Map on Scalaz Validation failure

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Question Description

import scalaz._
import Scalaz._


This will return a Validation[NumberFormatException, Int].
Is there a way I can apply a function on the failure side (such as toString) to get a Validation[String, Int]?

Practice As Follows

There is a pair of methods <-: and :-> defined on MAB[M[_,_], A, B] that map on the left and right side of any M[A, B] as long as there is a Bifunctor[M]. Validation happens to be a bifunctor, so you can do this:

((_:NumberFormatException).toString) <-: "123".parseInt

Scala's type inference generally flows from left to right, so this is actually shorter:


And requires less annotation.

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