/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2009-2016, University of Amsterdam VU University Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module('$dcg', [ dcg_translate_rule/2, % +Rule, -Clause dcg_translate_rule/4, % +Rule, ?Pos0, -Clause, -Pos phrase/2, % :Rule, ?Input phrase/3, % :Rule, ?Input, ?Rest call_dcg/3 % :Rule, ?State0, ?State ]). /******************************** * GRAMMAR RULES * *********************************/ /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - The DCG compiler. The original code was copied from C-Prolog and written by Fernando Pereira, EDCAAD, Edinburgh, 1984. Since then many people have modified and extended this code. It's a nice mess now and it should be redone from scratch. I won't be doing this before I get a complete spec explaining all an implementor needs to know about DCG. I'm a too basic user of this facility myself (though I learned some tricks from people reporting bugs :-) The original version contained '$t_tidy'/2 to convert ((a,b), c) to (a,(b,c)), but as the SWI-Prolog compiler doesn't really care (the resulting code is simply the same), I've removed that. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ dcg_translate_rule(Rule, Clause) :- dcg_translate_rule(Rule, _, Clause, _). dcg_translate_rule(((LP,MNT)-->RP), Pos0, (H:-B), Pos) :- !, f2_pos(Pos0, PosH0, PosRP0, Pos, PosH, PosRP), f2_pos(PosH0, PosLP0, PosMNT0, PosH, PosLP, PosMNT), '$current_source_module'(M), Qualify = q(M,M,_), dcg_extend(LP, PosLP0, S0, SR, H, PosLP), dcg_body(RP, PosRP0, Qualify, S0, S1, B0, PosRP), dcg_body(MNT, PosMNT0, Qualify, SR, S1, B1, PosMNT), dcg_optimise((B0,B1),B2,S0), dcg_optimise(B2,B,SR). dcg_translate_rule((LP-->RP), Pos0, (H:-B), Pos) :- f2_pos(Pos0, PosLP0, PosRP0, Pos, PosLP, PosRP), dcg_extend(LP, PosLP0, S0, S, H, PosLP), '$current_source_module'(M), Qualify = q(M,M,_), dcg_body(RP, PosRP0, Qualify, S0, S, B0, PosRP), dcg_optimise(B0,B,S0). %! dcg_optimise(+BodyIn, -Body, +S0) is det. % % Performs the following translations: % % - a(H,T) :- H = [a,b|T], b(T), ... into % a([a,b|T0]) :- b(T0, T). % - a(H,T) :- H = [a,b|T] into % a([a,b|T0]) % % @arg S0 is the initial input list of the rule. dcg_optimise((S00=X,B), B, S0) :- S00 == S0, !, S0 = X. dcg_optimise(S00=X, B, S0) :- S00 == S0, !, S0 = X, B = true. dcg_optimise(B, B, _). %! dcg_body(:DCG, ?Pos0, +Qualify, ?List, ?Tail, -Goal, -Pos) is det. % % Translate DCG body term. dcg_body(Var, P0, Q, S, SR, phrase(QVar, S, SR), P) :- var(Var), !, qualify(Q, Var, P0, QVar, P). dcg_body(M:X, Pos0, q(_,C,_), S, SR, Ct, Pos) :- !, f2_pos(Pos0, _, XP0, _, _, _), dcg_body(X, XP0, q(M,C,Pos0), S, SR, Ct, Pos). dcg_body([], P0, _, S, SR, S=SR, P) :- % Terminals !, dcg_terminal_pos(P0, P). dcg_body(List, P0, _, S, SR, C, P) :- ( List = [_|_] -> !, ( is_list(List) -> '$append'(List, SR, OL), % open the list C = (S = OL) ; '$skip_list'(_, List, Tail), var(Tail) -> C = '$append'(List, SR, S) % TBD: Can be optimized ; '$type_error'(list_or_partial_list, List) ) ; string(List) % double_quotes = string -> !, string_codes(List, Codes), '$append'(Codes, SR, OL), C = (S = OL) ), dcg_terminal_pos(P0, P). dcg_body(!, P0, _, S, SR, (!, SR = S), P) :- !, dcg_cut_pos(P0, P). dcg_body({}, P, _, S, S, true, P) :- !. dcg_body({T}, P0, Q, S, SR, (QT, SR = S), P) :- !, dcg_bt_pos(P0, P1), qualify(Q, T, P1, QT, P). dcg_body((T,R), P0, Q, S, SR, (Tt, Rt), P) :- !, f2_pos(P0, PA0, PB0, P, PA, PB), dcg_body(T, PA0, Q, S, SR1, Tt, PA), dcg_body(R, PB0, Q, SR1, SR, Rt, PB). dcg_body((T;R), P0, Q, S, SR, (Tt;Rt), P) :- !, f2_pos(P0, PA0, PB0, P, PA, PB), dcg_body(T, PA0, Q, S, S1, T1, PA), or_delay_bind(S, SR, S1, T1, Tt), dcg_body(R, PB0, Q, S, S2, R1, PB), or_delay_bind(S, SR, S2, R1, Rt). dcg_body((T|R), P0, Q, S, SR, (Tt;Rt), P) :- !, f2_pos(P0, PA0, PB0, P, PA, PB), dcg_body(T, PA0, Q, S, S1, T1, PA), or_delay_bind(S, SR, S1, T1, Tt), dcg_body(R, PB0, Q, S, S2, R1, PB), or_delay_bind(S, SR, S2, R1, Rt). dcg_body((C->T), P0, Q, S, SR, (Ct->Tt), P) :- !, f2_pos(P0, PA0, PB0, P, PA, PB), dcg_body(C, PA0, Q, S, SR1, Ct, PA), dcg_body(T, PB0, Q, SR1, SR, Tt, PB). dcg_body((C*->T), P0, Q, S, SR, (Ct*->Tt), P) :- !, f2_pos(P0, PA0, PB0, P, PA, PB), dcg_body(C, PA0, Q, S, SR1, Ct, PA), dcg_body(T, PB0, Q, SR1, SR, Tt, PB). dcg_body((\+ C), P0, Q, S, SR, (\+ Ct, SR = S), P) :- !, f1_pos(P0, PA0, P, PA), dcg_body(C, PA0, Q, S, _, Ct, PA). dcg_body(T, P0, Q, S, SR, QTt, P) :- dcg_extend(T, P0, S, SR, Tt, P1), qualify(Q, Tt, P1, QTt, P). or_delay_bind(S, SR, S1, T, (T, SR=S)) :- S1 == S, !. or_delay_bind(_S, SR, SR, T, T). %! qualify(+QualifyInfo, +Goal, +Pos0, -QGoal, -Pos) is det. % % @arg QualifyInfo is a term q(Module,Context,Pos), where Module % is the module in which Goal must be called and Context is the % current source module. qualify(q(M,C,_), X0, Pos0, X, Pos) :- M == C, !, X = X0, Pos = Pos0. qualify(q(M,_,MP), X, Pos0, M:X, Pos) :- dcg_qualify_pos(Pos0, MP, Pos). %! dcg_extend(+Head, +Extra1, +Extra2, -NewHead) % % Extend Head with two more arguments (on behalf DCG compilation). % The solution below is one option. Using =.. and append is the % alternative. In the current version (5.3.2), the =.. is actually % slightly faster, but it creates less garbage. :- dynamic dcg_extend_cache/4. :- volatile dcg_extend_cache/4. dcg_no_extend([]). dcg_no_extend([_|_]). dcg_no_extend({_}). dcg_no_extend({}). dcg_no_extend(!). dcg_no_extend((\+_)). dcg_no_extend((_,_)). dcg_no_extend((_;_)). dcg_no_extend((_|_)). dcg_no_extend((_->_)). dcg_no_extend((_*->_)). dcg_no_extend((_-->_)). %! dcg_extend(:Rule, ?Pos0, ?List, ?Tail, -Head, -Pos) is det. % % Extend a non-terminal with the DCG difference list List\Tail. % The position term is extended as well to reflect the layout of % the created term. The additional variables are located at the % end of the Rule. dcg_extend(V, _, _, _, _, _) :- var(V), !, throw(error(instantiation_error,_)). dcg_extend(M:OldT, Pos0, A1, A2, M:NewT, Pos) :- !, f2_pos(Pos0, MPos, P0, Pos, MPos, P), dcg_extend(OldT, P0, A1, A2, NewT, P). dcg_extend(OldT, P0, A1, A2, NewT, P) :- dcg_extend_cache(OldT, A1, A2, NewT), !, extended_pos(P0, P). dcg_extend(OldT, P0, A1, A2, NewT, P) :- ( callable(OldT) -> true ; throw(error(type_error(callable,OldT),_)) ), ( dcg_no_extend(OldT) -> throw(error(permission_error(define,dcg_nonterminal,OldT),_)) ; true ), ( compound(OldT) -> compound_name_arity(OldT, Name, Arity), compound_name_arity(CopT, Name, Arity) ; CopT = OldT, Name = OldT, Arity = 0 ), NewArity is Arity+2, functor(NewT, Name, NewArity), copy_args(1, Arity, CopT, NewT), A1Pos is Arity+1, A2Pos is Arity+2, arg(A1Pos, NewT, A1C), arg(A2Pos, NewT, A2C), assert(dcg_extend_cache(CopT, A1C, A2C, NewT)), OldT = CopT, A1C = A1, A2C = A2, extended_pos(P0, P). copy_args(I, Arity, Old, New) :- I =< Arity, !, arg(I, Old, A), arg(I, New, A), I2 is I + 1, copy_args(I2, Arity, Old, New). copy_args(_, _, _, _). /******************************* * POSITION LOGIC * *******************************/ extended_pos(Pos0, Pos) :- '$expand':extended_pos(Pos0, 2, Pos). f2_pos(Pos0, A0, B0, Pos, A, B) :- '$expand':f2_pos(Pos0, A0, B0, Pos, A, B). f1_pos(Pos0, A0, Pos, A) :- '$expand':f1_pos(Pos0, A0, Pos, A). %! dcg_bt_pos(?BraceTermPos, -Pos) is det. % % Position transformation for mapping of {G} to (G, S=SR). dcg_bt_pos(Var, Var) :- var(Var), !. dcg_bt_pos(brace_term_position(F,T,P0), term_position(F,T,F,F, [ P0, term_position(T,T,T,T,_) ])) :- !. dcg_bt_pos(Pos, _) :- expected_layout(brace_term, Pos). dcg_cut_pos(Var, Var) :- var(Var), !. dcg_cut_pos(F-T, term_position(F,T,F,T, [ F-T, term_position(T,T,T,T,_) ])). dcg_cut_pos(Pos, _) :- expected_layout(atomic, Pos). %! dcg_terminal_pos(+ListPos, -TermPos) dcg_terminal_pos(Pos, _) :- var(Pos), !. dcg_terminal_pos(list_position(F,T,_Elms,_Tail), term_position(F,T,_,_,_)). dcg_terminal_pos(F-T, term_position(F,T,_,_,_)). dcg_terminal_pos(Pos, _) :- expected_layout(terminal, Pos). %! dcg_qualify_pos(?TermPos0, ?ModuleCreatingPos, -TermPos) dcg_qualify_pos(Var, _, _) :- var(Var), !. dcg_qualify_pos(Pos, term_position(F,T,FF,FT,[MP,_]), term_position(F,T,FF,FT,[MP,Pos])) :- !. dcg_qualify_pos(_, Pos, _) :- expected_layout(f2, Pos). expected_layout(Expected, Found) :- '$expand':expected_layout(Expected, Found). /******************************* * PHRASE INTERFACE * *******************************/ %! phrase(:RuleSet, ?List). %! phrase(:RuleSet, ?List, ?Rest). % % Interface to DCGs :- meta_predicate phrase(//, ?), phrase(//, ?, ?), call_dcg(//, ?, ?). :- noprofile((phrase/2, phrase/3, call_dcg/3)). :- '$iso'((phrase/2, phrase/3)). phrase(RuleSet, Input) :- phrase(RuleSet, Input, []). phrase(RuleSet, Input, Rest) :- phrase_input(Input), phrase_input(Rest), call_dcg(RuleSet, Input, Rest). call_dcg(RuleSet, Input, Rest) :- ( strip_module(RuleSet, M, Plain), nonvar(Plain), dcg_special(Plain) -> dcg_body(Plain, _, q(M,M,_), S0, S, Body, _), Input = S0, Rest = S, call(M:Body) ; call(RuleSet, Input, Rest) ). phrase_input(Var) :- var(Var), !. phrase_input([_|_]) :- !. phrase_input([]) :- !. phrase_input(Data) :- throw(error(type_error(list, Data), _)). dcg_special(S) :- string(S). dcg_special((_,_)). dcg_special((_;_)). dcg_special((_|_)). dcg_special((_->_)). dcg_special(!). dcg_special({_}). dcg_special([]). dcg_special([_|_]). dcg_special(\+_).