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Scalaz: Convert ValidationNel of ValidationNel to ValidationNel

How to convert

val from: ValidationNel[E, ValidationNel[E, T]]

to

val to: ValidationNel[E, T]

while capturing all validation errors?

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2 answers


you can use from.fold(Failure(_), identity)

.



In general, flatMap (identity) or .join works for any Monad to convert F [F [A]] to F [A], however validation is not a monode and flatMap / join methods for Validation are deprecated.

+4


source


Just flatMap

that ValidationNel

:



from.flatMap(identity)
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