diff --git a/GPL/ctypes.pl b/GPL/ctypes.pl
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+/*  $Id$
+
+    Part of SWI-Prolog
+
+    Author:        Jan Wielemaker
+    E-mail:        wielemak@science.uva.nl
+    WWW:           http://www.swi-prolog.org
+    Copyright (C): 1985-2006, 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 Lesser 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(ctypes,
+	  [ is_alnum/1,
+	    is_alpha/1,
+	    is_ascii/1,
+	    is_cntrl/1,
+	    is_csym/1,
+	    is_csymf/1,
+	    is_digit/1,
+	    is_digit/3,
+	    is_endfile/1,
+	    is_endline/1,
+	    is_graph/1,
+	    is_lower/1,
+	    is_newline/1,
+	    is_newpage/1,
+	    is_paren/2,
+	    is_period/1,
+	    is_print/1,
+	    is_punct/1,
+	    is_quote/1,
+	    is_space/1,
+	    is_upper/1,
+	    is_white/1,
+	    to_lower/2,
+	    to_upper/2
+	  ]).
+
+/** <module> Character code classification
+
+This file implements the functionality of the corresponding Quintus
+library based on SWI-Prolog's code_type/2 predicate. Please check the
+documentation of this predicate to find the definitions of the classes.
+
+@see	code_type/2
+@see	char_type/2
+*/
+
+is_alnum(C)   :- code_type(C, alnum).
+is_alpha(C)   :- code_type(C, alpha).
+is_ascii(C)   :- code_type(C, ascii).
+is_cntrl(C)   :- code_type(C, cntrl).
+is_csym(C)    :- code_type(C, csym).
+is_csymf(C)   :- code_type(C, csymf).
+is_digit(C)   :- code_type(C, digit).
+is_graph(C)   :- code_type(C, graph).
+is_lower(C)   :- code_type(C, lower).
+is_upper(C)   :- code_type(C, upper).
+is_period(C)  :- code_type(C, period).
+is_endline(C) :- code_type(C, end_of_line).
+is_print(C)   :- is_graph(C).
+is_punct(C)   :- code_type(C, punct).
+is_quote(C)   :- code_type(C, quote).
+is_space(C)   :- code_type(C, space).
+is_white(C)   :- code_type(C, white).
+
+is_endfile(-1).
+is_newpage(12).				% Control-L
+is_newline(10).
+
+%%	is_paren(?Open, ?Close) is semidet.
+%
+%	True if Open is the open-parenthesis of Close.
+
+is_paren(0'(, 0')).			% Prolog is too good at this
+is_paren(0'[, 0']).
+is_paren(0'{, 0'}).
+
+%%	to_lower(+U, -L) is det.
+%%	to_lower(-U, +L) is det.
+%
+%	Succeeds  if  `U'  is  upper  case  character  and  `L'  is  the
+%	corresponding lower case character or `U' is an ascii character,
+%	but not an upper case letter and `L' is equal to `U'.
+
+to_lower(U, L) :-
+	code_type(L, to_lower(U)).
+
+to_upper(U, L) :-
+	code_type(L, to_upper(U)).
+
+%%	is_digit(+C, +Base, -Weight) is det.
+%%	is_digit(-C, +Base, +Weight) is det.
+%
+%	Succeeds if `C' is a digit using `Base'  as  base  and  `Weight'
+%	represents its value.  Only the base-10 case is handled by code_type.
+
+is_digit(C, Base, Weight) :-
+	Base == 10, !,
+	code_type(C, digit(Weight)).
+is_digit(C, Base, Weight) :-
+	between(2, 36, Base),
+	succ(X, Base),
+	between(0, X, Weight),
+	is_digit(C, Weight).
+
+is_digit(C, Weight) :-
+	Weight < 10, !,
+	plus(Weight, 0'0, C).
+is_digit(C, Weight) :-
+	plus(Weight, 87, C), !.		/* `a`-10 */
+is_digit(C, Weight) :-
+	plus(Weight, 55, C).		/* `A`-10 */
+