Given a list of goals representing a conjunction, I would like it to
fail as soon as any goal fails, but I would like *not* to cut on the
search space otherwise.
Here is my actual test case, only considering ground goals (otherwise
too many ways to play with it that seem immaterial to the problem):
```
red(1).
red(1).
and([]) :- !. % with Xs ground!
and([H:B|Xs]) :-
red(B), writeln(H:B),
and(Xs).
/*
Actual:
-------
?- and([x:1,y:1]), fail. % ok: full search space
x:1
y:1
y:1
x:1
y:1
y:1
false.
?- and([x:1,y:0]), fail. % KO: could fail earlier
x:1
x:1
false.
Expected:
---------
?- and([x:1,y:0]), fail. % ok: fails early!
x:1
false.
*/
```
Am I just missing something obvious? I am trying with "ancestral cuts" (SWI-Prolog has these), but I have not yet found a solution.
-Julio
First create a conjunction:
A1,...,An
Wrap each goal Aj into a soft cut:
(Aj *-> true; !).
The cut will abort all previous goals.
Julio Di Egidio schrieb:
Given a list of goals representing a conjunction, I would like it to
fail as soon as any goal fails, but I would like *not* to cut on the
search space otherwise.
Here is my actual test case, only considering ground goals (otherwise
too many ways to play with it that seem immaterial to the problem):
```
red(1).
red(1).
and([]) :- !. % with Xs ground!
and([H:B|Xs]) :-
red(B), writeln(H:B),
and(Xs).
/*
Actual:
-------
?- and([x:1,y:1]), fail. % ok: full search space
x:1
y:1
y:1
x:1
y:1
y:1
false.
?- and([x:1,y:0]), fail. % KO: could fail earlier
x:1
x:1
false.
Expected:
---------
?- and([x:1,y:0]), fail. % ok: fails early!
x:1
false.
*/
```
Am I just missing something obvious? I am trying with "ancestral
cuts" (SWI-Prolog has these), but I have not yet found a solution.
-Julio
Julio Di Egidio schrieb:
Given a list of goals representing a conjunction, I would like it to
fail as soon as any goal fails, but I would like *not* to cut on the
search space otherwise.
Here is my actual test case, only considering ground goals (otherwise
too many ways to play with it that seem immaterial to the problem):
First create a conjunction:
A1,...,An
Wrap each goal Aj into a soft cut:
(Aj *-> true; !).
The cut will abort all previous goals.
true; prolog_cut_to(ChF),
On 09/12/2024 15:14, Mild Shock wrote:
Julio Di Egidio schrieb:
Given a list of goals representing a conjunction, I would like it to
fail as soon as any goal fails, but I would like *not* to cut on the
search space otherwise.
Here is my actual test case, only considering ground goals (otherwise
too many ways to play with it that seem immaterial to the problem):
First create a conjunction:
A1,...,An
Wrap each goal Aj into a soft cut:
(Aj *-> true; !).
The cut will abort all previous goals.
Indeed soft-cuts do it, thank you very much!
Though with this scheme: `(Aj *-> true; !, fail)`.
I have also managed to abstract the recursive scheme away to a meta-predicate, by combining soft with ancestral cuts. But I am not
sure how good it is, especially since term rewriting also can do the
trick and quite more simply so...
On 09/12/2024 16:47, Julio Di Egidio wrote:
On 09/12/2024 15:14, Mild Shock wrote:
Julio Di Egidio schrieb:
Given a list of goals representing a conjunction, I would like it to
fail as soon as any goal fails, but I would like *not* to cut on the
search space otherwise.
Here is my actual test case, only considering ground goals
(otherwise too many ways to play with it that seem immaterial to the
problem):
First create a conjunction:
A1,...,An
Wrap each goal Aj into a soft cut:
(Aj *-> true; !).
The cut will abort all previous goals.
Indeed soft-cuts do it, thank you very much!
Though with this scheme: `(Aj *-> true; !, fail)`.
I have also managed to abstract the recursive scheme away to a
meta-predicate, by combining soft with ancestral cuts. But I am not
sure how good it is, especially since term rewriting also can do the
trick and quite more simply so...
Actually, this one works (no need for a soft cut in `scut`), and it at
least starts making sense:
```
scut(G, ChF) :-
( call(G, ChF), !
; prolog_cut_to(ChF),
fail
).
```
term rewriting also can do the
trick and quite more simply so...
On 09/12/2024 16:47, Julio Di Egidio wrote:
term rewriting also can do the trick and quite more simply so...
I take that back, too. I cannot find a way out of ancestral cuts in the recursive case. Some term rewriting could rather be useful *in
conjunction* with that `scut`, since that as written messes up with the
stack trace... Anyway, that's another story.
-Julio
7,d->8] applied, by this little Declarative (What) code:
A Timeless Confluence
By the banks of thought where rivers entwine,
Emmy Noether walked through a realm divine.
Her algebra wove the fabric of laws,
While echoes of logic gave her pause.
There stood Michael Kohlhase, a seeker of form,
Shaping machines through a digital storm.
“Madame,” he began, with respect in his tone,
“Your ideals still guide what we’ve come to own.
Noetherian rings, your towering art,
Anchor the systems of which I’m a part.
In rewriting paths, your truth remains,
Simplifying chaos, dissolving chains.”
Emmy smiled, her brilliance aglow,
"Through eras, the seeds of knowledge grow.
Yet tell me, dear traveler, in your machine’s frame,
Do ideals endure, or fade like a flame?”
Michael replied, “Your vision holds,
In logic’s rewrite, it gently unfolds.
Past meets the present where structures align,
A confluence of thought, eternal, divine.”
And so they stood, two eras combined,
Bound by the currents of the infinite mind.
https://en.m.wikipedia.org/wiki/Emmy_Noether
https://en.m.wikipedia.org/wiki/Michael_Kohlhase
Julio Di Egidio schrieb:
On 09/12/2024 16:47, Julio Di Egidio wrote:
term rewriting also can do the trick and quite more simply so...
I take that back, too. I cannot find a way out of ancestral cuts in
the recursive case. Some term rewriting could rather be useful *in
conjunction* with that `scut`, since that as written messes up with
the stack trace... Anyway, that's another story.
-Julio
Ok Confluence does indeed ring a bell. Lets show
Declarative (What) versus Procedural (How) in
@emiruz example, as a rewriting problem.
Lets permit that we write the input as [1,2,a,4,5,
b,c,8,9,10] and then have rewriting rules [a->3,b->6,
7,d->8] applied, by this little Declarative (What) code:
step(L,R) :- nth1(K,L,a,H), nth1(K,R,3,H).
step(L,R) :- nth1(K,L,b,H), nth1(K,R,6,H).
step(L,R) :- nth1(K,L,c,H), nth1(K,R,7,H).
step(L,R) :- nth1(K,L,d,H), nth1(K,R,8,H).
find(L,L) :- \+ step(L,_).
find(L,R) :- step(L,H), find(H,R).
Each derivation is a Procedural (How) execution:
?- find([1,2,a,4,5,b,c,8,9,10],X).
X = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
X = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
X = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Etc..
Can we count the number of Hows to solve the What?
?- aggregate_all(count, find([1,2,a,4,5,b,c,8,9,10],X), C).
C = 6.
So there are 6 different Procedures that tell
us which steps to exactly use when, to solve the
Declaratively given problem which leaves open
when to use each step.
Mild Shock schrieb:
A Timeless Confluence
By the banks of thought where rivers entwine,
Emmy Noether walked through a realm divine.
Her algebra wove the fabric of laws,
While echoes of logic gave her pause.
There stood Michael Kohlhase, a seeker of form,
Shaping machines through a digital storm.
“Madame,” he began, with respect in his tone,
“Your ideals still guide what we’ve come to own.
Noetherian rings, your towering art,
Anchor the systems of which I’m a part.
In rewriting paths, your truth remains,
Simplifying chaos, dissolving chains.”
Emmy smiled, her brilliance aglow,
"Through eras, the seeds of knowledge grow.
Yet tell me, dear traveler, in your machine’s frame,
Do ideals endure, or fade like a flame?”
Michael replied, “Your vision holds,
In logic’s rewrite, it gently unfolds.
Past meets the present where structures align,
A confluence of thought, eternal, divine.”
And so they stood, two eras combined,
Bound by the currents of the infinite mind.
https://en.m.wikipedia.org/wiki/Emmy_Noether
https://en.m.wikipedia.org/wiki/Michael_Kohlhase
Julio Di Egidio schrieb:
On 09/12/2024 16:47, Julio Di Egidio wrote:
term rewriting also can do the trick and quite more simply so...
I take that back, too. I cannot find a way out of ancestral cuts in
the recursive case. Some term rewriting could rather be useful *in
conjunction* with that `scut`, since that as written messes up with
the stack trace... Anyway, that's another story.
-Julio
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