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<message 
  url="2002/07/54c375615f0a29b27858964a3ea565a1"
  from="james woodyatt &lt;jhw@w...&gt;"
  author="james woodyatt"
  date="2002-07-04T02:02:06"
  subject="Re: [Caml-list] Re: generic programming"
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<thread subject="[Caml-list] generic programming">
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  from="Oleg &lt;oleg_inconnu@m...&gt;"
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  date="2002-07-03T02:46:19"
  subject="[Caml-list] generic programming">
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  from="Johan Baltié &lt;johan.baltie@w...&gt;"
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  date="2002-07-03T08:43:01"
  subject="Re: [Caml-list] generic programming">
<msg 
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  from="Anton Moscal &lt;msk@m...&gt;"
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  date="2002-07-05T13:28:26"
  subject="Re: [Caml-list] generic programming">
</msg>
</msg>
<msg 
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  from="Ketanu &lt;ketanu@w...&gt;"
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  date="2002-07-03T08:43:22"
  subject="[Caml-list] Re: generic programming">
<msg 
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  from="Chris Hecker &lt;checker@d...&gt;"
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  date="2002-07-03T17:43:58"
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  date="2002-07-03T20:04:53"
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  from="Alessandro Baretta &lt;alex@b...&gt;"
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  date="2002-07-03T20:28:21"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
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  from="John Max Skaller &lt;skaller@o...&gt;"
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  date="2002-07-07T20:35:55"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
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  from="John Max Skaller &lt;skaller@o...&gt;"
  author="John Max Skaller"
  date="2002-07-08T01:00:11"
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  date="2002-07-08T07:23:04"
  subject="Re: [Caml-list] Re: generic programming">
</msg>
</msg>
</msg>
</msg>
<msg 
  url="2002/10/9771c361af322c3ddf2c05c7693bd197"
  from="Eray Ozkural &lt;erayo@c...&gt;"
  author="Eray Ozkural"
  date="2002-10-15T10:29:08"
  subject="Re: [Caml-list] Re: generic programming">
</msg>
</msg>
</msg>
<msg 
  url="2002/07/bc290463a2fb18079bf6f399c5a50e6f"
  from="Peter Wood &lt;peter.wood@w...&gt;"
  author="Peter Wood"
  date="2002-07-03T21:53:52"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
  url="2002/07/54c375615f0a29b27858964a3ea565a1"
  from="james woodyatt &lt;jhw@w...&gt;"
  author="james woodyatt"
  date="2002-07-04T02:02:06"
  subject="Re: [Caml-list] Re: generic programming">
</msg>
</msg>
<msg 
  url="2002/07/f9169f3ec2d8758bc125264b2df6077c"
  from="John Max Skaller &lt;skaller@o...&gt;"
  author="John Max Skaller"
  date="2002-07-04T15:18:38"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
  url="2002/07/9ef27ddc21bed28306035ffd3faf0846"
  from="Francois Pottier &lt;francois.pottier@i...&gt;"
  author="Francois Pottier"
  date="2002-07-05T08:42:51"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
  url="2002/07/fa6f4b49227ef840303e76915d7f82e0"
  from="Xavier Leroy &lt;xavier.leroy@i...&gt;"
  author="Xavier Leroy"
  date="2002-07-05T09:25:54"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
  url="2002/07/dc781b0623ef875df91c3aafad01e44c"
  from="Chris Hecker &lt;checker@d...&gt;"
  author="Chris Hecker"
  date="2002-07-05T10:15:23"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
  url="2002/07/d32dd70947be26ad7baf537ea0fb45f5"
  from="Xavier Leroy &lt;xavier.leroy@i...&gt;"
  author="Xavier Leroy"
  date="2002-07-05T13:54:38"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
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  from="Chris Hecker &lt;checker@d...&gt;"
  author="Chris Hecker"
  date="2002-07-05T18:18:33"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
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  from="John Max Skaller &lt;skaller@o...&gt;"
  author="John Max Skaller"
  date="2002-07-05T20:31:27"
  subject="Re: [Caml-list] Re: generic programming">
</msg>
</msg>
<msg 
  url="2002/07/7d4406847b9935e88eb5bb1f37218e5b"
  from="John Max Skaller &lt;skaller@o...&gt;"
  author="John Max Skaller"
  date="2002-07-05T19:34:05"
  subject="Re: [Caml-list] Re: generic programming">
</msg>
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<msg 
  url="2002/07/3259c1827be396d71d70b2c7e2861447"
  from="John Max Skaller &lt;skaller@o...&gt;"
  author="John Max Skaller"
  date="2002-07-05T19:31:26"
  subject="Re: [Caml-list] Re: generic programming">
</msg>
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</msg>
<msg 
  url="2002/07/00fb705ed9a16fca4d7ec6fcdd19a976"
  from="Francois Pottier &lt;francois.pottier@i...&gt;"
  author="Francois Pottier"
  date="2002-07-05T08:33:25"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
  url="2002/07/e5a3d181643111354651fc4afd3d96ab"
  from="Dave Berry &lt;daveb@t...&gt;"
  author="Dave Berry"
  date="2002-07-05T23:02:14"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
  url="2002/08/d395639496023bb4daa54d843df08749"
  from="Diego Olivier Fernandez Pons &lt;Diego-Olivier.FERNANDEZ-PONS@c...&gt;"
  author="Diego Olivier Fernandez Pons"
  date="2002-08-02T14:52:44"
  subject="[Caml-list] Streams">
<msg 
  url="2002/08/929519264a1aa2fef08921548f609164"
  from="Alain Frisch &lt;frisch@c...&gt;"
  author="Alain Frisch"
  date="2002-08-02T15:29:07"
  subject="Re: [Caml-list] Streams">
<msg 
  url="2002/08/3ba1a139a7e1050e9b2233e0cc9eb5c2"
  from="Diego Olivier Fernandez Pons &lt;Diego-Olivier.FERNANDEZ-PONS@c...&gt;"
  author="Diego Olivier Fernandez Pons"
  date="2002-08-03T14:22:03"
  subject="Re: [Caml-list] Streams">
</msg>
</msg>
</msg>
<msg 
  url="2002/07/27f2e9a6fef12ae5f3dfeb79ca878644"
  from="Francois Pottier &lt;francois.pottier@i...&gt;"
  author="Francois Pottier"
  date="2002-07-08T09:54:55"
  subject="Re: [Caml-list] Re: generic programming">
<msg 
  url="2002/07/f49c4126b9e8f96224a3185f0b93557f"
  from="John Max Skaller &lt;skaller@o...&gt;"
  author="John Max Skaller"
  date="2002-07-08T15:49:08"
  subject="Re: [Caml-list] Re: generic programming">
</msg>
</msg>
</msg>
</msg>
</msg>
</msg>
<msg 
  url="2002/07/0f2535d349e6014a883b1f763837db62"
  from="Jun P.FURUSE &lt;Jun.Furuse@i...&gt;"
  author="Jun P.FURUSE"
  date="2002-07-03T09:10:27"
  subject="Re: [Caml-list] generic programming">
</msg>
</msg>
</thread>

<contents>
On Wednesday, July 3, 2002, at 02:55 PM, Peter Wood wrote:
&gt;
&gt; Here's an interesting (though old) article by Henry Baker, "Iterators:
&gt; Signs of Weakness in Object-Oriented Languages".
&gt;
&gt; http://linux.rice.edu/~rahul/hbaker/Iterator.html

Funny you should bring that up now.  I've been working on basically the 
same problem in recent days.

The approach I've been taking seems to me to be similar to what Baker 
describes in that paper.  I have a functional red-black binary tree 
functor that defines a pair of functions for creating generic functional 
streams of the objects in a tree (one in increasing order and the other 
in decreasing order).

I've written functions that map red-black trees (and other specialized 
collections) into objects of a functional stream class.  I've also 
written a library of functions that perform some generic algorithms on 
the contents of generic functional streams (and pairs of streams), e.g. 
fold, compare, etc.

It's true that the stream of elements in my red-black tree 
implementation requires a stack of previously visited parent nodes, but 
that's an artifact of my implementation of the red-black tree 
algorithm.  (If I had used the traditional mutable red-black tree 
algorithm, I could have avoided the stack in the stream object.)  So... 
I've also written "more efficient" variants that use the program stack 
when there's only one tree in the loop, though-- I've not yet measured 
the improvement.

I think the whole thing makes "rather tasteful use of objects and class 
types" to borrow a phrase from Dr. Leroy.  Let me poke at it some more, 
then I'll document it and throw it up for review.  You'll be able to 
judge for yourself.

Meanwhile, I'd say "generic programming" is quite "well-enabled" by 
Ocaml.  Whether you want to do it in the style of Stepanov's STL is a 
whole other question...  Personally, I'd rather be flensed alive by a 
gang of Welsh football hooligans armed with potato peelers than write 
another line of C++ using the STL.  (Okay, that's unnecessarily 
inflammatory.)


--
j h woodyatt &lt;jhw@wetware.com&gt;

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