scalaz.syntax.std.OptionOps.cata在scalaz中做什么？

Question

Here is a description about cata function from scalaz. But what is a purpose og using this function? By the way is there a scaladoc for scalaz with description, not only code.

Answer 1

It's the same as fold on scala.Option : it lets you map both the has-a-value branch and the empty branch into a single result value. Anywhere you might see

Option(x) match {
  case Some(y) => f(y)
  case None => y0
}

you can use fold on Option or cata on scalaz' variant instead.

(Note: for this particular case, pattern matching is typically more efficient, but not always more convenient.)