---
title: "+=(_:_:)"
framework: swift
role: symbol
role_heading: Operator
path: "swift/binaryinteger/+=(_:_:)"
---

# +=(_:_:)

Adds two values and stores the result in the left-hand-side variable.

## Declaration

```swift
override static func += (lhs: inout Self, rhs: Self)
```

## Parameters

- `lhs`: The first value to add.
- `rhs`: The second value to add.

## Discussion

Discussion The sum of the two arguments must be representable in the arguments’ type. In the following example, the result of 21 + 120 is greater than the maximum representable Int8 value: var x: Int8 = 21 x += 120 // Overflow error note: Overflow checking is not performed in -Ounchecked builds.

## See Also

### Arithmetic with Assignment

- [-=(_:_:)](swift/binaryinteger/-=(_:_:).md)
- [*=(_:_:)](swift/binaryinteger/*=(_:_:).md)
- [/=(_:_:)](swift/binaryinteger/_=(_:_:)-20xv1.md)