6. [Exercise] Flow Control in Scala

Activity

• For this activity, go ahead and import from the resource the file LearningScala2.scala

• For Scala, we can control the flow of code

• For example, if and else control flow in 1 line using Functional Programming

• You can also use if and else condition with {} syntax

    // Flow control
  
    // If / else syntax
    if (1 > 3) println("Impossible!") else println("The world makes sense.")
    //> The world makes sense.
  
    if (1 > 3) {
        println("Impossible!")
      } else {
          println("The world makes sense.")
      }

• You can also use case match for certain cases

    // Matching - like switch in other languages:
  
      val number = 3                               
    //> number  : Int = 3
  
    number match {
          case 1 => println("One")
          case 2 => println("Two")
          case 3 => println("Three")
          case _ => println("Something else")
     }
     //> Three

• This is the syntax for For Loop in Scala

    // For loops
    for (x <- 1 to 4) {
        val squared = x * x
        println(squared)
    }                                         
    //> 1
    //| 4                                              
    //| 9                                              
    //| 16

• This is the syntax for While Loop in Scala

    // While loops
  
    var x = 10                                      
    //> x  : Int = 10
  
    while (x >= 0) {
        println(x)
        x -= 1
    }                                             
    //> 10
    //| 9                                              
    //| 8                                              
    //| 7                                              
    //| 6                                              
    //| 5                                              
    //| 4                                              
    //| 3                                              
    //| 2                                              
    //| 1                                              
    //| 0

• This is the syntax for Do While Loop in Scala in 1 line using Functional Programming

    // Do While Loop
    x = 0
    //> 0
  
    do { println(x); x+=1 } while (x <= 10)
    //| 1
    //| 2
    //| 3
    //| 4
    //| 5
    //| 6
    //| 7
    //| 8
    //| 9
    //| 10

• In Scala, you can print the result returned by the expression, even while not assigning any val to it

    // Expressions
  
    // "Returns" the final value in a block automatically
    {val x = 10; x + 20}                           
    //> res0: Int = 30
  
    println({val x = 10; x + 20})            
    //> 30

Exercise

    // EXERCISE
    // Write some code that prints out the first 10 values of the Fibonacci sequence.
    // This is the sequence where every number is the sum of the two numbers before it.
    // So, the result should be 0, 1, 1, 2, 3, 5, 8, 13, 21, 34

    var prevVal = 0                          
    //> prevVal  : Int = 0
    var prevPrevVal = 1                      
    //> prevPrevVal  : Int = 1
    var i = 0                                
    //> i  : Int = 0

    do{
        println(prevVal)
        val sum = prevPrevVal + prevVal
        prevPrevVal = prevVal
        prevVal = sum
        i += 1
     } while (i < 10)                         
    //> 0
    //| 1
    //| 1
    //| 2
    //| 3
    //| 5
    //| 8
    //| 13
    //| 21
    //| 34