forked from boostorg/preprocessor
74 lines
2.1 KiB
C++
74 lines
2.1 KiB
C++
#ifndef BOOST_PREPROCESSOR_EMPTY_HPP
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#define BOOST_PREPROCESSOR_EMPTY_HPP
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// Copyright (C) 2001
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// Housemarque Oy
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// http://www.housemarque.com
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//
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// Permission to copy, use, modify, sell and distribute this software is
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// granted provided this copyright notice appears in all copies. This
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// software is provided "as is" without express or implied warranty, and
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// with no claim as to its suitability for any purpose.
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// See http://www.boost.org for most recent version.
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/*! \file
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<a href="../../../../boost/preprocessor/empty.hpp">Click here to see the header.</a>
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*/
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//! Expands to nothing. Used with BOOST_PREPROCESSOR_IF() and as an unused parameter.
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/*!
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Example usage as the implementation of BOOST_PREPROCESSOR_COMMA_IF(C):
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<PRE>\verbatim
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#define BOOST_PREPROCESSOR_COMMA_IF(C)\
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BOOST_PREPROCESSOR_IF(C,BOOST_PREPROCESSOR_COMMA,BOOST_PREPROCESSOR_EMPTY)()
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\endverbatim</PRE>
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Example usage as an unused macro parameter:
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<PRE>\verbatim
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#define BOOST_PREPROCESSOR_DEF(CV)\
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template<class base> \
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CV typename implement_subscript_using_begin_subscript<base>::value_type&\
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implement_subscript_using_begin_subscript<base>::operator[]\
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( index_type \
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i \
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) CV \
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{ return base::begin()[i]; \
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}
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BOOST_PREPROCESSOR_DEF(BOOST_PREPROCESSOR_EMPTY())
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BOOST_PREPROCESSOR_DEF(const)
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#undef BOOST_PREPROCESSOR_DEF
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\endverbatim</PRE>
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The above expands to:
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<PRE>\verbatim
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template<class base>
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typename implement_subscript_using_begin_subscript<base>::value_type&
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implement_subscript_using_begin_subscript<base>::operator[]
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( index_type
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i
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)
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{ return base::begin()[i];
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}
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template<class base>
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const typename implement_subscript_using_begin_subscript<base>::value_type&
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implement_subscript_using_begin_subscript<base>::operator[]
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( index_type
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i
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) const
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{ return base::begin()[i];
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}
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\endverbatim</PRE>
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In case you wonder, the above code is part of a generalized layer for
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implementing the subscripting operators of a random access container.
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*/
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#define BOOST_PREPROCESSOR_EMPTY()
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#endif
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