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Erlang Zlists: a lazy sequences library.

There are many possibilities to represent and handle lazy sequences.
For disambiguation reasons the approach implemented here will be referred to as Z-Lists, or simply zlists.


The core module is 'zlists', similar to module 'lists' in Erlang's STDLIB. It contains base operations supported over Z-Lists. The others, called 'zlists_X', are utility modules that bridge Z-Lists with standard Erlang modules which may be considered as data sources e.g. 'ets', 'dets', 'mnesia', 'disk_log', 'file' etc.


Integrate to your project

This is a rebar'ized project, so, if you are already using rebar, just insert a reference to this git repo at your rebar.config. Otherwise clone this repo, and run erl -make.


        1> Naturals=zlists:recurrent(1, fun(N)-> N+1 end).

        2> zlists:scroll(10,Naturals).

        3> zlists:scroll(10,zlists:drop(5,Naturals)).

        4> zlists:scroll(10,zlists:drop(500000,Naturals)).   

        5> Fibonacci=zlists:recurrent(1, 0, fun(X0,S0) -> {X0+S0, X0} end).

        6> zlists:expand(10, Fibonacci).

        7> zlists:expand(10, zlists:drop(10,Fibonacci)).

        8> zlists:scroll(10, zlists:drop(10,Fibonacci)).

Create your own Z-List

Creating your own custom zlist is quite easy, you can directly construct a special improper list like this:

[1|fun()-> L=deferred_work(),true=is_list(L),L end]

Note the | symbol between head element and tail function. You can use a proper list and tail function to construct a lazy list:

zlists:new([1,2,3], fun()-> [4,5] end)

If the lazy list you want to create has explicit recurrent nature, use zlists:recurrent/2/3 to easily create a lazy list.