Grouping instance for Float/Double

[mrgriffin]

I'm in need of a Grouping instance for Double. I'm not particularly worried about what happens with the different representations of NaNs, or with negative zeros, so I think I can get away with this:

import GHC.Float (castFloatToWord32, castDoubleToWord64)

instance Grouping Float where grouping = contramap castFloatToWord32 grouping
instance Grouping Double where grouping = contramap castDoubleToWord64 grouping

Any comments about my implementation are more than welcome, because have been cargo-culting examples from elsewhere in the code and can't say that I fully understand what I am doing.

I'd guess that groupingWord64 would work in my orphan instances (instead of grouping) if it was exported.

The functions from GHC.Float were introduced in GHC 8.4 by #4092, and Stack Overflow has a question that may contain solutions for earlier GHCs (but I haven't actually tried any of them).

[alexloomis]

I need the same and the same worked for me.