MPTCs and functional dependencies

Ross Paterson ross at
Mon Apr 10 05:19:02 EDT 2006

On Mon, Apr 10, 2006 at 01:31:18PM +0800, Martin Sulzmann wrote:
> You mention that nobody is really happy with FDs at the moment,
> but you don't provide concrete arguments why. I assume you
> refer to the following two issues:
> 1) FDs may threaten complete and decidable type inference
> 2) FDs are more verbose than say ATs

I find them unsatisfactory because the versions that are powerful enough
(e.g. to allow the instances in the monad transformer library) need
complex restrictions on the form of instances to ensure termination and
confluence.  They would make the language complex and unwieldy.

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