1

I am trying to figure out how to use the Boost.Preprocessor library http://www.boost.org/doc/libs/release/libs/preprocessor to unfold a "generic" type for different specific types. Below I will ask this for a simple point class example. Given:

struct Point##TYPE_SUFFIX_NAME
{
    TYPE X;
    TYPE Y;

    // Other code
};

I want to generate this type for different basic (POD) data types e.g.:

PointF32, PointF64, PointI32 etc.

where PointF32 would be:

struct PointF32
{
     float X;
     float Y;
};

That is, based on a list of types: 

short, int, long, float, double etc.

I want to "unfold" the above type for these. Preferably with the "template" definition in a separate include file and not as a macro, to allow for easier debugging.

NOTE: I am not interested in hearing about C++ templates. I know how to use templates. But these are not useful in my case. As an example imagine these types are going be used from .NET in C#, but are being generated in C++/CLI. So please stick to the question.

The problem, of course, stems from the lack of template support in .NET and due to generics not being suitable to solve my problem.

4

4 回答 4

2

根据 Benoît 的回答，我想出了以下答案。答案包含三个文件：

  • MyPointTypes.h
  • MyPointTypeImpl.h
  • MyPointTypes.cpp

MyPointTypes.h：

#ifndef __MYSTRUCTURES_H__
#define __MYSTRUCTURES_H__

#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/seq/size.hpp>

typedef signed char int8;
typedef unsigned char uint8;
typedef signed short int16;
typedef unsigned short uint16;
typedef signed int int32;
typedef unsigned int uint32;
typedef signed int int64;
typedef unsigned int uint64;

typedef float float32;
typedef double float64;

#define MY_SIGNED_INTEGER_SEQ    (int8)(int16)(int32)(int64)
#define MY_SIGNED_INTEGER_SUFFIX_SEQ    (I8)(I16)(I32)(I64)

#define MY_UNSIGNED_INTEGER_SEQ    (uint8)(uint16)(uint32)(uint64)
#define MY_UNSIGNED_INTEGER_SUFFIX_SEQ    (UI8)(UI16)(UI32)(UI64)

#define MY_SIGNED_UNSIGNED_INTEGER_SEQ    MY_SIGNED_INTEGER_SEQ MY_UNSIGNED_INTEGER_SEQ
#define MY_SIGNED_UNSIGNED_INTEGER_SUFFIX_SEQ    MY_SIGNED_INTEGER_SUFFIX_SEQ MY_UNSIGNED_INTEGER_SUFFIX_SEQ

#define MY_FLOAT_SEQ    (float32)(float64)
#define MY_FLOAT_SUFFIX_SEQ    (F32)(F64)

#define MY_BASIC_NUMERIC_TYPES_SEQ    MY_SIGNED_UNSIGNED_INTEGER_SEQ MY_FLOAT_SEQ
#define MY_BASIC_NUMERIC_TYPES_SUFFIX_SEQ    MY_SIGNED_UNSIGNED_INTEGER_SUFFIX_SEQ MY_FLOAT_SUFFIX_SEQ


#define MY_SEQ_OF_TYPES    MY_BASIC_NUMERIC_TYPES_SEQ
#define MY_SEQ_OF_SUFFICES    MY_BASIC_NUMERIC_TYPES_SUFFIX_SEQ

#define BOOST_PP_ITERATION_LIMITS (0, BOOST_PP_SEQ_SIZE(MY_SEQ_OF_TYPES) - 1)
#include BOOST_PP_ITERATE()

#undef MY_SEQ_OF_TYPES
#undef MY_SEQ_OF_SUFFICES

#endif

MyPointTypeImpl.h：

#include <boost/preprocessor/seq/elem.hpp>

#define n BOOST_PP_ITERATION()
#define PASTER(x,y) x ## y
#define EVALUATOR(x,y)  PASTER(x,y)
#define CONCATEVALUATED(x, y) EVALUATOR(x, y)

#define TYPE BOOST_PP_SEQ_ELEM(n, MY_SEQ_OF_TYPES)
#define SUFFIX BOOST_PP_SEQ_ELEM(n, MY_SEQ_OF_SUFFICES)

#define ADDSUFFIX(cls) CONCATEVALUATED(cls, SUFFIX)

struct ADDSUFFIX(Point)
{
  TYPE X;
  TYPE Y;
};

#undef n

MyPointTypes.cpp：

#define BOOST_PP_FILENAME_1 "MyPointTypeImpl.h"
#include "MyPointTypes.h"

这将定义类型：

PointI8, PointI16, PointI32, PointI64, 
PointUI8, PointUI16, PointUI32, PointUI64, 
PointF32, PointF64

然后想象一下 C++/CLI 值类型而不是 C++ 结构，即：

public value class Point

然后，我们有效地创建了所有基本数字类型的点类型，以便在 .NET 中使用，例如 C#。

于 2010-02-09T13:10:31.757 回答
1

以下代码未经测试，但应该是实现您想要的事情的良好开端。

在 my_structures.h 中：

#ifndef __MYSTRUCTURES_H__
#define __MYSTRUCTURES_H__

#define MY_LIST_OF_TYPES (F32, (I32, (BOOST_PP_NIL)))
#define MY_LIST_OF_SUFFICES (float, (int, (BOOST_PP_NIL)))

#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/list/size.hpp>

#define BOOST_PP_ITERATION_LIMITS (0, BOOST_PP_LIST_SIZE(MY_LIST_OF_TYPES))
#define BOOST_PP_FILENAME_1       "create_my_structures.h"
#include BOOST_PP_ITERATE()

#undef MY_LIST_OF_TYPES
#undef MY_LIST_OF_SUFFICES
#endif

并在 create_my_structures.h

#include <boost/preprocessor/list/at.hpp>

#define n BOOST_PP_ITERATION()

struct Point ## BOOST_PP_LIST_AT(MY_LIST_OF_SUFFICES, n)
{
  BOOST_PP_LIST_AT(MY_LIST_OF_TYPES, n) X;
  BOOST_PP_LIST_AT(MY_LIST_OF_TYPES, n) Y;
};

#undef n
于 2010-02-08T17:21:42.890 回答
1

C++ 编译器的旧（预模板）版本通常具有<generic.h>此类内容的标头。我会搜索旧版本的 g++。那是在我之前，所以我不知道它是否适合你。

或者，像

#define TYPE short
#define TYPES I16
#include "Point.def"
#undef TYPE
#undef TYPES
#define TYPE int
#define TYPES I32
#include "Point.def"

也可以帮助你。

或者显然是一个外部代码生成器（在 awk、perl、C++ 等中）。那可能是最好的解决方案。

于 2010-02-08T16:20:02.200 回答
0

这似乎是一个老问题，但是....我认为使用标准宏处理器（CPP）更容易做到

#define STRUCT_POINT( P_TYPE ) \
struct Point##_##P_TYPE        \
{                              \
   P_TYPE X;                   \
   P_TYPE Y;                   \
                               \
};

#define CREATE_STRUCT_POINTS \
  STRUCT_POINT( short    )     \
  STRUCT_POINT( int      )     \
  STRUCT_POINT( unsigned )     \
  STRUCT_POINT( float    )     \
  STRUCT_POINT( double   )

CREATE_STRUCT_POINTS

#undef CREATE_STRUCT_POINTS
#undef STRUCT_POINT

或者可能是这种变化（遵循“规范”）

#define STRUCT_POINT( P_TYPE, P_TYPE_ALIAS ) \
struct Point##P_TYPE_ALIAS     \
{                              \
   P_TYPE X;                   \
   P_TYPE Y;                   \
                               \
};

#define CREATE_STRUCT_POINTS \
  STRUCT_POINT( short    ,  I16  )     \
  STRUCT_POINT( int      ,  I32  )     \
  STRUCT_POINT( unsigned ,  U32  )     \
  STRUCT_POINT( float    ,  F32  )     \
  STRUCT_POINT( double   ,  F64  )

CREATE_STRUCT_POINTS

#undef CREATE_STRUCT_POINTS
#undef STRUCT_POINT
于 2010-08-18T21:17:08.253 回答