[m-users.] Inferring over dynamic data

[Stepp, Nigel D]

Hello all,

I am very interested in switching a prolog codebase to mercury, but parts of the codebase follow a pattern like:

- receive a list of facts
- assert facts
- do inference using static predicates
- retract facts

I'm well aware that mercury does not support assert/retract, and I read a very old thread that was an interesting discussion (https://lists.mercurylang.org/archives/users/2006-January/003388.html).

The issues in that thread were complicated by dynamic loading of modules, however. I am only interested in the list-of-facts part.

What is a good way (or I guess any way) of transforming a pattern like the above to something in mercury?

A tiny example is something like this:

:- dynamic factA/1.
:- dynamic factB/1.

p(A,B) :- factA(A), factB(B).

callP(Facts, ABs) :-
    assertFacts(Facts),
    findall(X, p(X,X), Xs),
    retractFacts(Facts).

Where assertFacts/1 and retractFacts/1 do the obvious-sounding things. Facts might be something like [factA(x),factB(y),factA(y)], with answer Xs=[y].

--
Nigel Stepp, Ph.D. Information and System Sciences Lab HRL Laboratories, LLC.
3011 Malibu Canyon Road, Malibu, CA 90265 Office: +1 310-317-5267

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