I’m thinking about how to save/load game state in SWI-Prolog. Here is the code skeleton of my game: main.pl :- dynamic script_iterator/2. init_iterator(Goal, Iterator) :- reset(Goal,YE,Cont), ( Cont == 0 -> Iterator = done ; YE = yield(Element) -> Iterator = next(Element, Cont) …

[image] jan: These days you can do such things using virtual machines. Sounds a bit like an overkill. As much as it is overkill it is practical, works and often used as a starting or stop gap measure but once in place and working tends to be left as is. I asked a related question concerning …

[image] jan: A continuation may be enough, but note that it doesn’t capture the entire state. Notably choice points are not part of it. I think so too. Other game data are all first-order (no closures, low-level pointers, etc), they can be serialized easily. [image] jan: You could work a…

[image] chansey97: Do you mean to modify the delimited continuations’ source code? This is a bit of a challenge for me :smiling_face: (this may require more WAM knowledge?). No. The continuation is just a Prolog term. The only problem is that it contains references to clauses that are in th…

[image] jan: Or are you also going to implement the whole continuation stuff in the meta interpreter? Yes, that is what I mean. Just give the meta interpreter an additional argument for continuations (a stack of goals), see Schrijvers et al., 2013 ( preprint PDF ) section 3 for details.

[image] jan: Now <clause>(0x55e67cad9680), is a reference to the t2/0 clause. You can figure that out using nth_clause/3 or clause_property/2 . So, you turn that into e.g. '$CLAUSE'(t20, 1) to indicate the clause. Then you have a term you can save. Now at restore you find the clause reference and…

I just used compound_name_arguments/3 to compose/decompose continuations: ?- nth_clause(t2, 1, Reference), compound_name_arguments(ContInternal, '$cont$', [[], Reference, 9 | []]), Cont = call_continuation([ContInternal]), call(Cont). b Reference = <clause>(0000000000354290), ContInternal = $con…

[image] chansey97: Yes, that is what I mean. Just give the meta interpreter an additional argument for continuations (a stack of goals), see Schrijvers et al., 2013 ( preprint PDF ) section 3 for details. You’d have to try, but I fear it is way too slow. I don’t recall all the details, but m…

Thanks. Disturb you again, could you explain a little further (it is not related to the topic though): It knows the term created by shift/1 has no internal references, while the one you have does. What do you mean by “the term created by shift/1 has no internal references” ? P.s. I also success…

A Prolog term is one of the usual things (atom, int, …, compound, var). Internally, there is one more thing: references. You can see the need for this best after running A = B. Now A and B become the same variable. This is done by making A a reference to B. Binding the combined variable wi…

[image] jan: there is one more thing: references Thanks. Is the reference you mentioned related to e.g. <clause>(0000000000354290)? My understanding is that the term created by shift/1 includes an actual reference, i.e. <clause>(0000000000354290), instead of a logic variable Reference, but …

Is there a way to serialize continuation or program execution state?

Help!

EricGT June 23, 2022, 2:20pm 15

Is a reference really a blob? e.g. Blob types

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Is there a way to serialize continuation or program execution state?

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