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yap-6.3/LGPL/apply_macros.pl
2009-02-10 22:47:47 +00:00

186 lines
5.5 KiB
Prolog

/* $Id: apply_macros.pl,v 1.3 2008-08-06 17:32:21 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(apply_macros,
[
]).
:- use_module(library(lists)).
:- use_module(library(occurs)).
/** <module> Goal expansion rules to avoid meta-calling
This module defines goal_expansion/2 rules to deal with commonly used,
but fundamentally slow meta-predicates. Notable maplist/2... defines a
useful set of predicates, but its exection is considerable slower than a
traditional Prolog loop. Using this library calls to maplist/2... are
translated into an call to a generated auxilary predicate that is
compiled using compile_aux_clauses/1. Currently this module supports:
* maplist/2..
* forall/2
* once/1
* ignore/1
* phrase/2
* phrase/3
@tbd Support more predicates
@author Jan Wielemaker
*/
:- dynamic
user:goal_expansion/2.
:- multifile
user:goal_expansion/2.
%% expand_maplist(+Callable, +Lists, -Goal) is det.
%
% Macro expansion for maplist/2 and higher arity.
expand_maplist(Callable0, Lists, Goal) :-
( Callable0 = _:_
-> strip_module(Callable0, M, Callable),
NextGoal = M:NextCall
; Callable = Callable0,
NextGoal = NextCall
),
Callable =.. [Pred|Args],
length(Args, Argc),
length(Argv, Argc),
length(Lists, N),
length(Vars, N),
MapArity is N + 1,
format(atom(AuxName), '__aux_maplist/~d_~w+~d', [MapArity, Pred, Argc]),
append(Lists, Args, AuxArgs),
Goal =.. [AuxName|AuxArgs],
AuxArity is N+Argc,
prolog_load_context(module, Module),
( current_predicate(Module:AuxName/AuxArity)
-> true
; empty_lists(N, BaseLists),
length(Anon, Argc),
append(BaseLists, Anon, BaseArgs),
BaseClause =.. [AuxName|BaseArgs],
heads_and_tails(N, NextArgs, Vars, Tails),
append(NextArgs, Argv, AllNextArgs),
NextHead =.. [AuxName|AllNextArgs],
append(Argv, Vars, PredArgs),
NextCall =.. [Pred|PredArgs],
append(Tails, Argv, IttArgs),
NextIterate =.. [AuxName|IttArgs],
NextClause = (NextHead :- NextGoal, NextIterate),
( predicate_property(NextGoal, transparent)
-> compile_aux_clauses([ (:- module_transparent(Module:AuxName/AuxArity)),
BaseClause,
NextClause
])
; compile_aux_clauses([BaseClause, NextClause])
)
).
empty_lists(0, []) :- !.
empty_lists(N, [[]|T]) :-
N2 is N - 1,
empty_lists(N2, T).
heads_and_tails(0, [], [], []).
heads_and_tails(N, [[H|T]|L1], [H|L2], [T|L3]) :-
N2 is N - 1,
heads_and_tails(N2, L1, L2, L3).
%% expand_apply(+GoalIn:callable, -GoalOut) is semidet.
%
% Macro expansion for `apply' predicates.
expand_apply(Maplist, Goal) :-
functor(Maplist, maplist, N),
N >= 2,
Maplist =.. [maplist, Callable|Lists],
callable(Callable), !,
expand_maplist(Callable, Lists, Goal).
expand_apply(forall(Cond, Action), \+((Cond, \+(Action)))).
expand_apply(once(Goal), (Goal->true;fail)).
expand_apply(ignore(Goal), (Goal->true;true)).
expand_apply(phrase(NT,Xs), NTXsNil) :-
expand_apply(phrase(NT,Xs,[]), NTXsNil).
expand_apply(phrase(NT,Xs0,Xs), NewGoal) :-
Goal = phrase(NT,Xs0,Xs),
nonvar(NT),
catch('$translate_rule'((pseudo_nt --> NT), Rule),
error(Pat,ImplDep),
( \+ harmless_dcgexception(Pat),
throw(error(Pat,ImplDep))
)),
Rule = (pseudo_nt(Xs0c,Xsc) :- NewGoal0),
Goal \== NewGoal0,
\+ contains_illegal_dcgnt(NT), !, % apply translation only if we are safe
( var(Xsc), Xsc \== Xs0c
-> Xs = Xsc, NewGoal1 = NewGoal0
; NewGoal1 = (NewGoal0, Xsc = Xs)
),
( var(Xs0c)
-> Xs0 = Xs0c,
NewGoal = NewGoal1
; ( Xs0 = Xs0c, NewGoal1 ) = NewGoal
).
harmless_dcgexception(instantiation_error). % ex: phrase(([1],x:X,[3]),L)
harmless_dcgexception(type_error(callable,_)). % ex: phrase(27,L)
%% contains_illegal_dcgnt(+Term) is semidet.
%
% True if Term contains a non-terminal we cannot deal with using
% goal-expansion. The test is too general approximation, but safe.
contains_illegal_dcgnt(NT) :-
sub_term(I, NT),
nonvar(I),
( I = ! ; I = phrase(_,_,_) ), !.
% write(contains_illegal_nt(NT)), % JW: we do not want to write
% nl.
/*******************************
* ACTIVATE *
*******************************/
% @tbd Should we only apply if optimization is enabled (-O)?
user:goal_expansion(GoalIn, M, GoalOut) :-
\+ current_prolog_flag(xref, true),
expand_apply(M:GoalIn, GoalOut).