scalaz

Having (Some(1), Some(2)) I expect to get Some((1, 2)) and having (Some(1), None) I expect to get None You can use the fact that Scalaz 7 provides a Bitraverse instance for tuples and then sequence as usual (but with bisequence instead of sequence ): scala> import scalaz._, std.option._, std.tuple._, syntax.bitraverse._ import scalaz._ import std.option._ import std.tuple._ import syntax.bitraverse._ scala> val p: (Option[Int], Option[String]) = (Some(1), Some("a")) p: (Option[Int], Option[String]) = (Some(1),Some(a)) scala> p.bisequence[Option, Int, String] res0: Option[(Int, String)] = Some(

I want to be able to apply an operation f: (T,T) => T to Option[T] values in Scala. I want the result to be None if any of the two values is None . More specifically, I want to know if there is a shorter way to do the following: def opt_apply[T](f: (T,T) => T, x: Option[T], y: Option[T]): Option[T] = { (x,y) match { case (Some(u),Some(v)) => Some(f(u,v)) case _ => None } } I have tryied (x zip y) map {case (u,v) => f(u,v)} but the result is an Iterator[T] not an Option[T] . scala> val (x, y) = (Some(4), Some(9)) x: Some[Int] = Some(4) y: Some[Int] = Some(9) scala> def f(x: Int, y: Int) = Math

I am trying to issue a simple POST request to a webservice which returns some XML in Scala. It seems that Dispatch is the standard library used for this task, but I cannot find documentation for it. The main site, which I link above, explains at length what is a promise and how to do asynchronous programming, but does not actually document the API. There is a periodic table - which looks a bit scary - but it only seems useful to people who already know what to do and only need a reminder for the cryptic syntax. It also seems that Scalaz has some facility for HTTP , but I cannot find any

I'm trying to find the 'right' actor implementation. I realized there is a bunch of them and it's a bit confusing to pick one. Personally I'm especially interested in remote actors, but I guess a complete overview would be helpful to many others. This is a pretty general question, so feel free to answer just for the implementation you know about. I know about the following Scala Actor implementations (SAI). Please add the missing ones. Scala 2.7 (difference to) Scala 2.8 Akka ( http://www.akkasource.org/ ) Lift ( http://liftweb.net/ ) Scalaz ( http://code.google.com/p/scalaz/ ) What are the

I tried googling for this but all I got were stories about minor celebrities. Given the lack of documentation, what is a DList ? retronym It's a Difference List, along the lines of "Difference List as functions" scala> val (l1, l2, l3) = (List(1, 2, 3), List(4, 5, 6), List(7, 8, 9)) l1: List[Int] = List(1, 2, 3) l2: List[Int] = List(4, 5, 6) l3: List[Int] = List(7, 8, 9) Efficient prepending: scala> l1 ::: l2 ::: l3 res8: List[Int] = List(1, 2, 3, 4, 5, 6, 7, 8, 9) Inefficient appending. This creates an intermediate list (l1 ++ l2), then ((l1 ++ l2) ++ l3) scala> l1 ++ l2 ++ l3 // inefficient

I want to transform a List[Option[T]] into a Option[List[T]] . The signature type of the function is def lo2ol[T](lo: List[Option[T]]): Option[List[T]] The expected behavior is to map a list that contains only Some s into a Some containing a list of the elements inside the elements Some 's. On the other hand, if the input list has at least one None , the expected behavior is to just return None . For example: scala> lo2ol(Some(1) :: Some(2) :: Nil) res10: Option[List[Int]] = Some(List(1, 2)) scala> lo2ol(Some(1) :: None :: Some(2) :: Nil) res11: Option[List[Int]] = None scala> lo2ol(Nil : List