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

# -=(_:_:)

Subtracts the second quaternion from the first and stores the difference in the left-hand-side variable.

## Declaration

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