1/*
2
3    Part of CLP(Q) (Constraint Logic Programming over Rationals)
4
5    Author:        Leslie De Koninck
6    E-mail:        Leslie.DeKoninck@cs.kuleuven.be
7    WWW:           http://www.swi-prolog.org
8		   http://www.ai.univie.ac.at/cgi-bin/tr-online?number+95-09
9    Copyright (C): 2006, K.U. Leuven and
10		   1992-1995, Austrian Research Institute for
11		              Artificial Intelligence (OFAI),
12			      Vienna, Austria
13
14    This software is based on CLP(Q,R) by Christian Holzbaur for SICStus
15    Prolog and distributed under the license details below with permission from
16    all mentioned authors.
17
18    This program is free software; you can redistribute it and/or
19    modify it under the terms of the GNU General Public License
20    as published by the Free Software Foundation; either version 2
21    of the License, or (at your option) any later version.
22
23    This program is distributed in the hope that it will be useful,
24    but WITHOUT ANY WARRANTY; without even the implied warranty of
25    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
26    GNU General Public License for more details.
27
28    You should have received a copy of the GNU Lesser General Public
29    License along with this library; if not, write to the Free Software
30    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
31
32    As a special exception, if you link this library with other files,
33    compiled with a Free Software compiler, to produce an executable, this
34    library does not by itself cause the resulting executable to be covered
35    by the GNU General Public License. This exception does not however
36    invalidate any other reasons why the executable file might be covered by
37    the GNU General Public License.
38*/
39
40:- module(itf_q,
41	[
42	    do_checks/8
43	]).
44:- use_module(library(apply), [maplist/2]).
45:- use_module(bv_q,
46	[
47	    deref/2,
48	    detach_bounds_vlv/5,
49	    solve/1,
50	    solve_ord_x/3
51	]).
52:- use_module(nf_q,
53	[
54	    nf/2
55	]).
56:- use_module(store_q,
57	[
58	    add_linear_11/3,
59	    indep/2,
60	    nf_coeff_of/3
61	]).
62:- use_module('../clpqr/class',
63	[
64	    class_drop/2
65	]).
66
67do_checks(Y,Ty,St,Li,Or,Cl,No,Later) :-
68	numbers_only(Y),
69	verify_nonzero(No,Y),
70	verify_type(Ty,St,Y,Later,[]),
71	verify_lin(Or,Cl,Li,Y),
72	maplist(call,Later).
73
74numbers_only(Y) :-
75	(   var(Y)
76	;   rational(Y)
77	;   throw(type_error(_X = Y,2,'a rational number',Y))
78	),
79	!.
80
81% verify_nonzero(Nonzero,Y)
82%
83% if Nonzero = nonzero, then verify that Y is not zero
84% (if possible, otherwise set Y to be nonzero)
85
86verify_nonzero(nonzero,Y) :-
87	(   var(Y)
88	->  (   get_attr(Y,itf,Att)
89	    ->  setarg(8,Att,nonzero)
90	    ;   put_attr(Y,itf,t(clpq,n,n,n,n,n,n,nonzero,n,n,n))
91	    )
92	;   Y =\= 0
93	).
94verify_nonzero(n,_). % X is not nonzero
95
96% verify_type(type(Type),strictness(Strict),Y,[OL|OLT],OLT)
97%
98% if possible verifies whether Y satisfies the type and strictness of X
99% if not possible to verify, then returns the constraints that follow from
100% the type and strictness
101
102verify_type(type(Type),strictness(Strict),Y) -->
103	verify_type2(Y,Type,Strict).
104verify_type(n,n,_) --> [].
105
106verify_type2(Y,TypeX,StrictX) -->
107	{var(Y)},
108	!,
109	verify_type_var(TypeX,Y,StrictX).
110verify_type2(Y,TypeX,StrictX) -->
111	{verify_type_nonvar(TypeX,Y,StrictX)}.
112
113% verify_type_nonvar(Type,Nonvar,Strictness)
114%
115% verifies whether the type and strictness are satisfied with the Nonvar
116
117verify_type_nonvar(t_none,_,_).
118verify_type_nonvar(t_l(L),Value,S) :- ilb(S,L,Value).
119verify_type_nonvar(t_u(U),Value,S) :- iub(S,U,Value).
120verify_type_nonvar(t_lu(L,U),Value,S) :-
121	ilb(S,L,Value),
122	iub(S,U,Value).
123verify_type_nonvar(t_L(L),Value,S) :- ilb(S,L,Value).
124verify_type_nonvar(t_U(U),Value,S) :- iub(S,U,Value).
125verify_type_nonvar(t_Lu(L,U),Value,S) :-
126	ilb(S,L,Value),
127	iub(S,U,Value).
128verify_type_nonvar(t_lU(L,U),Value,S) :-
129	ilb(S,L,Value),
130	iub(S,U,Value).
131
132% ilb(Strict,Lower,Value) & iub(Strict,Upper,Value)
133%
134% check whether Value is satisfiable with the given lower/upper bound and
135% strictness.
136% strictness is encoded as follows:
137% 2 = strict lower bound
138% 1 = strict upper bound
139% 3 = strict lower and upper bound
140% 0 = no strict bounds
141
142ilb(S,L,V) :-
143	S /\ 2 =:= 0,
144	!,
145	L =< V. % non-strict
146ilb(_,L,V) :- L < V. % strict
147
148iub(S,U,V) :-
149	S /\ 1 =:= 0,
150	!,
151	V =< U. % non-strict
152iub(_,U,V) :- V < U. % strict
153
154%
155% Running some goals after X=Y simplifies the coding. It should be possible
156% to run the goals here and taking care not to put_atts/2 on X ...
157%
158
159% verify_type_var(Type,Var,Strictness,[OutList|OutListTail],OutListTail)
160%
161% returns the inequalities following from a type and strictness satisfaction
162% test with Var
163
164verify_type_var(t_none,_,_) --> [].
165verify_type_var(t_l(L),Y,S) --> llb(S,L,Y).
166verify_type_var(t_u(U),Y,S) --> lub(S,U,Y).
167verify_type_var(t_lu(L,U),Y,S) -->
168	llb(S,L,Y),
169	lub(S,U,Y).
170verify_type_var(t_L(L),Y,S) --> llb(S,L,Y).
171verify_type_var(t_U(U),Y,S) --> lub(S,U,Y).
172verify_type_var(t_Lu(L,U),Y,S) -->
173	llb(S,L,Y),
174	lub(S,U,Y).
175verify_type_var(t_lU(L,U),Y,S) -->
176	llb(S,L,Y),
177	lub(S,U,Y).
178
179% llb(Strict,Lower,Value,[OL|OLT],OLT) and lub(Strict,Upper,Value,[OL|OLT],OLT)
180%
181% returns the inequalities following from the lower and upper bounds and the
182% strictness see also lb and ub
183llb(S,L,V) -->
184	{S /\ 2 =:= 0},
185	!,
186	[clpq:{L =< V}].
187llb(_,L,V) --> [clpq:{L < V}].
188
189lub(S,U,V) -->
190	{S /\ 1 =:= 0},
191	!,
192	[clpq:{V =< U}].
193lub(_,U,V) -->	[clpq:{V < U}].
194
195%
196% We used to drop X from the class/basis to avoid trouble with subsequent
197% put_atts/2 on X. Now we could let these dead but harmless updates happen.
198% In R however, exported bindings might conflict, e.g. 0 \== 0.0
199%
200% If X is indep and we do _not_ solve for it, we are in deep shit
201% because the ordering is violated.
202%
203verify_lin(order(OrdX),class(Class),lin(LinX),Y) :-
204	!,
205	(   indep(LinX,OrdX)
206	->  detach_bounds_vlv(OrdX,LinX,Class,Y,NewLinX),
207	    % if there were bounds, they are requeued already
208	    class_drop(Class,Y),
209	    nf(-Y,NfY),
210	    deref(NfY,LinY),
211	    add_linear_11(NewLinX,LinY,Lind),
212	    (   nf_coeff_of(Lind,OrdX,_)
213	    ->	% X is element of Lind
214		solve_ord_x(Lind,OrdX,Class)
215	    ;	solve(Lind)	% X is gone, can safely solve Lind
216	    )
217	;   class_drop(Class,Y),
218	    nf(-Y,NfY),
219	    deref(NfY,LinY),
220	    add_linear_11(LinX,LinY,Lind),
221	    solve(Lind)
222	).
223verify_lin(_,_,_,_).
224