/**
 * Comparison and Unification of Terms
 *
 * [SWI Prolog Documentation](https://www.swi-prolog.org/pldoc/man?section=compare)
 */
package prolog.builtins

import prolog.ast.terms.Atom
import prolog.ast.terms.Operator
import prolog.ast.terms.Term
import prolog.logic.Substituted
import prolog.logic.applySubstitution
import prolog.logic.equivalent

class Equivalent(private val term1: Term, private val term2: Term) : Operator(Atom("=="), term1, term2) {
    override fun prove(subs: Substituted): Sequence<Substituted> = sequence {
        val t1 = applySubstitution(term1, subs)
        val t2 = applySubstitution(term2, subs)

        if (equivalent(t1, t2)) {
            yield(emptyMap())
        }
    }
}