commonMain.it.unibo.tuprolog.solve.SolverStrategies.kt Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of solve-streams-jvm Show documentation

Experimental, functional-programming-based implementation of Prolog's SLDNF resolution principle

There is a newer version: 1.0.4

package it.unibo.tuprolog.solve

import it.unibo.tuprolog.core.Clause
import it.unibo.tuprolog.core.Term

/**
 * Interface representing internal strategies used by the [Solver]
 *
 * @author Enrico
 */
interface SolverStrategies {

    /** Selects the predication to be solved first, from provided sequence */
    fun  predicationChoiceStrategy(predicationSequence: Sequence
, context: ExecutionContext): P

    /** Selects the clause to be expanded in place of unifying predication, from provided sequence */
    fun  clauseChoiceStrategy(unifiableClauses: Sequence, context: ExecutionContext): C

    /** Determines "when and what" is considered successfully demonstrated, during solution process */
    fun successCheckStrategy(term: Term, context: ExecutionContext): Boolean

    companion object {

        /** Returns a strategy object containing the key solution strategies used by a Standard Prolog solver */
        val prologStandard = object : SolverStrategies {

            /** The default implementation, following the Prolog Standard, selects the first predication found */
            override fun 
 predicationChoiceStrategy(
                predicationSequence: Sequence,
                context: ExecutionContext
            ): P = predicationSequence.first()

            /** The default implementation, following the Prolog Standard, selects the first clause found */
            override fun  clauseChoiceStrategy(
                unifiableClauses: Sequence,
                context: ExecutionContext
            ): C = unifiableClauses.first()

            override fun successCheckStrategy(term: Term, context: ExecutionContext): Boolean = term.isTrue
        }
    }
}