scalaz

Often I face following situation: suppose I have these three functions def firstFn: Int = ... def secondFn(b: Int): Long = ... def thirdFn(x: Int, y: Long, z: Long): Long = ... and I also have calculate function. My first approach can look like this: def calculate(a: Long) = thirdFn(firstFn, secondFn(firstFn), secondFn(firstFn) + a) It looks beautiful and without any curly brackets - just one expression. But it's not optimal, so I end up with this code: def calculate(a: Long) = { val first = firstFn val second = secondFn(first) thirdFn(first, second, second + a) } Now it's several expressions

Many of the methods in scalaz have symbolic unicode equivalents, such as forever and ∞ (of course, I have this the wrong way round, the symbolic methods really have ASCII equivalents). The project contains a live templates XML file for IDEA so these can be auto-completed , I believe by using the forever+TAB shortcut (in the above instance). I can't figure out how to import this live template into IDEA and actually use it, though. How can I do that? CrazyCoder Live Templates XML file should be placed under IDEA configuration directory, templates subdirectory. IDEA configuration folder location

I'm currently working on a small project (< 10k loc) which is mainly pure but relies on mutable optimizations mainly based on iterators and some data-structure reuse for heavy-duty calculations. I'd like to learn a bit more functional programming and want to get more type safety, by e.g. wrapping mutable computations into state transformer monads and the like. For this purpose there exists the scalaz library. Question One When abstracting my computations on a larger scale by using all the fancy functional stuff, will I introduce performance killers that I won't get rid of? Like when my

I'm reading this great article about dependency injection in scala with Reader monad . The original example is working well, but I did a little bit change on the return types of the UserRepository.get/find . It was User , but I changed it to Try[User] . Then the code won't be compiled, I had tries many times, but still without lucky. import scala.util.Try import scalaz.Reader case class User(email: String, supervisorId: Int, firstName: String, lastName: String) trait UserRepository { def get(id: Int): Try[User] def find(username: String): Try[User] } trait Users { def getUser(id: Int) = Reader

Possible Duplicate: Good scalaz introduction I would like to learn more about Scalaz, possibly using Scalaz7 to be avoid rewiring my brain once it is declared stable. My problem is that Scalaz contains a lot of functionality. While most of it is meant to be independent of other parts, I would like to have a bird's eye view of the global funcitonality offered by Scalaz and how it is organized. As far as I know, Scalaz offers, among other things, Functor , Applicative and Monad traits, new monads such as Validation (edit: turns out it is only an applicative) monad transformers ( OptionT ,

Following watching Nick Partidge's presentation on deriving scalaz , I got to looking at this example, which is just awesome: import scalaz._ import Scalaz._ def even(x: Int) : Validation[NonEmptyList[String], Int] = if (x % 2 ==0) x.success else "not even: %d".format(x).wrapNel.fail println( even(3) <|*|> even(5) ) //prints: Failure(NonEmptyList(not even: 3, not even: 5)) I was trying to understand what the <|*|> method was doing, here is the source code: def <|*|>[B](b: M[B])(implicit t: Functor[M], a: Apply[M]): M[(A, B)] = <**>(b, (_: A, _: B)) OK, that is fairly confusing (!) - but it