Changes to Typeable

Ben Millwood haskell at
Wed Oct 3 23:59:19 CEST 2012

On Wed, Oct 3, 2012 at 10:25 PM, Ben Millwood <haskell at> wrote:
> On Wed, Oct 3, 2012 at 9:26 PM, Robin KAY <komadori at> wrote:
>> On 03/10/12 14:20, Edward Kmett wrote:
>>> I don't think anyone has proposed weakening parametricity in this way.
>> [snip]
>> I don't think so either, but is there any reason it shouldn't be done?
> Uh, because it weakens parametricity? :) Free theorems would promptly
> vanish, since we would have effectively added typecase to the
> language: it would no longer be possible to conclude from a type
> signature a -> a that the function was the identity, for example.

Oh goodness, I need to stop taking more than six minutes to write a reply :P

Feel free to ignore the above, the other comments along the same line
are better.

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