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yap-6.3/swi/library/error.pl

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/* $Id: error.pl,v 1.3 2008-07-22 23:34:49 vsc Exp $
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: wielemak@science.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2007, University of Amsterdam
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
As a special exception, if you link this library with other files,
compiled with a Free Software compiler, to produce an executable, this
library does not by itself cause the resulting executable to be covered
by the GNU General Public License. This exception does not however
invalidate any other reasons why the executable file might be covered by
the GNU General Public License.
*/
:- module(error,
[ type_error/2, % +Type, +Term
domain_error/2, % +Domain, +Term
existence_error/2, % +Type, +Term
permission_error/3, % +Action, +Type, +Term
instantiation_error/1, % +Term
representation_error/1, % +Reason
must_be/2, % +Type, +Term
is_of_type/2 % +Type, +Term
]).
:- if(current_prolog_flag(dialect, yap)).
:- use_module(library(lists),[memberchk/2]).
:- endif.
/** <module> Error generating support
This module provides predicates to simplify error generation and
checking. It's implementation is based on a discussion on the SWI-Prolog
mailinglist on best practices in error handling. The utility predicate
must_be/2 provides simple run-time type validation. The *_error
predicates are simple wrappers around throw/1 to simplify throwing the
most common ISO error terms.
@author Jan Wielemaker
@author Richard O'Keefe
@see library(debug) and library(prolog_stack).
*/
:- multifile
has_type/2.
%% type_error(+Type, +Term).
%% domain_error(+Type, +Term).
%% existence_error(+Type, +Term).
%% permission_error(+Action, +Type, +Term).
%% instantiation_error(+Term).
%% representation_error(+Reason).
%
% Throw ISO compliant error messages.
type_error(Type, Term) :-
throw(error(type_error(Type, Term), _)).
domain_error(Type, Term) :-
throw(error(domain_error(Type, Term), _)).
existence_error(Type, Term) :-
throw(error(existence_error(Type, Term), _)).
permission_error(Action, Type, Term) :-
throw(error(permission_error(Action, Type, Term), _)).
instantiation_error(_Term) :-
throw(error(instantiation_error, _)).
representation_error(Reason) :-
throw(error(representation_error(Reason), _)).
%% must_be(+Type, @Term) is det.
%
% True if Term satisfies the type constraints for Type. Defined
% types are =atom=, =atomic=, =between=, =boolean=, =callable=,
% =chars=, =codes=, =text=, =compound=, =constant=, =float=,
% =integer=, =nonneg=, =positive_integer=, =negative_integer=,
% =nonvar=, =number=, =oneof=, =list=, =list_or_partial_list=,
% =symbol=, =var=, =rational= and =string=.
%
% Most of these types are defined by an arity-1 built-in predicate
% of the same name. Below is a brief definition of the other
% types.
%
% | boolean | one of =true= or =false= |
% | chars | Proper list of 1-character atoms |
% | codes | Proper list of Unicode character codes |
% | text | One of =atom=, =string=, =chars= or =codes= |
% | between(L,U) | Number between L and U (including L and U) |
% | nonneg | Integer >= 0 |
% | positive_integer | Integer > 0 |
% | negative_integer | Integer < 0 |
% | oneof(L) | Ground term that is member of L |
% | list(Type) | Proper list with elements of Type |
% | list_or_partial_list | A list or an open list (ending in a variable |
%
% @throws instantiation_error if Term is insufficiently
% instantiated and type_error(Type, Term) if Term is not of Type.
must_be(Type, X) :-
( has_type(Type, X)
-> true
; is_not(Type, X)
).
%% is_not(+Type, @Term)
%
% Throws appropriate error. It is _known_ that Term is not of type
% Type.
%
% @throws type_error(Type, Term)
% @throws instantiation_error
is_not(list, X) :- !,
not_a_list(list, X).
is_not(list(_), X) :- !,
not_a_list(list, X).
is_not(list_or_partial_list, X) :- !,
type_error(list, X).
is_not(chars, X) :- !,
not_a_list(chars, X).
is_not(codes, X) :- !,
not_a_list(codes, X).
is_not(var,_X) :- !,
representation_error(variable).
is_not(rational, X) :- !,
not_a_rational(X).
is_not(Type, X) :-
( var(X)
-> instantiation_error(X)
; ground_type(Type), \+ ground(X)
-> instantiation_error(X)
; type_error(Type, X)
).
ground_type(ground).
ground_type(oneof(_)).
ground_type(stream).
ground_type(text).
ground_type(string).
not_a_list(Type, X) :-
'$skip_list'(_, X, Rest),
( var(Rest)
-> instantiation_error(X)
; type_error(Type, X)
).
not_a_rational(X) :-
( var(X)
-> instantiation_error(X)
; X = rdiv(N,D)
-> must_be(integer, N), must_be(integer, D),
type_error(rational,X)
; type_error(rational,X)
).
%% is_of_type(+Type, @Term) is semidet.
%
% True if Term satisfies Type.
is_of_type(Type, Term) :-
has_type(Type, Term).
%% has_type(+Type, @Term) is semidet.
%
% True if Term satisfies Type.
has_type(impossible, _) :- instantiation_error(_).
has_type(any, _).
has_type(atom, X) :- atom(X).
has_type(atomic, X) :- atomic(X).
has_type(between(L,U), X) :- ( integer(L)
-> integer(X), between(L,U,X)
; number(X), X >= L, X =< U
).
has_type(boolean, X) :- (X==true;X==false), !.
has_type(callable, X) :- callable(X).
has_type(chars, X) :- chars(X).
has_type(codes, X) :- codes(X).
has_type(text, X) :- text(X).
has_type(compound, X) :- compound(X).
has_type(constant, X) :- atomic(X).
has_type(float, X) :- float(X).
has_type(ground, X) :- ground(X).
has_type(integer, X) :- integer(X).
has_type(nonneg, X) :- integer(X), X >= 0.
has_type(positive_integer, X) :- integer(X), X > 0.
has_type(negative_integer, X) :- integer(X), X < 0.
has_type(nonvar, X) :- nonvar(X).
has_type(number, X) :- number(X).
has_type(oneof(L), X) :- ground(X), memberchk(X, L).
has_type(proper_list, X) :- is_list(X).
has_type(list, X) :- is_list(X).
has_type(list_or_partial_list, X) :- is_list_or_partial_list(X).
has_type(symbol, X) :- atom(X).
has_type(var, X) :- var(X).
has_type(rational, X) :- rational(X).
has_type(string, X) :- string(X).
has_type(stream, X) :- is_stream(X).
has_type(list(Type), X) :- is_list(X), element_types(X, Type).
chars(0) :- !, fail.
chars([]).
chars([H|T]) :-
atom(H), atom_length(H, 1),
chars(T).
codes(x) :- !, fail.
codes([]).
codes([H|T]) :-
integer(H), between(1, 0x10ffff, H),
codes(T).
text(X) :-
( atom(X)
; string(X)
; chars(X)
; codes(X)
), !.
element_types([], _).
element_types([H|T], Type) :-
must_be(Type, H),
element_types(T, Type).
is_list_or_partial_list(L0) :-
'$skip_list'(_, L0,L),
( var(L) -> true ; L == [] ).