May be I am reading it wrong.... Shouldn't the second "instance" in "The
instance's meaning is the meaning's instance" be plural as "meaning's
instances" rather than "meaning's instance"?
I am reading it similar to the "you are who you know" saying. It seems to
say that the meaning of your data types ("The instance's meaning") is
defined by the instances of known classes (with predefined meaning, defined
by it properties, as in functor, monoid..) that is defined for your type.
Daryoush
2009/2/19 Sjoerd Visscher
Hi,
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 language?
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 paper.
greetings, 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 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
-- Sjoerd Visscher sjoerd@w3future.com
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