[Haskell-cafe] is closing a class this easy?

[Wolfgang Jeltsch]

Am Samstag, 18. Juli 2009 08:58 schrieb Miguel Mitrofanov:
> Oops... Sorry, wrong line. Should be
>
> isAB :: forall p. p A -> p B -> p x

Is this a well-known approach for closing classes?

I came across the same idea and implemented a generic framework for closing 
classes in this way. I did this to simulate algebraic data kinds and kind 
polymorphism over such kinds. I needed this for the record system of 
Grapefruit. The code is here:

<http://code.haskell.org/grapefruit/main/grapefruit-records/src/>

Explaination of the techniques used in this code will probably follow as part 
of an IFL 2009 paper.

Now I wonder which of my ideas are actually new and which are just old hat. 
Could you maybe answer this question?

Best wishes,
Wolfgang