Basic Operators

Assignment Operator

                  let b = 10

var a = 5

a = b

// a is now equal to 10
                

                  let (x, y) = (1, 2)

// x is equal to 1, and y is equal to 2
                

                  if x = y {

    // This is not valid, because x = y does not return a value.

}
                

Arithmetic Operators

                  1 + 2       // equals 3

5 - 3       // equals 2

2 * 3       // equals 6

10.0 / 2.5  // equals 4.0
                

                  "hello, " + "world"  // equals "hello, world"
                

Remainder Operator

                  9 % 4    // equals 1
                

                  -9 % 4   // equals -1
                

Unary Minus Operator

                  let three = 3

let minusThree = -three       // minusThree equals -3

let plusThree = -minusThree   // plusThree equals 3, or "minus minus three"
                

Unary Plus Operator

                  let minusSix = -6

let alsoMinusSix = +minusSix  // alsoMinusSix equals -6
                

Compound Assignment Operators

                  var a = 1

a += 2

// a is now equal to 3
                

Comparison Operators

                  1 == 1   // true because 1 is equal to 1

2 != 1   // true because 2 is not equal to 1

2 > 1    // true because 2 is greater than 1

1 < 2    // true because 1 is less than 2

1 >= 1   // true because 1 is greater than or equal to 1

2 <= 1   // false because 2 is not less than or equal to 1
                

                  let name = "world"

if name == "world" {

    print("hello, world")

} else {

    print("I'm sorry \(name), but I don't recognize you")

}

// Prints "hello, world", because name is indeed equal to "world".
                

                  (1, "zebra") < (2, "apple")   // true because 1 is less than 2; "zebra" and "apple" are not compared

(3, "apple") < (3, "bird")    // true because 3 is equal to 3, and "apple" is less than "bird"

(4, "dog") == (4, "dog")      // true because 4 is equal to 4, and "dog" is equal to "dog"
                

                  ("blue", -1) < ("purple", 1)        // OK, evaluates to true

("blue", false) < ("purple", true)  // Error because < can't compare Boolean values
                

Ternary Conditional Operator

                  if question {

    answer1

} else {

    answer2

}
                

                  let contentHeight = 40

let hasHeader = true

let rowHeight = contentHeight + (hasHeader ? 50 : 20)

// rowHeight is equal to 90
                

                  let contentHeight = 40

let hasHeader = true

let rowHeight: Int

if hasHeader {

    rowHeight = contentHeight + 50

} else {

    rowHeight = contentHeight + 20

}

// rowHeight is equal to 90
                

Nil-Coalescing Operator

                  a != nil ? a! : b
                

                  let defaultColorName = "red"

var userDefinedColorName: String?   // defaults to nil



var colorNameToUse = userDefinedColorName ?? defaultColorName

// userDefinedColorName is nil, so colorNameToUse is set to the default of "red"
                

                  userDefinedColorName = "green"

colorNameToUse = userDefinedColorName ?? defaultColorName

// userDefinedColorName is not nil, so colorNameToUse is set to "green"
                

Closed Range Operator

                  for index in 1...5 {

    print("\(index) times 5 is \(index * 5)")

}

// 1 times 5 is 5

// 2 times 5 is 10

// 3 times 5 is 15

// 4 times 5 is 20

// 5 times 5 is 25
                

Half-Open Range Operator

                  let names = ["Anna", "Alex", "Brian", "Jack"]

let count = names.count

for i in 0..<count {

    print("Person \(i + 1) is called \(names[i])")

}

// Person 1 is called Anna

// Person 2 is called Alex

// Person 3 is called Brian

// Person 4 is called Jack
                

One-Sided Ranges

                  for name in names[2...] {

    print(name)

}

// Brian

// Jack



for name in names[...2] {

    print(name)

}

// Anna

// Alex

// Brian
                

                  for name in names[..<2] {

    print(name)

}

// Anna

// Alex
                

                  let range = ...5

range.contains(7)   // false

range.contains(4)   // true

range.contains(-1)  // true
                

Logical NOT Operator

                  let allowedEntry = false

if !allowedEntry {

    print("ACCESS DENIED")

}

// Prints "ACCESS DENIED"
                

Logical AND Operator

                  let enteredDoorCode = true

let passedRetinaScan = false

if enteredDoorCode && passedRetinaScan {

    print("Welcome!")

} else {

    print("ACCESS DENIED")

}

// Prints "ACCESS DENIED"
                

Logical OR Operator

                  let hasDoorKey = false

let knowsOverridePassword = true

if hasDoorKey || knowsOverridePassword {

    print("Welcome!")

} else {

    print("ACCESS DENIED")

}

// Prints "Welcome!"
                

Combining Logical Operators

                  if enteredDoorCode && passedRetinaScan || hasDoorKey || knowsOverridePassword {

    print("Welcome!")

} else {

    print("ACCESS DENIED")

}

// Prints "Welcome!"
                

Explicit Parentheses

                  if (enteredDoorCode && passedRetinaScan) || hasDoorKey || knowsOverridePassword {

    print("Welcome!")

} else {

    print("ACCESS DENIED")

}

// Prints "Welcome!"