From Newsgroup: comp.lang.prolog

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.
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.prolog

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.

--- Synchronet 3.21a-Linux NewsLink 1.2