用 const 源推 copy_if

Question

我的问题出在以下代码中：

过滤器函数编译，并在源不恒定时按其应有的方式运行（迭代器相应调整）。但是，当我将源代码更改为 const 时，编译器会为 copy_if 语句的前两个变量给出以下错误： “对象具有与成员函数不兼容的类型限定符”。

我相信某处存在 const to not const 转换错误，但坦率地说，我不知道在哪里。任何帮助，将不胜感激。

#include "thrust\device_vector.h"
#include "thrust\copy.h"

typedef thrust::device_vector<float>::const_iterator    Dc_FloatIterator;
typedef thrust::device_vector<float>::iterator          D_FloatIterator;

typedef thrust::device_vector<int>::const_iterator  Dc_IntIterator;
typedef thrust::device_vector<int>::iterator        D_IntIterator;

typedef thrust::tuple< Dc_IntIterator, Dc_IntIterator, Dc_FloatIterator> Dc_ListIteratorTuple;
typedef thrust::zip_iterator<Dc_ListIteratorTuple>   Dc_ListIterator;//type of the class const iterator

typedef thrust::tuple< D_IntIterator, D_IntIterator, D_FloatIterator > D_ListIteratorTuple;
typedef thrust::zip_iterator<D_ListIteratorTuple>    D_ListIterator;//type of the class iterator

struct selector{//selector functor for the copy if call
const int val;

selector(int _val) : val(_val) {}

__host__ __device__
bool operator()(const int& x ) {
return ( x == val );
   }
};

class Foo{    
public:
    thrust::device_vector<int>      ivec1;
    thrust::device_vector<int>      ivec2;
    thrust::device_vector<float>    fvec1;

    Foo(){;}
    ~Foo(){;}

    D_ListIterator begin(){//cast of begin iterator
        return D_ListIterator(D_ListIteratorTuple( ivec1.begin(), ivec2.begin(), fvec1.begin() ));
    }
    D_ListIterator end(){//cast of end iterator
        return D_ListIterator(D_ListIteratorTuple( ivec1.end(), ivec2.end(), fvec1.end() ));
    }

    Dc_ListIterator cbegin(){//cast of const begin iterator
        return Dc_ListIterator(Dc_ListIteratorTuple( ivec1.cbegin(), ivec2.cbegin(), fvec1.cbegin() ));
    }
    Dc_ListIterator cend(){//cast of const end iterator
        return Dc_ListIterator(Dc_ListIteratorTuple( ivec1.cend(), ivec2.cend(), fvec1.cend() ));
    }

    void const_filter( const Foo& TheOther, const int& target ){//doesnt work
        //This function should copy those member of the vectors where
        //the ivec2[i] == target is true
        thrust::copy_if(
            TheOther.cbegin(),
            TheOther.cend(),
            TheOther.ivec2.cbegin(),
            this->begin(),
            selector(target) );
    }
    void filter( Foo& TheOther, const int& target ){//works
        //This function should copy those member of the vectors where
        //the ivec2[i] == target is true
        thrust::copy_if(
            TheOther.begin(),
            TheOther.end(),
            TheOther.ivec2.cbegin(),
            this->begin(),
            selector(target) );
    }
    void insert(const int& one, const int& two,const float& three ){
        ivec1.push_back(one);
        ivec2.push_back(two);
        fvec1.push_back(three);
    }

    int size(){
        return ivec1.size();
    }
};

bool CheckIfSublistIsConnected(const Foo& list,const int& sublist_num){
Foo tmp;

tmp.const_filter( list, sublist_num );

return (bool)tmp.size();//for symplicity, othervise here is a function that check if
                        //the edge list represents a connected graph
}
int main(void){
Foo list;
bool connected;
list.insert(10,2,1.0);
list.insert(11,2,1.0);
list.insert(12,2,1.0);
list.insert(10,3,1.0);
list.insert(10,3,1.0);

connected=CheckIfSublistIsConnected(list,2); 

if( connected ) return 0;
else return -1;
}

我发现用以下编译器替换 TheOther.cbegin() / .cend() 可以接受它。这意味着我在 typedef 部分的某个地方搞砸了，但是在哪里？

    thrust::make_zip_iterator(
        thrust::make_tuple(
            TheOther.ivec1.cbegin(),
            TheOther.ivec2.cbegin(),
            TheOther.fvec1.cbegin() ))

Answer 1

当它出现时，我已经在 cend/cbegin 的定义中添加了 const 魔术字。

Dc_ListIterator cbegin() const {
        return Dc_ListIterator(Dc_ListIteratorTuple( ivec1.cbegin(), ivec2.cbegin(), fvec1.cbegin() ));
    }
Dc_ListIterator cend() const {
        return Dc_ListIterator(Dc_ListIteratorTuple( ivec1.cend(), ivec2.cend(), fvec1.cend() ));
    }