refactor: Rework

src/prolog/builtins/unificationOperators.kt

@@ -0,0 +1,25 @@
+/**
+ * Comparison and Unification of Terms
+ *
+ * [SWI Prolog Documentation](https://www.swi-prolog.org/pldoc/man?section=compare)
+ */
+package prolog.builtins
+
+import prolog.Answers
+import prolog.Substitutions
+import prolog.ast.terms.Atom
+import prolog.ast.terms.Operator
+import prolog.ast.terms.Term
+import prolog.logic.applySubstitution
+import prolog.logic.equivalent
+
+class Equivalent(private val term1: Term, private val term2: Term) : Operator(Atom("=="), term1, term2) {
+    override fun satisfy(subs: Substitutions): Answers = sequence {
+        val t1 = applySubstitution(term1, subs)
+        val t2 = applySubstitution(term2, subs)
+
+        if (equivalent(t1, t2, subs)) {
+            yield(Result.success(emptyMap()))
+        }
+    }
+}