[Haskell-cafe] Paper draft: "Denotational design with type class morphisms"

Sjoerd Visscher sjoerd at w3future.com
Thu Feb 19 15:37:46 EST 2009


Thanks for this very interesting and inspiring paper. I'm certainly  
going to try some other data types, and see what kind of  
implementations you get when using the TCM property.

I was wondering if any of this could be automated, given the semantic  
function? If not in Haskell, then could this be a nice basis for a new  

If something still needs to be cut, I'd consider much or even all of  
chapter 8. I found the tone and style unfitting for the rest of the  
paper, as it deals with the (imho) ugliness of bottom and strictness  
issues, instead of the beautiful relations found in the rest of the  

Sjoerd Visscher

On Feb 19, 2009, at 4:21 AM, Conal Elliott wrote:

> I have a draft paper some of you might enjoy, called "Denotational  
> design with type class morphisms".
> Abstract:
>     Type classes provide a mechanism for varied implementations of  
> standard
>     interfaces. Many of these interfaces are founded in mathematical
>     tradition and so have regularity not only of *types* but also of
>     *properties* (laws) that must hold. Types and properties give  
> strong
>     guidance to the library implementor, while leaving freedom as  
> well. Some
>     of the remaining freedom is in *how* the implementation works,  
> and some
>     is in *what* it accomplishes.
>     To give additional guidance to the *what*, without impinging on  
> the
>     *how*, this paper proposes a principle of *type class morphisms*  
> (TCMs),
>     which further refines the compositional style of denotational
>     semantics. The TCM idea is simply that *the instance's meaning  
> is the
>     meaning's instance*. This principle determines the meaning of  
> each type
>     class instance, and hence defines correctness of implementation.  
> In some
>     cases, it also provides a systematic guide to implementation,  
> and in
>     some cases, valuable design feedback.
>     The paper is illustrated with several examples of type,  
> meanings, and
>     morphisms.
> You'll find the paper at http://conal.net/papers/type-class- 
> morphisms/ .
> I'd sure appreciate feedback on it, especially if in time for the  
> *March 2* ICFP deadline.  Pointers to related work would be  
> particularly appreciated, as well as what's unclear and what could  
> be cut.  This draft is an entire page over the limit, so I'll have  
> to do some trimming before submitting.
> Enjoy, and thanks!
>    - Conal
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Sjoerd Visscher
sjoerd at w3future.com

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