Scalaz is a library that provides new datatypes like Validation and NonEmptyList as well as extensions to standard classes like Option and List. It implements general functions using ad-hoc polymorphism through traits, implicit parameters, and implicit conversions. Some key features include typeclasses for monoid, functor, monad, and more. The library uses implicit conversions called "pimps" to extend existing types with these functions and typeclasses in a clean way.

1. Nick Partridge
@nkpart
Scalaz
(scahla-zed)

2. Scalaz
New datatypes:
• Validation
• NonEmptyList
• Dlist
• More

3. Scalaz
Extensions to standard classes
• OptionW
• ListW
• etc.

4. Scalaz
Implementation of every single general
function you need.
• Ad-hoc Polymorphism
• Traits + Implicit Parameters + Implicit
Conversions.

5. Ad-hoc Polymorphism
• What is polymorphism?
def head[T](xs: List[T]): T = ...
Any T will be fine.

6. Ad-hoc Polymorphism
• What makes it ad-hoc? Restrictions.
def show[T](t: T): String =...
Not all T’s can be Strings.

7. Ad-hoc Polymorphism
• Typically achieved through interitance.
def show[T <: Show[T]](t: T) = ...

8. Ad-hoc Polymorphism
• In scalaz, we use Traits
• But no Inheritance.
• Make it nice:
• Implicit parameters and implicit
conversions.

9. Live Demo
def sum(xs: List[Int]) : Int
to
def sum[M[_], A](xs: M[A])(...): A

10. Typeclasses in Scalaz
• Monoid - append, zero
• FoldLeft
• Functor - map
• Monad - bind, return
• Many more...

11. Making it Nice
Questions?
Live code. Pimping time.

12. Making it Nice
The Pimps of Scalaz
• Identity -> A
• MA -> M[A]
• MAB -> M[A, B]
• More as necessary -> One per ‘kind’

13. Making it Nice
object Scalaz extends ... { ... }
• Includes all Implicit conversions
• Pimps and Extensions
• General constructors:
• some(x), none

14. Making it Nice
Usage:
import scalaz._
import Scalaz._
...
List(1,2) |+| List(3,4)

15. New Datatypes
• NonEmptyList
• Validation

16. NonEmptyList
• Guaranteed Not Empty.
• Construct via Identity:
• value.wrapNel
• General constructors:
• nel(head, tail)
• nel1(head, tail...) <- varargs

17. Validation
• Disjunction
• Right-biased Either
• Failures on the left.
• Constructors:
• value.fail, value.success
• success(value), failure(value)

18. Scalaz - Console
Live demo
• NonEmptyList
• Validation
• OptionW - ~

19. Learn More.
• scalaz/examples
• `Typeclassopedia`
• Haskell (particularly the wiki)
• #functionaljava
• Mailing list: http://code.google.com/p/scalaz
• Source: http://github.com/scalaz/scalaz