From 834e3ed5d06fe7a9a1cf4cb85fe598253db2e1f7 Mon Sep 17 00:00:00 2001
From: Vitor Santos Costa <vsc@dcc.fc.up.pt>
Date: Mon, 19 Jul 2010 14:38:17 +0100
Subject: [PATCH] make arg/3 compatible with SWI for atomic argument (fail
 silently).

---
 C/absmi.c | 38 +++++++++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 13 deletions(-)

diff --git a/C/absmi.c b/C/absmi.c
index 33ce51927..adb091505 100755
--- a/C/absmi.c
+++ b/C/absmi.c
@@ -7553,7 +7553,7 @@ Yap_absmi(int inp)
 	FAIL();
       }
       /* in case we call Execute */
-      YREG = ENV;
+      YREG = YENV = ENV;
       JMPNext();
       ENDBOp();
 
@@ -12155,9 +12155,12 @@ Yap_absmi(int inp)
 	ENDP(pt0);
       }
       else {
-	saveregs();
-	Yap_Error(TYPE_ERROR_COMPOUND, d1, "arg 2 of arg/3");
-	setregs();
+	/*
+	  don't complain here for SWI Prolog compatibility 
+	  saveregs();
+	  Yap_Error(TYPE_ERROR_COMPOUND, d1, "arg 2 of arg/3");
+	  setregs();
+	*/
 	FAIL();
       }
 
@@ -12243,9 +12246,12 @@ Yap_absmi(int inp)
 	ENDP(pt0);
       }
       else {
-	saveregs();
-	Yap_Error(TYPE_ERROR_COMPOUND, d1, "arg 2 of arg/3");
-	setregs();
+	/*
+	  keep SWI Prolog compatibility, just fail on trying to obtain an argument of a compound term.
+	  saveregs();
+	  Yap_Error(TYPE_ERROR_COMPOUND, d1, "arg 2 of arg/3");
+	  setregs();
+	*/
 	FAIL();
       }
 
@@ -12350,9 +12356,12 @@ Yap_absmi(int inp)
 	ENDP(pt0);
       }
       else {
-	saveregs();
-	Yap_Error(TYPE_ERROR_COMPOUND, d1, "arg 2 of arg/3");
-	setregs();
+	/*
+	  don't complain here for SWI Prolog compatibility 
+	  saveregs();
+	  Yap_Error(TYPE_ERROR_COMPOUND, d1, "arg 2 of arg/3");
+	  setregs();
+	*/
 	FAIL();
       }
 
@@ -12453,9 +12462,12 @@ Yap_absmi(int inp)
 	ENDP(pt0);
       }
       else {
-	saveregs();
-	Yap_Error(TYPE_ERROR_COMPOUND, d1, "arg 2 of arg/3");
-	setregs();
+	/*
+	  don't complain here for SWI Prolog compatibility 
+	  saveregs();
+	  Yap_Error(TYPE_ERROR_COMPOUND, d1, "arg 2 of arg/3");
+	  setregs();
+	*/
 	FAIL();
       }