iOS Swift Basics Swift Operators Unary Operators

Hai Huang
Hai Huang
12,675 Points
Posted by Hai Huang
Hai Huang
12,675 Points

Why are the unary operators unary operators?

(Maybe the title is a little stupid..)

I completely understand the usages of the unary operators introduced in this video, but some of them seem to me binary operators.

Let's say for an example.

var a: Int = 1

a += 1 a -= 1

In the two lines above, both "+=" and "-=" seem to me binary operators because they connect two operands (a and 1) and are located in between as infix.

Well, the negating operator (var a: Bool = true; a = !a) is for me a unary operator because it only affects one operand (a).

1 Answer

Michael Hulet
MOD
Michael Hulet
Treehouse Moderator 47,742 Points
Michael Hulet
Michael Hulet
Treehouse Moderator 47,742 Points

Your concept of unary and binary operators is correct. I don't know why the mathematical assignment operators were listed as unary operators in this video, because they're actually binary operators, as you suspected. There are only 3 unary operators in Swift by default:

  • The logical negation operator (!). This inverts a boolean expression, so !true is false, and !false is true
  • The mathematical negation operator (-). This makes a positive number negative, and a negative number positive (example: -42)
  • The unary plus operator (+). This simply returns its value as is. For example +42 is still just 42. This operator is entirely useless, but looks nice near a mathematical negation operator when you're choosing if you want something positive or negative