[Haskell-cafe] Seeking feedback for a tutorial paper draft about GADTs

Anton Dergunov anton.dergunov at mail.ru
Sat Jan 12 09:57:07 CET 2013

 I would like to thank Owen Stephens, Alexander Batischev, Denis Kasak and Mann mit Hut for the valuable comments! I am going to update the tutorial to fix the indicated issues. Also, I am going to improve description of kinds and singletons. Also, I will improve description of red-black tree example: I think I need to include the whole listing after every big step.

Are there any other topics you would like to be described in the context of a practical-oriented introductory-level tutorial on GADTs?

PS: Please let me know if I misspelled your names (to make sure that I do not put wrong names in acknowledgements section). You can do it by email to anton dot dergunov dog mail dot ru.

Best Regards,
Anton Dergunov

Среда,  9 января 2013, 17:13 +02:00 от Alexander Batischev <eual.jp at gmail.com>:
>On Tue, Jan 08, 2013 at 11:22:39PM +0400, Anton Dergunov wrote:
>> I have written a draft of an introductory-level tutorial paper about
>> GADTs in Haskell (for submittion to proceedings of the recent LASER
>> summer school) and I would like to seek initial feedback about its
>> content: what information is probably missing? are there any subtle
>> mistakes?
>Not exactly the feedback you asked for, but I hope it still can be of
>some use.
>As a person with no prior knowledge about GADTs, I found your paper a
>good introduction. Following proof of correctness of red-black tree
>insertions turned out to be a little bit of a challenge as type
>annotations quickly become tangled (made me wondering how one should
>prove correctness of the proof).
>I particularly liked how you handle things that are not central to
>tutorial, like phantom and existential types: you give single-sentence
>explanation that provides good enough intuition to follow you further.
>Talking of quick explanations, I would love to see kinds and singleton
>types explained in the same manner. You tried to explain singleton types
>at page 13, but I find explanation provided by GHC documentation[1] to
>be much more clear. As for kinds, it just puzzles me why you use the
>term but don't explain it.
>  1.  http://hackage.haskell.org/trac/ghc/wiki/TypeNats/Basics
>The same goes for type families - while I was able to quickly look up
>definition of singleton types, I failed to comprehend basics of type
>families by reading Haskell Wiki. I ended up pretending that type
>families are just type-level functions.
>I would love to see Yampa optimizations section expanded with more
>interesting examples. Are there any?
>Last but not least, a few minor typos and errors I spotted:
>* at page 8, "Than we need to declare type instances..." should be "Then
>  we need...";
>* probably due to excessive editing, parameters to repeatElem at page 13
>  are in the different order than before;
>* at page 14, you state:
>  > As in all binary search trees, for a particular node N c l x r
>  > values greater than x are stored in left sub-tree (in l) and values
>  > less than x are stored in right sub-tree (in r).
>  But later on, your code contradict that statement by recursing to left
>  sub-tree when x we look for is less than value in the node, and to
>  right sub-tree when x is greater than value in the node.
>Thank you once again for a nice introduction to GADTs!
>Alexander Batischev
>PGP key 356961A20C8BFD03
>Fingerprint: CE6C 4307 9348 58E3 FD94  A00F 3569 61A2 0C8B FD03

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