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Can Ulrich Neumerkel or Markus Triska fix that? (Was: Wikipedia is clueless about cyclic terms)

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Hi,

In case Scryer Prolog tries the this here:

Wikipedia entry for Scryer Prolog
https://github.com/mthom/scryer-prolog/discussions/3074

And considers these articles:

https://en.wikipedia.org/wiki/Occurs_check
https://en.wikipedia.org/wiki/Comparison_of_Prolog_implementations
https://en.wikipedia.org/wiki/Prolog

They might probably draw the same conclusion,
namely that there are some gaps or that
certain articles are a little dusty.

Again I think covering Scyer Prolog is
important for two reasons:

- Its not the C spaghetti code mess like SWI-Prolog
   which uses goto and macros to no end.

- It is not a Heap/Stack Prolog system, it even has
   no GC, still the Heap plays a role in the cyclic term algorithms

The later point is amazing, and its interesting to
see how Scryer Prolog fares performance wise.
They simply use Vec<> in some places to eliminate

the use of native stack. Is this "bold" , or only
the best thing one would anyway do inside a programming
language like Rust, that might have tread affine fast

malloc() and free(). So that bothering with placing
things on artificially created stack is not needed.
Just go with the ADT (Abstract Data Type) Vec<>.

Bye

Mild Shock schrieb:
> Hi,
> 
> They write nonsense like:
> 
>> Modern implementations, based on Colmerauer's Prolog II, [4] [5] [6] 
> [7] use rational tree unification to avoid looping.
> However it is difficult to keep the complexity time
> linear in the presence of cyclic terms. Examples
> where Colmerauers algorithm becomes quadratic [8] can
> be readily constructed, but refinement proposals exist.
> https://en.wikipedia.org/wiki/Occurs_check
> 
> Nobody uses Colmerauers algorithm , in the sense of equation
> saturation. I didn't find a single Prolog system that would use
> it. Its not clear what Colmerauers algorithm should be? The
> paper by Alberto Martelli and Gianfranco Rossi
> 
> does also not reflect modern implementations. Modern
> implementations are simply variantes of Hopecroft & Karp (1971).
> Which has linear complexity of (==)/2 cases. Non (==)/2
> cases of (=)/2 can anyway get exponential, right? (**)
> 
> At lest checking modern implementation I find nowhere,
> Martelli & Rossi used. Its all Hopecroft & Karp (1971)
> labeled as Folklore by Bart Demoen. But easy to recognize
> as Union Find data structure.
> 
> Bye
> 
> (**) Maybe I should construct such an example.
> I am not anymore sure about that, since Union Find
> detects structure sharing. But I doubt the bad cases
> are only quadratic, at least there are some easy
> 
> example of exponential behaviour of unifiction
> already published. But I don't remember what kind
> of unification they assume. So have to double check.
> 
> Mild Shock schrieb:
>> Hi,
>>
>> The diagram figure 2 here:
>>
>> Fifty Years of Prolog and Beyond (TPLP 2022)
>> KÖRNER P, LEUSCHEL M, BARBOSA J, et al. Fifty Years of Prolog and 
>> Beyond. Theory and Practice of Logic Programming.
>> 2022;22(6):776-858. doi:10.1017/S1471068422000102
>>
>> And reproduced here:
>>
>> Comparison of Prolog implementations
>> The page has also missing Scryer Prolog, which
>> I think is an important Prolog system written in
>> Rust, because it also pays tribute to Prolog II.
>> https://en.wikipedia.org/wiki/Comparison_of_Prolog_implementations
>>
>> Is pretty much brainwashed nonsense. Most Prolog
>> systems, that have cyclic terms, are derived from
>> Prolog II.  Adopting a non-canonical rational tree
>>
>> term approach. This includes:
>>
>> - SICStus Prolog
>> - Ciao Prolog
>> - YAP Prolog
>> - SWI-Prolog
>> - Scryer Prolog
>> - Trealla Prolog
>> - Dogelog Player
>> - What else?
>>
>> SICStus Prolog is possibly the most advanced, (*)
>> it also supports asserts and copying, whereas I found
>> not all Prolog systems listed above can even
>>
>> copy cyclic terms, despite they can unify them.
>> Basically the philogeny of Prolog systems is
>> not some "single inheritance" tree. Cyclic terms
>>
>> algorithm have nice side effect that they might
>> speed up acyclic term arguments as well. But
>> cyclic terms is one of the topics that is very
>>
>> badily  covered, for some individuals difficult (**)
>> to understand and sometimes even completely ignored.
>>
>> Bye
>>
>> (*)
>> SICStus Prolog unifies, compares (see ref-lte-cte),
>> asserts, and copies cyclic terms without looping.
>> The write_term/[2,3] built-in predicate can
>> optionally handle cyclic terms.
>> https://sicstus.sics.se/sicstus/docs/4.6.0/html/sicstus/ref_002dsem_002docc.html 
>>
>>
>> (**)
>> Because of the infinite looping, their brains might
>> also get into infinite loops. Even fuzzy testing does
>> not help anymore breaking these loops.
> 

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Cyclic terms are missing from "Fifty Years of Prolog and Beyond (TPLP 2022)" Mild Shock <janburse@fastmail.fm> - 2025-09-22 14:54 +0200
  Wikipedia is clueless about cyclic terms (Was: Cyclic terms are missing from "Fifty Years of Prolog and Beyond (TPLP 2022)") Mild Shock <janburse@fastmail.fm> - 2025-09-22 15:05 +0200
  Wikipedia is clueless about cyclic terms (Was: Cyclic terms are missing from "Fifty Years of Prolog and Beyond (TPLP 2022)") Mild Shock <janburse@fastmail.fm> - 2025-09-22 15:07 +0200
    Can Ulrich Neumerkel or Markus Triska fix that? (Was: Wikipedia is clueless about cyclic terms) Mild Shock <janburse@fastmail.fm> - 2025-09-22 15:14 +0200
      Quadratic Bound true, and Exponential false (Was: Can Ulrich Neumerkel or Markus Triska fix that?) Mild Shock <janburse@fastmail.fm> - 2025-09-22 15:36 +0200
        Jaxon Jaffar might be the inventor of Union Find Unification (Was: Quadratic Bound true, and Exponential false) Mild Shock <janburse@fastmail.fm> - 2025-09-22 23:01 +0200
          Conclusion quasi-linear time and linear space (Was: Jaxon Jaffar might be the inventor of Union Find Unification) Mild Shock <janburse@fastmail.fm> - 2025-09-22 23:34 +0200

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