learning scala for comprehensions

Posted 2022-04-02 lianghong881018

code:

package com.aura.scala.day01

object forComprehensions 
  def main(args: Array[String]): Unit = 
    val userBase = List(User("pan1", 29), User("pan2", 30), User("pan3", 23), User("pan5", 32))
    val twentySomethins = for (userYonger <- userBase if userYonger.age > 20 && userYonger.age < 30)
      yield userYonger.name
    twentySomethins.foreach(name => println(name))

    def foo(n: Int, v: Int) =
      for (i <- 0 until n; j <- i until n if i + j == v)
        yield (i, j)

    foo(10,10).foreach 
      case(i,j ) => println(s"($i,$j)")
    
  


case class User(name: String, age: Int)

result:

"D:\Program Files\Java\jdk1.8.0_201\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA 2019.1.3\lib\idea_rt.jar=10892:D:\Program Files\JetBrains\IntelliJ IDEA 2019.1.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\Program Files\Java\jdk1.8.0_201\jre\lib\charsets.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\deploy.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\access-bridge-64.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\cldrdata.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\dnsns.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\jaccess.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\jfxrt.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\localedata.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\nashorn.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunec.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunjce_provider.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunmscapi.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunpkcs11.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\zipfs.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\javaws.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\jce.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\jfr.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\jfxswt.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\jsse.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\management-agent.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\plugin.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\resources.jar;D:\Program Files\Java\jdk1.8.0_201\jre\lib\rt.jar;C:\Users\admin\IdeaProjects\ScalaDay\out\production\ScalaDay;C:\Program Files (x86)\scala\lib\scala-actors-2.11.0.jar;C:\Program Files (x86)\scala\lib\scala-actors-migration_2.11-1.1.0.jar;C:\Program Files (x86)\scala\lib\scala-library.jar;C:\Program Files (x86)\scala\lib\scala-parser-combinators_2.11-1.0.4.jar;C:\Program Files (x86)\scala\lib\scala-reflect.jar;C:\Program Files (x86)\scala\lib\scala-swing_2.11-1.0.2.jar;C:\Program Files (x86)\scala\lib\scala-xml_2.11-1.0.4.jar" com.aura.scala.day01.forComprehensions
pan1
pan3
(1,9)
(2,8)
(3,7)
(4,6)
(5,5)