Make decisions with if and else

Introduction to Scala

David Venturi

Curriculum Manager, DataCamp

A program for playing Twenty-One

Variables

val fourHearts: Int = 4
var aceClubs: Int = 1

Collections

val hands: Array[Int] = new Array[Int](3)`

Functions

// Define a function to determine if hand busts
def bust(hand: Int) = {
  hand > 21
}

Control structures

A control structure is a block of programming that analyses variables and chooses a direction in which to go based on given parameters. The term flow control details the direction the program takes (which way program control "flows").

if/else

¹ https://en.wikiversity.org/wiki/Control_structures

A single if

// This hand's point value
val hand = 24


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

This hand busts!

A single if

// This hand's point value
val hand = 18

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

if-else control flow

def maxHand(handA: Int, handB: Int): Int = {
  if (handA > handB) handA
  else handB
}

if-else control flow

// Point values for two competing hands
val handA = 17
val handB = 19

// Print the value of the hand with the most points
if (handA > handB) println(handA)
else println(handB)

if-else control flow

// Point values for two competing hands
val handA = 17
val handB = 19

// Print the value of the hand with the most points
if (handA > handB) {
  println(handA)
}
else {
  println(handB)
}

if-else control flow

// Point values for two competing hands
val handA = 17
val handB = 19

// Print the value of the hand with the most points
if (handA > handB)
  println(handA)
else
  println(handB)

if-else control flow

// Point values for two competing hands
val handA = 17
val handB = 19

// Print the value of the hand with the most points
if (handA > handB) println(handA)
else println(handB)

if-else control flow

// Point values for two competing hands
val handA = 17
val handB = 19

// Print the value of the hand with the most points
if (handA > handB) println(handA) else println(handB)

if-else if-else

// Point values for two competing hands
val handA = 26
val handB = 20


// If both hands bust, neither wins
if (bust(handA) & bust(handB)) println(0)

// If hand A busts, hand B wins
else if (bust(handA)) println(handB)

// If hand B busts, hand A wins
else if (bust(handB)) println(handA)

// If hand A is greater than hand B, hand A wins
else if (handA > handB) println(handA)

// Hand B wins otherwise
else println(handB)

if-else if-else

// Point values for two competing hands
val handA = 26
val handB = 20

// Find and print the best hand
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)

if expressions result in a value

scala> val handA = 17

handA: Int = 17

scala> val handB = 19

handB: Int = 19

scala> val maxHand = if (handA > handB) handA else handB

maxHand: Int = 19

Relational and logical operators

Relational

Greater than: >

Less than: <

Greater than or equal to: >=

Less than or equal to: <=

Equal to: ==

Not equal to: !=

Logical

And: &&

Or: ||

Not: !

These "operators" are actually methods!

Relational

Greater than: >

Less than: <

Greater than or equal to: >=

Less than or equal to: <=

Equal to: ==

Not equal to: !=

Logical

And: &&

Or: ||

Not: !

These "operators" are actually methods!

Relational

Greater than: >

Less than: <

Greater than or equal to: >=

Less than or equal to: <=

Equal to: ==

Not equal to: !=

Logical

And: &&

Or: ||

Not: !

¹ "Future music" is an oft-used phrase within DataCamp. It means "something you want or aspire to have but not for the near future" and is of Dutch origin.

Let's practice!

Introduction to Scala