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yap-6.3/packages/cplint/slg.pl

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/***************************************************************************/
/* */
/* The SLG System */
/* Authors: Weidong Chen and David Scott Warren */
/* Copyright (C) 1993 Southern Methodist University */
/* 1993 SUNY at Stony Brook */
/* See file COPYRIGHT_SLG for copying policies and disclaimer. */
/* */
/***************************************************************************/
/*==========================================================================
File : slg.pl
Last Modification : November 14, 2007 by Fabrizio Riguzzi
===========================================================================*/
/* ----------- beginning of system dependent features ---------------------
To run the SLG system under a version of Prolog other than Quintus,
comment out the following Quintus-specific code, and include the code
for the Prolog you are running.
*/
% Quintus
/* Begin Quintus specific code */
% :- use_module(library(basics)).
% :- dynamic 'slg$prolog'/1, 'slg$tab'/2.
% :- dynamic slg_expanding/0.
% :- dynamic wfs_trace/0.
/* End Quintus specific code */
% Sicstus
/* Begin Sicstus specific code */
/* append([],L,L).
append([X|L1],L2,[X|L3]) :- append(L1,L2,L3).
member(X,[X|_]).
member(X,[_|L]) :- member(X,L).
memberchk(X,[X|_]) :- !.
memberchk(X,[_|L]) :- memberchk(X,L).
*/
:- dynamic 'slg$prolog'/1, 'slg$tab'/2.
:- dynamic slg_expanding/0.
:- dynamic wfs_trace/0.
/* End Sicstus specific code */
% XSB
/* Begin XSB specific code */
/* To compile this under xsb, you must allocate more than the default stack
space when running xsb. E.g. use % xsb -m 2000
*/
%:- import member/2, memberchk/2, append/3, ground/1 from basics.
%:- import numbervars/3 from num_vars.
%:- dynamic slg_expanding/0.
%:- dynamic 'slg$prolog'/1, 'slg$tab'/2.
%:- dynamic wfs_trace/0.
/* End XSB specific code */
/* -------------- end of system dependent features ----------------------- */
/* -------------- beginning of slg_load routines -------------------------
An input file may contain three kinds of directives (in addition to
regular Prolog clauses and commands):
a) :- default(prolog).
:- default(tabled).
All predicates defined from now on are prolog (tabled) predicates
unless specified otherwise later.
b) :- tabled pred_name/arity.
pred_name/arity is a tabled predicate. A comma separated list
is also acceptable.
c) :- prolog pred_name/arity.
pred_name/arity is a prolog predicate. A comma separated list
is also acceptable.
Besides Prolog clauses, we allow general clauses where the body is a
universal disjunction of literals. Such clauses are specified in the form
Head <-- Body.
(Maybe <-- can be viewed as "All".) The head must be an atom of a tabled
predicate and the body should be a disjunction of literals (separated by ';')
and should not contain cut. The head must be ground whenever it is called.
All variables in the body that do not occur in the head are universally
quantified.
There is NO support for module facilities. In particular, ALL TABLED
PREDICATES SHOULD BE DEFINED IN MODULE 'user'.
*/
:- op(1200,xfx,<--).
:- op(1150,fx,[(tabled),(prolog),(default)]).
:- op(900,xfx,<-).
:- assert('slg$tabled'(0,0)), retractall('slg$tabled'(_,_)).
:- assert('slg$default'((prolog))).
do_term_expansion(end_of_file,_) :- !,
retractall('slg$default'(_)),
assert('slg$default'((prolog))),
retractall('slg$prolog'(_)),
retractall('slg$tab'(_,_)),
fail.
do_term_expansion((:-Com),Clauses) :- !,
expand_command(Com,Clauses).
do_term_expansion((H-->B),NewClause) :- !,
\+ slg_expanding,
assert(slg_expanding),
expand_term((H-->B),Clause),
retractall(slg_expanding),
do_term_expansion(Clause,NewClause).
do_term_expansion((Head <-- Body),Clauses) :- !,
functor(Head,P,A),
Pred = P/A,
( 'slg$tab'(P,A) ->
convert_univ_clause(Head,Body,Clauses)
; 'slg$prolog'(Pred) ->
write('Error: Prolog predicate '), write(Pred),
write(' in clauses with universal disjunction.'),nl,
write(' Clause ignored: '), write((Head <-- Body)), nl,
Clauses = []
; 'slg$default'(Default),
( Default == (prolog) ->
write('Error: Prolog predicate '), write(Pred),
write(' in clauses with universal disjunction.'),nl,
write(' Clause ignored: '), write((Head <-- Body)), nl,
Clauses = []
; assert('slg$tab'(P,A)),
retractall('slg$tabled'(P,A)),
assert('slg$tabled'(P,A)),
functor(NewHead,P,A),
Clauses = [(:- retractall('slg$tabled'(P,A)), assert('slg$tabled'(P,A))),
(NewHead :- slg(NewHead))|RestClauses],
convert_univ_clause(Head,Body,RestClauses)
)
).
do_term_expansion(Clause,Clauses) :-
( Clause = (Head :- Body) -> true; Head = Clause, Body = true ),
functor(Head,P,A),
Pred = P/A,
( 'slg$tab'(P,A) ->
convert_tabled_clause(Head,Body,Clauses)
; 'slg$prolog'(Pred) ->
Clauses = Clause
; 'slg$default'(Default),
( Default == (prolog) ->
Clauses = Clause
; ( 'slg$tab'(P,A) ->
convert_tabled_clause(Head,Body,Clauses)
; assert('slg$tab'(P,A)),
retractall('slg$tabled'(P,A)),
assert('slg$tabled'(P,A)),
functor(NewHead,P,A),
Clauses = [(:- retractall('slg$tabled'(P,A)), assert('slg$tabled'(P,A))),
(NewHead :- slg(NewHead))|RestClauses],
convert_tabled_clause(Head,Body,RestClauses)
)
)
).
expand_command(tabled(Preds),Clauses) :-
expand_command_table(Preds,Clauses,[]).
expand_command(prolog(Preds),Clauses) :-
expand_command_prolog(Preds,Clauses,[]).
expand_command(multifile(Preds),(:-multifile(NewPreds))) :-
add_table_preds(Preds,NewPreds,[]).
expand_command(dynamic(Preds),(:-dynamic(NewPreds))) :-
add_table_preds(Preds,NewPreds,[]).
expand_command(default(D),[]) :-
( (D == (prolog); D == (tabled)) ->
retractall('slg$default'(_)),
assert('slg$default'(D))
; write('Warning: illegal default '),
write(D),
write(' ignored.'),
nl
).
expand_command_table((Pred,Preds),Clauses0,Clauses) :- !,
expand_command_table_one(Pred,Clauses0,Clauses1),
expand_command_table(Preds,Clauses1,Clauses).
expand_command_table(Pred,Clauses0,Clauses) :-
expand_command_table_one(Pred,Clauses0,Clauses).
expand_command_table_one(Pspec,Clauses0,Clauses) :-
( Pspec = P/A -> true; P = Pspec, A = 0 ),
Pred = P/A,
functor(H,P,A),
( ( predicate_property(H,built_in); slg_built_in(H) ) ->
write('ERROR: Cannot table built_in '),
write(Pred), nl,
Clauses0 = Clauses
; 'slg$prolog'(Pred) ->
write('ERROR: '),
write(Pred),
write(' assumed to be a Prolog predicate'),
nl,
tab(7),
write('But later declared a tabled predicate.'),
nl,
Clauses0 = Clauses
; 'slg$tab'(P,A) ->
Clauses0 = Clauses
; assert('slg$tab'(P,A)),
retractall('slg$tabled'(P,A)),
assert('slg$tabled'(P,A)),
Clauses0 = [(:- retractall('slg$tabled'(P,A)), assert('slg$tabled'(P,A))),
(H :- slg(H))|Clauses]
).
expand_command_prolog((Pred,Preds),Clauses0,Clauses) :- !,
expand_command_prolog_one(Pred,Clauses0,Clauses1),
expand_command_prolog(Preds,Clauses1,Clauses).
expand_command_prolog(Pred,Clauses0,Clauses) :-
expand_command_prolog_one(Pred,Clauses0,Clauses).
expand_command_prolog_one(Pspec,Clauses0,Clauses) :-
( Pspec = P/A -> true; P = Pspec, A = 0 ),
Pred = P/A,
( 'slg$tab'(P,A) ->
write('ERROR: '),
write(Pred),
write(' assumed to be a tabled predicate'),
nl,
tab(7),
write('But later declared a Prolog predicate.'),
nl,
Clauses0 = Clauses
; retractall('slg$tab'(P,A)),
retractall('slg$tabled'(P,A)),
( 'slg$prolog'(Pred) ->
true
; assert('slg$prolog'(Pred))
),
Clauses0 = [(:- retractall('slg$tabled'(P,A)))|Clauses]
).
add_table_preds(Preds,NewPreds0,NewPreds) :-
( Preds == [] ->
NewPreds0 = NewPreds
; Preds = [P|Ps] ->
add_table_preds(P,NewPreds0,NewPreds1),
add_table_preds(Ps,NewPreds1,NewPreds)
; Preds = (P,Ps) ->
add_table_preds(P,NewPreds0,NewPreds1),
add_table_preds(Ps,NewPreds1,NewPreds)
; ( Preds = P/A -> true; P = Preds, A = 0 ),
( 'slg$tab'(P,A) ->
name(P,Pl),
name(NewP,[115,108,103,36|Pl]), % 'slg$'
NewA is A+1,
NewPreds0 = [P/A,NewP/NewA|NewPreds]
; NewPreds0 = [P/A|NewPreds]
)
).
convert_tabled_clause(Head,Body,Clauses0) :-
conj_to_list(Body,Blist),
extract_guard(Blist,Guard,[],Nbody,Clauses0,Clauses),
list_to_conj(Guard,Gconj),
new_slg_head(Head,Nbody,NewHead),
( Gconj == true ->
Clauses = [NewHead]
; Clauses = [(NewHead :- Gconj)]
).
convert_univ_clause(Head,Body,Clauses) :-
disj_to_list(Body,Blist),
new_slg_head(Head,all(Blist),NewHead),
Clauses = [(NewHead :- ( ground0(Head) ->
true
; write('Error: Non-ground call '),
write(Head),
write(' in a clause with universal disjunction.'),
nl
))].
ground0(X) :- ground(X).
conj_to_list(Term,List) :-
conj_to_list(Term,List,[]).
conj_to_list(Term,List0,List) :-
( Term = (T1,T2) ->
conj_to_list(T1,List0,List1),
conj_to_list(T2,List1,List)
; Term == true ->
List0 = List
; List0 = [Term|List]
).
disj_to_list(Term,List) :-
disj_to_list(Term,List,[]).
disj_to_list(Term,List0,List) :-
( Term = (T1;T2) ->
disj_to_list(T1,List0,List1),
disj_to_list(T2,List1,List)
; Term == true ->
List0 = List
; List0 = [Term|List]
).
extract_guard([],G,G,[],Cls,Cls).
extract_guard([Lit|List],G0,G,Rest,Cls0,Cls) :-
( Lit = (\+N) ->
Nlit = N
; Nlit = Lit
),
( ( predicate_property(Nlit,built_in); slg_built_in(Nlit) ) ->
G0 = [Lit|G1],
extract_guard(List,G1,G,Rest,Cls0,Cls)
; functor(Nlit,P,A),
Pred = P/A,
( 'slg$tab'(P,A) ->
G0 = G,
Rest = [Lit|List],
Cls0 = Cls
; 'slg$prolog'(Pred) ->
G0 = [Lit|G1],
extract_guard(List,G1,G,Rest,Cls0,Cls)
; 'slg$default'((prolog)) ->
G0 = [Lit|G1],
assert('slg$prolog'(Pred)),
Cls0 = [(:- 'slg$prolog'(Pred) -> true; assert('slg$prolog'(Pred)))|Cls1],
extract_guard(List,G1,G,Rest,Cls1,Cls)
; 'slg$default'((tabled)) ->
G0 = G,
Rest = [Lit|List],
assert('slg$tab'(P,A)),
retractall('slg$tabled'(P,A)),
assert('slg$tabled'(P,A)),
functor(Head,P,A),
Cls0 = [(:- retractall('slg$tabled'(P,A)), assert('slg$tabled'(P,A))),
(Head :- slg(Head))|Cls]
)
).
list_to_conj([],true).
list_to_conj([Lit|List],G0) :-
( List == [] ->
G0 = Lit
; G0 = (Lit,G),
list_to_conj(List,G)
).
new_slg_head(Head,Body,NewHead) :-
functor(Head,P,A),
name(P,Pl),
name(Npred,[115,108,103,36|Pl]), % 'slg$'
Narity is A+1,
functor(NewHead,Npred,Narity),
arg(Narity,NewHead,Body),
put_in_args(0,A,Head,NewHead).
put_in_args(A,A,_,_).
put_in_args(A0,A,Head,NewHead) :-
A0 < A,
A1 is A0+1,
arg(A1,Head,Arg),
arg(A1,NewHead,Arg),
put_in_args(A1,A,Head,NewHead).
slg_built_in(slg(_)).
slg_built_in(_<-_).
slg_built_in(slgall(_,_)).
slg_built_in(slgall(_,_,_,_)).
slg_built_in(emptytable(_)).
slg_built_in(st(_,_)).
slg_built_in(stnot(_,_)).
slg_built_in(stall(_,_,_)).
slg_built_in(stall(_,_,_,_,_)).
slg_built_in(stselect(_,_,_,_)).
slg_built_in(stselect(_,_,_,_,_,_)).
slg_built_in(xtrace).
slg_built_in(xnotrace).
/* ----------------- end of slg_load routines --------------------------- */
/* SLG tracing:
xtrace: turns SLG trace on, which prints out tables at various
points
xnotrace: turns off SLG trace
*/
xtrace :-
( wfs_trace ->
true
; assert(wfs_trace)
).
xnotrace :-
( wfs_trace ->
retractall(wfs_trace)
; true
).
/* isprolog(Call): Call is a Prolog subgoal */
isprolog(Call) :-
functor(Call,P,A),
\+ 'slg$tabled'(P,A).
/* slg(Call):
It returns all true answers of Call under the well-founded semantics
one by one.
*/
slg(Call) :-
( isprolog(Call) ->
call(Call)
; oldt(Call,Tab),
ground(Call,Ggoal),
find(Tab,Ggoal,Ent),
ent_to_anss(Ent,Anss),
member_anss(d(Call,[]),Anss)
).
/* Call<-Cons:
It returns all true or undefined answers of Call one by one. In
case of a true answer, Cons = []. For an undefined answer,
Cons is a list of delayed literals.
*/
Call<-Cons :-
( isprolog(Call) ->
call(Call),
Cons = []
; oldt(Call,Tab),
ground(Call,Ggoal),
find(Tab,Ggoal,Ent),
ent_to_anss(Ent,Anss),
member_anss(d(Call,Cons),Anss)
).
/* emptytable(EmptTab): creates an initial empty stable.
*/
emptytable(0:[]).
/* slgall(Call,Anss):
slgall(Call,Anss,N0-Tab0,N-Tab):
If Call is a prolog call, findall is used, and Tab = Tab0;
If Call is an atom of a tabled predicate, SLG evaluation
is carried out.
*/
slgall(Call,Anss) :-
slgall(Call,Anss,0:[],_).
slgall(Call,Anss,N0:Tab0,N:Tab) :-
( isprolog(Call) ->
findall(Call,Call,Anss),
N = N0, Tab = Tab0
; ground(Call,Ggoal),
( find(Tab0,Ggoal,Ent) ->
ent_to_anss(Ent,Answers),
Tab = Tab0
; new_init_call(Call,Ggoal,Ent,[],S1,1,Dfn1),
add_tab_ent(Ggoal,Ent,Tab0,Tab1),
oldt(Call,Ggoal,Tab1,Tab,S1,_S,Dfn1,_Dfn,maxint-maxint,_Dep,N0:[],N:_TP),
find(Tab,Ggoal,NewEnt),
ent_to_anss(NewEnt,Answers)
),
ansstree_to_list(Answers,Anss,[])
).
/* st(Call,PSM):
stnot(Call,PSM):
It finds a stable model in which Call must be true (false).
Call must be ground.
*/
st(Call,PSM) :-
st_true_false(Call,true,PSM).
stnot(Call,PSM) :-
st_true_false(Call,false,PSM).
st_true_false(Call,Val,PSM) :-
( isprolog(Call) ->
PSM = [],
call(Call)
; ground(Call) ->
wfs_newcall(Call,[],Tab1,0,_),
find(Tab1,Call,Ent),
ent_to_anss(Ent,Anss),
( succeeded(Anss) ->
( Val == true ->
PSM = []
; fail
)
; failed(Anss) ->
( Val == false ->
PSM = []
; fail
)
; assume_one(Call,Val,Tab1,Tab2,[],Abd1,A0,A1),
collect_unds(Anss,A1,A),
st(A0,A,Tab2,Tab3,Abd1,Abd,[],DAbd,[],_Plits),
final_check(Abd,Tab3,_Tab,DAbd,PSM)
)
; write('Error: non-ground call '),
write(Call),
write(' in st/2.'),
nl,
fail
).
/* stall(Call,Anss,PSM):
stall(Call,Anss,PSM,Tab0,Tab):
It computes a partial stable model PSM and collects all
answers of Call in that model.
*/
stall(Call,Anss,PSM) :-
stall(Call,Anss,PSM,0:[],_).
stall(Call,Anss,PSM,N0:Tab0,N:Tab) :-
( isprolog(Call) ->
findall(Call,Call,Anss),
PSM = [], N = N0, Tab = Tab0
; ground(Call,Ggoal),
( find(Tab0,Ggoal,Ent) ->
Tab1 = Tab0, N = N0
; wfs_newcall(Call,Tab0,Tab1,N0,N),
find(Tab1,Ggoal,Ent)
),
ent_to_delay(Ent,Delay),
( Delay == false ->
Fent = Ent, PSM = [], Tab = Tab1
; ent_to_anss(Ent,Anss0),
collect_unds(Anss0,A0,A),
st(A0,A,Tab1,Tab2,[],Abd,[],DAbd,[],_Plits),
final_check(Abd,Tab2,Tab,DAbd,PSM),
find(Tab,Ggoal,Fent)
),
ent_to_anss(Fent,Anss1),
ansstree_to_list(Anss1,Anss,[])
).
/* stselect(Call,PSM0,Anss,PSM):
stselect(Call,PSM0,Anss,PSM,N0:Tab0,N:Tab):
It computes a partial stable model PSM in which all ground
literals in PSM0 are true, and returns all answers of Call
in the partial stable model. Call must be an atom of a tabled
or stable predicate.
*/
stselect(Call,PSM0,Anss,PSM) :-
stselect(Call,PSM0,Anss,PSM,0:[],_).
stselect(Call,PSM0,Anss,PSM,N0:Tab0,N:Tab) :-
( isprolog(Call) ->
write('Error: Prolog predicate '),
write(Call),
write('stselect.'),
fail
; wfsoldt(Call,PSM0,Ent,Tab0,Tab1,N0,N),
ent_to_delay(Ent,Delay),
assume_list(PSM0,true,Tab1,Tab2,[],Abd0,A0,A1),
( Delay == false ->
A1 = A2
; ent_to_anss(Ent,Anss0),
collect_unds(Anss0,A1,A2)
),
st(A0,A2,Tab2,Tab3,Abd0,Abd,[],DAbd,[],_Plits),
final_check(Abd,Tab3,Tab,DAbd,PSM),
ground(Call,Ggoal),
find(Tab,Ggoal,Fent),
ent_to_anss(Fent,Anss1),
ansstree_to_list(Anss1,Anss,[])
).
wfsoldt(Call,PSM0,Ent,Tab0,Tab,N0,N) :-
ground(Call,Ggoal),
( find(Tab0,Ggoal,Ent) ->
Tab1 = Tab0, N1 = N0
; wfs_newcall(Call,Tab0,Tab1,N0,N1),
find(Tab1,Ggoal,Ent)
),
wfsoldt_ground(PSM0,Tab1,Tab,N1,N).
wfsoldt_ground([],Tab,Tab,N,N).
wfsoldt_ground([A|PSM],Tab0,Tab,N0,N) :-
( ground(A) ->
true
; write('Error: non-ground assumption in stable model selection: '),
write(A), nl, fail
),
( A = (\+G) ->
true
; A = G
),
( isprolog(G) ->
Tab1 = Tab0, N1 = N0,
call(A)
; find(Tab0,G,_) ->
Tab1 = Tab0, N1 = N0
; wfs_newcall(G,Tab0,Tab1,N0,N1)
),
wfsoldt_ground(PSM,Tab1,Tab,N1,N).
wfs_newcall(Call,Tab0,Tab,N0,N) :-
new_init_call(Call,Ggoal,Ent0,[],S1,1,Dfn1),
add_tab_ent(Ggoal,Ent0,Tab0,Tab1),
oldt(Call,Ggoal,Tab1,Tab,S1,_S,Dfn1,_Dfn,maxint-maxint,_Dep,N0:[],N:_TP).
/* collect_unds(Anss,A0,A):
collects all delayed literals in answers Anss in a open-ended difference
list A0/A. These delayed literals are assumed either false or true in the
stable model computation.
*/
collect_unds([],A,A).
collect_unds(l(_GH,Lanss),A1,A) :-
collect_unds_lanss(Lanss,A1,A).
collect_unds(n2(T1,_,T2),A1,A) :-
collect_unds(T1,A1,A2),
collect_unds(T2,A2,A).
collect_unds(n3(T1,_,T2,_,T3),A1,A) :-
collect_unds(T1,A1,A2),
collect_unds(T2,A2,A3),
collect_unds(T3,A3,A).
collect_unds_lanss([],A,A).
collect_unds_lanss([d(_,D)|Lanss],A1,A) :-
collect_unds_list(D,A1,A2),
collect_unds_lanss(Lanss,A2,A).
collect_unds_list([],A,A).
collect_unds_list([Lit|D],[Lit|A1],A) :-
collect_unds_list(D,A1,A).
/* st(A0,A,Tab0,Tab,Abd0,Abd,DAbd0,DAbd,Plits0,Plits):
A0/A is an open-ended difference list containing a list of
delayed literals. st tries for each delayed literal to
assume that it is true or false and checks to see if
it leads to a partial stable model. Propagation of assumed
truth values is carried out as much as possible. It will
fail if the relevant program contains p :- \+p.
Abd0/Abd is an accumulator for a table of assumed truth
values. They are checked against the table Tab0/Tab for
consistency later in check_consistency. DAbd0/DAbd is an
accumulator for truth values of undefined literals that
are derived from assumed truth values of other literals.
Plits0/Plits is an accumulator for avoiding positive
infinite loops in processing positive delayed literals.
*/
st(A0,A,Tab0,Tab,Abd0,Abd,DAbd0,DAbd,Plits0,Plits) :-
( % empty difference list
A0 == A ->
Tab = Tab0, Abd = Abd0, DAbd = DAbd0, Plits = Plits0
; A0 = [Lit|A1],
( % non-ground negative literals
Lit = (Ggoal - (\+GH)) ->
write('Error: cannot handle non-ground negative literals: '),
write(\+GH), nl, fail
; % positive undefined literal
Lit = Ggoal-GH ->
( % encountered before
find(Plits0,Lit,_) ->
st(A1,A,Tab0,Tab,Abd0,Abd,DAbd0,DAbd,Plits0,Plits)
; % otherwise, process undefined literals it depends upon
addkey(Plits0,Lit,_,Plits1),
find(Tab0,Ggoal,Ent),
ent_to_anss(Ent,Anss),
find(Anss,GH,Lanss),
collect_unds_lanss(Lanss,A,NewA),
st(A1,NewA,Tab0,Tab,Abd0,Abd,DAbd0,DAbd,Plits1,Plits)
)
; % negative undefined literal
Lit = (\+G) ->
( % has been assumed or derived to be true or false
( find(Abd0,G,_Val); find(DAbd0,G,_) ) ->
st(A1,A,Tab0,Tab,Abd0,Abd,DAbd0,DAbd,Plits0,Plits)
; find(Tab0,G,Gent),
ent_to_anss(Gent,Ganss),
( % found to be false already
failed(Ganss) ->
addkey(DAbd0,G,false,DAbd1),
st(A1,A,Tab0,Tab,Abd0,Abd,DAbd1,DAbd,Plits0,Plits)
; % found to be true already
succeeded(Ganss) ->
addkey(DAbd0,G,true,DAbd1),
st(A1,A,Tab0,Tab,Abd0,Abd,DAbd1,DAbd,Plits0,Plits)
; % create a choice point
addkey(Abd0,G,Val,Abd1),
( Ganss = l(G,[d(G,Ds)]), memberchk(\+G,Ds) ->
Val = false
; ( Val = false; Val = true )
),
propagate_forward(G,Val,Tab0,Tab1,Abd1),
A = [G-G|NewA], % make sure delayed literals of G are checked
propagate_backward(G,Val,Ganss,Tab1,Tab2,Abd1,Abd2,NewA,NNA),
st(A1,NNA,Tab2,Tab,Abd2,Abd,DAbd0,DAbd,Plits0,Plits)
)
)
)
).
/* propagate_forward(G,Val,Tab0,Tab,Abd):
G has been assumed to be Val, and this information is propagated
using simplification or forward chaining links as much as
possible.
*/
propagate_forward(G,Val,Tab0,Tab,Abd) :-
updatevs(Tab0,G,Ent0,Ent,Tab1),
Ent0 = e(Nodes,ANegs,Anss,Delay,Comp,Gdfn,Slist0),
Ent = e(Nodes,ANegs,Anss,Delay,Comp,Gdfn,Slist),
extract_known_by_abd(Slist0,Val,[],Slist,[],Klist),
simplify(Klist,Tab1,Tab,Abd).
/* The forward chaining is such that negative literals can fail
or succeed by assumption, and positive literals can fail
by assumption, but cannot succeed by assumption.
This avoids the construction of supported models that are
not stable.
*/
extract_known_by_abd([],_,Slist,Slist,Klist,Klist).
extract_known_by_abd([Link|Links],Val,Slist0,Slist,Klist0,Klist) :-
( Link = (_ : (\+ _)) ->
( Val == false ->
Slist1 = Slist0,
Klist1 = [succ-Link|Klist0]
; Val == true ->
Slist1 = Slist0,
Klist1 = [fail-Link|Klist0]
; Slist1 = [Link|Slist0],
Klist1 = Klist0
)
; % Link = (_ : _-GH) ->
( Val = false ->
Slist1 = Slist0,
Klist1 = [fail-Link|Klist0]
; % Val = true ->
Slist1 = [Link|Slist0],
Klist1 = Klist0
)
),
extract_known_by_abd(Links,Val,Slist1,Slist,Klist1,Klist).
/* propagate_backward(G,Val,Ganss,Tab0,Tab,Abd0,Abd,A,NewA):
It tried to propagate the Val of G backward through answers
if possible. If G is assumed to be true, and G has only one
answer clause, then all literals in the body of the answer
clause must be true. If G is assumed to be false, then all
literals in answer clauses of G that have a single literal
are assumed to be false too. Otherwise, it is no-op.
*/
propagate_backward(G,Val,Ganss,Tab0,Tab,Abd0,Abd,A,NewA) :-
( Ganss = l(G,Lanss) ->
( Val == true, Lanss = [d(G,Ds)] ->
assume_list(Ds,true,Tab0,Tab,Abd0,Abd,A,NewA)
; Val == false, findall(Lit,member(d(G,[Lit]),Lanss),Ds) ->
assume_list(Ds,false,Tab0,Tab,Abd0,Abd,A,NewA)
; Tab = Tab0, Abd = Abd0, A = NewA
)
; Tab = Tab0, Abd = Abd0, A = NewA
).
assume_list([],_Val,Tab,Tab,Abd,Abd,A,A).
assume_list([Lit|Lits],Val,Tab0,Tab,Abd0,Abd,A0,A) :-
assume_one(Lit,Val,Tab0,Tab1,Abd0,Abd1,A0,A1),
assume_list(Lits,Val,Tab1,Tab,Abd1,Abd,A1,A).
/* assume_one(Lit,Val,Tab0,Tab,Abd0,Abd,A0,A):
Due to back propagation, Lit is assumed to be Val.
However, this assumption is carried out only if
Lit is a delayed literal of a ground call or most
general call.
*/
assume_one(Ggoal-GH,_Val,Tab0,Tab,Abd0,Abd,A0,A) :-
Ggoal \== GH,
!,
Tab = Tab0, Abd = Abd0, A = A0.
assume_one(Lit,Val,Tab0,Tab,Abd0,Abd,A0,A) :-
( Lit = G-G ->
GVal = Val
; Lit = (\+G) ->
( Val == true -> GVal = false; GVal = true )
; Lit = G ->
GVal = Val
),
( find(Abd0,G,V) -> % already assumed
( V == GVal ->
Tab = Tab0, Abd = Abd0, A = A0
; fail
)
; find(Tab0,G,Gent),
ent_to_anss(Gent,Ganss),
( failed(Ganss) -> % already known
( GVal == true ->
fail
; Tab = Tab0, Abd = Abd0, A = A0
)
; succeeded(Ganss) -> % already known
( GVal == false ->
fail
; Tab = Tab0, Abd = Abd0, A = A0
)
; addkey(Abd0,G,GVal,Abd1), % otherwise, propagate
propagate_forward(G,GVal,Tab0,Tab1,Abd1),
A0 = [G-G|A1],
propagate_backward(G,Ganss,GVal,Tab1,Tab,Abd1,Abd,A1,A)
)
).
final_check(Abd,Tab0,Tab,DAbd,Alist) :-
check_consistency(Abd,Tab0,Tab,Alist0,Alist1),
add_dabd(DAbd,Alist1,[]),
sort(Alist0,Sorted),
listval_to_listlit(Sorted,Alist).
listval_to_listlit([],[]).
listval_to_listlit([Val|Vlist],[Lit|Llist]) :-
val_to_lit(Val,Lit),
listval_to_listlit(Vlist,Llist).
val_to_lit(G-true,G).
val_to_lit(G-false,\+G).
/* check_consistency(Abd,Tab0,Tab,Alist0,Alist):
A proposition may be assumed to be true, but no true answer
is derived at the end, which is inconsistency. A proposition
may be assumed to be false, but has a true answer. The latter
case is checked when the true answer is derived. Here Abd
indicates the assumed truth values, and answers in Tab0
indicate the derived values by a fixpoint computation of
forward chaining.
Also at the end of a fixpoint computation, a subgoal may
have only delayed answers with positive literals. These
have to be deleted in order for Tab0/Tab to be used
correctly later.
*/
check_consistency([],Tab,Tab,Alist,Alist).
check_consistency(l(G,Val),Tab0,Tab,Alist0,Alist) :-
updatevs(Tab0,G,Ent0,Ent,Tab),
Ent0 = e(Nodes,ANegs,Anss0,_Delay,Comp,Dfn,Slist),
Ent = e(Nodes,ANegs,Anss,false,Comp,Dfn,Slist),
( Val == true ->
succeeded(Anss0),
Anss = l(G,[d(G,[])]), % delete answers with positive delays
Alist0 = [G-Val|Alist]
; % Val == false ->
Anss = [],
Alist0 = [G-Val|Alist]
).
check_consistency(n2(T1,_,T2),Tab0,Tab,Alist0,Alist) :-
check_consistency(T1,Tab0,Tab1,Alist0,Alist1),
check_consistency(T2,Tab1,Tab,Alist1,Alist).
check_consistency(n3(T1,_,T2,_,T3),Tab0,Tab,Alist0,Alist) :-
check_consistency(T1,Tab0,Tab1,Alist0,Alist1),
check_consistency(T2,Tab1,Tab2,Alist1,Alist2),
check_consistency(T3,Tab2,Tab,Alist2,Alist).
add_dabd([],Alist,Alist).
add_dabd(l(G,Val),[G-Val|Alist],Alist).
add_dabd(n2(T1,_,T2),Alist0,Alist) :-
add_dabd(T1,Alist0,Alist1),
add_dabd(T2,Alist1,Alist).
add_dabd(n3(T1,_,T2,_,T3),Alist0,Alist) :-
add_dabd(T1,Alist0,Alist1),
add_dabd(T2,Alist1,Alist2),
add_dabd(T3,Alist2,Alist).
/* oldt(QueryAtom,Table): top level call for SLG resolution.
It returns a table consisting of answers for each relevant
subgoal. For stable predicates, it basically extract the
relevant set of ground clauses by solving Prolog predicates
and other well-founded predicates.
*/
oldt(Call,Tab) :-
new_init_call(Call,Ggoal,Ent,[],S1,1,Dfn1),
add_tab_ent(Ggoal,Ent,[],Tab1),
oldt(Call,Ggoal,Tab1,Tab,S1,_S,Dfn1,_Dfn,maxint-maxint,_Dep,0:[],_TP),
( wfs_trace ->
nl, write('Final '), display_table(Tab), nl
; true
).
/* oldt(Call,Ggoal,Tab0,Tab,Stack0,Stack,DFN0,DFN,Dep0,Dep,TP0,TP)
explores the initial set of edges, i.e., all the
program clauses for Call. Ggoal is of the form
Gcall-Gdfn, where Gcall is numbervar of Call and Gdfn
is the depth-first number of Gcall. Tab0/Tab,Stack0/Stack,
DFN0/DFN, and Dep0/Dep are accumulators for the table,
the stack of subgoals, the DFN counter, and the dependencies.
TP0/TP is the accumulator for newly created clauses during
the processing of general clauss with universal disjunctions
in the body. These clauses are created in order to guarantee
polynomial data complexity in processing clauses with
universal disjuntions in the body of a clause. The newly
created propositions are represented by numbers.
*/
oldt(Call,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
( number(Call) ->
TP0 = (_ : Tcl),
find(Tcl,Call,Clause),
edge_oldt(Clause,Ggoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1)
; findall(rule(d(Call,[]),Body),
(new_slg_head(Call,Body,NewHead),call(NewHead)),
Frames),
map_oldt(Frames,Ggoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1)
),
comp_tab_ent(Ggoal,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
map_oldt([],_Ggoal,Tab,Tab,S,S,Dfn,Dfn,Dep,Dep,TP,TP).
map_oldt([Clause|Frames],Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
edge_oldt(Clause,Ggoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
map_oldt(Frames,Ggoal,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
/* edge_oldt(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
Clause may be one of the following forms:
rule(d(H,Dlist),Blist)
rule(d(H,all(Dlist)),all(Blist))
where the second form is for general clauses with a universal
disjunction of literals in the body. Dlist is a list of delayed
literals, and Blist is the list of literals to be solved.
Clause represents a directed edge from Ggoal to the left most
subgoal in Blist.
*/
edge_oldt(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
Clause = rule(Ans,B),
( B == [] ->
ans_edge(Ans,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
; B = [Lit|_] ->
( Lit = (\+N) ->
neg_edge(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
; pos_edge(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
)
; B = all(Bl) ->
( Bl == [] ->
ans_edge(Ans,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
; Bl = [Lit|_],
( Lit = (\+N) ->
aneg_edge(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
; apos_edge(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
)
)
).
ans_edge(Ans,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
( add_ans(Tab0,Ggoal,Ans,Nodes,Mode,Tab1) ->
( Mode = new_head ->
returned_ans(Ans,Ggoal,RAns),
map_nodes(Nodes,RAns,Tab1,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
; Mode = no_new_head ->
Tab = Tab1, S = S0, Dfn = Dfn0, Dep = Dep0, TP = TP0
)
; Tab = Tab0, S = S0, Dfn = Dfn0, Dep = Dep0, TP = TP0
).
neg_edge(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
Clause = rule(_,[\+N|_]),
( ground(N) -> true
; write('Flounder: '), write(\+N), nl, fail
),
Node = (Ggoal:Clause),
Ngoal = N, % N is already ground
( isprolog(N) -> % if N is a Prolog predicate
( call(N) -> % then just call
Tab = Tab0, S = S0, Dfn = Dfn0, Dep = Dep0, TP = TP0
; apply_subst(Node,d(\+ N,[]),Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
)
; ( find(Tab0,Ngoal,Nent) ->
Tab2 = Tab0, S2 = S0, Dfn2 = Dfn0, Dep1 = Dep0, TP1 = TP0
; new_init_call(N,Ngoal,Ent,S0,S1,Dfn0,Dfn1),
add_tab_ent(Ngoal,Ent,Tab0,Tab1),
oldt(N,Ngoal,Tab1,Tab2,S1,S2,Dfn1,Dfn2,maxint-maxint,Ndep,TP0,TP1),
compute_mins(Dep0,Ndep,pos,Dep1),
find(Tab2,Ngoal,Nent)
),
ent_to_comp(Nent,Ncomp),
ent_to_anss(Nent,Nanss),
( succeeded(Nanss) ->
Tab = Tab2, S = S2, Dfn = Dfn2, Dep = Dep1, TP = TP1
; failed(Nanss), Ncomp == true ->
apply_subst(Node,d(\+N,[]),Tab2,Tab,S2,S,Dfn2,Dfn,Dep1,Dep,TP1,TP)
; apply_subst(Node,d(\+N,[\+N]),Tab2,Tab,S2,S,Dfn2,Dfn,Dep1,Dep,TP1,TP)
)
).
pos_edge(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
Clause = rule(_H,[N|_B]),
Node = (Ggoal:Clause),
ground(N,Ngoal),
( isprolog(N) ->
findall(d(N,[]),call(N),Nanss),
map_anss_list(Nanss,Node,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
; ( find(Tab0,Ngoal,Nent) ->
ent_to_comp(Nent,Ncomp),
ent_to_anss(Nent,Nanss),
( Ncomp \== true ->
update_lookup_mins(Ggoal,Node,Ngoal,pos,Tab0,Tab1,Dep0,Dep1),
map_anss(Nanss,Node,Ngoal,Tab1,Tab,S0,S,Dfn0,Dfn,Dep1,Dep,TP0,TP)
; % N is completed.
map_anss(Nanss,Node,Ngoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
)
; % otherwise N is new
new_pos_call(Ngoal,Node,Ent,S0,S1,Dfn0,Dfn1),
add_tab_ent(Ngoal,Ent,Tab0,Tab1),
oldt(N,Ngoal,Tab1,Tab2,S1,S,Dfn1,Dfn,maxint-maxint,Ndep,TP0,TP),
update_solution_mins(Ggoal,Ngoal,pos,Tab2,Tab,Ndep,Dep0,Dep)
)
).
aneg_edge(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
Clause = rule(_H,all([\+N|_B])),
Node = (Ggoal:Clause),
ground(N,Ngoal),
( isprolog(N) ->
findall(d(N,[]),call(N),Nanss),
return_to_disj_list(Nanss,Node,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
; ( find(Tab0,Ngoal,Nent) ->
ent_to_comp(Nent,Ncomp),
ent_to_anss(Nent,Nanss),
( Ncomp \== true ->
update_lookup_mins(Ggoal,Node,Ngoal,aneg,Tab0,Tab,Dep0,Dep),
S = S0, Dfn = Dfn0, TP = TP0
; % N is completed.
return_to_disj(Nanss,Node,Ngoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
)
; % otherwise N is new
new_aneg_call(Ngoal,Node,Ent,S0,S1,Dfn0,Dfn1),
add_tab_ent(Ngoal,Ent,Tab0,Tab1),
oldt(N,Ngoal,Tab1,Tab2,S1,S,Dfn1,Dfn,maxint-maxint,Ndep,TP0,TP),
update_solution_mins(Ggoal,Ngoal,pos,Tab2,Tab,Ndep,Dep0,Dep)
)
).
apos_edge(Clause,Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
Clause = rule(d(H,D),all([N|B])),
( ground(N) -> true
; write('Flounder in a universal disjunction: '),
write(N),
nl,
fail
),
pos_edge(rule(d(H,[]),[N]),Ggoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
edge_oldt(rule(d(H,D),all(B)),Ggoal,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
apply_subst(Ggoal:Cl,d(An,Vr),Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
copy_term(Cl,rule(d(Ac,Vc),Body)),
( Body = [Call|NBody] ->
Call = An,
append(Vr,Vc,Vn)
; Body = all([Call|Calls]),
% Call = An, % An is the numbervar-ed version of Call.
( Vc == [] ->
Vn = all(Vr)
; Vc = all(Vc0),
append(Vr,Vc0,Vn0),
Vn = all(Vn0)
),
NBody = all(Calls)
),
edge_oldt(rule(d(Ac,Vn),NBody),Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP).
/* map_nodes(Nodes,Ans,....):
return Ans to each of the waiting nodes in Nodes, where a node
is of the form Ggoal:Clause.
*/
map_nodes([],_Ans,Tab,Tab,S,S,Dfn,Dfn,Dep,Dep,TP,TP).
map_nodes([Node|Nodes],Ans,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
apply_subst(Node,Ans,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
map_nodes(Nodes,Ans,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
map_anss([],_Node,_Ngoal,Tab,Tab,S,S,Dfn,Dfn,Dep,Dep,TP,TP).
map_anss(l(_GH,Lanss),Node,Ngoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
( Lanss == [] ->
Tab = Tab0, S = S0, Dfn = Dfn0, Dep = Dep0, TP = TP0
; Lanss = [Ans|_],
returned_ans(Ans,Ngoal,RAns),
apply_subst(Node,RAns,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
).
map_anss(n2(T1,_,T2),Node,Ngoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
map_anss(T1,Node,Ngoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
map_anss(T2,Node,Ngoal,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
map_anss(n3(T1,_,T2,_,T3),Node,Ngoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
map_anss(T1,Node,Ngoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
map_anss(T2,Node,Ngoal,Tab1,Tab2,S1,S2,Dfn1,Dfn2,Dep1,Dep2,TP1,TP2),
map_anss(T3,Node,Ngoal,Tab2,Tab,S2,S,Dfn2,Dfn,Dep2,Dep,TP2,TP).
map_anss_list([],_Node,Tab,Tab,S,S,Dfn,Dfn,Dep,Dep,TP,TP).
map_anss_list([Ans|Lanss],Node,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
apply_subst(Node,Ans,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
map_anss_list(Lanss,Node,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
/* return_to_disj(Nanss,Node,Ngoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
Nanss: an answer table for Ngoal
Node: is of the form (Ggoal:Clause), where Clause is of the form
rule(d(H,D),all([\+N|B]))
It carries out resolution of each answer with Clause, and constructs
a new clause rule(Head,NBody), where the body is basically a
conjunction of all the resolvents. If a resolvent is a disjunction
or a non-ground literal, a new proposition is created (which is
actually represented by a number), which has a clause whose body
is the resolvent.
*/
return_to_disj(Nanss,Node,Ngoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
Node = (Ggoal : Clause),
Clause = rule(Head,all(Body)),
TP0 = (N0 : Tcl0),
negative_return_all(Nanss,Body,Ngoal,NBody,[],N0,N,Tcl0,Tcl),
TP1 = (N : Tcl),
edge_oldt(rule(Head,NBody),Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP1,TP).
negative_return_all([],_Body,_Ngoal,NBody,NBody,N,N,Tcl,Tcl).
negative_return_all(l(_GH,Lanss),Body,Ngoal,NBody0,NBody,N0,N,Tcl0,Tcl) :-
( Lanss == [] ->
NBody0 = NBody, N = N0, Tcl = Tcl0
; Lanss = [Ans|_],
negative_return_one(Ans,Body,Ngoal,NBody0,NBody,N0,N,Tcl0,Tcl)
).
negative_return_all(n2(T1,_,T2),Body,Ngoal,NBody0,NBody,N0,N,Tcl0,Tcl) :-
negative_return_all(T1,Body,Ngoal,NBody0,NBody1,N0,N1,Tcl0,Tcl1),
negative_return_all(T2,Body,Ngoal,NBody1,NBody,N1,N,Tcl1,Tcl).
negative_return_all(n3(T1,_,T2,_,T3),Body,Ngoal,NBody0,NBody,N0,N,Tcl0,Tcl) :-
negative_return_all(T1,Body,Ngoal,NBody0,NBody1,N0,N1,Tcl0,Tcl1),
negative_return_all(T2,Body,Ngoal,NBody1,NBody2,N1,N2,Tcl1,Tcl2),
negative_return_all(T3,Body,Ngoal,NBody2,NBody,N2,N,Tcl2,Tcl).
negative_return_one(d(H,Tv),Body,Ngoal,NBody0,NBody,N0,N,Tcl0,Tcl) :-
copy_term(Body,[\+Call|Bs]),
H = Call,
( Tv == [] -> % no delay
( (Bs = [Lit], ground(Lit)) -> % resovlent is a ground literal
NBody0 = [Lit|NBody],
N = N0, Tcl = Tcl0
; Lit = N0, % otherwise, replace it with a number
N is N0+1,
NBody0 = [Lit|NBody],
Clause = rule(d(Lit,[]),all(Bs)),
add_tab_ent(Lit,Clause,Tcl0,Tcl)
)
; ( ground(H) -> % if there is delay, always replace with number
NewTv = [\+H]
; ground(H,GH),
NewTv = [Ngoal - (\+GH)]
),
Lit = N0,
N is N0+1,
NBody0 = [Lit|NBody],
Clause = rule(d(Lit,all(NewTv)),all(Bs)),
add_tab_ent(Lit,Clause,Tcl0,Tcl)
).
return_to_disj_list(Lanss,Node,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
Node = (Ggoal : Clause),
Clause = rule(Head,all(Body)),
TP0 = (N0 : Tcl0),
negative_return_list(Lanss,Body,NBody,[],N0,N,Tcl0,Tcl),
TP1 = (N : Tcl),
edge_oldt(rule(Head,NBody),Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP1,TP).
negative_return_list([],_Body,NBody,NBody,N,N,Tcl,Tcl).
negative_return_list([d(H,[])|Lanss],Body,NBody0,NBody,N0,N,Tcl0,Tcl) :-
copy_term(Body,[\+Call|Bs]),
H = Call,
( Bs = [Lit], ground(Lit) ->
NBody0 = [Lit|NBody1],
N1 = N0, Tcl1 = Tcl0
; Lit = N0,
N1 is N0+1,
NBody0 = [Lit|NBody1],
Clause = rule(d(Lit,[]),all(Bs)),
add_tab_ent(Lit,Clause,Tcl0,Tcl1)
),
negative_return_list(Lanss,Body,NBody1,NBody,N1,N,Tcl1,Tcl).
/* comp_tab_ent(Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP)
check if Ggoal and subgoals on top of it on the stack are
completely evaluated.
*/
comp_tab_ent(Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
( Dep0 == maxint-maxint ->
process_pos_scc(Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep,TP0,TP)
; update_mins(Ggoal,Dep0,pos,Tab0,Tab1,Gdfn,Gdep),
Gdep = Gpmin-Gnmin,
( Gdfn @=< Gpmin, Gnmin == maxint ->
process_pos_scc(Ggoal,Tab1,Tab,S0,S,Dfn0,Dfn,Dep,TP0,TP)
; Gdfn @=< Gpmin, Gdfn @=< Gnmin ->
process_neg_scc(Ggoal,Tab1,Tab,S0,S,Dfn0,Dfn,Dep,TP0,TP)
; Tab = Tab1, S0 = S, Dfn = Dfn0, Dep = Gdep, TP = TP0
)
).
process_pos_scc(Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep,TP0,TP) :-
( wfs_trace ->
write('Stack: '), nl, display_stack(S0,Tab0),
write('Completed call found: '), write(Ggoal), nl,
display_table(Tab0),
write('Completing calls ......'), nl, nl
; true
),
pop_subgoals(Ggoal,S0,S1,[],Scc),
complete_comp(Scc,Tab0,Tab1,Alist,[]),
return_aneg_nodes(Alist,Tab1,Tab,S1,S,Dfn0,Dfn,maxint-maxint,Dep,TP0,TP).
/* pop_subgoals(Ggoal,S0,S,Scc0,Scc)
pop off the stack subgoals up to and including Ggoal
*/
pop_subgoals(Ggoal,S0,S,Scc0,Scc) :-
S0 = [Sent|S1],
( Ggoal == Sent ->
S = S1,
Scc = [Sent|Scc0]
; pop_subgoals(Ggoal,S1,S,[Sent|Scc0],Scc)
).
/* complete_comp(Scc,Tab0,Tab,Alist0,Alist):
process the list Scc of subgoals that are
completely evaluated.
*/
complete_comp([],Tab,Tab,Alist,Alist).
complete_comp([Ggoal|Scc],Tab0,Tab,Alist0,Alist) :-
complete_one(Ggoal,Tab0,Tab1,Alist0,Alist1),
complete_comp(Scc,Tab1,Tab,Alist1,Alist).
/* complete_one(Ggoal,Tab0,Tab,Alist0,Alist)
process one subgoal that has been completely
evaluated:
1. set its Nodes and Negs to [] and Comp to true;
2. simplify its answers and set up links
for further simplification later;
3. use the truth value of Ggoal to simplify
answers of other complete subgoals (possibly
including itself).
4. set Alist0/Alist: a list of negation nodes with
universal disjunctions with associated answers
for the selected negative literal.
*/
complete_one(Ggoal,Tab0,Tab,Alist0,Alist) :-
updatevs(Tab0,Ggoal,Ent0,Ent,Tab1),
Ent0 = e(_Nodes,ANegs,Anss0,Delay,_Comp,Gdfn,Slist0),
Ent = e([],[],Anss,Delay,true,Gdfn,Slist),
( Delay == true ->
reduce_ans(Anss0,Anss,Tab0),
setup_simp_links(Anss,Ggoal,Slist0,Slist1,Tab1,Tab2)
; % Delay == false
Anss = Anss0,
Tab2 = Tab1,
Slist1 = Slist0
),
extract_known(Ggoal,Anss,Slist1,Slist,Klist),
simplify(Klist,Tab2,Tab,[]),
( ANegs == [] ->
Alist0 = Alist
; Alist0 = [(Anss,Ggoal)-ANegs|Alist]
).
setup_simp_links([],_,Slist,Slist,Tab,Tab).
setup_simp_links(l(GH,Lanss),Ggoal,Slist0,Slist,Tab0,Tab) :-
setup_simp_links_list(Lanss,Ggoal-GH,Ggoal,Slist0,Slist,Tab0,Tab).
setup_simp_links(n2(T1,_,T2),Ggoal,Slist0,Slist,Tab0,Tab) :-
setup_simp_links(T1,Ggoal,Slist0,Slist1,Tab0,Tab1),
setup_simp_links(T2,Ggoal,Slist1,Slist,Tab1,Tab).
setup_simp_links(n3(T1,_,T2,_,T3),Ggoal,Slist0,Slist,Tab0,Tab) :-
setup_simp_links(T1,Ggoal,Slist0,Slist1,Tab0,Tab1),
setup_simp_links(T2,Ggoal,Slist1,Slist2,Tab1,Tab2),
setup_simp_links(T3,Ggoal,Slist2,Slist,Tab2,Tab).
/* setup_simp_link_list(Lanss,Ggoal-GH,Ggoal,Slist0,Slist,Tab0,Tab)
Ggoal-GH is to tell what portion of answers of Ggoal can be
simplified.
*/
setup_simp_links_list([],_,_,Slist,Slist,Tab,Tab).
setup_simp_links_list([d(_,D)|Anss],GHead,Ggoal,Slist0,Slist,Tab0,Tab) :-
( D = all(Ds) ->
true
; Ds = D
),
links_from_one_delay(Ds,GHead,Ggoal,Slist0,Slist1,Tab0,Tab1),
setup_simp_links_list(Anss,GHead,Ggoal,Slist1,Slist,Tab1,Tab).
/* A link ((Ggoal-GH):Lit) in an entry for Ngoal means that
the literal Lit in an answer with head GH in Ggoal can
be potentially simplified if we know answers for Ngoal.
*/
links_from_one_delay([],_,_,Slist,Slist,Tab,Tab).
links_from_one_delay([D|Ds],GHead,Ggoal,Slist0,Slist,Tab0,Tab) :-
( D = (\+ Ngoal) ->
( Ggoal == Ngoal ->
Tab1 = Tab0,
Slist1 = [GHead:D|Slist0]
; add_link_to_ent(Tab0,Ngoal,GHead:D,Tab1),
Slist1 = Slist0
)
; D = (Ngoal-_) ->
( Ggoal == Ngoal ->
Slist1 = [GHead:D|Slist0],
Tab1 = Tab0
; Slist1 = Slist0,
add_link_to_ent(Tab0,Ngoal,GHead:D,Tab1)
)
),
links_from_one_delay(Ds,GHead,Ggoal,Slist1,Slist,Tab1,Tab).
/* extract_known(Ggoal,Anss,Links,Slist,Klist):
Given Ggoal and its answers Anss, and its
simplification Links, it partitioned Links
into Slist and Klist of links, where Klist
is a list of links that are known to be either
true or false.
Klist is either of the form Val-Links, or a
list of the form Val-Link. In case of non-ground
calls, the corresponding portion of Anss has to
be searched.
*/
extract_known(Ggoal,Anss,Links,Slist,Klist) :-
( failed(Anss) ->
Klist = fail-Links,
Slist = []
; Anss = l(GH,Lanss) ->
( Ggoal == GH -> % Ground or most general call
( memberchk(d(_,[]),Lanss) ->
Klist = succ-Links,
Slist = []
; Klist = [],
Slist = Links
)
; % non-ground call
extract_known_anss(Links,Anss,[],Slist,[],Klist)
)
; % non-ground call
extract_known_anss(Links,Anss,[],Slist,[],Klist)
).
extract_known_anss([],_,Slist,Slist,Klist,Klist).
extract_known_anss([Link|Links],Anss,Slist0,Slist,Klist0,Klist) :-
Link = (_:Lit),
extract_lit_val(Lit,Anss,true,Val),
( Val == undefined ->
Slist1 = [Link|Slist0],
Klist1 = Klist0
; Slist1 = Slist0,
Klist1 = [Val-Link|Klist0]
),
extract_known_anss(Links,Anss,Slist1,Slist,Klist1,Klist).
/* extract_lit_val(Lit,Anss,Comp,Val):
extract the truth value of Lit according to Anss and Comp.
In case of a non-ground calls, the corresponding portion
of Anss has to be searched.
*/
extract_lit_val(Lit,Anss,Comp,Val) :-
( Lit = (\+ _) ->
( succeeded(Anss) ->
Val = fail
; failed(Anss), Comp == true ->
Val = succ
; Val = undefined
)
; Lit = (_ - (\+GH)) ->
( find(Anss,GH,Lanss) ->
( (\+ \+ memberchk(d(GH,[]),Lanss)) ->
Val = fail
; Lanss == [], Comp == true ->
Val = succ
; Val = undefined
)
; ( Comp == true ->
Val = succ
; Val = undefined
)
)
; Lit = (_-GH) ->
( find(Anss,GH,Lanss) ->
( (\+ \+ memberchk(d(GH,[]),Lanss)) ->
Val = succ
; Lanss == [], Comp == true ->
Val = fail
; Val = undefined
)
; ( Comp == true ->
Val = fail
; Val = undefined
)
)
).
/* simplify(KnownLinks,Tab0,Tab,Abd):
Given a list of KnownLinks, Tab0 and Abd,
it tries to simplify answers according to
KnownLinks. When a subgoal is found to be
true or false according to answers,
consistency with assumed truth values in Abd
is checked.
*/
simplify([],Tab,Tab,_Abd).
simplify([Val-Link|Klist],Tab0,Tab,Abd) :-
simplify_one(Val,Link,Tab0,Tab1,Abd),
simplify(Klist,Tab1,Tab,Abd).
simplify(Val-Links,Tab0,Tab,Abd) :-
simplify_list(Links,Val,Tab0,Tab,Abd).
simplify_list([],_,Tab,Tab,_Abd).
simplify_list([Link|Links],Val,Tab0,Tab,Abd) :-
Link = (_ : Lit),
( ( Lit = (\+_); Lit = (_ - (\+_)) ) ->
( Val = fail -> LVal = succ; LVal = fail )
; LVal = Val
),
simplify_one(LVal,Link,Tab0,Tab1,Abd),
simplify_list(Links,Val,Tab1,Tab,Abd).
simplify_one(Val,Link,Tab0,Tab,Abd) :-
Link = ((Ngoal - GH) : Lit),
updatevs(Tab0,Ngoal,Ent0,Ent,Tab1),
Ent0 = e(Nodes,ANegs,Anss0,Delay,Comp,Dfn,Slist0),
Ent = e(Nodes,ANegs,Anss,Delay,Comp,Dfn,Slist),
( updatevs(Anss0,GH,Lanss0,Lanss,Anss) ->
simplify_anss(Lanss0,Val,Lit,[],Lanss,C),
( C == true ->
( find(Abd,GH,Aval) ->
( Aval == true, Lanss == [] -> % deduced result inconsistent with assumption
fail
; Aval == false, memberchk( d(_ , []), Lanss) ->
fail
; true
)
; true
),
extract_known(Ngoal,Anss,Slist0,Slist,Klist),
simplify(Klist,Tab1,Tab,Abd)
; Tab = Tab0
)
; Tab = Tab0
).
/* simplify_anss(List,Val,Lit,Lanss0,Lanss,C):
Given a List of answers, Val of Lit, it
simplifies the List and construct a new list
Lanss0/Lanss of answers. C is unified with true
if some simplification is carried out.
As soon as a true answer is detected, all
other answers with the same head are deleted.
*/
simplify_anss([],_,_,Anss,Anss,_).
simplify_anss([Ans|Rest],Val,Lit,Anss0,Anss,C) :-
( simplified_ans(Ans,Val,Lit,NewAns,C) ->
( NewAns = d(_,[]) ->
Anss = [NewAns]
; Anss1 = [NewAns|Anss0],
simplify_anss(Rest,Val,Lit,Anss1,Anss,C)
)
; C = true,
simplify_anss(Rest,Val,Lit,Anss0,Anss,C)
).
simplified_ans(Ans,Val,Lit,NewAns,C) :-
Ans = d(H,Ds),
( Ds == [] ->
NewAns = Ans
; Ds = all(Dlist) ->
( Val == fail ->
delete_lit(Dlist,Lit,NewDlist,[],C),
( NewDlist == [] ->
fail
; NewAns = d(H,all(NewDlist))
)
; % Val == succ ->
( memberchk(Lit,Dlist) ->
NewAns = d(H,[]),
C = true
; NewAns = Ans
)
)
; % Ds is a conjunction
( Val == fail ->
( memberchk(Lit,Ds) ->
fail
; NewAns = Ans
)
; % Val == succ ->
delete_lit(Ds,Lit,NewDs,[],C),
NewAns = d(H,NewDs)
)
).
/* delete_lit(Delays,Lit,Ds0,Ds,C):
deletes Lit from Delays. Delays is
a list of delayed literals and it
is guaranteed to have no duplicates.
*/
delete_lit([],_,Ds,Ds,_).
delete_lit([D|Rest],Lit,Ds0,Ds,C) :-
( D == Lit ->
Ds0 = Rest,
C = true
; Ds0 = [D|Ds1],
delete_lit(Rest,Lit,Ds1,Ds,C)
).
% return answers to negative nodes within universal disjunctions
return_aneg_nodes([],Tab,Tab,S,S,Dfn,Dfn,Dep,Dep,TP,TP).
return_aneg_nodes([(Anss,Ngoal)-ANegs|Alist],Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
map_anegs(ANegs,Anss,Ngoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
return_aneg_nodes(Alist,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
map_anegs([],_Anss,_Ngoal,Tab,Tab,S,S,Dfn,Dfn,Dep,Dep,TP,TP).
map_anegs([Node|ANegs],Anss,Ngoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
return_to_disj(Anss,Node,Ngoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
map_anegs(ANegs,Anss,Ngoal,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
/* process a component of subgoals that may be involved in
negative loops.
*/
process_neg_scc(Ggoal,Tab0,Tab,S0,S,Dfn0,Dfn,Dep,TP0,TP) :-
( wfs_trace ->
write('Stack: '), nl, display_stack(S0,Tab0),
write('Possible negative loop: '), write(Ggoal), nl,
display_table(Tab0)
; true
),
extract_subgoals(Ggoal,S0,Scc,[]),
reset_nmin(Scc,Tab0,Tab1,Ds,[]),
( wfs_trace ->
write('Delaying: '), display_dlist(Ds)
; true
),
delay_and_cont(Ds,Tab1,Tab2,S0,S1,Dfn0,Dfn1,maxint-maxint,Dep1,TP0,TP1),
recomp_scc(Scc,Tab2,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
/* extract_subgoals(Ggoal,S0,Scc0,Scc)
extract subgoals that may be involved in negative loops,
but leave the stack of subgoals intact.
*/
extract_subgoals(Ggoal,[Sent|S],[Sent|Scc0],Scc) :-
( Ggoal == Sent ->
Scc0 = Scc
; extract_subgoals(Ggoal,S,Scc0,Scc)
).
/* reset_nmin(Scc,Tab0,Tab,Dnodes0,Dnodes)
reset NegLink and collect all waiting nodes that need to be
delayed. Dnodes0/Dnodes is a difference list.
*/
reset_nmin([],Tab,Tab,Ds,Ds).
reset_nmin([Ggoal|Scc],Tab0,Tab,Ds0,Ds) :-
get_and_reset_negs(Tab0,Ggoal,ANegs,Tab1),
( ANegs == [] ->
Ds0 = Ds1
; Ds0 = [Ggoal-ANegs|Ds1]
),
reset_nmin(Scc,Tab1,Tab,Ds1,Ds).
delay_and_cont([],Tab,Tab,S,S,Dfn,Dfn,Dep,Dep,TP,TP).
delay_and_cont([Ggoal-Negs|Dnodes],Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
map_nodes(Negs,d(\+Ggoal,[\+Ggoal]),Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
delay_and_cont(Dnodes,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
recomp_scc([],Tab,Tab,S,S,Dfn,Dfn,Dep,Dep,TP,TP).
recomp_scc([Ggoal|Scc],Tab0,Tab,S0,S,Dfn0,Dfn,Dep0,Dep,TP0,TP) :-
comp_tab_ent(Ggoal,Tab0,Tab1,S0,S1,Dfn0,Dfn1,Dep0,Dep1,TP0,TP1),
recomp_scc(Scc,Tab1,Tab,S1,S,Dfn1,Dfn,Dep1,Dep,TP1,TP).
/* routines for incremental update of dependency information
*/
/* update_mins(Ggoal,Dep,Sign,Tab0,Tab,Gdfn,Gdep)
update the PosLink and NegLink of Ggoal according to
Dep and Sign
*/
update_mins(Ggoal,Dep,Sign,Tab0,Tab,Gdfn,Gdep) :-
Ent0 = e(Nodes,ANegs,Anss,Delay,Comp,Gdfn:Gdep0,Slist),
Ent = e(Nodes,ANegs,Anss,Delay,Comp,Gdfn:Gdep,Slist),
updatevs(Tab0,Ggoal,Ent0,Ent,Tab),
compute_mins(Gdep0,Dep,Sign,Gdep).
/* update_lookup_mins(Ggoal,Node,Ngoal,Sign,Tab0,Tab,Dep0,Dep)
There is a lookup edge (Node) from Ggoal to Ngoal
with Sign. It adds Node to the corresponding waiting list
in Ngoal and then update the dependencies of Ggoal.
*/
update_lookup_mins(Ggoal,Node,Ngoal,Sign,Tab0,Tab,Dep0,Dep) :-
updatevs(Tab0,Ngoal,Ent0,Ent,Tab1),
( Sign == pos ->
pos_to_newent(Ent0,Ent,Node)
; Sign == aneg ->
aneg_to_newent(Ent0,Ent,Node)
),
Ent0 = e(_,_,_,_,_,_Ndfn:Ndep,_),
compute_mins(Dep0,Ndep,Sign,Dep),
update_mins(Ggoal,Ndep,Sign,Tab1,Tab,_,_).
/* update_solution_mins(Ggoal,Ngoal,Sign,Tab0,Tab,Ndep,Dep0,Dep)
There is an edge with Sign from Ggoal to Ngoal, where Ngoal is
a new subgoal. Ndep is the final dependency information of
Ngoal. Dep0/Dep is for the most recent enclosing new call.
This predicate is called after Ngoal is solved.
*/
update_solution_mins(Ggoal,Ngoal,Sign,Tab0,Tab,Ndep,Dep0,Dep) :-
find(Tab0,Ngoal,Nent),
ent_to_comp(Nent,Ncomp),
( Ncomp == true ->
( Ndep == maxint-maxint ->
Tab = Tab0, Dep = Dep0
; update_mins(Ggoal,Ndep,pos,Tab0,Tab,_,_),
compute_mins(Dep0,Ndep,pos,Dep)
)
; update_mins(Ggoal,Ndep,Sign,Tab0,Tab,_,_),
compute_mins(Dep0,Ndep,Sign,Dep)
).
compute_mins(Gpmin-Gnmin,Npmin-Nnmin,Sign,Newpmin-Newnmin) :-
( Sign == pos ->
min(Gpmin,Npmin,Newpmin),
min(Gnmin,Nnmin,Newnmin)
; % (Sign == neg; Sign == aneg) ->
Newpmin=Gpmin,
min(Gnmin,Npmin,Imin),
min(Imin,Nnmin,Newnmin)
).
min(X,Y,M) :- ( X @< Y -> M=X; M=Y ).
%%%%%%%%%%%%%%% Local table manipulation predicates %%%%%%%%%%
/* Table Entry Structure:
For each Call, its table entry is identified with its number-vared
version -- Ggoal. Its value is a term of the form
e(Nodes,ANegs,Anss,Delay,Comp,Dfn:Dep,Slist)
where
Nodes: positive suspension list
ANegs: negative suspension list (for universal disjunction clauss)
Anss: another table.
Delay: whether Anss contains any answer with delay
Comp: whether Call is completely evaluated or not
Dfn: depth-first number of Gcall
Dep: (PosLink-NegLink) --- dependency information
Slist: a list of nodes whose answers may be simplified
if the truth value of Ggoal is known. Each element of Slist
is of the form (Ngoal-GH):Literal.
Stack Entry Structure:
Ggoal
*/
/* routines for accessing individual fields of an entry
*/
ent_to_nodes(e(Nodes,_,_,_,_,_,_),Nodes).
ent_to_anegs(e(_,ANegs,_,_,_,_,_),ANegs).
ent_to_anss(e(_,_,Anss,_,_,_,_),Anss).
ent_to_delay(e(_,_,_,Delay,_,_,_),Delay).
ent_to_comp(e(_,_,_,_,Comp,_,_),Comp).
ent_to_dfn(e(_,_,_,_,_,Dfn,_),Dfn).
ent_to_slist(e(_,_,_,_,_,_,Slist),Slist).
get_and_reset_negs(Tab0,Ggoal,ANegs,Tab) :-
Ent0 = e(Nodes,ANegs,Anss,Delay,Comp,Gdfn: (Gpmin - _),Slist),
Ent = e(Nodes,[],Anss,Delay,Comp,Gdfn:Gpmin-maxint,Slist),
updatevs(Tab0,Ggoal,Ent0,Ent,Tab).
/* adding a new table entry
*/
add_tab_ent(Ggoal,Ent,Tab0,Tab) :-
addkey(Tab0,Ggoal,Ent,Tab).
/* The following three routines are for creating
new calls
*/
/* a new call with empty suspensions
*/
new_init_call(Call,Ggoal,Ent,S0,S,Dfn0,Dfn) :-
ground(Call,Ggoal),
S = [Ggoal|S0],
Dfn is Dfn0+1,
Ent = e([],[],[],false,false,Dfn0:Dfn0-maxint,[]).
/* a new call with an initial negative suspension from
inside a universal disjunction
*/
new_aneg_call(Ngoal,Neg,Ent,S0,S,Dfn0,Dfn) :-
S = [Ngoal|S0],
Dfn is Dfn0+1,
Ent = e([],[Neg],[],false,false,Dfn0:Dfn0-maxint,[]).
/* a new call with an initial positive suspension
*/
new_pos_call(Ngoal,Node,Ent,S0,S,Dfn0,Dfn) :-
S = [Ngoal|S0],
Dfn is Dfn0+1,
Ent = e([Node],[],[],false,false,Dfn0:Dfn0-maxint,[]).
/* routines for adding more information to a
table entry.
*/
aneg_to_newent(Ent0,Ent,ANeg) :-
Ent0 = e(Nodes,ANegs,Anss,Delay,Comp,Dfn,Slist),
Ent = e(Nodes,[ANeg|ANegs],Anss,Delay,Comp,Dfn,Slist).
pos_to_newent(Ent0,Ent,Node) :-
Ent0 = e(Nodes,ANegs,Anss,Delay,Comp,Dfn,Slist),
Ent = e([Node|Nodes],ANegs,Anss,Delay,Comp,Dfn,Slist).
add_link_to_ent(Tab0,Ggoal,Link,Tab) :-
updatevs(Tab0,Ggoal,Ent0,Ent,Tab),
link_to_newent(Ent0,Ent,Link).
link_to_newent(Ent0,Ent,Link) :-
Ent0 = e(Nodes,ANegs,Anss,Delay,Comp,Dfn,Slist),
Ent = e(Nodes,ANegs,Anss,Delay,Comp,Dfn,[Link|Slist]).
/* routines for manipulating answers */
ansstree_to_list([],L,L).
ansstree_to_list(l(_GH,Lanss),L0,L) :-
attach(Lanss,L0,L).
ansstree_to_list(n2(T1,_M,T2),L0,L) :-
ansstree_to_list(T1,L0,L1),
ansstree_to_list(T2,L1,L).
ansstree_to_list(n3(T1,_M2,T2,_M3,T3),L0,L) :-
ansstree_to_list(T1,L0,L1),
ansstree_to_list(T2,L1,L2),
ansstree_to_list(T3,L2,L).
attach([],L,L).
attach([d(H,B)|R],[X|L0],L) :-
( B == [] ->
X = H
; X = (H <- B)
),
attach(R,L0,L).
member_anss(Ans,Anss) :-
member_anss_1(Anss,Ans).
member_anss_1(l(_,Lanss),Ans) :-
member(Ans,Lanss).
member_anss_1(n2(T1,_,T2),Ans) :-
( member_anss_1(T1,Ans)
; member_anss_1(T2,Ans)
).
member_anss_1(n3(T1,_,T2,_,T3),Ans) :-
( member_anss_1(T1,Ans)
; member_anss_1(T2,Ans)
; member_anss_1(T3,Ans)
).
/* failed(Anss): Anss is empty */
failed([]).
failed(l(_,[])).
/* succeeded(Anss): Anss contains a single definite answer */
succeeded(l(_,Lanss)) :-
memberchk(d(_,[]),Lanss).
/* add_ans(Tab0,Goal,Ans,Nodes,Mode,Tab):
If Ans is not subsumed by any existing answer then
Ans is added to Anss(Goal);
If some existing answer also has head H then
Mode = no_new_head
else
Mode = new_head
else
fail.
*/
add_ans(Tab0,Ggoal,Ans,Nodes,Mode,Tab) :-
updatevs(Tab0,Ggoal,Ent0,Ent,Tab),
Ans = d(H,Ds),
( Ds == [] ->
new_ans_ent(Ent0,Ent,Ans,Nodes,Mode)
; setof(X,member(X,Ds),NewDs),
new_ans_ent(Ent0,Ent,d(H,NewDs),Nodes,Mode)
).
new_ans_ent(Ent0,Ent,Ans,Nodes,Mode) :-
Ent0 = e(Nodes,ANegs,Anss0,Delay0,Comp,Dfn,Slist),
Ent = e(Nodes,ANegs,Anss,Delay,Comp,Dfn,Slist),
Ans = d(H,D),
ground(H,GH),
( updatevs(Anss0,GH,Lanss0,Lanss,Anss) ->
( D == [] ->
\+(memberchk(d(_,[]),Lanss0)),
Lanss = [Ans]
; not_subsumed_ans(Ans,Lanss0),
Lanss = [Ans|Lanss0]
),
Mode = no_new_head
; addkey(Anss0,GH,[Ans],Anss),
Mode = new_head
),
( D == [] ->
Delay = Delay0
; Delay = true
).
/* returned_ans(Ans,Ggoal,RAns):
determines whether SLG resolution or SLG factoring should
be applied.
*/
returned_ans(d(H,Tv),Ggoal,d(H,NewTv)) :-
( Tv = [] ->
NewTv = []
; ground(H,GH),
NewTv = [Ggoal-GH]
).
% reduce a list of answers, by reducing delay list, and by subsumption
reduce_ans(Anss0,Anss,Tab) :-
reduce_completed_ans(Anss0,Anss,Tab).
% simplify all the delay lists in a list of answers.
reduce_completed_ans([],[],_Tab).
reduce_completed_ans(l(GH,Lanss0),l(GH,Lanss),Tab) :-
reduce_completed_anslist(Lanss0,[],Lanss,Tab).
reduce_completed_ans(n2(T1,M,T2),n2(NT1,M,NT2),Tab) :-
reduce_completed_ans(T1,NT1,Tab),
reduce_completed_ans(T2,NT2,Tab).
reduce_completed_ans(n3(T1,M2,T2,M3,T3),n3(NT1,M2,NT2,M3,NT3),Tab) :-
reduce_completed_ans(T1,NT1,Tab),
reduce_completed_ans(T2,NT2,Tab),
reduce_completed_ans(T3,NT3,Tab).
reduce_completed_anslist([],Lanss,Lanss,_Tab).
reduce_completed_anslist([d(G,D0)|List],Lanss0,Lanss,Tab) :-
( D0 = all(Dlist1) ->
( filter_delays(Dlist1,[],Dlist,disj,V,Tab) ->
( V == true -> % true answer
Lanss = [d(G,[])]
; Dlist == [] -> % false answer, ignore
reduce_completed_anslist(List,Lanss0,Lanss,Tab)
; reduce_completed_anslist(List,[d(G,all(Dlist))|Lanss0],Lanss,Tab)
)
; reduce_completed_anslist(List,Lanss0,Lanss,Tab)
)
; ( filter_delays(D0,[],D,conj,_V,Tab) ->
( D == [] ->
Lanss = [d(G,[])]
; reduce_completed_anslist(List,[d(G,D)|Lanss0],Lanss,Tab)
)
; reduce_completed_anslist(List,Lanss0,Lanss,Tab)
)
).
% simplify a delay list by the completed table: delete true negations,
% fail if a false one.
filter_delays([],Fds,Fds,_DC,_V,_Tab).
filter_delays([Lit|Ds],Fds0,Fds,DC,V,Tab) :-
lit_to_call(Lit,Gcall),
find(Tab,Gcall,Gent),
ent_to_comp(Gent,Gcomp),
ent_to_anss(Gent,Ganss),
extract_lit_val(Lit,Ganss,Gcomp,Val),
( Val == succ ->
( DC == conj ->
filter_delays(Ds,Fds0,Fds,DC,V,Tab)
; DC == disj ->
V = true
)
; Val == fail ->
( DC == conj ->
fail
; DC == disj ->
filter_delays(Ds,Fds0,Fds,DC,V,Tab)
)
; % Val == undefined
filter_delays(Ds,[Lit|Fds0],Fds,DC,V,Tab)
).
lit_to_call(\+G,G).
lit_to_call(Gcall-_,Gcall).
not_subsumed_ans(Ans,Lanss0) :-
\+
( numbervars(Ans,0,_),
subsumed_ans1(Ans,Lanss0)
).
% succeed if answer is subsumed by any in list1 or 2.
subsumed_ans(Tv,List1,List2) :-
\+
(numbervars(Tv,0,_),
\+ subsumed_ans1(Tv,List1),
\+ subsumed_ans1(Tv,List2)
).
% check if a delay is subsumed one of the element in the list
subsumed_ans1(d(T,V),List) :-
member(d(T,V1),List),
( V1 == []
; V = all(LV), V1 = all(LV1) ->
subset(LV,LV1)
; subset(V1,V)
).
/****************** auxiliary routines *******************/
% variantchk/2 finds a variant in a list of atoms.
variantchk(G,[G1|_]) :- variant(G,G1), !.
variantchk(G,[_|L]) :- variantchk(G,L).
variant(A, B) :-
A == B
-> true
; subsumes_chk(A, B),
subsumes_chk(B, A),
A = B.
/*
subsumes_chk(General, Specific) :-
\+ ( numbervars(Specific, 0, _),
\+ General = Specific
).
*/
ground(O,C) :- ground(O) -> C = O ; copy_term(O,C), numbervars(C,0,_).
subset([],_).
subset([E|L1],L2) :- memberchk(E,L2), subset(L1,L2).
reverse([],R,R).
reverse([Goal|Scc],R0,R) :- reverse(Scc,[Goal|R0],R).
/***************** routines for debugging *******************/
% Debugging help: pretty-prints strongly connected components and local table.
display_stack(Stack,Tab) :-
reverse(Stack,[],Rstack),
display_st(Rstack,Tab).
display_st([],_Tab).
display_st([Ggoal|Scc],Tab) :-
find(Tab,Ggoal,Ent),
ent_to_dfn(Ent,Dfn:Pmin-Nmin),
tab(2),
write(Ggoal-Dfn),
write(': '),
write('Pmin='),
write(Pmin),
write('; '),
write('Nmin='),
write(Nmin),
write('; '),
nl,
display_st(Scc,Tab).
display_dlist([]) :- nl,nl.
display_dlist([Ngoal-_|Dlist]) :-
write(\+ Ngoal),
write('; '),
display_dlist(Dlist).
display_table(Tab) :-
write('Table: '),
nl,
write_tab(Tab).
display_final(Tab) :-
write(' Final Set of Answers: '),
nl,
display_final1(Tab).
display_final1([]).
display_final1(l(_,e(_,_,Anss,_,_,_,_))) :-
write_anss(Anss).
display_final1(n2(X,_,Y)) :-
display_final1(X),
display_final1(Y).
display_final1(n3(X,_,Y,_,Z)) :-
display_final1(X),
display_final1(Y),
display_final1(Z).
write_tab([]).
write_tab(l(G,e(Nodes,ANegs,Anss,_,Comp,Dfn:_,_))) :-
write(' Entry: '),
write(G-Dfn),
write(': '),
( Comp == true ->
write('Complete!')
; write('Incomplete!')
),
nl,
( Anss == [] ->
true
; write(' Anss: '),
nl,
write_anss(Anss)
),
( ( Comp == true; Nodes == []) ->
true
; write(' Nodes: '),
write(Nodes),
nl
),
( ( Comp == true; ANegs == []) ->
true
; write(' ANegs: '),
write(ANegs),
nl
).
write_tab(n2(X,_,Y)) :-
write_tab(X),
write_tab(Y).
write_tab(n3(X,_,Y,_,Z)) :-
write_tab(X),
write_tab(Y),
write_tab(Z).
write_anss([]).
write_anss(l(_,Lanss)) :-
write_anss_list(Lanss).
write_anss(n2(T1,_,T2)) :-
write_anss(T1),
write_anss(T2).
write_anss(n3(T1,_,T2,_,T3)) :-
write_anss(T1),
write_anss(T2),
write_anss(T3).
write_anss_list([]).
write_anss_list([Ans|Anss]) :-
write_ans(Ans),
write_anss_list(Anss).
write_ans(d(H,Ds)) :-
write(' '),
write(H),
( Ds == [] ->
true
; write(' :- '),
( Ds = all([D|Ds1]) ->
( D = (_-GH) ->
write(GH)
; write(D)
),
write_delay(Ds1,'; ')
; Ds = [D|Ds1],
( D = (_-GH) ->
write(GH)
; write(D)
),
write_delay(Ds1,', ')
)
),
write('.'),
nl.
write_delay([],_).
write_delay([D|Ds1],Sep) :-
write(Sep),
( D = (_Gcall-GH) ->
write(GH)
; write(D)
),
write_delay(Ds1,Sep).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/*
This is a set of routines that supports indexed tables. Tables
are sets of key-value_list pairs. With each key is associated a list
of values. It uses 2-3 trees for the index (modified by D.S. Warren
from Ivan Bratko: ``Prolog Programming for Artificial
Intelligence'', Addison Wesley, 1986). Operations are:
Keys must be ground! (so numbervar them)
addkey(Tree,Key,V,Tree1) adds a new Key with value V, returning
new Tree1. Fails if the key is already there.
find(Tree,Key,V) finds the entry with Key and returns associated
values in V.
updatevs(Tree,Key,OldV,NewV,Tree1) replaces value of entry with key
Key and value OldV with NewV.
*/
addkey(Tree,X,V,Tree1) :-
ins2(Tree,X,V,Trees),
cmb0(Trees,Tree1).
addkey([],X,V,l(X,V)).
find(l(X,V),Xs,V) :- X == Xs.
find(n2(T1,M,T2),X,V) :-
M @=< X
-> find(T2,X,V)
; find(T1,X,V).
find(n3(T1,M2,T2,M3,T3),X,V) :-
M2 @=< X
-> (M3 @=< X
-> find(T3,X,V)
; find(T2,X,V)
)
; find(T1,X,V).
% updatevs(Tab0,X,Ov,Nv,Tab) updates Tab0 to Tab, by replacing
% Ov of entry with key X by Nv.
/*
updatevs(Tab0,X,Ov,Nv,Tab) :-
updatevs(Tab0,X,Ov,Nv),
Tab = Tab0.
updatevs(Tab,X,Ov,Nv) :-
( Tab = l(Xs,Ov), Xs == X ->
setarg(2,Tab,Nv)
; Tab = n2(T1,M,T2) ->
( M @=< X ->
updatevs(T2,X,Ov,Nv)
; updatevs(T1,X,Ov,Nv)
)
; Tab = n3(T1,M2,T2,M3,T3) ->
( M2 @=< X ->
( M3 @=< X ->
updatevs(T3,X,Ov,Nv)
; updatevs(T2,X,Ov,Nv)
)
; updatevs(T1,X,Ov,Nv)
)
).
*/
updatevs(l(X,Ov),Xs,Ov,Nv,l(X,Nv)) :- X == Xs.
updatevs(n2(T1,M,T2),X,Ov,Nv,n2(NT1,M,NT2)) :-
M @=< X
-> NT1=T1, updatevs(T2,X,Ov,Nv,NT2)
; NT2=T2, updatevs(T1,X,Ov,Nv,NT1).
updatevs(n3(T1,M2,T2,M3,T3),X,Ov,Nv,n3(NT1,M2,NT2,M3,NT3)) :-
M2 @=< X
-> (M3 @=< X
-> NT2=T2, NT1=T1, updatevs(T3,X,Ov,Nv,NT3)
; NT1=T1, NT3=T3, updatevs(T2,X,Ov,Nv,NT2)
)
; NT2=T2, NT3=T3, updatevs(T1,X,Ov,Nv,NT1).
ins2(n2(T1,M,T2),X,V,Tree) :-
M @=< X
-> ins2(T2,X,V,Tree1),
cmb2(Tree1,T1,M,Tree)
; ins2(T1,X,V,Tree1),
cmb1(Tree1,M,T2,Tree).
ins2(n3(T1,M2,T2,M3,T3),X,V,Tree) :-
M2 @=< X
-> (M3 @=< X
-> ins2(T3,X,V,Tree1),
cmb4(Tree1,T1,M2,T2,M3,Tree)
; ins2(T2,X,V,Tree1),
cmb5(Tree1,T1,M2,M3,T3,Tree)
)
; ins2(T1,X,V,Tree1),
cmb3(Tree1,M2,T2,M3,T3,Tree).
ins2(l(A,V),X,Vn,Tree) :-
A @=< X
-> (X @=< A
-> fail
; Tree = t(l(A,V),X,l(X,Vn))
)
; Tree = t(l(X,Vn),A,l(A,V)).
cmb0(t(Tree),Tree).
cmb0(t(T1,M,T2),n2(T1,M,T2)).
cmb1(t(NT1),M,T2,t(n2(NT1,M,T2))).
cmb1(t(NT1a,Mb,NT1b),M,T2,t(n3(NT1a,Mb,NT1b,M,T2))).
cmb2(t(NT2),T1,M,t(n2(T1,M,NT2))).
cmb2(t(NT2a,Mb,NT2b),T1,M,t(n3(T1,M,NT2a,Mb,NT2b))).
cmb3(t(NT1),M2,T2,M3,T3,t(n3(NT1,M2,T2,M3,T3))).
cmb3(t(NT1a,Mb,NT1b),M2,T2,M3,T3,t(n2(NT1a,Mb,NT1b),M2,n2(T2,M3,T3))).
cmb4(t(NT3),T1,M2,T2,M3,t(n3(T1,M2,T2,M3,NT3))).
cmb4(t(NT3a,Mb,NT3b),T1,M2,T2,M3,t(n2(T1,M2,T2),M3,n2(NT3a,Mb,NT3b))).
cmb5(t(NT2),T1,M2,M3,T3,t(n3(T1,M2,NT2,M3,T3))).
cmb5(t(NT2a,Mb,NT2b),T1,M2,M3,T3,t(n2(T1,M2,NT2a),Mb,n2(NT2b,M3,T3))).
start_slg:- assertz((
term_expansion(X,Y) :- !,
do_term_expansion(X,Y)
)).
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