first, next, prev, last in gb_trees

[Ulf Wiger]

When I use ordered_set ets over gb_trees it has more than once been due to the fact that you can do wonderful stuff with first, next, prev and last - and gb_trees doesn't have them.

I've made a stab at implementing these functions for the gb_trees data structure, together with a quickcheck spec to verify that they work as expected (you can use eqc mini to run the tests). I think they are reasonably efficient, but perhaps someone can think of a way to optimize them? Have at it, and pls use the spec to verify that you didn't break them* (recalling that an incorrect program can be made arbitrarily fast)

* e.g. eqc:quickcheck(gb1:prop_first())

BR,
Ulf W (hoping the list server won't chop the 150-line attachment)

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Ulf Wiger, CTO, Erlang Solutions, Ltd.
http://erlang-solutions.com