An introductory talk on Scala Programming Language and its features. This talk was presented at Jamia Developers Day 2013

1. JDevDay - Introduction to Scala
Saleem Ansari
10th March 2013
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2. Outline
1 Introduction to Scala
2 Setting up Scala
3 Absolute Scala basics
4 Functional Paradigm in Scala
5 Object Oriented Programming in Scala
6 Where to learn more Scala
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3. Topic
1 Introduction to Scala
2 Setting up Scala
3 Absolute Scala basics
4 Functional Paradigm in Scala
5 Object Oriented Programming in Scala
6 Where to learn more Scala
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4. What is Scala?
What is Scala? The name Scala stands for scalable language. The
language is so named because it was designed to grow with the
demands of its users.
What makes Scala a Scalable Language ?
Statically typed language with OOP + FP both.
Fast and expressive, and peasant to use.
Excellent type inference.
Runs on JVM.
Whats more?
Scala is compatible with Java
Scala is concise
Scala is high level
Scala is statically typed ( vs dynamically typed )
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5. What can you do with Scala today?
Write web applications
Play Web Framework http://www.playframework.com/
Lift Web Framework http://liftweb.net/
Write code that scales to huge amounts of data
Spark Project http://spark-project.org/
Scalding https://github.com/twitter/scalding
Process huge number of concurrent tasks
Akka http://akka.io/
Natural Language Processing and Machine Learning
ScalaNLP http://www.scalanlp.org/
And anything could do in Java, now more concisely :-)
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6. Topic
1 Introduction to Scala
2 Setting up Scala
3 Absolute Scala basics
4 Functional Paradigm in Scala
5 Object Oriented Programming in Scala
6 Where to learn more Scala
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7. Install the Scala Complier
yum install scala
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8. Install your faviourite Editor / IDE
yum install emacs
OR install Eclipse ( ScalaIDE )
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9. Scala compiler is
scalac ( just like javac command )
scala ( just like java command )
fsc ( fast scala compiler )
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10. Topic
1 Introduction to Scala
2 Setting up Scala
3 Absolute Scala basics
4 Functional Paradigm in Scala
5 Object Oriented Programming in Scala
6 Where to learn more Scala
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11. Hello Scala World
helloworld.scala
object HelloWorld {
def main(args: Array[String]) = {
println(Hello Scala World!)
}
}
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12. Compile and run Hello Scala World
Output
$ scalac helloworld.scala
$ ls
helloworld.scala
HelloWorld.class
HelloWorld$.class
$ scala HelloWorld
Hello Scala World!
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13. Values and Variables
An example in Ruby ( or maybe Python ) a dynamically typed
language
counter = Counter.new
counter = AtomicCounter.new
counter = File.new # this works here!
Scala's static type system, avoids runtime overhead of dynamic
types. The method dispatch is fast in a statically typed
language.
var counter = new Counter()
counter = new AtomicCounter() // this has to be a Counter
counter = new File() // this doesn't work in Scala
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14. Data Types
Almost everything is same as Java
Basic Data Types: ( all integers are signed two's complement )
Integers:Byte (8bit), Short (16bit), Int (32bit), Long (64bit)
Char (16 bit unicode character), String (squence of Chars)
Reals: Float (32bit), Double (64bit)
Boolean: true / false
Literal
basic data types i.e. 1, 0.123, 12L, `a', String
symbol literal: `identier
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15. More Concepts
Data Containers
Array
List
Set
Map
Tuple
Programming Abstraction Tools
Class
Object
Scala App
Package
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16. Expressions
Every thing is an expression
Basic expression: 1+2
An assignment is an expression
A function is an expression
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17. Control Constructs
if-else
while
do-while
for
match-case
try-catch-nally
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18. Topic
1 Introduction to Scala
2 Setting up Scala
3 Absolute Scala basics
4 Functional Paradigm in Scala
5 Object Oriented Programming in Scala
6 Where to learn more Scala
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19. Matematical Logic
Lambda Calculus ( see
Wikipedia )
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20. Factorial Function
Expressed as mathematical logic
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21. FP is guided by two main ideas:
Functions arest-class values
Functions have no side eects i.e. they can be replaced with
their values
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22. Hallmarks of Functional Programming
mapping
ltering
folding
reducing
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23. Topic
1 Introduction to Scala
2 Setting up Scala
3 Absolute Scala basics
4 Functional Paradigm in Scala
5 Object Oriented Programming in Scala
6 Where to learn more Scala
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24. Object Oriented
Decompose the problem into entities and interactions among
entities
Each entity and their interaction is represented using
class/object
internal state is the member variables
interactions are the member functions
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25. Functions
factorial.scala
def factorial(n:Int): Int =
if(n=0) 1 else n*factorial(n-1)
Placeholder syntax
Partially applied functions
Closures
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26. Traits
traits.scala
trait PartTime {
// trait definition
}
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27. Classes
classes.scala
class Employee(name: String, age: Int) {
override def toString = name + , + age
}
class Supervisor(name: String, age: Int
) extends Employee(name, age) with PartTime
{
override def toString = name + , + age
}
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28. Objects
objects.scala
object Employee {
override def toString = name + , + age
}
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29. Packages
package-example.scala
package in.tuxdna.scala
class Employee(name: String, age: Int) {
override def toString = name + , + age
}
object Main extends App {
val emp1 = new Employee(Tom, 21)
println(Employee 1: +emp1)
}
// $ scalac pacakge-example.scala
// Employee 1: Tom, 21
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30. Features to be convered later
XML Processing
Actors
Case Classes
Properties
Extistential Types
Implicits
Lazy Evaluation
Parser Combinations
Monads
Annotations
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31. Using Scala as a scripting language
scala scriptname.scala
employee.scala
class Employee(name: String, age: Int) {
override def toString = name + , + age
}
val emp1 = new Employee(Tom, 21)
println(Employee 1: +emp1)
// $ scala employee.scala
// Employee 1: Tom, 21
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32. Topic
1 Introduction to Scala
2 Setting up Scala
3 Absolute Scala basics
4 Functional Paradigm in Scala
5 Object Oriented Programming in Scala
6 Where to learn more Scala
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33. Books
Scala for the Impatient (free) http://blog.typesafe.com/free-
pdf-from-typesafe-scala-for-the-impatien-64715
Programming Scala (free)
http://ofps.oreilly.com/titles/9780596155957
Programming in Scala 2nd Ed.
http://www.amazon.com/Programming-Scala-Comprehensive-
Step-Step/dp/0981531644
Functional Programming Principles in Scala ( free online
course )
https://www.coursera.org/course/progfun
Blogs
Forums
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34. Questions?
tuxdna (at) gmail (dot) com
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35. Thank you!
twitter.com/tuxdna
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