On Fri, Dec 12, 2008 at 9:01 PM, Jeff Flinn <TriumphSprint2000@hotmail.com> wrote:
Dean Michael Berris wrote:
Hi,
Has anybody found a need for an "identity_iterator"? Something that you can initialize to a value and returns that value every time it's referenced? It could model a random access iterator, and a default constructed version will mark an "end" of the identity_iterator.
[snip wrong definition]
How about:
template< typename T > class identity_iterator : public boost::iterator_facade< identity_iterator<T>, T , boost::forward_traversal_tag, const T&> { public: identity_iterator(const T& value, int index) : m_value(value), m_index(index) {}
private: // virtual overrides friend class boost::iterator_core_access;
void increment() { ++m_index; }
const T& dereference() const { return m_value; } bool equal(literal_iterator<T> const& rhs) const { return m_index == rhs.m_index; }
private: T m_value; int m_index; };
The index allows use with algorithms where and end iterator is req'd.
Looks good to me. :)
Or even a "generate_iterator" which takes a nullary function object of signature "tuple<bool, T>()" where bool indicates whether it's at the end? It can be modeled as an input iterator. Something like:
[snip bad attempt at example]
Or is there already something out there which allows these iterator semantics?
See: http://www.boost.org/doc/libs/1_37_0/libs/iterator/doc/function_output_itera...
But that's an output iterator -- I'm looking for something that behaves like an _input_ iterator. Perhaps something like the above, but instead of returning a value calls an encapsulated function? Thanks for the quick response Jeff! -- Dean Michael C. Berris Software Engineer, Friendster, Inc.