AnyIterator and boost iterator facade

Is it possible to implement an any iterator with boost iterator facad开发者_开发技巧e? I don't want to define implementation details in my baseclass

class Base
{
public:
typedef std::vector<int>::iterator iterator;//implementation detail
...
virtual iterator begin()=0;
virtual iterator end()=0;
};

or do i have to write one completely from scratch;

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The code you've posted has fixed the type of iterators returned from Base and all it's implementantions to std::vector<int>::iterator which is probably not what you want. Jeremiah's suggestion is one way to go with one drawback: you loose compatibility with STL... I know of three implementations of a polymorphic iterator wrapper:

1. becker's any_iterator (which implements boost::iterator_facade)
2. the opaque_iterator library (google for it), or
3. Adobe's very interesting poly library which contains a hierarchy of STL conforming any_iterators.

The problem is harder than it might seem... I made an attempt myself mainly because I needed covariance in any_iterators type argument (any_iterator<Derived> should be automatically convertible to any_iterator<Base>) which is difficult to implement cleanly with STL like iterators. A C# like Enumerator<T> is easier to implement(*) (and imho generally a cleaner concept than STL-like pairs of iterators) but again, you "loose" the STL.

(*) = without 'yield' of course :-)

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I think this may be what you're looking for:

any_iterator: Type Erasure for C++ Iterators

Here's a snippet from that page::

Overview

The class template any_iterator is the analog to boost::function for iterators. It allows you to have a single variable and assign to it iterators of different types, as long as these iterators have a suitable commonality.