ACCU 2011 Introduction to Scala: An Object Functional Programming Language

Peter Pilgrim
Oracle Java Champion
INTRODUCTION INTO SCALA
THE OBJECT‐FUNCTIONAL
PROGRAMMING LANGUAGE
XeNoNiQUe.co.uk (c) 2011 4/14/2011 1

Blog: www.XeNoNiQUe.co.uk/blog/
ACCU: Member since 1993
Education: London South Bank University
Languages: Scala, Groovy, JavaFX, Java
Conferences: JavaOne, ACCU, QCon, Devoxx

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“If I were a pick a language
to use today other than
Java, it would be Scala”
James Gosling

http://www.adam‐bien.com/roller/abien/entry/java_net_javaone_which_programming

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Headline News

“More and more programmers are going to need to
understand functional programming at a productive
level. Especially over the next 5 to 10 years” ‐ IBM, Jason
Stidd, Functional Programming Blog, 2010
“Scala enjoys a singular advantage: performance. The
language is compiled to optimised byte codes and runs
as fast as native Java” Infoworld, 2010

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Demo

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Today’s Agenda

Classes and Companion Objects
Function Objects
Case classes and Pattern matching
Traits, Mix‐ins and Compositions
Scala Collections
Library Frameworks

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The Basics

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Scalable Language

Very Bright Future
Functional
Purely Object Oriented
Statically Typed
JVM Language

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Martin Odersky ‐ Language Designer

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A Brief History of Scala

Make Java Better
1996 – 2000: Pizza, GJ and javac

Make a Better Java
2003 : The Scala 1.0 Experiment
2005 : Scala 2.0, written in Scala
2006‐2011: Industrial strength

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A Java Class
public class Person {
public final String firstName, lastName;
public final float height;
public final int age;

public Person( String firstName,
String lastName,
float height, int age ) {
this.firstName; this.lastName = lastName;
this.height = height; this.age = age;
}
}
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Equivalent Scala class
class Person (
val firstName: String
val lastName: String,
val height: Float,
val age: Int ) { }

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Filtering Data with Java
import java.util.ArrayList;
Person[] people = getPeople();
Person[] tallFolk;
Person[] shortFolk;
{
ArrayList<Person> tallList = new ArrayList<Person>();
ArrayList<Person> shortList = new ArrayList<Person>();
for ( int j=0; j<people.length; ++j) {
(people[j].height < 5.0 ? shortList : tallList )
.add( people[j] );
}
shortFolk = smallList.toArray( people );
tallFolk = tallList.toArray( people );
}

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And in Scala
val people: Array[Person] = getPeople()

// Type inference
val ( smallFolk, bigFolk ) =
people partition ( _.height < 5.0 )

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Semicolon is optional

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Vals
and
Vars

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Variables
Two Types of variables:
val a immutable variable
var a re‐assignable variable

val s1 = “Purple Haze” // Type inference String
var s2 = “Barcelo”
s1 = “Hotel” // Won’t compile
s2 = “Electricona” // Ok!

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Variables Type Inferences
val s3: String = “Purple Haze”
val f1: Double = 3.141596527
val fruit = List(“orange”,”apple”)
// scala.collection.immutable.List[String]
val capitals = Map(“USA”-> “Washington”,
”Wales” -> “Cardiff”, “Germany” -> “Berlin”
)
// scala.collection.immutable.Map[String, String]

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Scope
val s1 = “Purple Haze”
{
val s1 = “Day Tripper”
println( s1 ) // "Day Tripper"
}
println( s1 ) // "Purple Haze"

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Scala Identifiers

Four forms of Scala identifiers
Alphanumeric: A letter followed by a sequence of
letters or digits
_ count as a letter (but single _ is reserved)
$ is reserved for system use
Operator: One of more symbolic characters such
+ , *, /, ‐ , %, #, !
Mixed: gamma_!
Quoted: any character sequence in back‐quotes:
`yield`

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Basic Scala Literals
Integer: 1, 882, ‐1
Boolean: true, false
Double: 1.0, 1d, 1e3, 1.234e‐6
Long: 42L
Float: 19.73f
Characters: ‘6’, ‘@’, ‘?’, `K’
String: “Hello world”

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Express
Yourself

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Expressions == Results
val msg = “Macro Economics”
val hasA =
if ( msg contains ‘a’)
“yes”
else
“no”
println(hasA) // “yes”

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Expressions On Everything
val z1 =
try {
“play havoc”
}
finally {
“yes”
}
// z1 is “yes”

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Expressions Initialise Vals
val powerSeries = {
var x = 2.0;
var sum = 1.0
for ( c <- 1 to 7 ) yield {
sum += x; x = x * x; sum
}
}
// scala.collection.immutable.IndexedSeq[Double]
= Vector(3.0, 7.0, 23.0, 279.0, 65815.0,
4.295033111E9, 1.8446744078004584E19)

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How To Declare Functions
def volumePrice( price: Float, vol: Int ): Float = {
if ( vol >= 1000 )
price * 0.90
else if ( vol >= 100 )
price * 0.95
else
price
}

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Functions Written Concisely
def max( x: Double, y: Double ): Double
= if ( x > y) x else y

def min( x: Double, y: Double ): Double
= if ( x < y) y else x

// type inference on the return type: Double
def cube( x: Double ) = x * x * x

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Procedures and The Unit Type
def sideEffect(): Unit = println(“Say hi!”)
// sayHi: ()Unit

sideEffect() // prints “Say hi!”

• Unit has a value, written as ()
• Unit roughly corresponds to void in Java

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Classes

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How To Declare Classes
class Foo
val f1 = new Foo()
val f2 = new Foo

class Bar ( val name: String )
val b1 = new Bar(“Twix”)
val b2 = new Bar(“Curly-Wurly”)

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The Primary Constructor
class Person (
val firstName: String
val lastName: String,
val height: Float,
val age: Int ) {
if ( age < 0 )
throw new Exception("age?")
if ( height <= 0.5 )
throw new Exception("height?")
}

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Class ‐ Better Style
class Person (
val firstName: String, val lastName: String,
val height: Float, val age: Int ) {
require( age > 0, "age > 0" )
require( height >= 0.5, "height >= 0.5" )

override def toString = "%s %s %3d %5.2f (ft)".
format( firstName, lastName,
age, height )
}

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Class ‐ Auxiliary Constructors
class Complex( real: Float, imag: Float {
def this() = this(0)
def this( r: Float ) = this ( r, 0 )
def this( r: String ) =
this ( java.lang.Float.parseFloat(r), 0 );
def this( r: String, i: String ) =
this ( java.lang.Float.parseFloat(r),
java.lang.Float.parseFloat(i) )
// ...
}

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Built‐In Control Structures #1

var x1 = 3.0
var r1 = if ( x1 >= 0 )
"positive" else "negative"

x1 = -9.25
println( if ( x1 < 0 )
"negative" else "positive" )

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Built‐In Control Structures #2

While ... Do Do ... While
var c1 = 0 var c2 = 0
var y1 = "" var y2 = ""
while ( c1 < 4 ) { do {
y1 = y1 + "#" + c1 y2 = y2 + "#" + c2
c1 += 1 c2 += 1
} }
println(y2) while ( c2 < 4 )
println(y2)

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Scala Fixes Java Mishaps

Scala Removes Scala Innovates
Break and Continue Operator overloading
Static members Function objects
Primitive types Companion Objects
Special treatment of Case classes
interfaces User control abstractions
Mix‐ins
Pattern matching
Implicit conversions

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Infix Operators in Classes
class Complex( val re:Float, val im: Float ) {
def +( x:Complex ): Complex = {
new Complex( this.re + x.re, this.im + x.im )
}
def -( x:Complex ): Complex = {
new Complex( this.re - x.re, this.im - x.im )
}
// ...
override def toString = re +
(if (im < 0 ) "-" +(-im) else "+" +im )+"i"
}

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Using Operator Overloading
val z1 = new Complex(3,4)
val z2 = new Complex(1,2)
val z3 = z1 + z2 // = z1.+(z2)
val z4 = z1 * z2 // = z1.*(z2)
val z5 = z1 - z2 // = z1.-(z2)
val z6 = z1 / z2 // = z1./(z2)

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Infix Operator Associativity
Normally expressions associate from LEFT to RIGHT
val x = 1 + 2 + 3 + 4
val x = ((1 + 2) + 3 ) + 4

Except for those operators that end with a colon(:)
They associate from RIGHT to LEFT
val list = 1 :: 2 :: 3 :: 4 :: Nil
val list = 1 :: ( 2 :: ( 3 :: (4 :: Nil )))

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Companion Objects
• Represents a single instance of a class
• Serves the analogous role of “static” in Java
• Frequently defines two methods apply() and
unapply() for factories and extraction

object Complex {
val i = new Complex( 0, 1 )

def apply( re: Float, im: Float ) =
new Complex( re, im )
}

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Comprehensions
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For‐Loop Expressions
for ( j <- 1 to 4 )
println( "Iteration "+j )
// Iteration 1 .. 4

for ( j <- 1 until 4 )
println( "Iteration "+j )
// Iteration 1 .. 3

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Looping Over Collections

val fruits = List("apple",
"orange","pear",
"kiwi", "plum" )
for ( fruit <- fruits )
println( fruit )

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For‐Filter Comprehensions
for ( trade <- trades
if trade.tradeType == "FX" &&
trade.amount >= 75000 &&
trade.counterparty.toUpperCase
.startsWith("North")
)
processLayerDown( trade )

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For‐Nested‐Filter Comprehension

for ( trade <- trades
if trade.tradeType == "MM" ;
if trade.origin == "Summit";
settlement <- trade.settlements
settlement.exists( _.name == Standard )
)
settleStandard( settlement )

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Function Objects

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Function Object ‐ Long Hand
val isEven = new Function1 [ Int, Boolean ] {
def apply( k: Int ) = k % 2 == 0
}

Syntactic definition for function type that:
• Accepts an Integer parameter
• Returns a Boolean value
• Defines a method called apply to invoke the
function definition.

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First‐Class Functions

val isEven: (Int => Boolean) = (k: Int) => k % 2 == 0

// The verbose short‐hand notion

Functions are values, values are object
Ergo, functions are objects in Scala

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First‐Class Functions

val isEven = (k: Int ) => k % 2 == 0

// The short‐hand notion
// Scala infers the function type for the LHS

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Calling Function Objects
isEven.apply(24) // true

isEven(11) // false

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Filter Out Even Numbers
val numbers = List(0,1,2,3,4,5,6,7)
// List[Int] = List(0,1,2,3,4,5,6,7)

numbers.filter( isEven )
// List[Int] = List(0,2,4,6)

Apply the function object isEven to all
members of the sequence

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numbers.filter( (k: Int) => k % 2 == 0 )
// in-lined function value:
// List[Int] = List(0,2,4,6)

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numbers.filter( k => k % 2 == 0 )
// 0,2,4,6

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numbers.filter( _ % 2 == 0 )
// 0,2,4,6

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Function Object Summary

( x: Float ) => sin(pi * x)
/ (pi * x )

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Closures

( x: Float ) => extra +
sin(pi * x) / (pi * x )

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Real World Closures
var extra = computeFudgeFactor()

reactions += {
case e:MouseClicked =>
plotXY( -1.0, 1.0, -2.0, 2.0,
( x: Float ) =>
extra + sin(pi * x) / (pi * x ) )
}

The variable extra defined in the enclosing scope is
bounded to the lexical scope of the function
object.

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Closure Lexical Scope
var extra = 4
val addExtra = (x: Int) => x + extra

addExtra(2) // 6
extra = 7
addExtra(2) // 9

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Curried Functions

( x: Float )( y: Float ) =>
y * cos ( sin (pi * x ) )

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Functions Can Return Functions

def foo1( x: Float)(y: Float ) = x*y-2*x

def foo1( x: Float) = { (y: Float ) => x*y-2*x }

val a1 = foo1( 3 ) ( 4 ) // a1 is 6.0

val a2 = foo1( 3 )
// a2 is (Float) => Float = <function1>
val a3 = a2(4) // a3 = 6.0

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Parameterised Types

class Holder [T] ( val value: T )

val chipBox = new Holder( 555 )
val z1 = chipBox.value // 555

val fruitBox = new Holder( "apple" )
val z2 = fruitBox.value // “apple”

fruitBox.value = "orange" // re-assign error
chipBox.value = 73 // re-assign error

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Call‐By‐Value versus Call‐By‐Name

Call By Value Call By Name
Expression are evaluated   Expressions are evaluated
before being passed as a inside the function
parameter to a function Computational nice
Useful for library writers to
create custom control
abstractions

def debug( s: String ):Unit def debug( s:  => String ):Unit

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Custom Control Abstractions
def using[ T <: { def close() }, A ]
( closable: T ) ( body: T => A ) = {
try {
body( closable )
} finally {
if ( closable != null ) {
try { closable.close() } catch {
case e: Exception => // Log this error
}
}
}
}
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Closures As Control Abstraction
import java.io._
val file = new File( "poem.txt" )

using(
new BufferedReader(
new FileReader( file )) ) {
r => println( r.readLine() )
}

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Pattern Matching

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Case Classes

Convenience data types for pattern matching
Scala compiler creates :
Class with hashCode(), equalsTo(), copy() methods
Nice toString() method
Defaults to immutable data members
Companion object
Defines apply() and unapply() (extractor) methods

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Case Classes
case class Stock( name: String, size: Int )

val st1 = Stock( "EDH", 15000 )
val st2 = Stock( “XNF", 40000 )
val nameAndValue = st2.name + “ “ +st1.value
// “EDH 15000”
val st3 = st2.copy()
val st4 = st3.copy( name = "AXA")

assert( st2 == st3 ) // true
assert( st2 != st4 ) // true

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Pattern Matching on Types
val list = List( 1967, "Legacy", '£', 51.50F )

for ( e <- list ) {
e match {
case f: Float => println("A decimal "+f )
case s: String => println("A string "+s )
case c: Char => println("A character "+c )
case _ => println("I do not know “+e )
}
}

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Pattern Matching on Sequences
val list = List( 1967, "Legacy", '£', 51.50F )

list match {
case 1967 :: _ :: ‘£’ :: _ => println("got it")
case _ => println("not found" )
}

list match {
case List( 1967, "Legacy", _* ) => println("got
two" )
case _ => println("not found")
}

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Pattern Matching Algorithms
def fib( n: Int ): Long = {
n match {
case 0 => 0
case 1 => 1
case n => fib(n-2) + fib(n-1)
}
}

val z1 = fib(3) // 2

val series = (0 to 25).map( fib _ ).mkString("n")

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Case Classes Abstract Data Types

abstract class BinTree[T]

case object Empty extends BinTree

case class Node (
elem: T, left: BinTree[T], right: BinTree[T]
) extends BinTree

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Pattern Matching Algorithm
// Traverse tree in-order by algorithmic cases
def inOrder[T]( n: BinTree[T] ) : List[T] = {
n match {
case Empty => List()
case BinTree(e,l,r) =>
inOrder(l) ::: List(e) ::: inOrder(r)
}
}

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Pattern Matching Algorithm
// Recursively find the depth of the binary tree
def depth[T]( n: BinTree[T] ): Int = {
n match {
case Empty => 0
case Node( _, Empty, r ) => 1 + depth(r)
case Node( _, l, Empty ) => 1 + depth(l)
case Node( _, l, r ) =>
Math.max( depth(l), depth(r)) + 1
}
}

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Composition

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Traits and Mix‐ins

Trait is provides composition of behaviour
type in Scala
Traits can define abstract methods
Traits can define implementation methods
Traits can define data members
Linearisation of behaviour is prioritised from
left to right
Traits can inherit from other traits

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Mix‐Ins and Traits
trait Vehicle
trait Car extends Vehicle
trait Bicycle extends Vehicle
trait Motorcycle extends Vehicle
trait Powered
trait HasWheels

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Mix‐In Composition
class Ford extends Car with Powered with HasWheels

class Chopper extends Bicycle with HasWheels

val myCar = new Ford
val myBike = new Chopper

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Mix‐Ins Refactored
trait Powered {
def kickdown() = "Vrroom!!"
}

trait HasWheels {
def turn() = "Wheels are turning"
}

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Mix‐ins Refactored #2
trait Vehicle
trait Car extends Vehicle with HasWheels
with Powered
trait Bicycle extends Vehicle with HasWheels
trait Motorcycle extends Vehicle with HasWheels
with Powered

trait Bus extends Car
trait Truck extends Car
trait SUV extends Car

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Motorway Responsibility
def motorway( x: Vehicle with Powered ) =
println( "on the motorway: " +x.kickdown )

val aCar = new Ford
val aBike = new Chopper

motorway( aCar ) // Ok
motorway( aBike ) // Won’t compile!

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Collections

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Immutable Lists
scala.collection.immutable.List

• Insertion at front O(1)
• Insertion at end O(n)

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Creating List Collections
import scala.collection.immutable.List

val xs0 = List(1,2,3,4)

val xs1 = 1 :: 2 :: 3 :: 4 :: Nil

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Creating Nested Lists
val xs2 = ( 1 :: 2 :: 3 :: Nil) ::
( 4 :: 5 :: Nil ) ::
( 6 :: Nil ) ::
Nil

// xs2: List[List[Int]] =
List(List(1, 2, 3), List(4, 5), List(6))

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List Functions
val list = List(1,2,3,4,5)

val z0 = list.head // 1
val z1 = list.tail // List(2,3,4)
val z2 = list.isEmpty // false
val z3 = list.size // 4

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Higher Order Operations
val list = List(1,2,3,4,5)

val z0 = list.last // Int 5
val z1 = list.map( _ + 3 ) // List( 4,5,6,7,8 )
val z2 = list.take( 2 ) // List(1,2)
val z3 = list.drop( 2 ) // List(3,4,5)
val z4 = list.slice( 2,4 ) // List(3,4)
val z5 = list.reverse // List(5,4,3,2,1)
val z7 = list.contains(3) // true
val z8 = list.filter( _ < 3 ) // List( 1,2 )

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Sorting List Collections
val xs = List( 11, 7, 2, 15, 9, 1 )

val x0 = xs.sort( _ < _ )
// List[Int](1, 2, 7, 9, 11, 15)

val x1 = xs.sort( _ > _ )
// List[Int](15, 11, 9, 7, 2, 1)

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More Higher Operations
val xs = List( "apple", “plum", "orange" )
val z0 = xs.zipWithIndex
// List((apple,0), (plum,1), (orange,2))

val ys = List( "usa", "uk", "france" )
val z1 = xs zip ys
// List((apple,usa), (plum,uk), (orange,france))

val zs = List( List(1,2,3), List(4,5), List(6))
val z2 = zs flatten
// List(1, 2, 3, 4, 5, 6)

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Map Collections Types
var capitals = Map( "England" -> "London",
"Scotland" -> "Edinburgh", "Wales" -> "Cardiff",
"Northern Ireland" -> "Belfast" )

capitals += ( "Brasil" -> "Brasilia" )
val z0 = capitals( "Brasil“ ) // “Brasilia”
val z1 = capitals.isEmpty // false
val z2 = capitals.size // 4

for ( (k,v) <- capitals )
println("Capital of "+k+" is "+v )

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Set Collections Types
import scala.collection.immutable.SortedSet
var xs = SortedSet( 3,2,1 )
println(xs) // TreeSet(1,2,3 )
xs += 4
xs += 3
println(xs) // TreeSet(1,2,3,4 )
xs -= 2
println(xs) // TreeSet(1,3,4 )
xs ++= List( 5,6)
println(xs) // TreeSet(1,2,4,5,6 )

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Implicit Conversions

“Can you make an ADT from a library and make
it look just like it is part of the language?”,
Guy Steele, Benchmark of Languages

Implicit informs the compiler about a custom
default conversion method
Power enabler for writing embedded DSL in
Scala

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Declare Implicit Conversions
object Complex {
implicit def doubleToComplex( x: Double ) =
new Complex( x, 0 )

val i = new Complex( 0, 1 )

def apply( re: Float, im: Float ) =
new Complex( re, im )
}

XeNoNiQUe.co.uk (c) 2011 4/14/2011 92

Using Implicit Conversion
import xenonique.numerics.Complex

val z1 = new Complex( 4.7, -2.3 )
val z4 = 2 + c1
val z2 = 2.50 * c1
val z3 = (2.50).*(c1)

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Tools

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Builders

Scala – Launcher / REPL
Scalac ‐ Compiler
Scaladoc – Documentation Generator
SBT ‐ Simple Build Tool
Maven Scala Plug‐in
Apache Ant Plug‐In
Gradle

XeNoNiQUe.co.uk (c) 2011 4/14/2011 95

Tools ‐ IDEs

Intellij IDEA v10.2
Eclipse Helios v3.6
Net Beans v7.0
Emacs
JEdit, NotePad++, TextPad, TextMate

XeNoNiQUe.co.uk (c) 2011 4/14/2011 96

Tools ‐ Frameworks

Testing Domain Specific

Scala Test Lift
Specs Akka
Scala Check Play!
Camel DSL
Wicket
Squeryl, Pinky, Sweet

XeNoNiQUe.co.uk (c) 2011 4/14/2011 97

End Game
XeNoNiQUe.co.uk (c) 2011 4/14/2011 98

Breaking The Mono‐Culture

“Do not throw the baby out with the bath water
by clinging to a Java‐only monoculture approach:
it matters not that what current systems are
written in, when running on the JVM, only what
happens in the future”
Dr. Russel Winder, Consultant
http://groups.google.com/group/javaposse
Thread: “Your Experience of Alternative JVM Languages
in Organisations, Divisions and Teams”

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Beyond Java Today

XeNoNiQUe.co.uk (c) 2011 4/14/2011 100

Beyond Java Future 2016?

XeNoNiQUe.co.uk (c) 2011 4/14/2011 101

Scalable Language

Powerful
Comprehensive
Deep Language
Responsible
Expressive Concise

XeNoNiQUe.co.uk (c) 2011 4/14/2011 102

Learn more

http://xenonique.co.uk/blog/
peter.pilgrim@gmail.com
http://scala‐lang.org/
twitter:peter_pilgrim

XeNoNiQUe.co.uk (c) 2011 4/14/2011 103

Professional Services

peter.pilgrim@gmail.com
Scala Adoption in Enterprises
Contracting
Training with Consultancy
Technical Leadership

XeNoNiQUe.co.uk (c) 2011 4/14/2011 104

Introduction to Scala
The Object‐Functional Programming Language

Peter Pilgrim
Java Champion ‐Java EE specialist w/ Scala enthusiasm
XeNoNiQUe.co.uk/blog

XeNoNiQUe.co.uk (c) 2011 4/14/2011 105

Recommended References
Programming in Scala by Martin Odersky, Lex Spoon, Bill Venners ; Artima;
2nd Edition 2010 http://www.artima.com/shop/programming_in_scala
Programming Scala by Wampler, Payne; O’Reilly; 2010; http://programming‐
scala.labs.oreilly.com/
Beginning Scala by David Pollak; Apress; 2009;
http://www.apress.com/book/view/1430219890
Steps in Scala by Loverdos , Syropoulos; Cambridge Univ Press; 2010;

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Popular Scala Frameworks
Scala Test http://www.scalatest.org/
Scala Check https://www.ohloh.net/p/scalacheck
Lift http://www.liftweb.net/
Akka http://akka.io/
Play! Scala module http://www.playframework.org/modules/scala
Camel DSL http://camel.apache.org/scala‐dsl.html
Squeryl http://squeryl.org/
Pinky https://github.com/pk11/pinky/wiki
Sweet [Scala] http://code.google.com/p/sweetscala/

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Attributions
All images are Creative Commons (CC) License from Flickr.com
– “You must attribute the source and you cannot change the content”

Tim Ellis http://www.flickr.com/photos/tim_ellis/
Lego Basics http://www.flickr.com/photos/tim_ellis/338755101/sizes/l/

*PaysImaginaire* http://www.flickr.com/photos/nevrlndtink/
Variable Plastic Bag http://www.flickr.com/photos/nevrlndtink/232906118/sizes/m/

~Deiby http://www.flickr.com/photos/deiby/
Expression http://www.flickr.com/photos/deiby/5489382677/sizes/l/

Lisa Sinclair http://www.flickr.com/photos/plumandjello/
fruit http://www.flickr.com/photos/plumandjello/2333263539/sizes/l/

Nerovivo http://www.flickr.com/photos/dominik99/
http://www.flickr.com/photos/dominik99/407716865/sizes/z/in/photostream/

XeNoNiQUe.co.uk (c) 2011 4/14/2011 108

Attributions
All images are Creative Commons (CC) License from Flickr.com
– “You must attribute the source and you cannot change the content”

.Guilty http://www.flickr.com/photos/roll_initiative/
Arbitrary Function Generator http://www.flickr.com/photos/roll_initiative/3278642272/

Loop Oh Rupert Grazer http://www.flickr.com/photos/loop_oh/
Pattern at the Senckenberg Museum in Frankfurt am Main / Germany. http://www.flickr.com/photos/loop_oh/4571485915/

Lili Vieira de Carvalho, Vancouver, Canada http://www.flickr.com/people/lilivc/
Composition of Bowls http://www.flickr.com/photos/lilivc/367582911/sizes/l/

Mykl Roventine http://www.flickr.com/people/myklroventine/
19/365 Game Over http://www.flickr.com/photos/myklroventine/3210068573/sizes/l/

superciliousness / Bentley Smith http://www.flickr.com/people/superciliousness/
200510 carpenter's tools ‐ inside the workman's shed ‐ all his old tools http://www.flickr.com/photos/superciliousness/57486288/

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ACCU 2011 Introduction to Scala: An Object Functional Programming Language

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ACCU 2011 Introduction to Scala: An Object Functional Programming Language