BOOST_PP_FOR_r

Boost , ,

Usage

Arguments

r

The next available BOOST_PP_FOR repetition.

state

The initial state.

pred

A binary predicate of the form pred(r, state).  This macro must expand to an integer in the range of 0 to BOOST_PP_LIMIT_MAG.  BOOST_PP_FOR repeatedly expands macro while this predicate returns non-zero.  This macro is called with the next available BOOST_PP_FOR repetition and the current state.

op

A binary operation of the form op(r, state).  This operation is expanded by BOOST_PP_FOR with the next available BOOST_PP_FOR repetition and the current state.  This macro is repeatedly applied to the state, each time producing a new state, until pred returns 0.

macro

A binary macro of the form macro(r, state).  This macro is expanded by BOOST_PP_FOR with the next available BOOST_PP_FOR repetition and the current state.  This macro is is repeated by BOOST_PP_FOR until pred returns 0.

Remarks

See Also

• BOOST_PP_CAT
• BOOST_PP_FOR
• BOOST_PP_LIMIT_MAG
• Макрос с R-формами вхождения

Requirements

Sample Code

#include <boost/preprocessor/arithmetic/dec.hpp>
#include <boost/preprocessor/arithmetic/inc.hpp>
#include <boost/preprocessor/comparison/not_equal.hpp>
#include <boost/preprocessor/punctuation/comma_if.hpp>
#include <boost/preprocessor/repetition/for.hpp>
#include <boost/preprocessor/tuple/elem.hpp>
#define PRED(r, state) \
   BOOST_PP_NOT_EQUAL( \
      BOOST_PP_TUPLE_ELEM(4, 0, state), \
      BOOST_PP_INC( \
         BOOST_PP_TUPLE_ELEM(4, 1, state) \
      ) \
   ) \
   /**/
#define OP(r, state) \
   ( \
      BOOST_PP_INC( \
         BOOST_PP_TUPLE_ELEM(4, 0, state) \
      ), \
      BOOST_PP_TUPLE_ELEM(4, 1, state), \
      BOOST_PP_TUPLE_ELEM(4, 2, state), \
      BOOST_PP_INC( \
         BOOST_PP_TUPLE_ELEM(4, 3, state) \
      ) \
   ) \
   /**/
#define MACRO(r, state) \
   BOOST_PP_COMMA_IF( \
      BOOST_PP_TUPLE_ELEM(4, 3, state) \
   ) template< \
      BOOST_PP_FOR_ ## r( \
         (0, BOOST_PP_TUPLE_ELEM(4, 0, state), _, 0), \
         PRED_2, OP, MACRO_2 \
      ) \
   > class BOOST_PP_CAT( \
      BOOST_PP_TUPLE_ELEM(4, 2, state), \
      BOOST_PP_TUPLE_ELEM(4, 0, state) \
   ) \
   /**/
#define PRED_2(r, state) \
   BOOST_PP_NOT_EQUAL( \
      BOOST_PP_TUPLE_ELEM(4, 0, state), \
      BOOST_PP_TUPLE_ELEM(4, 1, state) \
   ) \
   /**/
#define MACRO_2(r, state) \
   BOOST_PP_COMMA_IF( \
      BOOST_PP_TUPLE_ELEM(4, 0, state) \
   ) class \
   /**/
#define TEMPLATE_TEMPLATE(low, high, name) \
   BOOST_PP_FOR( \
      (low, high, name, 0), \
      PRED, OP, MACRO \
   ) \
   /**/
TEMPLATE_TEMPLATE(2, 4, T)
/*
   expands to...
   template<class, class> class T2,
   template<class, class, class> class T3,
   template<class, class, class, class> class T4
*/

Статья BOOST_PP_FOR_r раздела может быть полезна для разработчиков на c++ и boost.

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