Cython是否可能有C ++风格的内部typedef？ [英] Are C++-style internal typedefs possible in Cython?

问题描述

在C ++中，可以声明类或别名成员的类型别名：

  struct Foo 
 {
 //内部类型别名
 typedef int DataType; 
 
 // ... 
}; 
  

有没有办法在Cython中做同样的事？我尝试了最明显的方法：

  cdef struct Foo：
 ctypedef int DataType 
  

但这不起作用：

 编译Cython文件时出错：
 ------------------------------------- ----------------------- 
 ... 
＃distutils：language = c ++ 
 
 cdef struct Foo：
 ctypedef int DataType 
 ^ 
 -------------------------------- ---------------------------- 
 
 internal_typedefs_example.pyx：4：4：需要一个标识符，这是Cython的一个根本限制（我使用的是v0.21.2），或者是Cython的基本限制。是否有解决方法？
 
 
 
 
 
 
为什么要处理内部typedef？有几个一般原因 -  此前的SO问题涵盖了其中的一些。
 
 
 
我感兴趣的特定情况是包装一组模板化的C ++类，看起来像这样：
  struct FooDataset 
 {
 typedef int DataType; 
 typedef float ReturnType; 
 
 //方法，其他重要的东西
}; 
 
 struct BarDataset 
 {
 typedef long DataType; 
 typedef double ReturnType; 
 
 //方法，其他重要的东西
}; 
 
 template< class Dataset> 
 class DataProcessor {
 
 DataProcessor（Dataset& input_data）; 
 
 typedef typename Dataset :: DataType T; 
 typedef typename Dataset :: ReturnType R; 
 
 T getDataItem（）; 
 R computeSomething（）; / *等* / 
 
 //做其他一些可能涉及T和/或R 
}的东西; 
  
 struct的内部有typedef赋予我更好的封装，因为我只需要传递一个模板参数（ Dataset 类），而不是单独指定 Dataset  ... 特定于数据集类型。
 
 
 
我意识到，很难找到这种情况的解决方法 - 我大多只想获得一个确定的答案，关于内部typedef是否目前可能在Cython中。
解决方案
据我所知，这在Cython目前不支持。但是你不能只在结构之外定义它呢？
 
 
 
 Cython目前不是为C ++而设计的，而是一种加快python代码中的热点的方法。如果你需要更多的东西，只需写在C ++中并公开python绑定。
 
In C++ it's possible to declare type aliases that are members of a class or struct:
struct Foo
{
    // internal type alias
    typedef int DataType;

    // ...
};
Is there any way to do the same thing in Cython? I've tried the most obvious approach:
cdef struct Foo:
    ctypedef int DataType
But this doesn't work:
Error compiling Cython file:
------------------------------------------------------------
...
# distutils: language=c++

cdef struct Foo:
    ctypedef int DataType
   ^
------------------------------------------------------------

internal_typedefs_example.pyx:4:4: Expected an identifier, found 'ctypedef'
Is this just a fundamental limitation of Cython (I'm using v0.21.2), or is there a workaround?



Why bother with internal typedefs? There are several general reasons - this previous SO question covers a few of them.

The specific case I'm interested in is wrapping a set of templated C++ classes that look something like this:
struct FooDataset
{
    typedef int DataType;
    typedef float ReturnType;

    // methods, other important stuff
};

struct BarDataset
{
    typedef long DataType;
    typedef double ReturnType;

    // methods, other important stuff
};

template <class Dataset>
class DataProcessor{

    DataProcessor(Dataset& input_data);

    typedef typename Dataset::DataType T;
    typedef typename Dataset::ReturnType R;

    T getDataItem();
    R computeSomething(); /* etc. */

    // do some other stuff that might involve T and/or R
};
Having typedef(s) internal to the struct gives me better encapsulation since I only need to pass a single template parameter (the Dataset class) rather than individually specifying the Dataset plus T, R, ... specific to that Dataset type.

I realise that it's not too difficult to find workarounds for this case - I'm mostly just interested in getting a definitive answer as to whether or not internal typedefs are currently possible in Cython.
解决方案
As far as I know this is not currently supported in Cython. But can't you just define it outside of the struct?

Cython is not currently designed as a replacement for C++, rather a way to speed up hot spots in python code. If you need something more involved just write it in C++ and expose python bindings.

                        
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