[Haskell-cafe] Client-extensible heterogeneous types

[Stephen Tetley]

On 14 October 2010 10:15, Jacek Generowicz <Jacek.Generowicz at cern.ch> wrote:
> [Gregory: Sorry about duplicate, accidentally took it off-list.]
>
>> On 2010 Oct 14, at 09:46, Gregory Collins wrote:
>> There is more information about the different ways of doing this kind of
>> thing in Haskell in the OOHaskell paper:
>> http://homepages.cwi.nl/~ralf/OOHaskell/
>
> Abstract looks good. On the one hand I want to explore how Haskell allows me
> to do things in a way that doesn't resemble OO at all. On the other, it's
> good to see how OO-like things might be done in Haskell.

I find Section 2 in "Unfolding Abstract Datatypes" by Jeremy Gibbons a
more pleasant example of existentials as its limited to abstract
datatypes rather than fully blown OO (personally I don't particularly
agree that the OO-Haskell style should be used more...)

http://www.comlab.ox.ac.uk/jeremy.gibbons/publications/adt.pdf

A typographical note, if you want to run the code in the paper
/backwards E/ should be replaced with /forall/.