From cd586aab8c69376b680992c40d172af4005f8565 Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Wed, 15 Mar 2023 19:56:02 +0100
Subject: [PATCH 1/2] show remaining queue/2 attributes as residual goals

This lets us verify that all attributes are correctly removed earlier.
---
 src/lib/clpz.pl | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/src/lib/clpz.pl b/src/lib/clpz.pl
index fd5d9d18..afc6f8cd 100644
--- a/src/lib/clpz.pl
+++ b/src/lib/clpz.pl
@@ -7683,10 +7683,6 @@ intervals_to_drep([A0-B0|Rest], Drep0, Drep) :-
         ),
         intervals_to_drep(Rest, Drep0 \/ D1, Drep).
 
-attribute_goals(X) -->
-        { get_atts(X, queue(_,_)) },
-        !,
-        { put_atts(X, -queue(_,_)) }.
 attribute_goals(X) -->
         % { get_attr(X, clpz, Attr), format("A: ~w\n", [Attr]) },
         { get_attr(X, clpz, clpz_attr(_,_,_,Dom,fd_props(Gs,Bs,Os),_)),

From 01285f12c3ddca4666f5b70163fe3d1ec31a38aa Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Wed, 15 Mar 2023 21:17:06 +0100
Subject: [PATCH 2/2] remove no longer needed queue attributes after
 propagation

---
 src/lib/clpz.pl | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/lib/clpz.pl b/src/lib/clpz.pl
index afc6f8cd..acf4738f 100644
--- a/src/lib/clpz.pl
+++ b/src/lib/clpz.pl
@@ -3943,10 +3943,7 @@ put_terminating(X, Dom, Ps) -->
             )
         ).
 
-new_queue(queue(Goals,Fast,Slow,_Aux)) :-
-        put_atts(Goals, +queue([],_)),
-        put_atts(Fast, +queue([],_)),
-        put_atts(Slow, +queue([],_)).
+new_queue(queue(_Goals,_Fast,_Slow,_Aux)).
 
 queue_goal(Goal) --> insert_queue(Goal, 1).
 queue_fast(Prop) --> insert_queue(Prop, 2).
@@ -3955,11 +3952,10 @@ queue_slow(Prop) --> insert_queue(Prop, 3).
 insert_queue(Element, Which) -->
         state(Queue),
         { arg(Which, Queue, Arg),
-          get_atts(Arg, queue(Head0,Tail0)),
-          (   Head0 == [] ->
-              Head = [Element|Tail]
-          ;   Head = Head0,
+          (   get_atts(Arg, queue(Head0,Tail0)) ->
+              Head = Head0,
               Tail0 = [Element|Tail]
+          ;   Head = [Element|Tail]
           ),
           put_atts(Arg, +queue(Head,Tail)) }.
 
@@ -4187,11 +4183,15 @@ do_queue -->
         ;   true
         ).
 
+:- meta_predicate(ignore(0)).
+
+ignore(Goal) :- ( Goal -> true ; true ).
+
 print_queue -->
         state(queue(Goal,Fast,Slow,_)),
-        { get_atts(Goal, +queue(GHs,_)),
-          get_atts(Fast, +queue(FHs,_)),
-          get_atts(Slow, +queue(SHs,_)),
+        { ignore(get_atts(Goal, +queue(GHs,_))),
+          ignore(get_atts(Fast, +queue(FHs,_))),
+          ignore(get_atts(Slow, +queue(SHs,_))),
           format("Current queue:~n   goal: ~q~n   fast: ~q~n   slow: ~q~n~n", [GHs,FHs,SHs]) }.
 
 
@@ -4208,7 +4208,7 @@ queue_get_arg_(Queue, Which, Element) :-
         arg(Which, Queue, Arg),
         get_atts(Arg, +queue([Element|Elements],Tail)),
         (   var(Elements) ->
-            put_atts(Arg, +queue([],_))
+            put_atts(Arg, -queue(_,_))
         ;   put_atts(Arg, +queue(Elements,Tail))
         ).