Re: Proxy and new-typeable

Right now Data.Typeable is proxy-agnostic. The proposal is just to export a Proxy type for convenience (alternatively, the user can define her own Proxy or use one from tagged). What exactly forces you to support both proxies in your code? (I'm reluctant to have many proxy types scattered around mainly because of unnecessary name conflicts, but I'd like to understand your concerns too.) Roman * Edward Kmett [2013-03-20 04:48:49-0400]

If you insist on adding Proxy to Data.Typeable, I'd like to strongly suggest that we might want to look at promoting Data.Proxy from the tagged package to base.

It offers a lot of instances that I currently rely upon in production code and is already in use in a large portion of the ~42 reverse dependencies of that package:

http://packdeps.haskellers.com/reverse/tagged

Of course we could invert the dependencies from packages outside of base at that time.

Exporting a crippled Proxy from Data.Typeable *without* those instances will basically just ensure that I need to somehow support both, fight needlessly with orphans and/or deal with qualified imports everywhere, and it will break about 3 dozen modules of mine, and impact others.

All in all this makes me personally rather strongly opposed to the idea of just randomly throwing a Proxy type in the module without ensuring we don't lose existing functionality along the way.

-Edward

On Wed, Mar 20, 2013 at 4:04 AM, José Pedro Magalhães wrote:

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Data.Typeable no longer uses Proxy, yet I think it is convenient to have a Proxy datatype defined somewhere in base, and re-export it from Data.Typeable, as you might often often want to use it.

Cheers, Pedro

On Wed, Mar 20, 2013 at 12:35 AM, Edward Kmett wrote:

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+1 for finding a resolution. The idea of another Proxy floating around fills me with unease.

-Edward

On Tue, Mar 19, 2013 at 7:48 PM, Ben Gamari wrote:

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José Pedro Magalhães writes:

...

Yes, it's entirely unproblematic, and a good suggestion.

What happened to this proposal? As far as I can tell the new-typeable work is in (or rather, the branch has been deleted) yet Data.Typeable still seems to have its own Proxy. Given that there has been talk of a 7.8 release, this should probably be resolved quickly (although it's not clear to me from the massive thread where that discussion concluded).

Cheers,

- Ben

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