1		:- multifile generate/2.
2
3		% shrinking of all mutations defined in mutation.pl
4
5		:- use_module(library(lists),[is_list/1]).
6		:- use_module(library(sets),[subtract/3]).
7		:- use_module(library(random),[random_permutation/2,random_member/2,random/3]).
8
9		% mutation of ProB ast predicates
10		generate(mutation(Predicate:prob_ast_pred),NewPredicate) :-
11		\+is_list(Predicate) ,
12		random_pred_mutation(Predicate,NewPredicate).
13		% list of predicates, random concatenation of predicates then
14		% mutation of consisting integer and set expressions
15		generate(mutation(Predicates:prob_ast_pred),NewPredicate) :-
16		concatenate_ast(Predicates,[conjunct,disjunct,implication,equivalence],Predicate) ,
17		random_pred_mutation(Predicate,NewPredicate).
18
19		% randomly replaces ground integer, set or sequence ast nodes with a matching
20		% expression all over the predicate, ProB values get permutated
21
22		% two argument predicates
23		random_pred_mutation(b(Predicate,pred,Info),b(NewPredicate,pred,Info)) :-
24		Predicate =.. [Type,Expr1,Expr2] ,
25		random_mutation(Expr1,NewExpr1) ,
26		random_mutation(Expr2,NewExpr2) ,
27		% randomly swap predicates with a matching one
28		random(0,9,R) ,
29		(R > 4
30		-> swap_type(Type,MutatedType)
31		; MutatedType = Type) ,
32		NewPredicate =.. [MutatedType,NewExpr1,NewExpr2].
33
34		% one argument predicates
35		random_pred_mutation(b(Predicate,pred,Info),b(NewPredicate,pred,Info)) :-
36		Predicate =.. [Type,Expr] ,
37		random_mutation(Expr,NewExpr) ,
38		NewPredicate =.. [Type,NewExpr].
39
40		random_pred_mutation(Value,Value).
41
42		% apply respective mutation
43		random_mutation(Expr,Mutation) :-
44		Expr = b(_,set(_),_) ,
45		random_set_expr_mutation(Expr,Mutation).
46		random_mutation(Expr,Mutation) :-
47		Expr = b(_,seq(_),_) ,
48		random_seq_expr_mutation(Expr,Mutation).
49		random_mutation(Expr,Mutation) :-
50		Expr = b(_,integer,_) ,
51		random_int_expr_mutation(Expr,Mutation).
52		random_mutation(Expr,Mutation) :-
53		random_pred_mutation(Expr,Mutation).
54
55		% concatenate a list of expressions or predicates by using one expression of argument Nodes
56		concatenate_ast(ListOfExpressions,Nodes,Expression) :-
57		random_permutation(ListOfExpressions,[H|Permutation]) ,
58		% use an accumulator
59		concatenate_ast(Permutation,H,Nodes,Expression).
60		concatenate_ast([],NewExpression,_,NewExpression).
61		concatenate_ast([Expression|T],Current,Nodes,NewExpression) :-
62		concatenate(Expression,Current,Nodes,NewCurrent) ,
63		% permutate rest of list
64		random_permutation(T,Permutation) ,
65		concatenate_ast(Permutation,NewCurrent,Nodes,NewExpression).
66
67		concatenate(Expression1,Expression2,Nodes,NewExpression) :-
68		random_member(SurroundingType,Nodes) ,
69		InnerType =.. [SurroundingType,Expression1,Expression2] ,
70		NewExpression = b(InnerType,integer,[]).
71
72		% change some types for mutation
73		swap_type(Type,NType) :-
74		ValidTypes = [less,less_equal,greater,greater_equal] ,
75		member(Type,ValidTypes) ,
76		% don't choose the same type for replacement
77		subtract(ValidTypes,Type,NewValidTypes) ,
78		random_member(NType,[equal,not_equal|NewValidTypes]).
79		swap_type(disjunct,conjunct).
80		swap_type(conjunct,disjunct).
81		swap_type(implication,equivalence).
82		swap_type(equivalence,implication).
83		swap_type(equal,not_equal).
84		swap_type(not_equal,equal).
85		swap_type(subset,subset_strict).
86		swap_type(subset_strict,subset).
87		swap_type(member,not_member).
88		swap_type(not_member,member).
89		swap_type(Type,Type).