Book info

Title: Programming in Scala, First Edition
Authors: Martin Odersky, Lex Spoon, and Bill Venners
Pages: 852
Language: English
Link: http://www.amazon.com/Programming-Scala-Comprehensive-Step-Step/dp/0981531644

Iterate with for and foreach

for

All elements:

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2
3
4 val lst = List(1, 2, 3, 4, 5)
for(i <- lst) {
  println(i)
}

Range:

1
2
3 for (i <- 0 to 2) {
  println(i)
}

foreach

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2 val lst = List(1, 2, 3, 4, 5)
lst.foreach(i => println(i))

If a function literal consists of one statement that takes a single argument, you need not explicitly name and specify the argument. Thus, the following code also works:

1 lst.foreach(println)

Collections

Arrays

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2
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4 val a1: Array[String] = new Array[String](3)
val a2 = new Array[String](3)
val a3: Array[String] = Array("zero", "one", "two")
val a4 = Array("zero", "one", "two")

Lists

Class: scala.collection.immutable.List

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2 val l1: List[Int] = List(1, 2, 3)
val l2 = List(1, 2, 3)

Concatenation

List has a method named ‘:::’ for list concatenation.

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2
3
4
5 val oneTwo = List(1, 2)
val threeFour = List(3, 4)
val oneTwoThreeFour = oneTwo ::: threeFour
println(""+ oneTwo +" and "+ threeFour +" were not mutated.")
println("Thus, "+ oneTwoThreeFour +" is a new list.")

Adding elem to the beginning

List has a method ‘::’ named ‘cons’. It adds element to the beginning of the list.

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2
3 val twoThree = List(2, 3)
val oneTwoThree = 1 :: twoThree
println(oneTwoThree)

Tuples

Like lists, tuples are immutable, but unlike lists, tuples can contain different types of elements.

Tuples are useful when you want to return more than one object from a method. Tuples are indexed from 1.

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2
3
4
5 val t1 = (1, "Jan")
val t2 = ('a', 'b', "and", 4, "five", 0x6)

println(t1._1) // returns 1
println(t2._5) // returns "five"

Sets

Classes:

scala.collection.mutable.Set
scala.collection.immutable.Set - default

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2 val s1: Set[Int] = Set(2, 1, 3)
val s1 = Set(2, 1, 3)

Maps