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jrwest/traverse.scala

Created May 29, 2012 21:29
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traverse.scala
scala> type Validated[X] = Option[X]
defined type alias Validated
scala> badData.traverse[Validated,Int](i => if (i < 0) none[Int] else i.point[Validated])
res3: Validated[List[Int]] = None
scala> goodData.traverse[Validated,Int](i => if (i < 0) none[Int] else i.point[Validated])
res4: Validated[List[Int]] = Some(List(4, 5, 123, 6, 7))
scala> import scalaz.syntax.validation._; import scalaz.Validation; import Validation._; import scalaz.std.string._
...
scala> type Validated[X] = Validation[String,X]
defined type alias Validated
scala> badData.traverse[Validated,Int](i => if (i < 0) "invalid data".fail else i.point[Validated])
res10: Validated[List[Int]] = Failure(invalid data)
scala> goodData.traverse[Validated,Int](i => if (i < 0) "invalid data".fail else i.point[Validated])
res11: Validated[List[Int]] = Success(List(4, 5, 123, 6, 7))
scala> import scalaz.ValidationNEL
import scalaz.ValidationNEL
scala> type Validated[X] = ValidationNEL[Int,X]
defined type alias Validated
scala> badData.traverse[Validated,Int](i => if (i < 0) i.failNel else i.point[Validated])
res16: Validated[List[Int]] = Failure(NonEmptyList(-1))
scala> goodData.traverse[Validated,Int](i => if (i < 0) i.failNel else i.point[Validated])
res17: Validated[List[Int]] = Success(List(4, 5, 123, 6, 7))
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