Bir sırayı açmak için boost :: preprocessor nasıl kullanılır?

Question

Boost :: preprocessor nasıl kullanılır?

Örneğin, (farketmez arasındaki virgül)

(int,x)(double,y)(float,z) or 
(int,x),(double,y),(float,z) or 
((int)(x))((double)(y))((float)(z)) 

aşağıdaki gibi bir diziye sahip ve kullanılarak

int,double,float 

ve

x,y,z 

dönüştürmek istediğiniz macor,

UNZIP(i, seq) 

i dizinidir.

Answer 1

Sıkıştırılmış (int, x, 10)(double, y, 20)(float, z, 30) arasında, diğer bir deyişle sekansı.

LIVE DEMO

#include <boost/preprocessor/punctuation/comma_if.hpp> 
#include <boost/preprocessor/seq/for_each_i.hpp> 
#include <boost/preprocessor/seq/pop_front.hpp> 
#include <boost/preprocessor/seq/for_each.hpp> 
#include <boost/preprocessor/variadic/elem.hpp> 
#include <boost/preprocessor/cat.hpp> 

// Such technique is used at: 
// http://www.boost.org/doc/libs/1_56_0/boost/fusion/adapted/struct/define_struct.hpp 
#define AUXILIARY_0(...) ((__VA_ARGS__)) AUXILIARY_1 
#define AUXILIARY_1(...) ((__VA_ARGS__)) AUXILIARY_0 
#define AUXILIARY_0_END 
#define AUXILIARY_1_END 

#define REMOVE_PARENTHESES(...) __VA_ARGS__ 

#define COMMA_SEPARATED(r, data, i, elem) \ 
    BOOST_PP_COMMA_IF(i) BOOST_PP_VARIADIC_ELEM(data, REMOVE_PARENTHESES elem) \ 
/**/ 

#define ZIPPED_TO_SEQ(zipped) \ 
    BOOST_PP_SEQ_POP_FRONT(BOOST_PP_CAT(AUXILIARY_0(0)zipped,_END)) \ 
/**/ 

#define FOR_EACH_ZIPPED_I(macro, data, zipped) \ 
    BOOST_PP_SEQ_FOR_EACH_I(macro, data, ZIPPED_TO_SEQ(zipped)) \ 
/**/ 

#define UNZIP(i, zipped) FOR_EACH_ZIPPED_I(COMMA_SEPARATED, i, zipped) 

/*******************************************************************/ 
// DEMO: 

#define zipped (int, x, 10)(double, y, 20)(float, z, 30) 

FIRST: UNZIP(0, zipped) 
SECOND: UNZIP(1, zipped) 
THIRD: UNZIP(2, zipped) 

Preprocessor çıkışı:

FIRST: int , double , float 
SECOND: x , y , z 
THIRD: 10 , 20 , 30 

Answer 2

, Boost.PP büyük çalışır ((int,x),(double,y),(float,z)) virgül anlamına varsayarak: elemanları arasında virgül olmadan

#include <boost/preprocessor.hpp> //or smaller individual headers 

//SEQ_ENUM adds commas between each element of the sequence 
//the sequence is transformed from what's passed into the ... 
//the invocation of UNZIP_MACRO is given the index to use in each element as data 
#define UNZIP(i, ...)        \ 
    BOOST_PP_SEQ_ENUM(       \ 
     BOOST_PP_SEQ_TRANSFORM(     \ 
      UNZIP_MACRO,       \ 
      i,         \ 
      BOOST_PP_VARIADIC_TO_SEQ(__VA_ARGS__) \ 
     )           \ 
    ) 

//called with each element of the sequence 
#define UNZIP_MACRO(s, data, elem) \ 
    BOOST_PP_TUPLE_ELEM(data, elem) 


#define ZIPPED_SEQUENCE (int,x),(double,y),(float,z) 

UNZIP(0, ZIPPED_SEQUENCE) //int, double, float 
UNZIP(1, ZIPPED_SEQUENCE) //x, y, z