From 91e5f03121e18ea86c3c1c44c69ff7eb433e2478 Mon Sep 17 00:00:00 2001
From: Vitor Santos Costa <vsc@dcc.fc.up.pt>
Date: Tue, 10 May 2016 09:25:52 +0100
Subject: [PATCH] Aleph uses system_predicate/2

---
 pl/preds.yap | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/pl/preds.yap b/pl/preds.yap
index 0850c16cd..626d760d1 100644
--- a/pl/preds.yap
+++ b/pl/preds.yap
@@ -652,6 +652,26 @@ system_predicate(P0) :-
                 system_predicate(P0))
     ).
 
+/** @pred  system_predicate( ?A, ?P )
+
+  Succeeds if _A_ is the name of the system predicate _P_. It can be used to test and to enumerate all system predicates.
+
+  YAP also supports the ISO standard built-in system_predicate/1, that
+  provides similar functionality and is compatible with most other Prolog
+  systems.
+  
+*/
+system_predicate(A, P0) :-
+	'$yap_strip_module'(P0, M, P),
+    (
+      nonvar(P)
+    ->
+     '$current_predicate'(A, M, P, system),
+     '$is_system_predicate'( P,  M)
+    ;
+     '$current_predicate'(A, M, P, system)
+    ).
+
 
 /**
   @pred  current_predicate( _F_) is iso