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empty.hpp File Reference


Defines

#define BOOST_PP_EMPTY()
 Expands to nothing. Used with BOOST_PP_IF() and as an unused parameter. More...

#define BOOST_PREPROCESSOR_EMPTY()
 Obsolete. Use BOOST_PP_EMPTY(). More...

Detailed Description

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Define Documentation

 
#define BOOST_PP_EMPTY (    ) 
 

Expands to nothing. Used with BOOST_PP_IF() and as an unused parameter.

Example usage as the implementation of BOOST_PP_COMMA_IF(C): 

  #define BOOST_PP_COMMA_IF(C)\
    BOOST_PP_IF(C,BOOST_PP_COMMA,BOOST_PP_EMPTY)()

Example usage as an unused macro parameter: 

  #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)
  #undef BOOST_PP_DEF

The above expands to: 

  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];
  }

In case you wonder, the above code is part of a generalized layer for implementing the subscripting operators of a random access container.

 
#define BOOST_PREPROCESSOR_EMPTY (    ) 
 

Obsolete. Use BOOST_PP_EMPTY().

© Copyright Housemarque Oy 2001

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