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iOS Swift Basics Swift Operators Unary Operators

Al Hughes
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.a{fill-rule:evenodd;}techdegree
Al Hughes
iOS Development Techdegree Student 469 Points

Can't make sense of this

Can someone explain to my why the below question would not result on Zero instead of -100

What is the value of totalScore?

var levelScore = 100 var totalScore = -levelScore

1 Answer

Shade Wilson
Shade Wilson
9,002 Points

You are confusing the -= operator and the negative (-) operator here. The value of totalScore would have been 0 if the code were written as follows:

var levelScore = 100 
var totalScore = 100
totalScore -= levelScore

This is because using -= here is the same as saying:

totalScore = totalScore - levelScore.

However, the question is stated differently:

var levelScore = 100 
var totalScore = -levelScore

Here the declaration of the variable totalScore is equivalent to the following:

var totalScore = -1 * levelScore

Thus, totalScore is simply -100.