1		:- multifile generate/2.
2		:- multifile shrink/3.
3
4		:- use_module(library(lists)).
5		:- use_module(library(random),[random/3,random_member/2]).
6
7		% Options:
8		% size:X with X the amount of elements in the list
9
10		% list of any type
11		generate(list(Options),Value) :-
12		is_list(Options) ,
13		generate(ground_type,Type) ,
14		generate(list(Type,Options),Value).
15
16		generate(list(Type),Value) :-
17		generate(list(Type,[]),Value).
18
19		generate(list(_,Options),[]) :-
20		member(size:0,Options),
21		!.
22
23		% list of given type
24		generate(list(Type,Options),Value) :-
25		(member(size:Size,Options)
26		-> Size > 0
27		; random(1,50,Size)) ,
28		length(Value,Size) ,
29		maplist(generate(Type),Value).
30
31		% shrink list of list
32		shrink(Type,Value,Shrunken) :-
33		Type =..[list|_] ,
34		\+ flattened(Value) ,
35		maplist(shrink(list),Value,Shrunken).
36
37		% check empty list
38		shrink(Type,[_],[]) :-
39		Type =..[list|_].
40
41		% remove random elements
42		shrink(Type,L,NL) :-
43		Type =.. [list|_] ,
44		is_list(L) ,
45		random_member(E,L) ,
46		delete(L,E,NL).
47
48		% remove last element of a list
49		remove_last([],[]).
50		remove_last([_],[]).
51		remove_last([H|T],[H|T2]) :-
52		remove_last(T,T2).