[Haskell-cafe] Default implementation of Floating (**)

[Henning Thielemann]

On Wed, 19 May 2021, Viktor Dukhovni wrote:

> On Wed, May 19, 2021 at 11:50:22AM -0300, Fabrício Olivetti de França wrote:
>
>> So I was wondering, is there any reason to have this (potentially
>> dangerous) default implementation on base?
>
> The behaviour for negative inputs seems to be correct:
>
>    λ> log(-2)
>    NaN
>    λ> exp(log(-2))
>    NaN
>    λ> exp(log(-2) * (-2))
>    NaN
>    λ> log(0)
>    -Infinity
>
> were you expecting these to check for non-positive inputs and to throw a
> floating point exception?


I guess he expects (-2)**(-2) = 1/4.

But defined this way, (**) would be rather discontinuous.