Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Swift Basics Swift Operators Quiz: Operator Precedence

Posted by malcolm henry
malcolm henry
1,089 Points

I've gotten every choice EXCEPT 20 -- please explain

let y = 25 - 5 * 2 + 5 XCODE is given me 20 and I have gotten 10 / -10 / and 45 but dont see how this equals 20 in the slightest.

2 Answers

Steven Parker
Steven Parker
231,198 Points
Steven Parker
Steven Parker
231,198 Points

The result is a combination of operator precedence and order of evaluation:

  • multiplication has precedence so it is done first, leaving :point_right: 25 - 10 + 5
  • then the subtraction is done next because of left-to-right evaluation order, leaving :point_right: 15 + 5
  • then performing the addition yields the final result :point_right: 20
malcolm henry
malcolm henry
1,089 Points
malcolm henry
malcolm henry
1,089 Points

Gotcha - i went every direction except left to right -- well said!