diff --git a/library/ypp.yap b/library/ypp.yap
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+%====================================================================================
+%
+% YPP: Yap PreProcessing
+%
+% Author: Nuno Fonseca (nunofonseca@acm.org)
+% Date: 2005-05-14
+% $Id: ypp.yap,v 1.1 2005-06-06 05:10:37 vsc Exp $
+%
+%====================================================================================
+
+%====================================================================================
+% Module declarations
+%====================================================================================
+
+:-module(ypp,[
+	      ypp_state/1,	% ypp_state(on|off)
+	      ypp_define/2,     % persistent defines  ypp_define(+NAME,VALUE)
+	      ypp_undefine/1,   % persistent defines  ypp_undefine(+NAME)
+	      ypp_extcmd/1,	% ypp_extcmd(?command)
+	      ypp_consult/1,    % similiar to standard consult but with preprocessing
+	      ypp_reconsult/1
+    ]
+    ).
+%====================================================================================
+% Public Predicates
+%====================================================================================
+
+ypp_state(State):-
+	ground(State),!,
+	set_state(State).
+
+ypp_state(State):-
+	get_state(State),
+	!.
+
+ypp_define(Name,Value):-
+	ground(Name),ground(Value),
+	store_define(Name,Value).
+
+ypp_undefine(Name):-
+	ground(Name),
+ypp_extcmd(Cmd):-
+	ground(Cmd),!,
+	eraseall('____ypp_extcmd'),
+	recorda('____ypp_extcmd',Cmd,_).
+ypp_extcmd(Cmd):-
+	\+ ground(Cmd),
+	recorded('____ypp_extcmd',Cmd,_).
+
+ypp_consult(File):-
+	(get_state(on)->ypp_file(File,NFile);NFile=File),
+	consult(NFile).
+
+ypp_reconsult(File):-
+	(get_state(on)->ypp_file(File,NFile);NFile=File),
+	reconsult(NFile),
+%====================================================================================
+% Private Predicates
+%====================================================================================
+
+set_state(on):-set_value('____ypp_state',1).
+set_state(off):-set_value('____ypp_state',0).
+
+get_state(State):-
+	get_value('____ypp_state',Val),
+	(Val==0->State=off;State=on).
+
+
+store_define(Name,Value):-
+	(recorded('___ypp',def(Name,_),Ref)->erase(Ref);true),
+	recordz('___ypp',def(Name,Value),_).
+
+del_define(Name):-
+	(recorded('___ypp',def(Name,_),Ref)->erase(Ref);true),
+	!.
+
+%defines2string(-DefineString)
+defines2string(S):-
+	findall(d(Name,Val),recorded('___ypp',def(Name,Val),_),AllDefs),
+	mergedefs(AllDefs,'-D',S),
+	!.
+
+mergedefs([],_,'').
+mergedefs([d(Name,Val)|RDefs],Pref,S):-
+	mergedefs(RDefs,Pref,S1),
+	atom_concat([Pref,Name,'=',Val,' ',S1],S).
+
+
+ypp_file(File,PPFile):-
+	% ppfile
+	atom_concat([File,'.ypp'],PPFile),
+	% Cmdline
+	defines2string(Defs),ypp_extcmd(Cmd),
+	atom_concat([Cmd,' ',PPFile,' ',Defs,' ',File],Cmdline),
+	write(Cmdline),nl,
+%	current_module(M1,M2),
+%	write(M1:M2),nl,
+	system(Cmdline),
+	!.
+
+% initialization
+:-set_state(on),
+	ypp_extcmd('cpp -E -w -o ').
+%	ypp_extcmd('gpp -o').
+