Allow arr ∧ (first ∨ (***)) as minimal definition of Arrow instance

Add default definitions of first, second in terms of (***) to let one define an Arrow instance in terms of (***) rather than first, which is sometimes more elegant or convenient.

changed weight to 5

added Tbug Trac import core libraries labels

Attached file 0001-Allow-arr-first-as-minimal-definition-of-Arrow-insta.patch (download).

This would also necessitate a change to the MINIMAL pragma, I suppose.

No objection here, BTW. This makes Arrow's internals far more symmetrical.

I suggest that

• You add a description to the ticket that explains what you are doing, and why it is a good thing. Perhaps add comments in the code to explain subtleties?
• Pursue it through the core libraries committee (Edward clearly has it on his radar, which is good).

Simon

changed the description

Replying to [ticket:10216#comment:98163 simonpj]:

Perhaps add comments in the code to explain subtleties?

I'm not sure what is subtle here; you mean any subtleties in particular?

Pursue it through the core libraries committee (Edward clearly has it on his radar, which is good).

Any action required from me until further notice? Should I notify core-libraries-committee@?

Yes, I think it would be best to put together a formal proposal and send it through the core libraries committee. It needn't be much effort and it sounds like it shouldn't be terribly controversial but I would like to make sure that this goes through the correct channels.

changed the description

Replying to [ticket:10216#comment:103347 bgamari]:

Yes, I think it would be best to put together a formal proposal and send it through the core libraries committee.

Done. (I wasn't sure earlier whether to do so as the core-libraries-committee chair had already seen this ticket.)

changed milestone to %8.0.1

Milestone renamed

I sent a proposal to libraries@haskell.org and no one complained so I'm setting the status back to patch

Edward, can we have your ok?

Granted.

Trac metadata

Trac field	Value
CC	core-libraries-committee@haskell.org → core-libraries-committee@haskell.org, ekmett

closed

Thanks, merged!

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed