add symbol, symbols

[ocramz]

Add smart constructors for Symbol , with the long-term goal of deprecating the IsList instance.

I should note in passing that the GHC DEPRECATE pragma doesn't work with class instances, which leaves the fix up to a judicious versioning schedule

Addresses (partly) #297

[snowleopard]

Thanks! The change looks good to me. I left a little suggestion.

I think we can drop the IsList instance altogether if it's problematic.

I should note in passing that the GHC DEPRECATE pragma doesn't work with class instances, which leaves the fix up to a judicious versioning schedule

I didn't quite get what you meant here. Could you elaborate?

[ocramz]

judicious versioning schedule

I didn't quite get what you meant here. Could you elaborate?

Just that removing class instances would need bumping a major version number, and possibly warning users beforehand.

[ocramz]

Also, I removed mention of the Dioid (Label a) instance because I couldn't find it.

[snowleopard]

Just that removing class instances would need bumping a major version number, and possibly warning users beforehand.

Ah, got it now. Agreed.

[snowleopard]

Thanks, merged!