Talk given to the Melbourne Scala User Group, walking through why (and how) Scalaz came about.

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