bitSize/bitSizeMaybe (was: Proposal: Add hasBitSize to Data.Bits.Bits)

[Edward Kmett]

I believe the resolution was to explicitly leave bitSizeMaybe _not_
implemented in terms of bitSize to help ensure it gets filled in correctly.

Im rather neutral on whether we should supply a definition in the other
direction.

-Edward


On Wed, Sep 18, 2013 at 7:56 AM, Herbert Valerio Riedel <hvr at gnu.org> wrote:

> On 2012-09-24 at 01:28:20 +0200, Henning Thielemann wrote:
> >> On Wed, Aug 22, 2012 at 07:49:49PM -0400, Edward Kmett wrote:
> >>> We want to add
> >>>
> >>>> class Bits b where
> >>>>     bitSizeMaybe :: b -> Maybe Int
> >>>
> >>> and deprecate, but not remove bitSize this iteration, and make a
> separate
> >>> class FiniteBits for things with a finite, fixed number of bits:
> >>>
> >>>> class Bits b => FiniteBits b where
> >>>>    finiteBitSize :: b -> Int
> >>>>    finiteBitSize = bitSize
> >>
> >> I've just pushed a patch implementing what I think the conclusion was.
> >> Please let me know if you think I got it wrong.
> >
> > My last comment was, that FiniteBits is not an appropriate name, and
> > then we arrived at FixedBits:
> >    http://www.haskell.org/pipermail/libraries/2012-August/018349.html
>
> As it stands, the current implementation state is at
>
>
> http://git.haskell.org/packages/base.git/commitdiff/cddc9024e67a6d4c01bb190839d0134af8c907e0
>
> Now I have two questions:
>
>  1.) Currently, bitSizeMaybe and bitSize have no default implementation
>      defined. Shall we define mutually recursive default implementations
>      for these two functions to help smooth the transition?
>
>      e.g. in the style (just an example, not an actual proposal) of:
>
>        bitSize = fromJust . bitSizeMaybe
>
>        bitSizeMaybe = Just . bitSize
>
>
>  2.) As it's probably not to late to easily fix any bikeshedding/naming
>      issues: Shall the naming remain as implemented?
>
> Cheers,
>   hvr
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