Re: [Boost-users] Using single-pass ranges.

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I have a class that hands out a sequence of Things through a getNextThing() interface, ie.,

struct Thing { };

struct ThingFeed { Thing * getNextThing( ); };

returning null when there's no more things. I'd like to be able to feed this into the Boost range-based algorithms, something like

Since we are not in a position to offer range primitives, there is more work required than one would like. To maximize interoperability with algorithms and existing C++ code the ranges in Boost.Range are limited to being implemented on top of iterators. Therefore the getNextThing() would need to be part of an increment operator / operators upon a forward traversal iterator. This is not difficult to implement using Boost.Iterator.

Here's how you might do such a thing (untested): class ThingIterator : public boost::iterator_facade { public:    // Public interface    ThingIterator(ThingFeed& feed, Thing* cur = NULL) : m_feed(feed), m_cur(cur) {} private:    // Interface to boost::iterator_facade    void increment() { m_cur = m_feed.getNextThing(); }    Thing& dereference() const { return *m_cur; }    bool equal(const ThingIterator& other) const { return m_cur == other.m_cur; } private:    // Implementation    ThingFeed& m_feed;    Thing* m_cur; }; class ThingRange : public boost::iterator_range<ThingIterator> { public:     ThingRange(ThingFeed& feed)         : boost::iterator_range<ThingIterator>(              ThingIterator(feed, feed.getNextThing()),              ThingIterator(feed))     {} }; ... ThingFeed feed; ... boost::for_each( ThingRange(feed) | filter( someCondition ), doSomething ); Regards, Nate