tdpeuter/2025LogProg-project-GhentProlog
tdpeuter/2025LogProg-project-GhentProlog
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fix: Evaluation

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This commit is contained in:
Tibo De Peuter 2025-04-06 17:29:23 +02:00
parent d702b9b081
commit 1acd1cfb67
Signed by: tdpeuter
GPG key ID: 38297DE43F75FFE2
17 changed files with 189 additions and 120 deletions
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36
src/prolog/components/expressions/Clause.kt
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@ -1,6 +1,8 @@
package prolog.components.expressions
import prolog.Substitution
import prolog.Substituted
import prolog.builtins.True
import prolog.builtins.equivalent
import prolog.components.Resolvent
import prolog.components.terms.*
import prolog.unifyLazy
@ -13,31 +15,29 @@ import prolog.unifyLazy
* @see [prolog.components.terms.Variable]
* @see [Predicate]
*/
abstract class Clause(private val head: Head, private val body: Body? = null) : Resolvent {
abstract class Clause(private val head: Head, private val body: Body) : Resolvent {
val functor: Functor = head.functor
override fun solve(goal: Goal): Sequence<Substitution> = sequence {
if (body == null) {
// If the clause is a fact, unify the goal with the head, and return the substitutions.
// Do this in a lazy way.
yieldAll(unifyLazy(goal, head))
} else {
// If the clause is a rule, unify the goal with the head and then try to prove the body.
// Only if the body can be proven, the substitutions should be returned.
// Do this in a lazy way.
unifyLazy(goal, head).forEach { subs ->
// If the body can be proven, yield the (combined) substitutions
body.prove().forEach { bodySubs ->
yield(subs + bodySubs)
}
override fun solve(goal: Goal, subs: Substituted): Sequence<Substituted> = sequence {
// If the clause is a rule, unify the goal with the head and then try to prove the body.
// Only if the body can be proven, the substitutions should be returned.
// Do this in a lazy way.
unifyLazy(goal, head, subs).forEach { newHeadSubs ->
// If the body can be proven, yield the (combined) substitutions
body.prove(subs + newHeadSubs).forEach { newBodySubs ->
yield(newHeadSubs + newBodySubs)
// Unbind the newly bound variables, so they can be reused.
newBodySubs.keys.forEach { it.unbind() }
}
// Unbind the newly bound variables, so they can be reused.
newHeadSubs.keys.forEach { it.unbind() }
}
}
override fun toString(): String {
return when {
body == null -> head.toString()
else -> "$head :- $body"
body == True() -> head.toString()
else -> "$head :- $body"
}
}
}