Using boost :: iterator_facade <>

Question

I have a linked list structure:

struct SomeLinkedList
{
    const char* bar;
    int lots_of_interesting_stuff_in_here;
    DWORD foo;
    SomeLinkedList* pNext;
};

This is part of the existing API, and I cannot change it.

I would like to add iterator support. The library boost::iterator_facade<>seemed perfect for this purpose.

class SomeIterator
    : public boost::iterator_facade< SomeIterator, 
                                     const SomeLinkedList, 
                                     boost::forward_traversal_tag >
{
public:
    SomeIterator() : node_( NULL ) {};

    explicit SomeIterator( const SomeLinkedList* p ) : node_( p ) {};

private:
    friend class boost::iterator_core_access;

    void increment() { node_ = node_->pNext; };

    bool equal( SomeIterator const& other ) const { /*some comparison*/; };

    SomeLinkedList const& dereference() const { return *node_; };

    SomeLinkedList const* node_;
}; // class SomeIterator

The goal is to be able to use it in standard library functions such as std::for_each

void DoSomething( const SomeLinkedList* node );

SomeLinkedList* my_list = CreateLinkedList();
std::for_each( SomeIterator( my_list ), SomeIterator(), DoSomething );

Unfortunately, I am getting an error trying to pass a list by value, not a pointer.

error C2664: 'void (const SomeLinkedList *)' : cannot convert parameter 1 from 'const SomeLinkedList' to 'const SomeLinkedList *'

How can I change SomeIteratorto do it right?

Thanks PaulH

---

Edit: I tried this:

class SomeIterator
    : public boost::iterator_facade< SomeIterator, 
                                     SomeLinkedList, 
                                     boost::forward_traversal_tag,
                                     SomeLinkedList* >
{
    // ...

but I get this error:

error C2664: 'boost::implicit_cast' : cannot convert parameter 1 from 'SomeLinkedList **' to 'boost::detail::operator_arrow_proxy<T>

---

Edit 2:

I tried changing the dereference type:

class SomeIterator
    : public boost::iterator_facade< SomeIterator, 
                                     const SomeLinkedList, 
                                     boost::forward_traversal_tag >
{
    // ...

    const SomeLinkedList* dereference() const { return node_; };

but, I get the original error:

error C2664: 'void (const SomeLinkedList *)' : cannot convert parameter 1 from 'const SomeLinkedList' to 'const SomeLinkedList *'

Answer 1

, const SomeLinkedList&, DoSomething const SomeLinkedList*. , - DoSomething.

---

EDIT :

boost:: iterator_facade , , , , , .

class SomeIterator
    : public boost::iterator_facade< SomeIterator, 
                                     SomeLinkedList, 
                                     boost::forward_traversal_tag,
                                     SomeLinkedList* >
{

const SomeLinkedList* dereference() const { return node_; };

?

, , :

class SomeIterator
    : public boost::iterator_facade< SomeIterator, 
                                     SomeLinkedList*, 
                                     boost::forward_traversal_tag>
{

const SomeLinkedList* dereference() const { return node_; };

, , , DoSomething? :

void DoSomethingWrapper( const SomeLinkedList& node )
{
    DoSomething(&node);
}

, , , , , , .

Answer 2

boost:: iterator_facade. () , . , , , , .

, for_each() . , NULL ( , ), , , .equal() :

bool equal( SomeIterator const& other ) const { return node_ == other.node_; }

, DoSomething() ptr , , . .

void DoSomething( const SomeLinkedList& node )
{
    std::cout << "DoSomething " << node.foo << "\n";
}

int main()
{
    SomeLinkedList temp[5];
    memset(temp,0,sizeof(temp));
    temp[0].pNext = &temp[1];
    temp[1].pNext = &temp[2];
    temp[2].pNext = &temp[3];
    temp[3].pNext = &temp[4];
    temp[4].pNext = 0;
    temp[0].foo   = 0;
    temp[1].foo   = 1;
    temp[2].foo   = 2;
    temp[3].foo   = 3;
    temp[4].foo   = 4;
    SomeLinkedList* my_list = &temp[0];
    std::for_each( SomeIterator( my_list ), SomeIterator(), DoSomething );
    return 0;
}