Re: proposal #4095: add Applicative instance for Either

Hello, Are there any uses of this instance that are not related to error handing? If not, I would propose that we avoid prolonging the confusing use of "Either" for error handling and define a separate type with properly labelled constructors, to be used as "Maybe" but with multiple reasons for failure. -Iavor On Wed, May 26, 2010 at 4:44 AM, Ross Paterson wrote:

Ashley Yakeley writes:

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I currently have my own implementations for these:

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     instance Foldable Identity      instance Traversable Identity      instance Applicative Identity

The transformers package has such instances (but currently for a different Identity type).

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     instance Foldable (Either p)      instance Traversable (Either p)      instance Applicative (Either p)

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     instance Foldable ((,) p)      instance Traversable ((,) p)

The Applicative one is proposed here.  The others should also be added. _______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries