Restricted Data Types: A reformulation

Jan-Willem Maessen jmaessen at
Wed Feb 8 08:26:48 EST 2006

On Feb 7, 2006, at 11:45 PM, John Meacham wrote:

> Ashley Yakeley has convinced me this proposal won't work as is. I knew
> that dropping of the a type parameter in the dictionary passing scheme
> would bite me :). though, perhaps it will inspire another proposal? In
> the meantime, I will see about implementing the 'wft' constraints as
> mentioned in the paper. though, the example ashley gave gives me pause
> about how useful these will be in general. hmm...

It occurs to me to muse that the "wft" constraints look a whole lot  
like "Typeable" constraints (ie (Typeable (m (a -> a))) => m Int ).

Should there be a class which is implemented by every well-formed  
type of kind (*)?  Should that class have one or more of the following:
   * Structural decomposition and reconstruction a la Generics?
   * Scrapped-boilerplate traversal a la Typeable?
   * Ability to coerce to Dynamic?

It would be a special source of amusement to me if such a class were  
called All or Forall... :-)  (though a moment's thought will tell you  
it's Wrong.)

-Jan-Willem Maessen

>         John
> -- 
> John Meacham - ⑆⑆john⑈
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