1		:- multifile generate/2.
2		:- multifile shrink/3.
3
4		:- use_module(library(random),[random/3]).
5
6		% Options:
7		% positive, negative
8
9		generate(rational(Options),Value) :-
10		member(positive,Options) ,
11		!,
12		delete(Options,positive,NOptions) ,
13		random(0,2,R) ,
14		generate_rational_aux(positive,NOptions,R,Z,N) ,
15		Value = Z/N.
16
17		generate(rational(Options),Value) :-
18		member(negative,Options) ,
19		!,
20		delete(Options,negative,NOptions) ,
21		random(0,2,R) ,
22		generate_rational_aux(negative,NOptions,R,Z,N) ,
23		Value = Z/N.
24
25		generate(rational(Options),Value) :-
26		random_member(Pol,[positive,negative]) ,
27		generate(rational([Pol|Options]),Value).
28
29		generate_rational_aux(positive,Options,0,Z,N) :-
30		generate(integer([positive|Options]),Z) ,
31		generate(integer([positive|Options]),N) ,
32		N \= 0.
33		generate_rational_aux(positive,Options,1,Z,N) :-
34		generate(integer([negative|Options]),Z) ,
35		generate(integer([negative|Options]),N) ,
36		N \= 0.
37		generate_rational_aux(negative,Options,0,Z,N) :-
38		generate(integer([positive|Options]),Z) ,
39		generate(integer([negative|Options]),N) ,
40		N \= 0.
41		generate_rational_aux(negative,Options,1,Z,N) :-
42		generate(integer([negative|Options]),Z) ,
43		generate(integer([positive|Options]),N) ,
44		N \= 0.
45
46		shrink(rational(_),Val1/Val2,ShrunkenVal1/ShrunkenVal2) :-
47		shrink(integer([]),Val1,ShrunkenVal1) ,
48		shrink(integer([]),Val2,ShrunkenVal2) ,
49		ShrunkenVal2 \= 0.
50
51		shrink(rational(_),Value,Value).