Convert a List of Options to an Option of List using Scalaz
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by Rafael de F. Ferreira
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Published on 2010-04-02T20:28:52Z
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The following function transforms a list of Option[T] into a list of Some[T], in the case where all members are Some's, or None, in the case where there is at least one None member. I guess the code is clearer that this explanation:
def lo2ol[T](lo: List[Option[T]]): Option[List[T]] = {
lo.foldRight[Option[List[T]]](Some(Nil)){(o, ol) => (o, ol) match {
case (Some(x), Some(xs)) => Some(x :: xs);
case _ => None : Option[List[T]];
}}}
I remember seeing somewhere a similar example, but using Scalaz to simplify the code. How would it look like?
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