[m-dev.] for review: assoc_list__keys_and_values

[Zoltan Somogyi]

library/assoc_list.m:
	Add a predicate to get the keys and values as separate lists
	simultaneously.

Zoltan.

Index: assoc_list.m
===================================================================
RCS file: /home/mercury1/repository/mercury/library/assoc_list.m,v
retrieving revision 1.12
diff -u -b -r1.12 assoc_list.m
--- assoc_list.m	2000/11/12 08:51:32	1.12
+++ assoc_list.m	2001/01/02 07:42:20
@@ -1,5 +1,5 @@
 %---------------------------------------------------------------------------%
-% Copyright (C) 1995-1997, 1999-2000 The University of Melbourne.
+% Copyright (C) 1995-1997, 1999-2001 The University of Melbourne.
 % This file may only be copied under the terms of the GNU Library General
 % Public License - see the file COPYING.LIB in the Mercury distribution.
 %---------------------------------------------------------------------------%
@@ -56,6 +56,9 @@
 
 :- func assoc_list__values(assoc_list(K, V)) = list(V).
 
+:- pred assoc_list__keys_and_values(assoc_list(K, V), list(K), list(V)).
+:- mode assoc_list__keys_and_values(in, out, out) is det.
+
 	% Find the first element of the association list that matches
 	% the given key, and return the associated value.
 
@@ -122,6 +125,10 @@
 assoc_list__values([], []).
 assoc_list__values([_ - V | KVs], [V | Vs]) :-
 	assoc_list__values(KVs, Vs).
+
+assoc_list__keys_and_values([], [], []).
+assoc_list__keys_and_values([K - V | KVs], [K | Ks], [V | Vs]) :-
+	assoc_list__keys_and_values(KVs, Ks, Vs).
 
 assoc_list__search([K - V | KVs], Key, Value) :-
 	( K = Key ->
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