Re: Why are there no Show instances for internal types

On 18-03-17 16:13:52, Ben Gamari wrote:

On March 18, 2017 9:03:48 AM EDT, Tom Sydney Kerckhove wrote:

Snip.

...

My questions for you:

- Is there a reason that there are no derived 'Show' instances for most types?

As Richard mentioned, we don't derive Show due to code size and compilation time concerns.

Okay.

Show in particular is rather expensive to derive and seeing as we already have Outputable I don't it would make sense to derive it by default.

Show and Outputable have very different goals though.

I would really like to avoid introducing more CPP into the code base for this particular problem.

Fair enough.

One alternative which will work in many cases is to simply derive Show yourself using StandaloneDeriving. Does this help?

That doesn't work if some type doesn't have the constructors exposed. I tried this already, and it would be a good solution if all constructors were exposed, ...

Cheers,

- Ben

-- Sent from my Android device with K-9 Mail. Please excuse my brevity.

-- Tom Sydney Kerckhove