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From: oleg@okmij.org
To: ivg@ieee.org
CC: Didier.Cassirame@gmail.com, caml-list@inria.fr
In-reply-to: <87wqxrtjtq.fsf@golf.niidar.ru>
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Subject: [Caml-list] Re: Higher order functors over tuples


> And, by the way, I've met the following signatures many times in
> different frameworks written in different languages (matlab functional
> objects, GnuRadio blocks, to name a few):

>>    module type Generator =
>>    sig
>>      type t
>>      type r
>>      val create: unit  -> t
>>      val result: t -> r option
>>      val step:   t -> t option
>>    end

Well, if we re-write it in object style, but without objects, we obtain

    type 'r stream_v = EOF | Stream of 'r option * 'r stream
    and 'r stream = unit -> 'r stream_v

which is what it says. Here's the important paper that describes the
pattern in great detail and with many applications:

	Duncan Coutts and Roman Leshchinskiy and Don Stewart
	Stream Fusion. From Lists to Streams to Nothing at All
	ICFP 07
	http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.104.7401

Incidentally, iteratees are somewhat similar.