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Question

I have two simple container: one that stores a pointer and another one that stores a flat_set of pointers. In order to be able to use for(auto ...) on both of them (or stl algorithms), I would like to add begin/end to them. For the one with the flat_set, I just have to return the iterators of the flat_set but how can I do the same for the container that just holds a pointer?

I would like to avoid having to create a complete iterator class just for that... Basically, I would like to do something like that:

class Container
{
    ...
    Iterator begin() { return the_pointer; }
    Iterator end() { return the_pointer+1; }
    private:
    int* the_pointer;
}

But I don't know which signature Iterator must have.

Thanks !

Answer 1

Pointers to object types are valid iterator types, so you can just return a pointer. In fact std::array<T,N> has T* as its iterator type.

Answer 2

If your container holds sequence of pointers (they stored in memory like normal array), then you can simply return pointer from your class

int * begin();
int * end();

It is because for ( ... : ... ) syntax is expanded to something like:

for ( auto begin = container.begin(), end = container.end();
      begin != end; ++begin )
 // ...

Answer 3

C pointers are legal iterators. Here you can check an useful guide on them with a section on how to implement iterators from pointers. Basically you need to implement begin() and end() returning first and last valid pointers.