S. Alexander Jacobson writes:
> Are we talking about documentation for the H98 libraries?
> Are these libraries relevant? Don't MPTC, Existential Types, Restricted
> Type Synonyms, Arrows, and an FFI substantial change the architecture,
> interface, and implementation of the libraries? As these language
> features are becoming more accepted (implemented in GHC & Hugs), is it
> worth investing time in supporting what are in fact really strange library
> APIs.
You're not the only one interested in these features. I remember you recently
mentioning dependent types (as in Cayenne) too - I think they would be
enormously useful, and of course they would alter the libraries a great deal.
> Whatever happened to the arrows proposal? Whatever happened to the
> categorical prelude?
Good questions. Arrows are important for parser combinators, CGI, and probably
Edison. Another feature is extensible records, which are needed for HaskellDB.
As to the categorical prelude, in June I posted the following to this list, but
received no response:
> I have been reading "On the expressive power of Constructor Classes" by Erik
> Meijer and Luc Duponcheel, where they describe a categorical prelude for
> Haskell.
> I have three questions:
> The paper refers to a forthcoming RUU Research Report, which is to contain a
> fuller description of the prelude. Is that report available and where ?
> Is the code of the prelude available and where ?
> Would it be feasible to use the categorical prelude to write real programs in a
> categorical style ?
Since then I have looked a little into the categorical language Charity, and
have the impression that trying to do categorical programming in a language like
Haskell is like trying to do functional programming in C++ - it is an
illuminating exercise, but not practical because the target language is
unsuitable. It also seems that to do proper categorical programming, one would
need to be very good at category theory, and also understand how to use it to
write programs.
There is a "Categorial Prelude with Arrows" [sic] item on the Haskell Wish List, but
it seems to refer to the use of arrows rather than a categorical prelude (as in
the above paper).
Tim
