Monoid over reciprocal of reciprocal sum

Henning Thielemann lemming at
Sun May 6 06:44:03 UTC 2018

On Sun, 6 May 2018, 박신환 wrote:

> instance Fractional a => Monoid (RecipSum a) where
>     mempty = RecipSum (1 / 0)

This would fail for Rational. I'd prefer to simply use Sum monoid on 
reciprocal values. It also has the advantage that you only need to call 
'recip' once after a sequence of (<>).

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