tdpeuter/2025LogProg-project-GhentProlog
tdpeuter/2025LogProg-project-GhentProlog
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Cleanup 1

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This commit is contained in:
Tibo De Peuter 2025-05-09 14:43:20 +02:00
parent 026218ddbd
commit 2089e20da5
Signed by: tdpeuter
GPG key ID: 38297DE43F75FFE2
4 changed files with 88 additions and 97 deletions
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59
src/prolog/builtins/delimitedContinuationsOperators.kt
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@ -4,52 +4,54 @@ import prolog.Answers
import prolog.Substitutions
import prolog.ast.arithmetic.Integer
import prolog.ast.terms.Atom
import prolog.ast.terms.CompoundTerm
import prolog.ast.terms.Goal
import prolog.ast.terms.Structure
import prolog.ast.terms.Term
import prolog.flags.AppliedShift
import prolog.logic.applySubstitution
import prolog.logic.unifyLazy
class Reset(private val goal: Goal, private val term1: Term, private val cont: Term) :
Structure(Atom("reset"), listOf(goal, term1, cont)) {
/**
* These classes provide support for delimited continuations in Prolog.
* More specifically, they implement the reset/3 and shift/1 operators.
*
* See also [SWI-Prolog 4.9 Delimited Continuations](https://www.swi-prolog.org/pldoc/man?section=delcont)
*/
/**
* Call [Goal]. If Goal calls [Shift], and the arguments of Shift can be unified with Ball, Shift causes Reset to
* return, unifying Cont with a Goal that represents the continuation after shift.
*/
class Reset(private val goal: Goal, private val ball: Term, private val cont: Term) :
Structure(Atom("reset"), listOf(goal, ball, cont)) {
override fun satisfy(subs: Substitutions): Answers = sequence {
goal.satisfy(subs).forEach { goalResult ->
goalResult.fold(
// If Goal succeeds, then reset/3 also succeeds and binds Cont and Term1 to 0.
onSuccess = { goalSubs ->
// Unify Cont with 0
unifyLazy(cont, Integer(0), goalSubs).forEach { contResult ->
contResult.map { contSubs ->
yield(Result.success(goalSubs + contSubs))
// // Unify Term1 with 0
// unifyLazy(term1, Integer(0), goalSubs + contSubs).forEach { termResult ->
// termResult.map { termSubs ->
// yield(Result.success(goalSubs + termSubs + contSubs))
// }
// }
}
}
// TODO
// val conjunction = Conjunction(Unify(term1, Integer(0)), Unify(cont, Integer(0)))
// yieldAll(conjunction.satisfy(goalSubs))
},
onFailure = { failure ->
// If at some point Goal calls shift(Term2), then its further execution is suspended.
// Reset/3 succeeds immediately, binding Term1 to Term2 and Cont to the remainder of Goal.
// If Goal fails, then reset also fails.
// yield(Result.failure(failure))
// Unify Term1 with the ball
if (failure is AppliedShift) {
require(failure.cont != null) { "Shift must have a continuation" }
val newSubs: Substitutions = mapOf(
term1 to failure.ball,
cont to failure.cont
)
yield(Result.success(failure.subs + newSubs))
// Reset/3 succeeds immediately, binding Term1 to Term2 and Cont to the remainder of Goal.
val shiftSubs = failure.subs
val appliedBall = applySubstitution(failure.ball, shiftSubs)
val appliedCont = applySubstitution(failure.cont, shiftSubs)
Conjunction(Unify(ball, appliedBall), Unify(appliedCont, cont))
.satisfy(shiftSubs)
.forEach { conResult ->
conResult.map { conSubs ->
yield(Result.success(shiftSubs + conSubs))
}
}
} else {
// If Goal fails, then reset also fails.
yield(Result.failure(failure))
}
}
@ -62,5 +64,12 @@ class Reset(private val goal: Goal, private val term1: Term, private val cont: T
* Variables that have been bound during the procedure called by reset/3 stay bound after a shift/1:
*/
class Shift(private val ball: Term) : Structure(Atom("shift"), listOf(ball)) {
override fun satisfy(subs: Substitutions): Answers = sequenceOf(Result.failure(AppliedShift(subs, ball)))
override fun satisfy(subs: Substitutions): Answers = sequence {
val shift = AppliedShift(
subs = subs,
ball = ball,
cont = null
)
yield(Result.failure(shift))
}
}