根据stackoverflow中的这个问题/答案，在cython中不可能直接重写c++嵌套类型。我有这样一个问题，我不知道哪是正确的/最佳的方式进行。
让我举一个更具体的例子。下面，您可以找到两个c++文件(一个header.h和一个.cpp)和两个相应的cython文件(一个.pxd和一个.pyx)的内容。在c++头文件cpp_graph.h中，你可以看到嵌套的类型定义声明;例如，对应Graph::iterator::nn_iterator。我不知道如何在相应的graph.pxd文件中暴露它。或者，换句话说，我不知道做这件事的"官方"或"标准"的方式是什么。
一些相关信息。如果您检查python包装器中的STL，您可以找到嵌套类型。例如这里的utility.pxd或这里的vector.pxd文件。然而，ctypedef的嵌套用法仅用于模板声明。是否嵌套类型仅在cython中用于模板声明?
c++头文件:
// file : cpp_graph.h
#ifndef Included_cpp_graph
#define Included_cpp_graph
#include <cassert>
#include <cstddef>
#include <set>
#include <map>
#include <iostream>
#include <string>
#include <sstream>
#include "to_string_patch.h"
#ifndef Defined_bint
#define Defined_bint
typedef int bint;
#endif
class Graph {
public:
typedef std::set< int > t_nn;
typedef std::set< int >::iterator nn_iterator;
typedef std::map< int , t_nn > t_node_to_nn;
class iterator
{
// To iterate over nodes.
friend class Graph;
public:
typedef iterator self_type;
typedef int value_type;
typedef int & reference;
typedef int * pointer;
typedef t_node_to_nn::iterator map_iterator;
typedef std::forward_iterator_tag iterator_category;
iterator( map_iterator map_it ) : _map_it( map_it ) { }
self_type operator++() { _map_it++; return *this; } // PREFIX
self_type operator++(int junk) { self_type i = *this; _map_it++; return i; } // POSTFIX
value_type operator*() { return ( * _map_it ).first; } // Return the index "i"
Graph::t_nn * operator->() { return & ( * _map_it ).second; } // Return a pointer to the contained t_nn.
bool operator==( const self_type & rhs ) { return _map_it == rhs._map_it; }
bool operator!=( const self_type & rhs ) { return _map_it != rhs._map_it; }
private:
map_iterator _map_it;
};
class const_iterator
{
friend class Vertex;
public:
typedef const_iterator self_type;
typedef int value_type;
typedef int & reference;
typedef int * pointer;
typedef t_node_to_nn::iterator map_iterator;
typedef std::forward_iterator_tag iterator_category;
const_iterator( map_iterator map_it ) : _map_it( map_it ) { }
self_type operator++() { _map_it++; return *this; } // PREFIX
self_type operator++(int junk) { self_type i = *this; _map_it++; return i; } // POSTFIX
const value_type operator*() { return ( * _map_it ).first; } // Return the index "i"
const Graph::t_nn * operator->() { return & ( * _map_it ).second; } // Return a pointer to the contained t_nn.
bool operator==( const self_type& rhs ) { return _map_it == rhs._map_it; }
bool operator!=( const self_type& rhs ) { return _map_it != rhs._map_it; }
private:
map_iterator _map_it;
};
iterator begin() { _node_to_nn.begin(); }
iterator end() { _node_to_nn.end(); }
const_iterator begin() const { _node_to_nn.begin(); }
const_iterator end() const { _node_to_nn.end(); }
nn_iterator nn_begin( int i ) { assert( has_node( i ) ); return _node_to_nn[ i ].begin(); }
nn_iterator nn_end( int i ) { assert( has_node( i ) ); return _node_to_nn[ i ].end(); }
Graph() : _num_links( 0 ) {}
~Graph() { _node_to_nn.clear(); _num_links = 0; }
Graph & subgraph( std::set< int > & nodes ) {
Graph * S = new Graph();
for ( std::set< int >::iterator n_it = nodes.begin() ; n_it != nodes.end() ; n_it++ ) {
int i = ( * n_it );
assert( has_node( i ) );
for ( nn_iterator j_it = nn_begin( i ) ; j_it != nn_end( i ) ; j_it++ ) {
int j = ( * j_it );
if ( nodes.count( j ) > 0 ) { S -> add_link( i , j ); }
}
}
return ( * S );
}
int num_nodes() { return _node_to_nn.size(); }
int num_links() { return _num_links; }
int degree( int i ) { return _node_to_nn[ i ].size(); }
double avrg_degree() { return ( ( double ) 2 * num_nodes() ) / ( ( double ) _num_links ); }
bool has_node( int i ) { return _node_to_nn.count( i ) > 0; }
bool has_nn( int i , int j ) {
if ( has_node( i ) ) { return _node_to_nn[ i ].count( j ) > 0; }
return false;
}
bool has_link( int i , int j ) { return has_nn( i , j ); }
void add_node( int i ) { _node_to_nn[ i ].count( 0 ); } // Trick...
void add_link( int i , int j ) {
if ( has_link( i , j ) ) { return; }
_node_to_nn[ i ].insert( j );
_node_to_nn[ j ].insert( i );
_num_links += 1;
}
void del_link( int i , int j ) {
if ( has_link( i , j ) ) {
_node_to_nn[ i ].erase( j );
_node_to_nn[ j ].erase( i );
_num_links -= 1;
}
}
void del_node( int i ) {
iterator i_it = _node_to_nn.find( i );
for( nn_iterator j_it = i_it -> begin() ; j_it != i_it -> end() ; j_it++ ) { del_link( i , ( * j_it ) ); }
_node_to_nn.erase( i_it._map_it );
}
void clear_node( int i ) { del_node( i ); add_node( i ); } // Trick...
private:
t_node_to_nn _node_to_nn;
int _num_links;
};
std::ostream& operator<<( std::ostream& os , Graph & G );
typedef Graph::t_nn Graph_t_nn
typedef
#endif // Included_cpp_graph
c++ .cpp文件:
// cpp_graph.cpp
#include <cassert>
#include <cstddef>
#include <set>
#include <map>
#include <iostream>
#include <string>
#include <sstream>
#include "to_string_patch.h"
#include "cpp_graph.h"
std::ostream& operator<<( std::ostream& os , Graph & G ) {
os << "Graph{";
// Print nodes.
for ( Graph::iterator i_it = G.begin() ; i_it != G.end() ; i_it++ ) {
int i = ( * i_it );
os << " " << patch::to_string( i );
}
os << " |";
// Print edges.
for ( Graph::iterator i_it = G.begin() ; i_it != G.end() ; i_it++ ) {
int i = ( * i_it );
for ( Graph::nn_iterator j_it = G.nn_begin( i ) ; j_it != G.nn_end( i ) ; j_it++ ) {
int j = ( * j_it );
if ( i < j ) { os << " " + patch::to_string( i ) << ":" << patch::to_string( j ); }
}
}
os << " }"; // << std::endl;
return os;
}
// === For testing purposes ===.
/*
int main() {
Graph G;
G.add_link( 1 , 2 );
G.add_link( 1 , 3 );
G.add_link( 2 , 3 );
G.add_link( 3 , 4 );
G.add_link( 4 , 5 );
G.add_link( 4 , 6 );
G.add_link( 5 , 6 );
std::cout << G << std::endl;
G.del_link( 3 , 4 );
std::cout << G << std::endl;
G.del_node( 3 );
std::cout << G << std::endl;
G.clear_node( 2 );
std::cout << G << std::endl;
G.add_link( 100 , 101 );
std::cout << G << std::endl;
std::cout << "N = " << G.num_nodes() << " M = " << G.num_links() << std::endl;
}
*/
python .pxd文件:
# file : graph.pxd
# === Cython cimports ===
from libcpp cimport bool
from libcpp.set cimport set as cset
from libcpp.map cimport map as cmap
from cython.operator cimport dereference as deref, preincrement as inc
# === Exposing the C++ Graph class ===
cdef extern from "cpp_graph.h":
cdef cppclass Graph:
#public:
ctypedef cset[ int ] t_nn
ctypedef cset[ int ].iterator nn_iterator
ctypedef cmap[ int , t_nn ] t_node_to_nn
cppclass iterator:
#friend class Graph;
#public:
typedef iterator self_type
typedef int value_type
typedef int & reference
typedef int * pointer
typedef t_node_to_nn::iterator map_iterator
typedef std::forward_iterator_tag iterator_category
iterator( map_iterator map_it )
self_type operator++()
self_type operator++(int junk)
value_type operator*()
Graph::t_nn * operator->()
bool operator==( const self_type & rhs )
bool operator!=( const self_type & rhs )
#private:
# map_iterator _map_it;
cppclass const_iterator:
#friend class Vertex;
#public:
typedef const_iterator self_type
typedef int value_type
typedef int & reference
typedef int * pointer
typedef t_node_to_nn::iterator map_iterator
typedef std::forward_iterator_tag iterator_category
const_iterator( map_iterator map_it )
self_type operator++()
self_type operator++(int junk)
const value_type operator*()
const Graph::t_nn * operator->()
bool operator==( const self_type& rhs )
bool operator!=( const self_type& rhs )
#private:
# map_iterator _map_it;
iterator begin()
iterator end()
const_iterator begin() const
const_iterator end() const
nn_iterator nn_begin( int i )
nn_iterator nn_end( int i )
Graph()
~Graph()
Graph & subgraph( std::set< int > & nodes )
int num_nodes()
int num_links()
int degree( int i )
double avrg_degree()
bool has_node( int i )
bool has_nn( int i , int j )
bool has_link( int i , int j )
void add_node( int i )
void add_link( int i , int j )
void del_link( int i , int j )
void del_node( int i )
void clear_node( int i )
#private:
#t_node_to_nn _node_to_nn;
#int _num_links;
std::ostream& operator<<( std::ostream& os , Graph & G )
# === Python Wrapper for the C++ Graph class ===
cdef class PyGraph:
# === Data-members ===
# Pointer to a C++ Graph object.
cdef Graph * _c_graph
# === Function-members ===
# @ graph.pyx
和cython .pyx文件:
# file : graph.pyx
# === Cython cimports ===
from libcpp cimport bool
from libcpp.set cimport set as cset
from libcpp.map cimport map as cmap
from cython.operator cimport dereference as deref, preincrement as inc
# === Ctypedefs for Graph class ===
# @ graph.pxd
# === Exposing the C++ Graph class ===
cdef extern from "cpp_graph2.h":
cdef cppclass Graph:
#public:
ctypedef cset[ int ] t_nn
ctypedef cset[ int ].iterator nn_iterator
ctypedef cmap[ int , t_nn ] t_node_to_nn
cppclass iterator:
#friend class Graph;
#public:
typedef iterator self_type
typedef int value_type
typedef int & reference
typedef int * pointer
typedef t_node_to_nn::iterator map_iterator
typedef std::forward_iterator_tag iterator_category
iterator( map_iterator map_it )
self_type operator++()
self_type operator++(int junk)
value_type operator*()
Graph::t_nn * operator->()
bool operator==( const self_type & rhs )
bool operator!=( const self_type & rhs )
#private:
# map_iterator _map_it;
cppclass const_iterator:
#friend class Vertex;
#public:
typedef const_iterator self_type
typedef int value_type
typedef int & reference
typedef int * pointer
typedef t_node_to_nn::iterator map_iterator
typedef std::forward_iterator_tag iterator_category
const_iterator( map_iterator map_it )
self_type operator++()
self_type operator++(int junk)
const value_type operator*()
const Graph::t_nn * operator->()
bool operator==( const self_type& rhs )
bool operator!=( const self_type& rhs )
#private:
# map_iterator _map_it;
iterator begin()
iterator end()
const_iterator begin() const
const_iterator end() const
nn_iterator nn_begin( int i )
nn_iterator nn_end( int i )
Graph()
~Graph()
Graph & subgraph( std::set< int > & nodes )
int num_nodes()
int num_links()
int degree( int i )
double avrg_degree()
bool has_node( int i )
bool has_nn( int i , int j )
bool has_link( int i , int j )
void add_node( int i )
void add_link( int i , int j )
void del_link( int i , int j )
void del_node( int i )
void clear_node( int i )
#private:
#t_node_to_nn _node_to_nn;
#int _num_links;
# === Python Wrapper for the C++ Graph class ===
cdef class PyGraph:
# === Data-members ===
# @ graph.pxd
# === Function-members ===
def __cinit__( self ):
self._c_graph = new Graph()
def __dealloc__( self ):
del self._c_graph
# TODO : implement the methods for adding and deleting nodes/links.
最后，当我试图编译/构建这个时，我得到以下错误:
###########################################################
# setup build_ext...
###########################################################
Error compiling Cython file:
------------------------------------------------------------
...
# === Exposing the C++ Graph class ===
cdef extern from "cpp_graph2.h":
cdef cppclass Graph:
#public:
ctypedef cset[ int ] t_nn
^
------------------------------------------------------------
ExcessDegreeModel/graph.pxd:51:8: Expected an identifier, found 'ctypedef'
...
我已经使用namespace关键字获得了嵌套定义，指定了嵌套声明。例如，如果您在名为mystuff.hpp的c++头文件中有以下内容:
namespace MyStuff {
struct Outer {
struct Inner {
int value;
};
Inner member;
};
}
…你可以像这样循环这些结构:
cdef extern from "mystuff.hpp" namespace "MyStuff::Outer":
cppclass Inner:
int value
cdef extern from "mystuff.hpp" namespace "MyStuff":
cppclass Outer:
Inner member
…它读起来更连贯，如果你实际上把所有的c++语言都包装在一个命名空间中，就像写的那样(否则第二个cdef在它的声明中没有namespace，这看起来更奇怪)。
我有一些现实世界中正在工作的例子:一个这样的例子在这里，另一个在这里。