Re: Changes to Typeable

On Wed, Oct 3, 2012 at 10:25 PM, Ben Millwood wrote:

On Wed, Oct 3, 2012 at 9:26 PM, Robin KAY wrote:

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On 03/10/12 14:20, Edward Kmett wrote:

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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.