Scala for

• 基本形（ジェネレーター） [/2011-03-26]
• 指定回数繰り返し（to） [/2013-06-08]
• フィルター（if） [/2011-03-26]
• 値を返す（yield） [2010-12-02]
• 二重ループ [/2011-03-26]
• for式の実体 [2011-02-15]

• Scala構文全般

• plasticscafeさんのLL脳がscalaの勉強を始めたよ その18
• RoNorさんのScala 制御式メモ

• Javaのfor文

scala> for (s <- Array("a","b","c")) println(s)
a
b
c

scala> val list = List(3,4,5)
list: List[Int] = List(3, 4, 5)

scala> for (i <- list) println(i)
3
4
5

for (Integer i : list) {
  System.out.println(i);
}

scala> val r = for (i <- list) i
r: Unit = ()

scala> for (i <- list) i = 9
<console>:6: error: reassignment to val
       for (i <- list) i = 9
                         ^

scala> for (val i <- list) println(i)
warning: there were deprecation warnings; re-run with -deprecation for details
3
4
5

scala> for (i:Int <- list) println(i)
3
4
5

scala> for (i:Long <- list) println(i)
<console>:7: error: type mismatch;
 found   : (Long) => Unit
 required: (Int) => ?
       for (i:Long <- list) println(i)
                   ^

scala> val tupleList = List((1,"one"),(2,"two"),(3,"three"))
tupleList: List[(Int, java.lang.String)] = List((1,one), (2,two), (3,three))

scala> for ((n,s) <- tupleList) printf("%d = %s%n", n, s)
1 = one
2 = two
3 = three

scala> val map = Map(1 -> "one", 2 -> "two", 3 -> "three")
map: scala.collection.immutable.Map[Int,java.lang.String] = Map((1,one), (2,two)
, (3,three))

scala> for ((k,v) <- map) printf("%d = %s%n", k, v)
1 = one
2 = two
3 = three

scala> for (t <- map) println(t.getClass)
class scala.Tuple2
class scala.Tuple2
class scala.Tuple2

scala> val list = List(1->"o", 2->"t", 3->"t", 4->"f", 5->"f")
list: List[(Int, java.lang.String)] = List((1,o), (2,t), (3,t), (4,f), (5,f))

scala> for ((n, "t") <- list) println(n)
2
3

scala> for (t @ (_, "f") <- list) println(t)
(4,f)
(5,f)

for (i <- 1 to 10) {
  println(i)
}

for (int i = 1; i <= 10; i++) {
  System.out.println(i);
}

FOR I = 1 TO 10
  PRINT I
NEXT I

for (i <- 0 until 10) {
  println(i)
}

for (int i = 0; i < 10; i++) {
  System.out.println(i);
}

FOR I = 0 TO 9
  PRINT I
NEXT I

for (i <- 9 to 0 by -1) {
  println(i)
}

for (int i = 9; i >= 0; i--) {
  System.out.println(i);
}

FOR I = 9 TO 0 STEP -1
  PRINT I
NEXT I

scala> for(_ <- 1 to 3) println("zzz")
zzz
zzz
zzz

for (val i <- 1 to 10) println(i)

import scala.Predef$;
import scala.ScalaObject;
import scala.collection.immutable.Range;
import scala.runtime.RichInt;

def main(args: Array[String]) {
  val r1 = 0 to 9
  println(r1)
  val r2 = 0 until 10
  println(r2)
  val r3 = 9 to 0 by -1
  println(r3)
}

public void main(String args[]) {
  scala.collection.immutable.Range.Inclusive r1 = Predef$.MODULE$.intWrapper(0).to(9);
  Predef$.MODULE$.println(r1);
  scala.collection.immutable.Range.ByOne r2 = Predef$.MODULE$.intWrapper(0).until(10);
  Predef$.MODULE$.println(r2);
  Range r3 = Predef$.MODULE$.intWrapper(9).to(0).by(-1);
  Predef$.MODULE$.println(r3);
}

scala> for (i <- 0 until 10 if i % 2 == 0) println(i)
0
2
4
6
8

scala> for (i <- 0 until 10; if i % 2 == 0) println(i)

scala> for (i <- 0 until 10 if i%2==0; if i%3==0) println(i)
0
6

scala> for (i <- 0 until 10
     | if i % 2 == 0
     | if i % 3 == 0)
     | println(i)
0
6

scala> for (i <- 1 to 10; val n = i * i if n%3==0) println(i,n)
(3,9)
(6,36)
(9,81)

for(i <- 1 to 20; val n=i%3; val m=i%4 if n==m) println(i,n,m)

scala> for (i <- 1 to 5) yield i
res4: scala.collection.immutable.IndexedSeq[Int] = Vector(1, 2, 3, 4, 5)

scala> for (i <- 1 to 5) yield "i=" + i
res5: scala.collection.immutable.IndexedSeq[java.lang.String] = Vector(i=1, i=2,
i=3, i=4, i=5)

scala> for (s <- Array("a","b","c")) yield s
res6: Array[java.lang.String] = Array(a, b, c)

scala> for (s <- List("a","b","c")) yield s
res7: List[java.lang.String] = List(a, b, c)

scala> val map = Map(1->"one", 2->"two", 3->"three")
map: scala.collection.immutable.Map[Int,java.lang.String] = Map((1,one), (2,two)
, (3,three))

scala> for((k,v)<-map) yield k
res8: scala.collection.immutable.Iterable[Int] = List(1, 2, 3)

scala> for((k,v)<-map) yield v
res9: scala.collection.immutable.Iterable[java.lang.String] = List(one, two, thr
ee)

scala> for (i <- 1 to 2; j <- 1 to 3) printf("%d-%d%n", i, j)
1-1
1-2
1-3
2-1
2-2
2-3

scala> for (i <- 1 to 2; j <- 1 to 3) yield "%d-%d".format(i, j)
res29: scala.collection.immutable.IndexedSeq[String] = Vector(1-1, 1-2, 1-3, 2-1
, 2-2, 2-3)

scala> for (i <- 1 to 2
     |      j <- 1 to 3) printf("%d-%d%n", i, j)
<console>:2: error: ')' expected but '<-' found.
            j <- 1 to 3) printf("%d-%d%n", i, j)
              ^

scala> for (i <- 1 to 2;
     |      j <- 1 to 3) printf("%d-%d%n", i, j)

scala> for (i <- 1 to 2
     |     ;j <- 1 to 3) printf("%d-%d%n", i, j)

scala> for {i <- 1 to 2
     |      j <- 1 to 3} printf("%d-%d%n", i, j)

scala> for (i <- 1 to 2 if i%2==0; j <- 1 to 3) printf("%d-%d%n", i, j)
2-1
2-2
2-3

scala> for (i <- 1 to 2; j <- 1 to 3 if i%2==0) printf("%d-%d%n", i, j)
2-1
2-2
2-3

scala> for (i <- 1 to 2 if j%2==0; j <- 1 to 3) printf("%d-%d%n", i, j)
<console>:6: error: not found: value j
       for (i <- 1 to 2 if j%2==0; j <- 1 to 3) printf("%d-%d%n", i, j)
                           ^

scala> for (i <- 0 to 10 if i%2==0; if i%3==0; j <- 1 to 3)
     | printf("%d-%d%n", i, j)
0-1
0-2
0-3
6-1
6-2
6-3

scala> for (i <- 1 to 2 if i % 2 == 0;
     |      j <- 1 to 3 if j % 3 == 0)
     |   printf("%d-%d%n", i, j)
2-3