Checkpoint

src/prolog/components/expressions/Operator.kt

@@ -0,0 +1,23 @@
+package prolog.components.expressions
+
+import prolog.components.Provable
+import prolog.components.terms.Atom
+import prolog.components.terms.CompoundTerm
+import prolog.components.terms.Goal
+
+typealias Operand = Goal
+
+abstract class Operator(
+    val symbol: Atom,
+    val leftOperand: Operand? = null,
+    val rightOperand: Operand
+) : CompoundTerm(symbol, listOfNotNull(leftOperand, rightOperand)), Provable {
+    abstract override fun prove(): Boolean
+
+    override fun toString(): String {
+        return when (leftOperand) {
+            null -> "${symbol.name} $rightOperand"
+            else -> "$leftOperand ${symbol.name} $rightOperand"
+        }
+    }
+}