1		% minimize ProB AST set expressions for shrinking stage
2
3		:- use_module(library(sets)).
4		:- use_module(library(lists),[is_list/1]).
5		:- use_module(library(avl),[avl_to_list/2,list_to_avl/2]).
6
7		minimize_set_expr(b(set_extension(Set),set(Type),Info),b(set_extension(ShrunkenSet),set(Type),Info)) :-
8		is_list(Set) , Set \= [b(_,set(_),_)] ,
9		shrink(list(_),Set,ShrunkenSet).
10
11		% minimize set of set
12		minimize_set_expr(b(set_extension([Set]),set(Type),Info),Shrunken) :-
13		minimize_set_expr(Set,ShrunkenSet) ,
14		(ShrunkenSet = b(value([]),set(_),Info)
15		-> Shrunken = ShrunkenSet
16		; Shrunken = b(set_extension([ShrunkenSet]),set(Type),Info)).
17
18		minimize_set_expr(b(set_extension([]),set(Inner),Info),b(set_extension([]),set(Inner),Info)).
19
20		minimize_set_expr(b(value(Set),set(Inner),Info),Shrunken) :-
21		shrink(prob_value_set,Set,ShrunkenSet) ,
22		(ShrunkenSet = []
23		-> Shrunken = b(value([]),set(Inner),Info)
24		; Shrunken = b(value(ShrunkenSet),set(Inner),Info)).
25
26		% shrink both sides of interval down to one integer
27		minimize_set_expr(b(interval(b(integer(Value1),integer,Info1),b(integer(Value2),integer,Info2)),set(integer),Info),Shrunken) :-
28		NewValue1 is Value1 + 1 ,
29		NewValue2 is Value2 - 1 ,
30		(NewValue1 >= NewValue2
31		-> Shrunken = b(set_extension([b(integer(NewValue1),integer,Info1)]),set(integer),Info)
32		; Shrunken = b(interval(b(integer(NewValue1),integer,Info1),b(integer(NewValue2),integer,Info2)),set(integer),Info)).
33
34		% union, intersection, set_subtraction
35		% shrink expression to its value when both arguments are set expressions
36		minimize_set_expr(b(Expression,set(Inner),Info),Shrunken) :-
37		Expression =.. [Type,Arg1,Arg2] ,
38		member(Type,[union,intersection,set_subtraction]) ,
39		prob_is_ground(Arg1,true) ,
40		prob_is_ground(Arg2,true) ,
41		sint_avl(b(Expression,set(Inner),Info),NewSet) ,
42		(NewSet = avl_set(empty)
43		-> Shrunken = b(value([]),set(Inner),Info)
44		; Shrunken = b(value(NewSet),set(Inner),Info)).
45		minimize_set_expr(b(Expression,set(Inner),Info),Shrunken) :-
46		Expression =.. [Type,Arg1,Arg2] ,
47		member(Type,[union,intersection,set_subtraction]) ,
48		prob_is_ground(Arg1,Res1) ,
49		prob_is_ground(Arg2,Res2) ,
50		% hold set and minimize expression
51		( Res1 = true , Res2 = false
52		-> minimize_set_expr(Arg2,NewArg2) ,
53		NewExpr =.. [Type,Arg1,NewArg2] ,
54		Shrunken = b(NewExpr,set(Inner),Info)
55		; Res1 = false , Res2 = true
56		-> minimize_set_expr(Arg1,NewArg1) ,
57		NewExpr =.. [Type,NewArg1,Arg2] ,
58		Shrunken = b(NewExpr,set(Inner),Info)
59		; % minimize both expressions
60		minimize_set_expr(Arg1,NewArg1) ,
61		minimize_set_expr(Arg2,NewArg2) ,
62		NewExpr =.. [Type,NewArg1,NewArg2] ,
63		Shrunken = b(NewExpr,set(Inner),Info)).
64
65		% general_union, general_intersection
66		minimize_set_expr(b(Expression,set(Inner),Info),Shrunken) :-
67		Expression =.. [Type,Arg] ,
68		Arg = b(set_extension([Set]),_,_) ,
69		member(Type,[general_union,general_intersection]) ,
70		prob_is_ground(Set,Res) ,
71		(Res = true
72		-> sint_avl(b(Expression,set(Inner),Info),NewSet) ,
73		% don't shrink to an empty set
74		(NewSet = avl_set(empty)
75		-> Shrunken = b(Expression,set(Inner),Info)
76		; Shrunken = b(value(NewSet),set(Inner),Info))
77		; minimize_set_expr(Arg,NewArg) ,
78		NewExpr =.. [Type,NewArg] ,
79		Shrunken = b(NewExpr,set(Inner),Info)).
80
81		% skip identifier
82		minimize_set_expr(b(identifier(Name),Type,Info),b(identifier(Name),Type,Info)).