REPL checkpoint

src/prolog/ast/logic/Clause.kt

@@ -18,7 +18,7 @@ import prolog.logic.unifyLazy
  * @see [prolog.ast.terms.Variable]
  * @see [Predicate]
  */
-abstract class Clause(private val head: Head, private val body: Body) : Resolvent {
+abstract class Clause(val head: Head, val body: Body) : Resolvent {
     val functor: Functor = head.functor
 
     override fun solve (goal: Goal, subs: Substitutions): Answers = sequence {

src/prolog/ast/logic/Predicate.kt

@@ -39,6 +39,11 @@ class Predicate : Resolvent {
      */
     fun add(clause: Clause) {
         require(clause.functor == functor) { "Clause functor does not match predicate functor" }
+
+        if (Debug.on) {
+            println("Adding clause $clause to predicate $functor")
+        }
+
         clauses.add(clause)
     }