1		:- multifile generate/2.
2		:- multifile shrink/3.
3
4		:- use_module(library(random),[random/3,random_member/2]).
5		:- use_module(library(trees),[list_to_tree/2,tree_to_list/2]).
6
7		% Options:
8		% size:X with X the amount of elements in the tree
9
10		% random binary tree
11		generate(tree(Options),Value) :-
12		is_list(Options) ,
13		generate(tree(any,Options),Value).
14
15		generate(tree(Type),Value) :-
16		generate(tree(Type,[]),Value).
17
18		% tree of given type
19		generate(tree(Type,Options),Value) :-
20		% size specifies amount of elements in the tree
21		(member(size:Size,Options)
22		-> Size > 0
23		; random(1,20,Size)) ,
24		generate(list(Type,[size:Size]),List) ,
25		list_to_tree(List,Value).
26
27		% shrink binary tree
28		% empty tree
29		shrink(Type,t(_,t,t),t) :-
30		Type =..[tree|_].
31
32		shrink(Type,Value,Shrunken) :-
33		Type =.. [tree|_] ,
34		tree_to_list(Value,List) ,
35		% refer to shrinking of lists
36		shrink(list(_),List,ShrunkenList) ,
37		list_to_tree(ShrunkenList,Shrunken).