[Haskell-cafe] Re: Polymorphic variants

[Al Falloon]

The proposal that I like the most is this one:
"Open Data Types and Open Functions"
http://lambda-the-ultimate.org/node/1453

However, it doesn't readily admit using the variants as overlapping 
enumerations like John suggested in a previous thread:
http://article.gmane.org/gmane.comp.lang.haskell.cafe/23362

In fact it doesn't really support structural sub-typing at all (the way 
that polymorphic variants in Ocaml do), but it does support independent 
extension (which PV's don't do).

Dan Doel wrote:
> P.S.: Some papers:
> 
> http://www.cse.ogi.edu/PacSoft/publications/2000/extensiblerecords.pdf
> 
> http://research.microsoft.com/users/daan/download/papers/scopedlabels.pdf
> 
> The second actually discusses all the operations on variants and whatnot. The 
> first just mentions that it's a related topic.