forked from boostorg/preprocessor
73 lines
1.9 KiB
C++
73 lines
1.9 KiB
C++
#ifndef BOOST_PREPROCESSOR_EMPTY_HPP
|
|
#define BOOST_PREPROCESSOR_EMPTY_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.
|
|
*/
|
|
|
|
/** <P>Expands to nothing. Used with BOOST_PP_IF() and as an unused parameter.</P>
|
|
|
|
<P>Example usage as the implementation of BOOST_PP_COMMA_IF(C):</P>
|
|
|
|
<PRE>
|
|
#define BOOST_PP_COMMA_IF(C)\
|
|
BOOST_PP_IF(C,BOOST_PP_COMMA,BOOST_PP_EMPTY)()
|
|
</PRE>
|
|
|
|
<P>Example usage as an unused macro parameter:</P>
|
|
|
|
<PRE>
|
|
#define BOOST_PP_DEF(CV)\
|
|
template<class base>\
|
|
CV() typename implement_subscript_using_begin_subscript<base>::value_type&\
|
|
implement_subscript_using_begin_subscript<base>::operator[]\
|
|
( index_type\
|
|
i\
|
|
) CV()\
|
|
{ return base::begin()[i];\
|
|
}
|
|
|
|
BOOST_PP_DEF(BOOST_PP_EMPTY)
|
|
BOOST_PP_DEF(const BOOST_PP_EMPTY)
|
|
#undef BOOST_PP_DEF
|
|
</PRE>
|
|
|
|
<P>The above expands to:</P>
|
|
|
|
<PRE>
|
|
template<class base>
|
|
typename implement_subscript_using_begin_subscript<base>::value_type&
|
|
implement_subscript_using_begin_subscript<base>::operator[]
|
|
( index_type
|
|
i
|
|
)
|
|
{ return base::begin()[i];
|
|
}
|
|
|
|
template<class base>
|
|
const typename implement_subscript_using_begin_subscript<base>::value_type&
|
|
implement_subscript_using_begin_subscript<base>::operator[]
|
|
( index_type
|
|
i
|
|
) const
|
|
{ return base::begin()[i];
|
|
}
|
|
</PRE>
|
|
|
|
<P>In case you wonder, the above code is part of a generalized layer for
|
|
implementing the subscripting operators of a random access container.</P>
|
|
*/
|
|
#define BOOST_PP_EMPTY()
|
|
|
|
/** <P>Obsolete. Use BOOST_PP_EMPTY().</P> */
|
|
#define BOOST_PREPROCESSOR_EMPTY()
|
|
#endif
|