scala introduction
TRANSCRIPT
Presented by Mohana Rao
INTRODUCTION
SCALA - BACKGROUND
SCALA - BACKGROUND
Groovy’s Creator , James Strachan wrote on his blog in 2009 about scala
“I can honestly say if someone had shown me the Programming in Scala book by Martin Odersky, Lex Spoon & Bill Venners back in 2003 I’d probably have never created Groovy.”
Scala
Akka
Play
Slick
Spark
JVM
Kafka
Mesos
Chisel
scalaz
cats
scalding
ScalaCheck
scodec Specssqueryl
Samza
Finagle
ScalaTest
shapelesssbt
Lift
BlueEyesscalatra
JS
ADAM
SCALA ECOSYSTEM
Feb 5, 2015:Scala.JS 0.6 released
No longer experimental!
Fast
Great interop with Javascript libraries
SCALA.JS
Scala ranked as #14 in RedMonk Language Rankings of January 2015
REDMONK RANKING
SCALA JOB TRENDS
Scala – “Scalable Language” : A language which grows with user demands
Designed by Martin Odersky at EPFL
Compiles to java byte code and runs on JVM
Adopted at companies like Twitter, LinkedIn and many
Used in development of well renowned frameworks like Play, Spark, Akka, Kafka, Spray and many
Completed 10+ years. Announced in 2004
SCALA - BACKGROUND
Statically Typed.
Functional.
Object Oriented.
Expressive.
DSL-friendly
SCALABLE LANGUAGE
JAVA int square(int x) {
return x * x;
}
have to define method parameters to be final to have immutability
Integer intVariable = 3
final Integer intConstant = 3.17
SCALA def square(x:Int):Int = {
x * x
}
function/method parameters are by default final
var intVariable = 3
val intConstant = 3.17
IMMUTABILITY
JAVA String companyName = “Synerzip”;
int square(int x) {
return x * x;
}
Integer result = square(2)
SCALA val companyName = “Synerzip”
def square(x:Int) = {
x * x
}
val result = square(2)
or
val result:Int = square(2)
STATICALLY TYPED WITH TYPE INFERENCE
JAVA List<String> cities = new
ArrayList<String>();
cities.add(“Pune”);
cities.add(“Mumbai”);
Map<String,List<Integer>> citiesMap= new
Map<String,List<Integer>();
List<Integer> pincodes = new ArrayList<Integer>();
pincodes.add(411027);
pincodes.add(411038);
citiesMap.put(“Pune”,pincodes);
SCALA
val cities = List(“Pune”,”Mumbai”)
val citiesMap = Map(“Pune” -> List(410027,411038))
STATICALLY TYPED WITH TYPE INFERENCE
JAVA List<String> cities = new
ArrayList<String>();
cities.add(“Pune”);
cities.add(“Mumbai”);
Map<String,List<Integer>> citiesMap= new
Map<String,List<Integer>();
List<Integer> pincodes = new ArrayList<Integer>();
pincodes.add(411027);
pincodes.add(411038);
citiesMap.put(“Pune”,pincodes);
SCALA
val cities: List[String] = List(“Pune”,”Mumbai”)
val citiesMap :Map[String,List[Int]] = Map(“Pune” -> List(411027,411038))
STATICALLY TYPED WITH TYPE INFERENCE
Lambda’s Anonymous functions
(x:Int) = x * 10
Defining Functions def multiplyByTen(x:Int) = x * 10
Functions assigning to variables/Functions as values val addTen:Int=>Int = (x => x + 10)
Clousures Allow closures
val message = “Hello “; def greet(name:String) = message + name + “!”;
FUNCTIONS ARE FIRST-CLASS CITIZENS
High Order Functions
def poly[A,B,C](f:A=>B, g:B=>C) = f andThen g
def composedFunction = poly(multiplyByTen , addTen)
composedFunction(6) results to 70
(addTen compose multiplyByTen)(6) result to 70
HIGH ORDER FUNCTIONS
Default Parameter values def greet(greeting:String = “Hello ” , person:String = “Synerzipian”) = {
println(greeting + “ “ + person)
}
greet() Hello Synerzipian
greet(“Hey”) Hey Synerzipian
greet(“Welcome”, “to Scala”) Welcome to Scala
FUNCTIONAL FUN
Named Parameter values def greet(greeting:String = “Hello ” , person:String = “Synerzipian”) = {
println(greeting + “ “ + person)
}
greet(person=“World”) Hello World
greet(greeting=“Welcome”) Welcome Synerzipian
greet(person=“to Scala”,greeting=“Welcome”) Welcome to Scala
FUNCTIONAL FUN
def factorial(n: Int) = {
def fact(n: Int, acc: Int): Int = {
if (n == 0) acc
else fact(n - 1, n * acc)
}
fact(n, 1)
}
TAIL RECURSION
Call By Name (Lazy Evaluation of parameters) def greet(greeting:String = “Hello ” , person: =>String) = {
println(“Greet Called”);
println(greeting + “ “ + person)
}
def getPerson() = {
println(“Generated Person Name”)
“Synerzipian”
}
greet(person=getPerson())
Greet Called
Generated Person Name
Hello Synerzipian
FUNCTIONAL FUN
DSL’S
var x = 0
object Do {
def apply(body: => Unit) = new DoBody(body)
}
class DoBody(body: => Unit) {
def until(cond: =>Boolean): Unit = {
body;
while(cond)
body
}
}
Do { x = x + 1 } until (x < 10)
DSL’S
JAVA public class Employee {
private String name;
private Integer age;
public Employee(String name, Integer age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setAge(Integer age){
this.age = age;
}
public Integer getAge() {
return age;
}
}
SCALA class Employee(val name:String, var
age:Int)
or
case class Employee(val name:String, var age:Int)
SCALA CLASSES
JAVA public class Employee {
private String name;
private Integer age;
public Employee(String name, Integer age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setAge(Integer age){
this.age = age;
}
public Integer getAge() {
return age;
}
}
SCALA class Employee(val name:String, var
age:Int)
or
case class Employee(val name:String, var age:Int)
SCALA CLASSES
Traits are Stackable
They are fundamental unit for code reuse in Scala
A Trait encapsulates method and field definitions, which can be reused by mixing them in classes
Unlike class inheritance , in which class must inherit from just one
superclass, a class may mix in any number of Traits
Unlike Interfaces they can have concrete methods
TRAITS
t ra i t Language {
val name:Str ing
overr ide def toStr ing = name
}
t ra i t JVM {
overr ide def toStr ing = super. toStr ing + “ runs on JVM”
}
t ra i t Stat ic {
overr ide def toStr ing = super. toStr ing + “ is stat ic”
}
class Scala extends Language wi th JVM with Stat ic {
val name = “Scala”
}
pr int ln(new Scala()) “Scala runs on JVM is stat ic”
PATTERN MATCHING
All default Scala collections are immutableEvery collection type has lot of higher order functions
val xs = List(1 to 10)
xs.filter(x => x%2 ==0)
xs.map(_*2)
COLLECTIONS
For ComprehensionsFuturesImplicitStructural TypingCurryingPartially Applied FunctionsCovariant/Contravariant/Nonvariant Type ParamatersAnd much more…
IF I HAD MORE TIME
