Checkpoint

src/prolog/components/Operator.kt

@@ -0,0 +1,19 @@
+package prolog.components
+
+import prolog.components.terms.Argument
+import prolog.components.terms.Atom
+
+open class Operator(
+    val symbol: Atom,
+    val leftOperand: Operand? = null,
+    val rightOperand: Operand
+) {
+    override fun toString(): String {
+        return when (leftOperand) {
+            null -> "${symbol.name} $rightOperand"
+            else -> "$leftOperand ${symbol.name} $rightOperand"
+        }
+    }
+}
+
+typealias Operand = Argument