boost_preprocessor/include/boost/preprocessor/arithmetic/sub.hpp

#ifndef BOOST_PREPROCESSOR_ARITHMETIC_SUB_HPP
#define BOOST_PREPROCESSOR_ARITHMETIC_SUB_HPP

// Copyright (C) 2001
// Housemarque Oy
// http://www.housemarque.com
//
// Permission to copy, use, modify, sell and distribute this software is
// granted provided this copyright notice appears in all copies. This
// software is provided "as is" without express or implied warranty, and
// with no claim as to its suitability for any purpose.

// See http://www.boost.org for most recent version.

/*! \file

<a href="../../../../boost/preprocessor/arithmetic/sub.hpp">Click here to see the header.</a>
*/

#include <boost/preprocessor/dec.hpp>
#include <boost/preprocessor/tuple/elem.hpp>
#include <boost/preprocessor/while.hpp>

//! Expands to the difference of X and Y.
/*!
For example, BOOST_PP_SUB(4,3) expands to 1 (a single token).
*/
#define BOOST_PP_SUB(X,Y) BOOST_PP_SUB_D(0,X,Y)

#ifndef DOXYGEN_SHOULD_SKIP_THIS
#define BOOST_PP_SUB_D(D,X,Y) BOOST_PP_TUPLE_ELEM(2,0,BOOST_PP_WHILE##D(BOOST_PP_SUB_C,BOOST_PP_SUB_F,(X,Y)))
#define BOOST_PP_SUB_C(D,P) BOOST_PP_TUPLE2_ELEM1 P
#define BOOST_PP_SUB_F(D,P) (BOOST_PP_DEC(BOOST_PP_TUPLE2_ELEM0 P),BOOST_PP_DEC(BOOST_PP_TUPLE2_ELEM1 P))
#endif

//! Obsolete. Use BOOST_PP_SUB(X,Y).
#define BOOST_PREPROCESSOR_SUB(X,Y) BOOST_PP_SUB(X,Y)
#endif