Sample run of chapter's interpreter examples
scala> val colors = List("red", "blue", "green") colors: List[java.lang.String] = List(red, blue, green) scala> colors.head res0: java.lang.String = red scala> colors.tail res1: List[java.lang.String] = List(blue, green)
scala> val fiveInts = new Array[Int](5) fiveInts: Array[Int] = Array(0, 0, 0, 0, 0)
scala> val fiveToOne = Array(5, 4, 3, 2, 1) fiveToOne: Array[Int] = Array(5, 4, 3, 2, 1)
scala> fiveInts(0) = fiveToOne(4) scala> fiveInts res3: Array[Int] = Array(1, 0, 0, 0, 0)
scala> import scala.collection.mutable.ListBuffer import scala.collection.mutable.ListBuffer scala> val buf = new ListBuffer[Int] buf: scala.collection.mutable.ListBuffer[Int] = ListBuffer() scala> buf += 1 res4: buf.type = ListBuffer(1) scala> buf += 2 res5: buf.type = ListBuffer(1, 2) scala> buf res6: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2) scala> 3 +=: buf res7: buf.type = ListBuffer(3, 1, 2) scala> buf.toList res8: List[Int] = List(3, 1, 2)
scala> import scala.collection.mutable.ArrayBuffer import scala.collection.mutable.ArrayBuffer
scala> val buf = new ArrayBuffer[Int]() buf: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()
scala> buf += 12 res9: buf.type = ArrayBuffer(12) scala> buf += 15 res10: buf.type = ArrayBuffer(12, 15) scala> buf res11: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(12, 15)
scala> buf.length res12: Int = 2 scala> buf(0) res13: Int = 12
scala> def hasUpperCase(s: String) = s.exists(_.isUpper) hasUpperCase: (s: String)Boolean scala> hasUpperCase("Robert Frost") res14: Boolean = true scala> hasUpperCase("e e cummings") res15: Boolean = false
object Predef { type Map[A, +B] = collection.immutable.Map[A, B] type Set[A] = collection.immutable.Set[A] val Map = collection.immutable.Map val Set = collection.immutable.Set // ... }
scala> import scala.collection.mutable import scala.collection.mutable
scala> val mutaSet = mutable.Set(1, 2, 3) mutaSet: scala.collection.mutable.Set[Int] = Set(3, 1, 2)
scala> val text = "See Spot run. Run, Spot. Run!" text: java.lang.String = See Spot run. Run, Spot. Run! scala> val wordsArray = text.split("[ !,.]+") wordsArray: Array[java.lang.String] = Array(See, Spot, run, Run, Spot, Run)
scala> val words = mutable.Set.empty[String] words: scala.collection.mutable.Set[String] = Set()
scala> for (word <- wordsArray) | words += word.toLowerCase scala> words res17: scala.collection.mutable.Set[String] = Set(spot, run, see)
scala> val map = mutable.Map.empty[String, Int] map: scala.collection.mutable.Map[String,Int] = Map()
scala> val map = mutable.Map.empty[String, Int] map: scala.collection.mutable.Map[String,Int] = Map()
scala> map("hello") = 1 scala> map("there") = 2 scala> map res20: scala.collection.mutable.Map[String,Int] = Map(hello -> 1, there -> 2)
scala> map("hello") res21: Int = 1
scala> def countWords(text: String) = { | val counts = mutable.Map.empty[String, Int] | for (rawWord <- text.split("[ ,!.]+")) { | val word = rawWord.toLowerCase | val oldCount = | if (counts.contains(word)) counts(word) | else 0 | counts += (word -> (oldCount + 1)) | } | counts | } countWords: (text: String)scala.collection.mutable.Map[String,Int] scala> countWords("See Spot run! Run, Spot. Run!") res22: scala.collection.mutable.Map[String,Int] = Map(see -> 1, run -> 3, spot -> 2)
scala> import scala.collection.immutable.TreeSet import scala.collection.immutable.TreeSet scala> val ts = TreeSet(9, 3, 1, 8, 0, 2, 7, 4, 6, 5) ts: scala.collection.immutable.TreeSet[Int] = TreeSet(0, 1, 2, 3, 4, 5, 6, 7, 8, 9) scala> val cs = TreeSet('f', 'u', 'n') cs: scala.collection.immutable.TreeSet[Char] = TreeSet(f, n, u)
scala> import scala.collection.immutable.TreeMap import scala.collection.immutable.TreeMap scala> var tm = TreeMap(3 -> 'x', 1 -> 'x', 4 -> 'x') tm: scala.collection.immutable.TreeMap[Int,Char] = Map(1 -> x, 3 -> x, 4 -> x) scala> tm += (2 -> 'x') scala> tm res30: scala.collection.immutable.TreeMap[Int,Char] = Map(1 -> x, 2 -> x, 3 -> x, 4 -> x)
scala> val people = Set("Nancy", "Jane") people: scala.collection.immutable.Set[java.lang.String] = Set(Nancy, Jane) scala> people += "Bob" <console>:11: error: reassignment to val people += "Bob" ^
scala> var people = Set("Nancy", "Jane") people: scala.collection.immutable.Set[java.lang.String] = Set(Nancy, Jane) scala> people += "Bob" scala> people res34: scala.collection.immutable.Set[java.lang.String] = Set(Nancy, Jane, Bob)
scala> people -= "Jane" scala> people ++= List("Tom", "Harry") scala> people res37: scala.collection.immutable.Set[java.lang.String] = Set(Nancy, Bob, Tom, Harry)
// In file collections/Capitals.scala var capital = Map("US" -> "Washington", "France" -> "Paris") capital += ("Japan" -> "Tokyo") println(capital("France"))
// In file collections/Capitals.scala import scala.collection.mutable.Map // only change needed! var capital = Map("US" -> "Washington", "France" -> "Paris") capital += ("Japan" -> "Tokyo") println(capital("France"))
scala> var roughlyPi = 3.0 roughlyPi: Double = 3.0 scala> roughlyPi += 0.1 scala> roughlyPi += 0.04 scala> roughlyPi res40: Double = 3.14
scala> List(1, 2, 3) res41: List[Int] = List(1, 2, 3) scala> Set('a', 'b', 'c') res42: scala.collection.immutable.Set[Char] = Set(a, b, c) scala> import scala.collection.mutable import scala.collection.mutable scala> mutable.Map("hi" -> 2, "there" -> 5) res43: scala.collection.mutable.Map[java.lang.String,Int] = Map(hi -> 2, there -> 5) scala> Array(1.0, 2.0, 3.0) res44: Array[Double] = Array(1.0, 2.0, 3.0)
scala> import scala.collection.mutable import scala.collection.mutable scala> val stuff = mutable.Set(42) stuff: scala.collection.mutable.Set[Int] = Set(42) scala> stuff += "abracadabra" <console>:15: error: type mismatch; found : java.lang.String("abracadabra") required: Int stuff += "abracadabra" ^
scala> val stuff = mutable.Set[Any](42) stuff: scala.collection.mutable.Set[Any] = Set(42)
scala> val colors = List("blue", "yellow", "red", "green") colors: List[java.lang.String] = List(blue, yellow, red, green)
scala> import scala.collection.immutable.TreeSet import scala.collection.immutable.TreeSet scala> val treeSet = TreeSet(colors) <console>:15: error: could not find implicit value for parameter ord: Ordering[List[java.lang.String]] val treeSet = TreeSet(colors) ^
scala> val treeSet = TreeSet[String]() ++ colors treeSet: scala.collection.immutable.TreeSet[String] = TreeSet(blue, green, red, yellow)
scala> treeSet.toList res50: List[String] = List(blue, green, red, yellow)
scala> treeSet.toArray res51: Array[String] = Array(blue, green, red, yellow)
scala> import scala.collection.mutable import scala.collection.mutable scala> treeSet res52: scala.collection.immutable.TreeSet[String] = TreeSet(blue, green, red, yellow) scala> val mutaSet = mutable.Set.empty ++= treeSet mutaSet: scala.collection.mutable.Set[String] = Set(yellow, blue, red, green) scala> val immutaSet = Set.empty ++ mutaSet immutaSet: scala.collection.immutable.Set[String] = Set(yellow, blue, red, green)
scala> val muta = mutable.Map("i" -> 1, "ii" -> 2) muta: scala.collection.mutable.Map[java.lang.String,Int] = Map(ii -> 2, i -> 1) scala> val immu = Map.empty ++ muta immu: scala.collection.immutable.Map[java.lang.String,Int] = Map(ii -> 2, i -> 1)
// In file collections/Misc.scala (1, "hello", Console)
def longestWord(words: Array[String]) = { var word = words(0) var idx = 0 for (i <- 1 until words.length) if (words(i).length > word.length) { word = words(i) idx = i } (word, idx) }
scala> val longest = | longestWord("The quick brown fox".split(" ")) longest: (String, Int) = (quick,1)
scala> longest._1 res53: String = quick scala> longest._2 res54: Int = 1
scala> val (word, idx) = longest word: String = quick idx: Int = 1 scala> word res55: String = quick
scala> val word, idx = longest word: (String, Int) = (quick,1) idx: (String, Int) = (quick,1)
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