Re: Recursion, Yo

On 14.04.2024 02:29, Michael S wrote:

On Sun, 14 Apr 2024 00:23:44 +0100
Ben Bacarisse <ben.usenet@bsb.me.uk> wrote:
 

Michael S <already5chosen@yahoo.com> writes:
>

On Sat, 13 Apr 2024 00:13:36 -0000 (UTC)
Lawrence D'Oliveiro <ldo@nz.invalid> wrote:
 

On Fri, 12 Apr 2024 14:35:47 +0200, Janis Papanagnou wrote:
 

It seems that's one of the fundamental differences between
(low-level) languages that want to provide such technical factors
explicit to the user and between languages that want to provide a
higher abstraction.
>
Algol 60, Pascal, Simula 67 and Algol 60, Eiffel, etc. all took
that approach.   

>
Pascal had explicit pointers, though. Algol 68 and Ada did not. 

>
Of course, Ada has pointers. The are called access types.
https://en.wikibooks.org/wiki/Ada_Programming/Types/access
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I never learned Algol-68, but considering your reputation I'd want
to see confirmation from more reliable source. 

>
I suppose it all depends on what constitutes a pointer, but Algol 68
has pointers to this extent:
>
BEGIN
   INT i := 42;
   [3] INT a := (1, 2, 3);
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   REF INT p := i;   CO p is a "pointer" to i
CO REF INT(p) := 99; CO changes i via p
CO p := a[2];        CO p now points to the second element of array a
CO REF INT(p) := 99; CO change that element via p
CO
>
   print((i, a[1], a[2], a[3]))
END
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I'd call p a pointer.
>

 
Thank you.
It looks closer to C than to Pascal, i.e. pointer can point to any
object rather than just to dynamically allocated object.

>
The major difference is that they are closely bound to the type.
In that respect they are more like Pascal pointers. C pointers
open the can of issues with arithmetic on pointer values. You
don't find that in Pascal or Algol 68.