Re: Recursion, Yo

On 13.04.2024 02:13, Lawrence D'Oliveiro 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.

Pascal has pointers bound to the object (as opposed to C pointers).
It's similar in Algol 68 were you model your complex linked object
structures with "references" on the heap. (WRT Ada, I'm not deeply
familiar with it, so cannot tell.)

[...]
 

In Algol 68 everything is an expression. Statements are of type 'void'.
You have, to keep it most simple here, for example,
>
  PROC f = INT : 3.1415
>
  PROC p = VOID : SKIP
>
There's nothing "thrown away" (as in C).

 
Yes there is--it’s called “voiding”.

What do you mean - mind to elaborate with examples? (Then it will
be simpler for me to explain our probably different views.)

For the moment I just want to expand on the samples above (and
thereby fixing the INT/REAL typo)...

   PROC f = REAL : 3.1415;
   PROC p = VOID : SKIP;

   PROC n = VOID : 2.71828;
   PROC q = REAL : SKIP;

   REAL x = f;
   p;
   REAL y = n;
   q;
   REAL z = q;

This is *not* functioning Algol 68 code! - But maybe you can explain
where or how there's something "thrown away".

I suppose you have something in mind like C's   (void) f();   ?

Janis