feat: Cut

src/prolog/ast/logic/Predicate.kt

@@ -4,6 +4,7 @@ import prolog.Answers
 import prolog.Substitutions
 import prolog.ast.terms.Functor
 import prolog.ast.terms.Goal
+import prolog.exceptions.AppliedCut
 
 /**
  * Collection of [Clause]s with the same [Functor].
@@ -53,6 +54,23 @@ class Predicate : Resolvent {
         require(goal.functor == functor) { "Goal functor does not match predicate functor" }
         // Try to unify the goal with the clause
         // If the unification is successful, yield the substitutions
-        clauses.forEach { yieldAll(it.solve(goal, subs)) }
+        clauses.forEach { clause ->
+            clause.solve(goal, subs).forEach { clauseResult ->
+                clauseResult.fold(
+                    onSuccess = {
+                        yield(Result.success(it))
+                    },
+                    onFailure = {
+                        if (it is AppliedCut) {
+                            // If it's a cut, yield the result with the left substitutions
+                            yield(Result.failure(AppliedCut(it.subs)))
+                            return@sequence
+                        } else {
+                            yield(Result.failure(it))
+                        }
+                    }
+                )
+            }
+        }
     }
 }