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Merge pull request #1179 from cmpitg/master
[scala/en] Consistent code format & some minor language corrections
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@@ -5,6 +5,7 @@ contributors:
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- ["George Petrov", "http://github.com/petrovg"]
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- ["George Petrov", "http://github.com/petrovg"]
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- ["Dominic Bou-Samra", "http://dbousamra.github.com"]
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- ["Dominic Bou-Samra", "http://dbousamra.github.com"]
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- ["Geoff Liu", "http://geoffliu.me"]
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- ["Geoff Liu", "http://geoffliu.me"]
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- ["Ha-Duong Nguyen", "http://reference-error.org"]
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filename: learn.scala
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filename: learn.scala
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---
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---
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@@ -16,15 +17,16 @@ Scala - the scalable language
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Set yourself up:
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Set yourself up:
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1) Download Scala - http://www.scala-lang.org/downloads
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1) Download Scala - http://www.scala-lang.org/downloads
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2) unzip/untar in your favourite location and put the bin subdir on the path
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2) Unzip/untar to your favourite location and put the bin subdir in your `PATH` environment variable
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3) Start a scala REPL by typing scala. You should see the prompt:
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3) Start a Scala REPL by running `scala`. You should see the prompt:
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scala>
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scala>
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This is the so called REPL (Read-Eval-Print Loop). You may type any valid
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This is the so called REPL (Read-Eval-Print Loop). You may type any Scala
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Scala expression into it, and the result will be printed. We will explain what
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expression, and the result will be printed. We will explain what Scala files
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Scala files look like further into this tutorial, but for now, let's start
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look like further into this tutorial, but for now, let's start with some
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with some basics.
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basics.
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*/
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*/
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@@ -32,10 +34,10 @@ Scala - the scalable language
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// 1. Basics
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// 1. Basics
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/////////////////////////////////////////////////
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/////////////////////////////////////////////////
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// Single line comments start with two forward slashes
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// Single-line comments start with two forward slashes
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/*
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/*
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Multi line comments, as you can already see from above, look like this.
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Multi-line comments, as you can already see from above, look like this.
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*/
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*/
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// Printing, and forcing a new line on the next print
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// Printing, and forcing a new line on the next print
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@@ -46,7 +48,7 @@ println(10)
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print("Hello world")
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print("Hello world")
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// Declaring values is done using either var or val.
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// Declaring values is done using either var or val.
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// val declarations are immutable, whereas var's are mutable. Immutability is
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// val declarations are immutable, whereas vars are mutable. Immutability is
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// a good thing.
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// a good thing.
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val x = 10 // x is now 10
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val x = 10 // x is now 10
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x = 20 // error: reassignment to val
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x = 20 // error: reassignment to val
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@@ -176,7 +178,7 @@ addWithDefault(1) // => 6
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// Anonymous functions look like this:
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// Anonymous functions look like this:
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(x:Int) => x * x
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(x: Int) => x * x
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// Unlike defs, even the input type of anonymous functions can be omitted if the
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// Unlike defs, even the input type of anonymous functions can be omitted if the
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// context makes it clear. Notice the type "Int => Int" which means a function
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// context makes it clear. Notice the type "Int => Int" which means a function
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@@ -218,19 +220,19 @@ def foo(x: Int): Int = {
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1 to 5
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1 to 5
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val r = 1 to 5
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val r = 1 to 5
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r.foreach( println )
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r.foreach(println)
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r foreach println
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r foreach println
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// NB: Scala is quite lenient when it comes to dots and brackets - study the
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// NB: Scala is quite lenient when it comes to dots and brackets - study the
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// rules separately. This helps write DSLs and APIs that read like English
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// rules separately. This helps write DSLs and APIs that read like English
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(5 to 1 by -1) foreach ( println )
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(5 to 1 by -1) foreach (println)
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// A while loops
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// A while loops
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var i = 0
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var i = 0
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while (i < 10) { println("i " + i); i+=1 }
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while (i < 10) { println("i " + i); i += 1 }
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while (i < 10) { println("i " + i); i+=1 } // Yes, again. What happened? Why?
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while (i < 10) { println("i " + i); i += 1 } // Yes, again. What happened? Why?
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i // Show the value of i. Note that while is a loop in the classical sense -
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i // Show the value of i. Note that while is a loop in the classical sense -
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// it executes sequentially while changing the loop variable. while is very
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// it executes sequentially while changing the loop variable. while is very
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@@ -239,19 +241,19 @@ i // Show the value of i. Note that while is a loop in the classical sense -
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// A do while loop
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// A do while loop
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do {
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do {
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println("x is still less than 10");
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println("x is still less than 10")
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x += 1
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x += 1
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} while (x < 10)
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} while (x < 10)
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// Tail recursion is an idiomatic way of doing recurring things in Scala.
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// Tail recursion is an idiomatic way of doing recurring things in Scala.
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// Recursive functions need an explicit return type, the compiler can't infer it.
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// Recursive functions need an explicit return type, the compiler can't infer it.
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// Here it's Unit.
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// Here it's Unit.
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def showNumbersInRange(a:Int, b:Int):Unit = {
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def showNumbersInRange(a: Int, b: Int): Unit = {
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print(a)
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print(a)
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if (a < b)
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if (a < b)
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showNumbersInRange(a + 1, b)
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showNumbersInRange(a + 1, b)
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}
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}
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showNumbersInRange(1,14)
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showNumbersInRange(1, 14)
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// Conditionals
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// Conditionals
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@@ -305,13 +307,13 @@ s(1)
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(a, 2, "three")
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(a, 2, "three")
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// Why have this?
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// Why have this?
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val divideInts = (x:Int, y:Int) => (x / y, x % y)
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val divideInts = (x: Int, y: Int) => (x / y, x % y)
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divideInts(10,3) // The function divideInts gives you the result and the remainder
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divideInts(10, 3) // The function divideInts gives you the result and the remainder
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// To access the elements of a tuple, use _._n where n is the 1-based index of
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// To access the elements of a tuple, use _._n where n is the 1-based index of
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// the element
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// the element
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val d = divideInts(10,3)
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val d = divideInts(10, 3)
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d._1
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d._1
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@@ -446,7 +448,7 @@ def matchEverything(obj: Any): String = obj match {
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case List(1, b, c) => s"Got a list with three elements and starts with 1: 1, $b, $c"
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case List(1, b, c) => s"Got a list with three elements and starts with 1: 1, $b, $c"
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// You can nest patterns:
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// You can nest patterns:
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case List(List((1, 2,"YAY"))) => "Got a list of list of tuple"
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case List(List((1, 2, "YAY"))) => "Got a list of list of tuple"
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}
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}
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// In fact, you can pattern match any object with an "unapply" method. This
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// In fact, you can pattern match any object with an "unapply" method. This
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@@ -493,7 +495,7 @@ sSquared.reduce (_+_)
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// The filter function takes a predicate (a function from A -> Boolean) and
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// The filter function takes a predicate (a function from A -> Boolean) and
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// selects all elements which satisfy the predicate
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// selects all elements which satisfy the predicate
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List(1, 2, 3) filter (_ > 2) // List(3)
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List(1, 2, 3) filter (_ > 2) // List(3)
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case class Person(name:String, age:Int)
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case class Person(name: String, age: Int)
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List(
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List(
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Person(name = "Dom", age = 23),
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Person(name = "Dom", age = 23),
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Person(name = "Bob", age = 30)
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Person(name = "Bob", age = 30)
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@@ -594,7 +596,7 @@ import scala.collection.immutable._
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import scala.collection.immutable.{List, Map}
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import scala.collection.immutable.{List, Map}
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// Rename an import using '=>'
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// Rename an import using '=>'
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import scala.collection.immutable.{ List => ImmutableList }
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import scala.collection.immutable.{List => ImmutableList}
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// Import all classes, except some. The following excludes Map and Set:
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// Import all classes, except some. The following excludes Map and Set:
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import scala.collection.immutable.{Map => _, Set => _, _}
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import scala.collection.immutable.{Map => _, Set => _, _}
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@@ -629,13 +631,8 @@ writer.close()
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## Further resources
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## Further resources
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[Scala for the impatient](http://horstmann.com/scala/)
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* [Scala for the impatient](http://horstmann.com/scala/)
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* [Twitter Scala school](http://twitter.github.io/scala_school/)
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[Twitter Scala school](http://twitter.github.io/scala_school/)
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* [The scala documentation](http://docs.scala-lang.org/)
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* [Try Scala in your browser](http://scalatutorials.com/tour/)
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[The scala documentation](http://docs.scala-lang.org/)
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* Join the [Scala user group](https://groups.google.com/forum/#!forum/scala-user)
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[Try Scala in your browser](http://scalatutorials.com/tour/)
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Join the [Scala user group](https://groups.google.com/forum/#!forum/scala-user)
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