Just my notes

Basic Scala

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Massimiliano Figini
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2 min read

Variables

Two kinds of variables: val (immutable, can't be reassigned once initialized) and var (mutable).
// for comments.

val two: Int = 2
var a: String = "massy"

// you can also use type inference
val one = 1

// println to print
println(one)

Functions

// define function to see if the variable hand is greater than 21
def bust(hand: Int) = {
   hand > 21
}

// call the function
println(bust(20))

Arrays and Lists

Mutable collections of values, can be updated or extended.

// I use val, so names is immutable
val names = Array("Massy", "Ceci", "Cooper")

// but arrays are mutable, so I can change a value to another of the same type
names(2) = "Alvise"

// you can use the supertype Any if you want an array with different element types
val MixedTypes = new Array[Any](3)
MixedTypes(0) = "Hello world!"
MixedTypes(1) = 2
MixedTypes(2) = true

Lists are immutable collections, can't be changed.

val OtherNames = List("Massy", "Ceci", "Cooper")

// Lists are immutable, if I want to add an element I have to create a new list
// :: is the cons operator to add a new element to the beginning of an existing List
val NewOtherNames = "Alvise" :: OtherNames 

// Nil is an empty List in Scala, so a common way to create a new list is this:
val AllNames = "Massy" :: "Ceci" :: "Cooper" :: Nil

// ::: to concatenate Lists
Val NamesNames = OtherNames ::: NewOtherNames

Control Structures

if - else

// If this hand busts, print to output
if (hand > 21) {
   println("This hand busts")
}

// If we have and else condition, no { are needed
if (handA > handB) println(handA)
else println(handB)

// we can use also elseifs
if (bust(handA) & bust(handB)) println(0)
else if (bust(handA)) println(handB)
else if (bust(handB)) println(handA)
else if (handA > handB) println(handA)
else println(handB)

Relational operators:
Greater than: >
Less than: <
Greater than or equal to: >=
Less than or equal to: <=
Equal to: ==
Not equal to: !=

Logical operators:
And: &&
Or: ||
Not: !

While Loops

// define the counter
var i = 0

// repetition
var NumRepetitions = 3

// while Loop
while (i < NumRepetition) {
   println("Hip Hip Hooray!")
   i = i+1
}

// loop over a collection (bust is our previous defined function)
var hands = Array(19,21,22)

while (i < hands.length) {
   println(bust(hands(i)))
   i = i+1
}

Foreach Loops

foreach is a method

var hands = Array(19,21,22)

// bust is the function we have defined over
hands.foreach(bust)
Scala