IO Operators

src/prolog/ast/terms/Operator.kt

@@ -6,7 +6,7 @@ abstract class Operator(
     private val symbol: Atom,
     private val leftOperand: Operand? = null,
     private val rightOperand: Operand
-) : CompoundTerm(symbol, listOfNotNull(leftOperand, rightOperand)) {
+) : CompoundTerm(symbol, listOfNotNull(leftOperand, rightOperand)), Term {
     override fun toString(): String {
         return when (leftOperand) {
             null -> "${symbol.name} $rightOperand"

src/prolog/ast/terms/Structure.kt

@@ -22,4 +22,15 @@ open class Structure(val name: Atom, var arguments: List<Argument>) : Goal(), He
             else -> "${name.name}(${arguments.joinToString(", ")})"
         }
     }
-}
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is Structure) return false
+        if (functor != other.functor) return false
+        return arguments.zip(other.arguments).all { (a, b) -> a == b }
+    }
+
+    override fun hashCode(): Int {
+        return javaClass.hashCode()
+    }
+}