# &+=(_:_:) Adds two values and stores the result in the left-hand-side variable, wrapping any overflow. ``` static func &+= (lhs: inout Self, rhs: Self) ``` ## Parameters `lhs` The first value to add. `rhs` The second value to add. ## Discussion The masking addition assignment operator (`&+=`) silently wraps any overflow that occurs during the operation. In the following example, the sum of `100` and `121` is greater than the maximum representable `Int8` value, so the result is the partial value after discarding the overflowing bits. ``` var x: Int8 = 10 x &+= 21 // x == 31 var y: Int8 = 100 y &+= 121 // y == -35 (after overflow) ``` For more about arithmetic with overflow operators, see [Overflow Operators](https://docs.swift.org/swift-book/LanguageGuide/AdvancedOperators.html#ID37) in *[The Swift Programming Language](https://docs.swift.org/swift-book/)*. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)