

OTOH, if you're inclined to read Usenet on a Sunday your potential fees
might be unjustified anyway. ;-)

> Merry New Year!

And all the best!

Janis

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Algol 68 (or generally) - arbitrarily nested arrays of arrays Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-26 12:25 +0100
  Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Andy Walker <anw@cuboid.co.uk> - 2025-12-28 12:53 +0000
    Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays ram@zedat.fu-berlin.de (Stefan Ram) - 2025-12-28 14:13 +0000
      Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays ram@zedat.fu-berlin.de (Stefan Ram) - 2025-12-28 14:29 +0000
        Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays ram@zedat.fu-berlin.de (Stefan Ram) - 2025-12-28 14:41 +0000
          Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays ram@zedat.fu-berlin.de (Stefan Ram) - 2025-12-28 14:45 +0000
            Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays ram@zedat.fu-berlin.de (Stefan Ram) - 2025-12-28 23:22 +0000
        Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-28 15:53 +0100
    Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-28 15:47 +0100
      Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Andy Walker <anw@cuboid.co.uk> - 2025-12-30 16:29 +0000
        Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-01-01 12:21 +0100
          Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays David Brown <david.brown@hesbynett.no> - 2026-01-01 17:18 +0100
  Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays bart <bc@freeuk.com> - 2025-12-28 15:32 +0000
    Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-28 23:48 +0100
    Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-28 22:54 +0000
      Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays bart <bc@freeuk.com> - 2025-12-28 23:07 +0000
        Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-12-28 23:29 +0000
  Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays antispam@fricas.org (Waldek Hebisch) - 2025-12-28 21:43 +0000
    Re: Algol 68 (or generally) - arbitrarily nested arrays of arrays Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-12-28 23:50 +0100

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