Scala Tutorials

ScalaBasic0.sc

val a = 4
var b = 3

// if-else
val greater_4: Boolean = a>b
if(!greater_4)
  val asquared = a*a
  asquared*2
else
  val bsquared = b*b
  bsquared*2

// in try-catch-finally finally is always run 
// but it'll not affect the returned value, 
// so only use of finally is side-effecting
try{
    val zero = y/0
  }
  catch{
    case e : ArithmeticException =>0
  }
finally{
   println("finally always runs but it'll not affect the returned value")
  42
}

ScalaBasics1.sc

println("Scala journey starts")
val first: Int = 42
println(s"around the orld in $first days")

/* As Scala is a multi-paradign including functional language, 
variables are preferred to be immutable objects to avoid undesirable 
change in values of variables.*/
val a = 4
println(f"printing 4 as double $a%.3f")
var b = 3
println(s"sum of two variabes ${a+b}")

// if-else
val greater_4: Boolean = a>b
if(!greater_4)
  println("4 is greater")
else
  println("3 is greater")

// switch
/*Automatically breaks after the match*/
/*That implies if you put the default case at some not the last option 
the control-flow will break there*/
val month="Winter"
month match{
  case "Summer" => println("Summer has come")
  case "Winter" => println("Winter has come")
  case "Autumn" => println("Autumn has come")
  case _ => println("option not present")
}

/*That implies if you put the default case at some not the last option 
the control-flow will break there*/
val number=420
number match{
  case 789 => println("Summer has come")
  case 999 => println("Winter has come")
  case _ => println("option not present")
  case 420 => println("Autumn has come")
}

var s_square = 0
// for
for(x <- 1 to 3){
  var squared = x*x
  // while
  while(squared>0){
    s_square += squared
    squared -=1;
  }
  println(s"sum of squares  with while $s_square")
  squared = x*x
  // do while
  do{
    s_square += squared
    squared -=1;
  }while(squared>0)
  println(s"sum of squares with do-while $s_square")
}
println(s"Final sum of squares $s_square")

//expression
/*{var x=10; x + 20 } - this is an expression
Bcs functional programming paradigm, here the expression has a value, value of the last statement.
This expression has a value 30.*/
println({var x=10; println("winter"); x + 20 })

ScalaBasics2.sc

def squareIt(x: Int) : Int = {
  x*x
}

//function can take other function too
def transformer(x:Int, f:Int=>Int):Int={
    x*f(x)
}

println(squareIt(9))
println(transformer(9,squareIt))

/*In place of pre defined function we can use "lambda function"/
"function literal", "anonymous function"*/
println(transformer(3,x=>x*7))
println(transformer(12,x=>{val y = x*2;y*y;}))

//To-do : the follwoing is giving undefined in return value in line 30
def transformerMegatron(y:Int) {
  try{
    val zero = y/0
  }
  catch{
    case e : ArithmeticException =>{
      println("Arithmatic exception")
    }
  }
}

println(transformerMegatron(3))

ScalaBasics3.sc

//tuple
val states = ("UP","AP","Odisha")
//can be accessed with 1 based index
println("State name "+states._3)

val capital = "Odisha"->"Bhubaneswar"
println("Capital of states "+capital._2)

val student = ("Ram",23,"BSc",true)
println(student._4)

//list
val cntry_list = List("India","US","Sweden","Uk")
//can be accessed with 0 based index
println(cntry_list(2))

for(cntry <- cntry_list){
  println(cntry)
}

println(cntry_list.head)
println(cntry_list.tail)

for(cntry <- cntry_list.reverse){
  println(cntry)
}

//reduce
val n_array = List(1,2,3,4,5)
val sum = n_array.reduce((x : Int, y:Int)=>x+y)
println(sum)

//filter
var hatingtwos = n_array.filter((x:Int)=> x!=2)
println(hatingtwos)

hatingtwos = n_array.filter(_ !=2)
println(hatingtwos)

// More list fun
val numberList = n_array
val reversed = numberList.reverse                 //> reversed  : List[Int] = List(5, 4, 3, 2, 1)
val sorted = reversed.sorted                      //> sorted  : List[Int] = List(1, 2, 3, 4, 5)
val lotsOfDuplicates = numberList ++ numberList   //> lotsOfDuplicates  : List[Int] = List(1, 2, 3, 4, 5, 1, 2, 3, 4, 5)
val distinctValues = lotsOfDuplicates.distinct    //> distinctValues  : List[Int] = List(1, 2, 3, 4, 5)
val maxValue = numberList.max                     //> maxValue  : Int = 5
val total = numberList.sum                        //> total  : Int = 15
val hasThree = hatingtwos.contains(3)            //> hasThree  : Boolean = false

val atlas = Map("India"->"NewDelhi","Canada"->"Toronto","UK"->"London")
if(atlas.contains("India")){
  println(atlas("India"))
}

val usacapital = util.Try(atlas.get("India")) getOrElse "USA not present in atlas"  //check the capital 'O' and 'E'
println(usacapital)