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Problematic solution for Validation semigroup instance #24

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chetnashah opened this issue Oct 16, 2019 · 1 comment
Open

Problematic solution for Validation semigroup instance #24

chetnashah opened this issue Oct 16, 2019 · 1 comment

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@chetnashah
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If we see the text for Validation in book it is

instance Semigroup a =>Semigroup (Validation a b) where
(<>) = undefined

So it means the author intends the failures be combine via <> operation since it is provided in constraint.

We can probably refactor to pattern match with Failure a and Failure b and return Failure (a <> b)
@chetnashah
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https://github.com/andrewMacmurray/haskell-book-solutions/blob/master/src/ch15/Semigroup.hs#L241 for reference

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@chetnashah