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txominpelu/traverse-validation

Created August 9, 2013 07:22
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How to traverse a list of validation
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traverse-validation
import scalaz._
import scalaz.syntax.validation._
import scalaz.syntax.traverse._
import scalaz.std.list._
scala> List("1".successNel[String], "2".failNel[String], "3".failNel[String]).sequenceU
res5: scalaz.Validation[scalaz.NonEmptyList[String],List[String]] = Failure(NonEmptyList(2, 3))
scala> List("2".failNel[String], "3".failNel[String]).sequenceU
res6: scalaz.Validation[scalaz.NonEmptyList[String],List[String]] = Failure(NonEmptyList(2, 3))
scala> List("1".successNel[String], "2".successNel[String]).sequenceU
res8: scalaz.Validation[scalaz.NonEmptyList[String],List[String]] = Success(List(1, 2))
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