Removing bitSize

[Andrew Martin]

I'm in favor of removing it entirely. Making it an alias may help people
who want to keep code compatible with base < 4.7, but it could also
introduce some confusion. Some thoughts:

- It doesn't help people who want to write a `Bits` instance for their data
type. That will still require CPP.
- People writing bit-type-polymorphic code will have to upgrade to
FiniteBits when using newer base, which will force CPP for compatibility
anyway.
- People writing bit-type monomorphic code don't even need this function,
since they can just write out the number of bits (except for with Int and
Word, whose sizes vary by platform).


On Sun, Feb 4, 2018 at 4:15 PM, David Feuer <david.feuer at gmail.com> wrote:

> Quite some time has passed since I first raised this question. There
> doesn't seem to have been much discussion, but we really need to do
> something! Just leaving bitSize as deprecated seems like the worst
> option. Does anyone else have anything to add?
>
> On Mon, Jul 10, 2017 at 11:50 PM, David Feuer <david.feuer at gmail.com>
> wrote:
> > The long-deprecated bitSize method of the Bits class is slated to be
> > removed in base-4.11 (GHC 8.4). There is one remaining question:
> > should we replace it with a *function* by that name with a FiniteBits
> > constraint? I don't feel very strongly either way, but Ryan Scott
> > seems in favor and Edward Kmett seems opposed. So it seems best to
> > bring it to the libraries list and let the CLC make the call. If the
> > function is added, it would look like this:
> >
> > bitSize :: FiniteBits a => a -> Int
> > bitSize = finiteBitSize
> >
> > The biggest downside I see is that we might one day want to reuse the
> > name for something with a better type, such as
> >
> > bitSize :: forall proxy a. FiniteBits a => proxy a -> Int
> > bitSize _ = finiteBitSize (undefined :: a)
> >
> > or
> >
> > bitSize :: forall a. FiniteBits a => Tagged a Int
> > bitSize = Tagged (finiteBitSize (undefined :: a))
> >
> > or (with type applications)
> >
> > bitSize :: forall a. FiniteBits a => Int
> > bitSize = finiteBitSize (undefined :: a)
> >
> > Thanks,
> > David Feuer
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-- 
-Andrew Thaddeus Martin
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