refactor: Herstructurering

src/prolog/ast/terms/Operator.kt

@@ -0,0 +1,21 @@
+package prolog.ast.terms
+
+import prolog.ast.logic.Provable
+import prolog.logic.Substituted
+
+abstract class Operator(
+    private val symbol: Atom,
+    val leftOperand: Operand? = null,
+    val rightOperand: Operand
+) : CompoundTerm(symbol, listOfNotNull(leftOperand, rightOperand)), Provable {
+    abstract override fun prove(subs: Substituted): Sequence<Substituted>
+
+    override fun toString(): String {
+        return when (leftOperand) {
+            null -> "${symbol.name} $rightOperand"
+            else -> "$leftOperand ${symbol.name} $rightOperand"
+        }
+    }
+}
+
+typealias Operand = Goal