programming_languages:scala

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programmiersprachen:scala [2015/10/10 16:51] – [Control structures] phreazerprogrammiersprachen:scala [2017/02/19 15:36] – phreazer
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-Scala+====== Scala ======
  
-**Sca**lable **la**nga 
  
-====== Start ======+**Sca**lable **la**nguage 
 + 
 +===== Start ===== 
  
   * No primitive types, everything is an object   * No primitive types, everything is an object
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-===== Hello World =====+==== Hello World ====
 <code scala> <code scala>
 object HelloWorld { object HelloWorld {
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 ==== for loop ==== ==== for loop ====
 +<code scala>
 for (i <- 1 to 10) println(i) for (i <- 1 to 10) println(i)
 +</code>
  
 +
 +<code scala>
 +
 +// different steps
 +for (i <- 4 to (17,3)) println(i)
 +// other data types than int
 +for (s <- myList) println(s)
 +
 +// multiple generators
 +for (i <- 0 to 2; j <- 3 to 4) println(i+" "+j)
 +
 +// filter
 +    for {i <- 1 to 6         
 +         j <- 1 to 6
 +         if (i % 2 == 0)
 +         if (j % 2 != 0)} println(i+" "+j)
 +// yield
 +    val list: List[Int] = List(1,2,3,4)
 +    val result = for (i <- list) yield i * 2
 +    println(result)
 +</code>
 ==== match ==== ==== match ====
 +Implizites break
  
 <code scala> <code scala>
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 } }
 </code> </code>
 +
 +===== Singleton objects =====
 +
 +There are no static methods/vars in scala and singleton objects can't be constructed using a constructor with new.
 +<code scala>
 +object ScalaObject {
 +
 +  val b = 5
 +  
 +  def test(a: Double) : Double = {
 +    3.* + b 
 +  }
 +}
 +</code>
 +
 +===== Companion object =====
 +
 +Prerequisite: object and class have the same name and are defined in the same file. Companion objects can access their private variables. Singleton objects without companion clases are standalone objects.
 +
 +===== Case classes =====
 +
 +  * Use a factory method for construction
 +  * All passed parameters are a val-variable of the class
 +  * Can be used for pattern matching
 +  * Implement toString, hashCode, equals and have a copy method
 +
 +<code scala>
 +case class Person (firstName : String, lastName : String, age : Int){
 +  def isAdult : Boolean = if (age >= 18) true else false
 +}
 +</code>
 +
 +===== Inheritance =====
 +
 +Scala doesn't support multiple inheritance.
 +
 +class B(arg:Int) extends A {}
 +
 +Functions can be overridden with overide before func definition.
 +
 +Overridding classes, functions or variables can be forbidden with prefix final.
 +
 +
 +==== Abstract classes ====
 +
 +Difference to Traits: Abstract classes can have constructors. A class which inherits from an abstract class can't inherit from another.
 +
 +The usage of override is optional.
 +
 +==== Packages object ====
 +
 +Objects which are visible in a whole package.
 +
 +
 +
 +===== Identity and equality =====
 +
 +==-Operator checks equality (identity in Java)
 +eq-Operator checks identity
 +
 +eq and ne are only defined for clases of type scala.AnyRef.
 +
 +
  
 ===== Learning sources ===== ===== Learning sources =====
  
 http://www.scalatutorial.de/topic143.html http://www.scalatutorial.de/topic143.html
  • programming_languages/scala.txt
  • Last modified: 2017/02/19 15:46
  • by phreazer