1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
|
% Logic and control predicates
\+ Goal :- call(Goal), !, fail.
\+ Goal.
once(Goal) :-
call(Goal),
!.
repeat :- true ; repeat.
% Control structures.
true.
If -> Then :-
If, !, Then.
If -> Then ; _ :-
If, !, Then.
_ -> _ ; Else :-
!, Else.
If ; _ :-
If.
_ ; Else :-
Else.
A , B :- A , B.
% Term unification
A = A.
A \= B :-
\+ A = B.
% Comparison of terms using the standard order
A == B :-
compare(=, A, B).
A \== B :-
\+ A == B.
A @< B :-
compare(<, A, B).
A @=< B :-
A == B.
A @=< B :-
A @< B.
A @> B :-
compare(>, A, B).
A @>= B :-
A == B.
A @>= B :-
A @> B.
% List predicates
length([], 0).
length([_|Tail], Length) :-
length(Tail, Length0),
Length is Length0 + 1.
member(X, [X|_]).
member(X, [_|Tail]) :-
member(X, Tail).
% Standard exceptions
instantiation_error :-
throw(error(instantiation_error, _)).
type_error(ValidType, Culprit) :-
throw(error(type_error(ValidType, Culprit), _)).
domain_error(ValidDomain, Culprit) :-
throw(error(domain_error(ValidDomain, Culprit), _)).
existence_error(ObjectType, Culprit) :-
throw(error(existence_error(ObjectType, Culprit), _)).
permission_error(Operation, PermissionType, Culprit) :-
throw(error(permission_error(Operation, PermissionType, Culprit), _)).
representation_error(Flag) :-
throw(error(representation_error(Flag), _)).
evaluation_error(Error) :-
throw(error(evaluation_error(Error), _)).
resource_error(Resource) :-
throw(error(resource_error(Resource), _)).
syntax_error(Error) :-
throw(error(syntax_error(Error), _)).
|