1		:- multifile generate/2.
2		:- multifile shrink/3.
3
4		:- use_module(library(random),[random/3]).
5		:- use_module(library(sets),[subset/2]).
6
7		% Options:
8		% small, positive, negative, nozero, between(A,B) or none
9
10		generate(integer(Options),Value) :-
11		member(between(A,B),Options) ,
12		generate(between(A,B),Value).
13
14		generate(integer(Options),Value) :-
15		subset([small,positive,nozero],Options) ,
16		!,
17		random(1,128,Value).
18
19		generate(integer(Options),Value) :-
20		subset([small,positive],Options) ,
21		!,
22		random(0,128,Value).
23
24		generate(integer(Options),Value) :-
25		subset([small,negative],Options) ,
26		!,
27		random(-128,-1,Value).
28
29		generate(integer(Options),Value) :-
30		subset([positive,nozero],Options) ,
31		!,
32		random(1,20000,Value).
33
34		generate(integer(Options),Value) :-
35		member(positive,Options) ,
36		!,
37		random(0,20000,Value).
38
39		generate(integer(Options),Value) :-
40		member(negative,Options) ,
41		!,
42		random(-20000,-1,Value).
43
44		generate(integer(Options),Value) :-
45		member(small,Options) ,
46		!,
47		random(-64,64,Value).
48
49		generate(integer(_),Value) :-
50		random(-20000,20000,Value).
51
52		% try 0
53		shrink(integer(_),_,0).
54
55		% divide by two for big numbers
56		shrink(integer(_),Value,Shrunken) :-
57		(Value > 100 ; Value < -100) ,
58		Shrunken is round(Value / 2).
59
60		% smaller steps
61		shrink(integer(_),Value,Shrunken) :-
62		Value > 0 ,
63		Shrunken is Value - 1 .
64		shrink(integer(_),Value,Shrunken) :-
65		Value < 0 ,
66		Shrunken is Value + 1.