1		% (c) 2009-2019 Lehrstuhl fuer Softwaretechnik und Programmiersprachen,
2		% Heinrich Heine Universitaet Duesseldorf
3		% This software is licenced under EPL 1.0 (http://www.eclipse.org/org/documents/epl-v10.html)
4
5
6		:- module(tools_lists,
7		[count_occurences/2,
8		ord_member_nonvar_chk/2
9		]).
10
11		:- use_module(module_information).
12
13		:- module_info(group,infrastructure).
14		:- module_info(description,'A few utilities on lists seperated out from tools.pl to avoid cyclic module dependencies.').
15
16
17		% self-check in tools to avoid dependency on self_check module
18		%:- assert_must_succeed((tools:count_occurences([a,b,a,a,b],R),R == [a-3,b-2])).
19		:- use_module(library(avl), [avl_fetch/3, avl_to_list/2, avl_store/4,empty_avl/1]).
20
21		% count number of occurences inside a list
22		count_occurences(L,R) :- empty_avl(E), count_occ_aux(L,E,R).
23		count_occ_aux([Term|T],A,Res) :- (avl_fetch(Term,A,Count) -> C is Count+1 ; C = 1),
24		avl_store(Term,A,C,A2),
25		count_occ_aux(T,A2,Res).
26		count_occ_aux([],A,L) :- avl_to_list(A,L).
27
28		% like ord_member but also allows nonvar lookup terms
29		% note that this test fails for ord_member:
30		%:- assert_must_succeed((tools:ord_member_nonvar_chk(p(b,X),[p(a,c),p(b,d)]),R == d)).
31		ord_member_nonvar_chk(X, [H|T]) :-
32		(X=H -> true
33		; X @>H -> ord_member_nonvar_chk(X,T)).