268 lines
7.2 KiB
Prolog
268 lines
7.2 KiB
Prolog
/**
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@file pl/error.yap
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@author Jan Wielemaker
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@author Richard O'Keefe
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@author adapted to YAP by Vitor Santos Costa
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*/
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:- module(system(error),
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[ must_be_of_type/2, % +Type, +Term
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must_be_of_type/3, % +Type, +Term, +Comment
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must_be/2, % +Type, +Term
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must_be/3, % +Type, +Term, +Comment
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type_error/2, % +Type, +Term
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% must_be_in_domain/2, % +Domain, +Term
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% must_be_in_domain/3, % +Domain, +Term, +Comment
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domain_error/3, % +Domain, +Values, +Term
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existence_error/2, % +Type, +Term
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permission_error/3, % +Action, +Type, +Term
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must_be_instantiated/1, % +Term
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instantiation_error/1, % +Term
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representation_error/1, % +Reason
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is_of_type/2 % +Type, +Term
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]).
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/**
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@defgroup error Error generating support
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@ingroup YAPError
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This SWI module provides predicates to simplify error generation and
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checking. Adapted to use YAP built-ins.
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Its implementation is based on a discussion on the SWI-Prolog
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mailinglist on best practices in error handling. The utility predicate
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must_be/2 provides simple run-time type validation. The *_error
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predicates are simple wrappers around throw/1 to simplify throwing the
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most common ISO error terms.
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YAP reuses the code with some extensions, and supports interfacing to some C-builtins.
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@{
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*/
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:- multifile
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has_type/2.
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%% @pred type_error(+Type, +Term).
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%% @pred domain_error(+Type, +Value, +Term).
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%% @pred existence_error(+Type, +Term).
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%% @pred permission_error(+Action, +Type, +Term).
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%% @pred instantiation_error(+Term).
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%% @pred representation_error(+Reason).
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%
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% Throw ISO compliant error messages.
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type_error(Type, Term) :-
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throw(error(type_error(Type, Term), _)).
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domain_error(Type, Term) :-
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throw(error(domain_error(Type, Term), _)).
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existence_error(Type, Term) :-
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throw(error(existence_error(Type, Term), _)).
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permission_error(Action, Type, Term) :-
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throw(error(permission_error(Action, Type, Term), _)).
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instantiation_error(_Term) :-
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throw(error(instantiation_error, _)).
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representation_error(Reason) :-
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throw(error(representation_error(Reason), _)).
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%% must_be_of_type(+Type, @Term) is det.
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%
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% True if Term satisfies the type constraints for Type. Defined
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% types are =atom=, =atomic=, =between=, =boolean=, =callable=,
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% =chars=, =codes=, =text=, =compound=, =constant=, =float=,
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% =integer=, =nonneg=, =positive_integer=, =negative_integer=,
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% =nonvar=, =number=, =oneof=, =list=, =list_or_partial_list=,
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% =symbol=, =var=, =rational= and =string=.
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%
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% Most of these types are defined by an arity-1 built-in predicate
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% of the same name. Below is a brief definition of the other
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% types.
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%
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% | boolean | one of =true= or =false= |
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% | chars | Proper list of 1-character atoms |
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% | codes | Proper list of Unicode character codes |
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% | text | One of =atom=, =string=, =chars= or =codes= |
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% | between(L,U) | Number between L and U (including L and U) |
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% | nonneg | Integer >= 0 |
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% | positive_integer | Integer > 0 |
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% | negative_integer | Integer < 0 |
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% | oneof(L) | Ground term that is member of L |
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% | list(Type) | Proper list with elements of Type |
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% | list_or_partial_list | A list or an open list (ending in a variable) |
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% | predicate_indicator | a predicate indicator of the form M:N/A or M:N//A |
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%
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% @throws instantiation_error if Term is insufficiently
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% instantiated and type_error(Type, Term) if Term is not of Type.
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must_be(Type, X) :-
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must_be_of_type(Type, X).
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must_be(Type, X, Comment) :-
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must_be_of_type(Type, X, Comment).
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must_be_of_type(callable, X) :-
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!,
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is_callable(X, _).
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must_be_of_type(atom, X) :-
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!,
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is_atom(X, _).
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must_be_of_type(predicate_indicator, X) :-
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!,
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is_predicate_indicator(X, _).
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must_be_of_type(Type, X) :-
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( has_type(Type, X)
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-> true
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; is_not(Type, X)
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).
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inline(must_be_of_type( callable, X ), error:is_callable(X, _) ).
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inline(must_be_of_type( callable, X ), error:is_callable(X, _) ).
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must_be_of_type(predicate_indicator, X, Comment) :-
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!,
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is_predicate_indicator(X, Comment).
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must_be_of_type(callable, X, Comment) :-
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!,
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is_callable(X, Comment).
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must_be_of_type(Type, X, _Comment) :-
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( has_type(Type, X)
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-> true
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; is_not(Type, X)
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).
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%% @predicate is_not(+Type, @Term)
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%
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% Throws appropriate error. It is _known_ that Term is not of type
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% Type.
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%
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% @throws type_error(Type, Term)
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% @throws instantiation_error
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is_not(list, X) :- !,
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not_a_list(list, X).
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is_not(list(_), X) :- !,
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not_a_list(list, X).
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is_not(list_or_partial_list, X) :- !,
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type_error(list, X).
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is_not(chars, X) :- !,
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not_a_list(chars, X).
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is_not(codes, X) :- !,
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not_a_list(codes, X).
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is_not(var,_X) :- !,
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representation_error(variable).
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is_not(rational, X) :- !,
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not_a_rational(X).
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is_not(Type, X) :-
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( var(X)
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-> instantiation_error(X)
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; ground_type(Type), \+ ground(X)
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-> instantiation_error(X)
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; type_error(Type, X)
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).
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ground_type(ground).
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ground_type(oneof(_)).
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ground_type(stream).
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ground_type(text).
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ground_type(string).
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not_a_list(Type, X) :-
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'$skip_list'(_, X, Rest),
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( var(Rest)
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-> instantiation_error(X)
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; type_error(Type, X)
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).
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not_a_rational(X) :-
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( var(X)
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-> instantiation_error(X)
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; X = rdiv(N,D)
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-> must_be(integer, N), must_be(integer, D),
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type_error(rational,X)
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; type_error(rational,X)
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).
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%% is_of_type(+Type, @Term) is semidet.
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%
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% True if Term satisfies Type.
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is_of_type(Type, Term) :-
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has_type(Type, Term).
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%% has_type(+Type, @Term) is semidet.
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%
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% True if Term satisfies Type.
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has_type(impossible, _) :- instantiation_error(_).
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has_type(any, _).
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has_type(atom, X) :- atom(X).
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has_type(atomic, X) :- atomic(X).
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has_type(between(L,U), X) :- ( integer(L)
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-> integer(X), between(L,U,X)
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; number(X), X >= L, X =< U
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).
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has_type(boolean, X) :- (X==true;X==false), !.
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has_type(callable, X) :- callable(X).
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has_type(chars, X) :- chars(X).
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has_type(codes, X) :- codes(X).
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has_type(text, X) :- text(X).
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has_type(compound, X) :- compound(X).
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has_type(constant, X) :- atomic(X).
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has_type(float, X) :- float(X).
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has_type(ground, X) :- ground(X).
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has_type(integer, X) :- integer(X).
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has_type(nonneg, X) :- integer(X), X >= 0.
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has_type(positive_integer, X) :- integer(X), X > 0.
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has_type(negative_integer, X) :- integer(X), X < 0.
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has_type(nonvar, X) :- nonvar(X).
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has_type(number, X) :- number(X).
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has_type(oneof(L), X) :- ground(X), lists:memberchk(X, L).
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has_type(proper_list, X) :- is_list(X).
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has_type(list, X) :- is_list(X).
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has_type(list_or_partial_list, X) :- is_list_or_partial_list(X).
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has_type(symbol, X) :- atom(X).
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has_type(var, X) :- var(X).
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has_type(rational, X) :- rational(X).
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has_type(string, X) :- string(X).
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has_type(stream, X) :- is_stream(X).
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has_type(list(Type), X) :- is_list(X), element_types(X, Type).
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chars(0) :- !, fail.
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chars([]).
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chars([H|T]) :-
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atom(H), atom_length(H, 1),
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chars(T).
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codes(x) :- !, fail.
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codes([]).
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codes([H|T]) :-
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integer(H), between(1, 0x10ffff, H),
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codes(T).
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text(X) :-
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( atom(X)
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; string(X)
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; chars(X)
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; codes(X)
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), !.
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element_types([], _).
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element_types([H|T], Type) :-
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must_be(Type, H),
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element_types(T, Type).
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is_list_or_partial_list(L0) :-
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'$skip_list'(_, L0,L),
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( var(L) -> true ; L == [] ).
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must_be_instantiated(X) :-
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( var(X) -> instantiation_error(X) ; true).
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must_be_instantiated(X, Comment) :-
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( var(X) -> instantiation_error(X, Comment) ; true).
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%% @}
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