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

# +=(_:_:)

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

## Declaration

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