Laws for Show and Read?

[Sven Panne]

Am Mi., 5. Juni 2019 um 17:02 Uhr schrieb David Feuer <david.feuer at gmail.com
>:

> We already have the law
>
>   read . show = id
>
> which implies the injectivity and surjectivity conditions you specify.
>

I think this doesn't hold for the standard Read/Show instances for
Double/Float: IEEE-754 NaNs have a sign bit and a payload, and  both parts
are probably lost by the "read . show"-combination. The 2 infinities are
probably OK, but what about -0 vs. +0?
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