This document discusses Scala and compares it to other languages like Ruby and Java. It covers Scala's features like functional programming, object-oriented programming, pattern matching, implicit parameters, monads, actors and testing frameworks. Pros and cons are listed for Scala and other languages like Clojure and Erlang. The document encourages learning Scala through online courses and exercises.

1. Scala for Rubyists
Make your ideas come true
by Michel Perez
www.mrkaspa.com

2. Ruby :D
FELICIDAD TIPADO DINAMICO GEMS
NO IDE DOCUMENTACION FACIL DE APRENDER

3. Ruby :(
PERFORMANCE ESCALABILIDAD PROG FUNCIONAL
MANTENIBILIDAD CONCURRENCIA

5. I <3 Java
- JVM
- Libraries
- Performance
- Escalabilidad
- Mantenibilidad
SCALA CLOJURE
JRUBYGROOVY

6. 6

7. 7
PROS CONS
Primitivas de concurrencia
Desarrollado por Google
Tiempo de compilación
Lenguaje compilado
Lenguaje tipado
Sintaxis old style
Demasiado imperativo
Poco funcional
Inmutabilidad

8. 8
PROS CONS
Primitivas de concurrencia
Erlang
Lenguaje interpretado
Funcional
Muy nuevo

9. 9
PROS CONS
Primitivas de concurrencia
Funcional
JVM
Lenguaje interpretado
Sistema de tipado opcional
LISP

10. 10
PROS CONS
Akka
Funcional
JVM
Tipado
Compilado
Tiempo de compilación
Curva de aprendizaje
Gestión de dependencias

11. Programacion funcional
FUNCIONES Y MAS FUNCIONES INMUTABILIDAD
CURRYING CLOSURES
LAZY EVALUATION PATTERN MATCHING
CAMBIA LA MANERA EN COMO
PROGRAMAS

12. Scala Variables?
12
val labels = Set(“")
val labels = Set[String](“”)
var labels = Set[String](“”)
Y los tipos?
Colecciones Inmutables
Syntaxis para generics <?>
NO HAY ; :D
Que es val ?

13. Scala OOP + FP
13
No es la OOP el demonio?
Un buen programador de scala no usa
side efect
Funciones puras
Usa OOP para abstraer datos
class Rational(x: Int, y: Int) {
def this(x: Int) = this(x, 1)
private def gcd(a: Int, b: Int): Int = if (b == 0) a else gcd(b, a % b)
private val g = gcd(x, y)
def numer = x / g
def denom = y / g
def < (o: Rational) = numer * o.denom < o.numer * denom
def > (o: Rational) = !(this < o)
def +(o: Rational) = {
new Rational(numer * o.denom + denom * o.numer, denom * o.denom)
}
def -(o: Rational) = {
this + (-o)
}
def unary_- = Rational(-numer, denom)
override def toString = {
numer + "/" + denom
}
} Cada cambio de estado genera un
nuevo objeto

14. Scala OOP
14
Case class -> get, set, constructor auto
Traits son similares a los modulos
en Ruby
Generic clases/traits
Singleton Object
case class SocialNetwork(id: String, name: String)
trait LinkedList[+A] {
def isEmpty: Boolean
def head: A
def tail: LinkedList[A]
def at(index: Int): A
def prepend[B >: A](elem: B): LinkedList[B] =
new Cons(elem, this)
}
object Nil extends LinkedList[Nothing] {
class Cons[A](val head: A, val tail: LinkedList[A]) extends LinkedList[A] {

15. Scala Functions
15
Toda funciona debe tener un tipo de
retorno(type inference)
Funciones como parámetros
Retorna funciones
Vector.fill(queens.length)("* “)
.updated(col, "X ").mkString
def lambda = (x: Int) => x + 1
val multiplier = (i:Int) => i * 10
def sumComp(a: Int): (Int) => Int = {
def sum(b: Int) = a + b
}
val fun = sumComp(5)
fun(1)
def sumComp(a: Int)(b: Int): Int = {
a + b
}
Currying

16. Pattern Matching
16
Es un Super Switchval secondElement = List(1,2,3) match {
case x :: y :: xs => y
case _ => 0
}
val foodItem = "porridge"
def goldilocks(expr: Any) = expr match {
case (`foodItem`, _) => "eating"
case ("chair", "Mama") => "sitting"
case ("bed", "Baby") => "sleeping"
case _ => "what?"
}
goldilocks(("porridge", "Papa"))
Compara y extrae al mismo tiempo

17. Implicits
17
Parametros inyectados en un metodo
o constructor de manera implicita
Sirve para realizar conversiones
automaticas
implicit def implChange(str:String):Int =
new Integer(str)
def sum(a:Int, b:Int):Int = a +b
sum("1", 2)

18. Monads
18
map, flatMap, filter
for comprehension
def readAsync(): Future[Option[List[String]]] =
Future { readFile() }
def readFile(): Option[List[String]] =
Try { Source.fromURL("/tmp/file.txt").getLines().toList
} toOption
val futSize: Future[Int] =
for {
result <- readAsync()
list <- result
} yield list.size
val futSizeMap: Future[Option[Int]] =
readAsync().map { result: Option[List[String]] =>
result.map((list: List[String]) => list.size)
}
Future, Option, Try, Either

19. Actors
19
Hilos livianos
Orientados a eventos
class BloodRequester extends Actor {
implicit val executor = context.dispatcher
override def receive: Receive = {
case BloodRequest(request) =>
DonorDAO.findNear(request).map { donors =>
donors.foreach { donor =>
facebookNotifier ! FacebookNotify(donor, request)
}
}
}
}
Se reinician en caso de fallas
Supervisión

20. ScalaTest
20
Test Unit
trait NeoTest
extends FunSpec
with MustMatchers
with BeforeAndAfterAll
with BeforeAndAfterEach {
override def beforeEach(): Unit = {
NeoDBCleaner.cleanDB()
}
describe("UserDAOs") {
it("creates an user an checks the default group") {
withUser { (user, saved) =>
saved must be(true)
val query = s"""match (a:user {id: "${user.id.getOrElse("")}"})-[c:has_group]->(b:group) return a, b, c"""
val result = Await.result(NeoQuery.executeQuery[UserLogin, Group, HasGroupLogin](query), 2 seconds)
result.length must be(1)
}
}
}
}
Multiples Pardigmas
TDD
BDD

21. Scala wants U ;)
21
https://www.coursera.org/course/progfun
http://scala-exercises.47deg.com/koans