for review: new library predicate

[Thomas Charles CONWAY]

Hi

For whoever to review (trd? - you've already seen it once).

-- 
ZZ:wq!
^X^C
Thomas Conway               				      conway at cs.mu.oz.au
AD DEUM ET VINUM	  			   Nail here [] for new monitor.

library/queue.m:
	add a queue__delete_all predicate to remove instances of an element
	from a queue.

Index: library/queue.m
===================================================================
RCS file: /home/staff/zs/imp/mercury/library/queue.m,v
retrieving revision 1.18
diff -u -r1.18 queue.m
--- queue.m	1998/01/23 12:33:29	1.18
+++ queue.m	1998/02/19 04:09:00
@@ -89,6 +89,12 @@
 :- pred queue__list_to_queue(list(T), queue(T)).
 :- mode queue__list_to_queue(in, out) is det.
 
+	% `queue__delete_all(Queue0, Elem, Queue)' is true iff `Queue' is
+	% the same queue as `Queue0' with all occurences of `Elem' removed
+	% from it.
+:- pred queue__delete_all(queue(T), T, queue(T)).
+:- mode queue__delete_all(in, in, out) is det.
+
 %--------------------------------------------------------------------------%
 
 :- implementation.
@@ -157,5 +163,9 @@
 	Length is LengthOn + LengthOff.
 
 queue__list_to_queue(List, [] - List).
+
+queue__delete_all(On0 - Off0, Elem, On - Off) :-
+	list__delete_all(On0, Elem, On),
+	list__delete_all(Off0, Elem, Off).
 
 %--------------------------------------------------------------------------%