基于结构中的字段数编译时间开关生成 [英] Compile time switch generation based on number of fields in structure

问题描述

在C ++ 03中如何在编译时获得所选结构的成员数？我正在试验BOOST_FUSION_ADAPT_STRUCT，但我没有得到任何工作示例。

编辑：
我想在编译时生成switch语句，每个成员一个病例。所以让我们说我们有3个成员的结构，然后我想生成这个开关：

  switch（val）
 { 
 case 0：
 break; 
 case 1：
 break; 
 case 2：
 break; 
} 
  

我如何做这样的事情？

编辑2：
在每个语句中我将调用带有一些参数的模板函数。其中一个参数是结构成员。

编辑3：
经过长时间的搜索，阅读和查找本文 http://boost.2283326.n4.nabble.com/Preprocessor-sequence- of-quot-pairs-quot-td4636239.html

我设法迭代成员从0到count - 1（从创建switch语句很容易）。

  #include< iostream> 
 #include< string> 
 #include< vector> 
 #include< boost / fusion / include / adapt_struct.hpp> 
 #include< boost / preprocessor / repetition / repeat.hpp> 
 #include< boost / fusion / include / define_struct.hpp> 
 #include< boost / preprocessor / seq / size.hpp> 
 #include< boost / preprocessor / seq / seq.hpp> 
 #include< boost / preprocessor / seq / cat.hpp> 
 
 struct MyStruct 
 {
 int x; 
 int y; 
}; 
 
 #define GO（r，data，elem）elem 
 #define SEQ1（（int，x））（（int，y））
 
 BOOST_FUSION_ADAPT_STRUCT 
 MyStruct，
 BOOST_PP_SEQ_FOR_EACH（GO，，SEQ1）
）
 
 #define PRINT（unused，number，data）\ 
 std :: cout <<数字<< std :: endl; 
 
 int main（）
 {
 BOOST_PP_REPEAT（BOOST_PP_SEQ_SIZE（SEQ1），PRINT，data）
} 
  
 
 
 
现在BOOST_PP_REPEAT可能创建case语句...：）
解决方案
解决方案... 
 
 
 
经过长时间的搜索，阅读和查找本文 http://boost.2283326.n4.nabble.com/Preprocessor-sequence-of-quot-pairs-quot-td4636239 .html  
 
 
 
我设法迭代成员从0到count  -  1（从创建switch语句很容易）。
  #include< iostream> 
 #include< string> 
 #include< vector> 
 #include< boost / fusion / include / adapt_struct.hpp> 
 #include< boost / preprocessor / repetition / repeat.hpp> 
 #include< boost / fusion / include / define_struct.hpp> 
 #include< boost / preprocessor / seq / size.hpp> 
 #include< boost / preprocessor / seq / seq.hpp> 
 #include< boost / preprocessor / seq / cat.hpp> 
 
 struct MyStruct 
 {
 int x; 
 int y; 
}; 
 
 #define GO（r，data，elem）elem 
 #define SEQ1（（int，x））（（int，y））
 
 BOOST_FUSION_ADAPT_STRUCT 
 MyStruct，
 BOOST_PP_SEQ_FOR_EACH（GO，，SEQ1）
）
 
 #define PRINT（unused，number，data）\ 
 std :: cout <<数字<< std :: endl; 
 
 int main（）
 {
 BOOST_PP_REPEAT（BOOST_PP_SEQ_SIZE（SEQ1），PRINT，data）
} 
  
 
 
 
现在，BOOST_PP_REPEAT可能创建案例语句...：）
 
How in C++03 get in compile time number of members of chosen struct? I was experimenting with BOOST_FUSION_ADAPT_STRUCT but i did't get any working example.

EDIT:
I want to generate switch statement in compile time, where there will be one case per each member. So lets say we have struct with 3 members then I want to generate this switch:
switch(val)
{
   case 0:
       break;
   case 1:
       break;
   case 2:
       break;
}
How I can do something like this?

EDIT 2:
in each statement I will call template function with some parameters. One of this parameters is a member of structure.

EDIT 3:
After long searching, reading and finding this article http://boost.2283326.n4.nabble.com/Preprocessor-sequence-of-quot-pairs-quot-td4636239.html

I managed to iterate over members from 0 to count - 1 (from that creating switch statement is easy).
#include <iostream>
#include <string>
#include <vector>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/preprocessor/repetition/repeat.hpp>
#include <boost/fusion/include/define_struct.hpp>
#include <boost/preprocessor/seq/size.hpp>
#include <boost/preprocessor/seq/seq.hpp>
#include <boost/preprocessor/seq/cat.hpp>

struct MyStruct
{
    int x;
    int y;
};

#define GO(r, data, elem) elem
#define SEQ1 ((int,x))((int,y))

BOOST_FUSION_ADAPT_STRUCT( 
    MyStruct,
    BOOST_PP_SEQ_FOR_EACH(GO, ,SEQ1)      
    )

#define PRINT(unused, number, data) \
    std::cout << number << std::endl;

int main()
{
    BOOST_PP_REPEAT(BOOST_PP_SEQ_SIZE(SEQ1), PRINT, "data")
}
Now BOOST_PP_REPEAT may create case statements ... :)
解决方案
Solution...

After long searching, reading and finding this article http://boost.2283326.n4.nabble.com/Preprocessor-sequence-of-quot-pairs-quot-td4636239.html

I managed to iterate over members from 0 to count - 1 (from that creating switch statement is easy).
#include <iostream>
#include <string>
#include <vector>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/preprocessor/repetition/repeat.hpp>
#include <boost/fusion/include/define_struct.hpp>
#include <boost/preprocessor/seq/size.hpp>
#include <boost/preprocessor/seq/seq.hpp>
#include <boost/preprocessor/seq/cat.hpp>

struct MyStruct
{
    int x;
    int y;
};

#define GO(r, data, elem) elem
#define SEQ1 ((int,x))((int,y))

BOOST_FUSION_ADAPT_STRUCT( 
    MyStruct,
    BOOST_PP_SEQ_FOR_EACH(GO, ,SEQ1)      
    )

#define PRINT(unused, number, data) \
    std::cout << number << std::endl;

int main()
{
    BOOST_PP_REPEAT(BOOST_PP_SEQ_SIZE(SEQ1), PRINT, "data")
}
Now BOOST_PP_REPEAT may create case statements ... :)

                        
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