第8章：Scalaのコレクション(Seq, Set, Map)入門 ref: http://qiita.com/f81@github/items/dc79819d23ce4889d552

file0.txt

scala> val numbers = Set(1, 2, 3)
numbers: scala.collection.immutable.Set[Int] = Set(1, 2, 3)

file1.txt

scala> import scala.collection.mutable.Set
import scala.collection.mutable.Set

scala> var numbers = Set(1, 2, 3)
numbers: scala.collection.mutable.Set[Int] = Set(1, 2, 3)

file2.txt

scala> val numbers = List(1, 2, 3)
numbers: List[Int] = List(1, 2, 3)

scala> val numbers = 1 :: 2 :: 3 :: Nil
numbers: List[Int] = List(1, 2, 3)

scala> val numbers = 1 :: (2 :: (3 :: Nil))
numbers: List[Int] = List(1, 2, 3)

file3.txt

scala> val numbers = List(1, 2, 3)
numbers: List[Int] = List(1, 2, 3)

scala> numbers.tail.head
res5: Int = 2

scala> numbers.tail.tail.head
res6: Int = 3

scala> numbers.tail.tail.isEmpty
res7: Boolean = false

scala> numbers.tail.isEmpty
res8: Boolean = false

scala> numbers.tail.tail.tail.isEmpty
res9: Boolean = true

file4.txt

scala> val numbers = Set(1, 2, 3)
numbers: scala.collection.mutable.Set[Int] = Set(1, 2, 3)

scala> numbers.contains(1)
res15: Boolean = true

scala> numbers.contains(4)
res16: Boolean = false

file5.txt

scala> val colors = Map(1 -> "red", 2 -> "blue", 3 -> "black")
colors: scala.collection.immutable.Map[Int,String] = Map(1 -> red, 2 -> blue, 3 -> black

scala> colors(1)
res13: String = red

scala> colors(3)
res14: String = black