[Haskell] Re: Re: RE: Extensible records: Static duck typing

Barney Hilken b.hilken at ntlworld.com
Fri Feb 22 05:12:41 EST 2008

> While I agree with your general argument, I wonder if you realize
> that functional dependencies have a strong, general, and elegant
> mathematical foundation that long predates their use in Haskell?
> If you want even a brief glimpse, there's s short article at
> http://en.wikipedia.org/wiki/Functional_dependencies that might
> give you some ideas.  The mathematics of functional dependencies
> plays an important role in the theory of relational databases.
> I don't know what you consider as the mathematical foundations
> for associated types, nor do I know why you consider that to be
> either more general or more "mathematical" (whatever that means)
> but I hope you'll enjoy the material on functional dependencies.

I admit I was being unfair on fundeps in calling them less  
mathematical. Nonetheless, something about their addition to Haskell  
grates on my mathematical sensitivities. They feel "bolted on" in a  
way that associated types don't. Probably this is because of my own  
bias which leads me to see Haskell as a subset of dependent type  
theory, and ATs as some kind of sigma type (though I've never tried to  
make this precise).


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