---
title: "isnan(_:)"
framework: simd
role: symbol
role_heading: Function
path: "simd/isnan(_:)-94v5c"
---

# isnan(_:)

Returns true for each element that is not a number (NaN) in a vector.

## Declaration

```swift
func isnan(_ x: simd_double4) -> simd_long4
```

## See Also

### Classification Functions

- [isfinite(_:)](simd/isfinite(_:)-1870d.md)
- [isinf(_:)](simd/isinf(_:)-4gutc.md)
- [isnormal(_:)](simd/isnormal(_:)-35fxl.md)