Code Chronicle: April 2016

Requirements to Run Scala

Ide: There are a couple of IDE to run scala. Depends on your own preference.

How do you define Variables in Scala

Scala doesn't need you to declare type of variables if the compiler can detect the type.
However if the type can't be inferred automatically you have to provide the type.

var num=10


var x: Int = 5

var lng: Long = 100000000L

var sht: Short = 1

var dbl: Double = 2.50

var flt: Float = 2.50f

var str: String = "Hello Scala"

var bte: Byte = 0xa

var chr: Char = 'D'

These variables are also known as mutable types. Mutable types means its values can be changed. Scala prefers you to use as little mutable types as possible.

Constants

Constants are immutable types. It essentially means that these values can't be changed. Constants are declared in Scala using the val keyword

val x=10x=20  //Wrong.. Will generate an error

Variables with No Initialization

var test:String=_

When the variable is not initialized it's type must be declared

If else construct in Scala

If else construct in scala is similar to java. However if else can also be used as an expression in scala.

val x=10if(x==10)
  println("X is equal to 10")
else  println("X is not equal to 10")

println is used for output

Generally it is a good idea to enclose your statements in { } braces.

if(x<10){
  println("Value of x ")
  println("X is less than 10")
}
else if (x >10)
{
  println("X is greater than 10")
}
else {
  println("X is equal to 10")
}

Note: You don't need a semicolon to terminate your expression in scala.

Loops

In Scala, loops are not used as often as in other languages. Instead most often the values are processed by applying a function to all values. Its known as functional programming.

Simple Loop

println("Step 1: A simple for loop from 1 to 10 ")
for(i <- 1 to 10){
  println(s"Loop Number = $i")
}

Use "until" instead of "to" to exclude the last iteration.

println("Step 1: A simple for loop from 1 to 10 ")
for(i <- 1 until 10){
  println(s"Loop Number = $i")
}

While Loop

While loop in scala is the same as Java/C++

while (x > 0) {
  r = r * n
  x -= 1}

Scala doesn't have ++ and -- increment. Instead use += or -=

Scala Lists

Scala lists are similar to arrays in a sense that they consist the same type of data.

val colors:List[String]=List("red","blue","green")

val nums:List[Int]=List(1,2,3,4)

Two Dimensional Lists

val twoDimensional: List[List[Int]] =
  List(
    List(1, 0, 0),
    List(0, 1, 0),
    List(0, 0, 1)
  )

Lists are Immutable

Lists have the following methods.

println( "Head of colors : " + colors.head )
println( "Tail of fruit : " + colors.tail )
println( "Check if fruit is empty : " + colors.isEmpty )
println( "Check if nums is empty : " + colors.isEmpty )

Lists can also be concatenated by List.concat(list1,list2,listn)
List.fill() method creates a list consisting of zero or more copies of the same element
List.reverse method reverses all elements of the list

For further info on lists visit https://www.scala-lang.org/api/2.12.3/scala/collection/immutable/List.html

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