Checkpoint

src/prolog/components/terms/Goal.kt

@@ -1,16 +1,17 @@
 package prolog.components.terms
 
 import prolog.components.Program
+import prolog.components.Provable
 
 /**
- * Question stated to the Prolog engine.
+ * Ask the Prolog engine.
  *
- * A goal is either an [atom][prolog.components.terms.Atom] or a [compound term][prolog.components.terms.CompoundTerm].
+ * A goal is either an [Atom] or a [CompoundTerm].
  * A goal either [succeeds][prolog.builtins.True], in which case the variables in the compound terms have a binding,
  * or it fails if Prolog fails to prove it.
  */
-abstract class Goal : Head() {
-    fun prove(): Boolean {
-        return Program.query(this)
-    }
+abstract class Goal : Term, Provable {
+    abstract val functor: Functor
+
+    override fun prove(): Boolean = Program.query(this)
 }