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iOS Swift Basics Swift Operators Quiz: Operator Precedence

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
208,478 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

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