# FloatingPointRoundingRule.towardZero Round to the closest allowed value whose magnitude is less than or equal to that of the source. ``` case towardZero ``` ## Discussion The following example shows the results of rounding numbers using this rule: ``` (5.2).rounded(.towardZero) // 5.0 (5.5).rounded(.towardZero) // 5.0 (-5.2).rounded(.towardZero) // -5.0 (-5.5).rounded(.towardZero) // -5.0 ``` This rule is equivalent to the C `trunc` function and implements the `roundToIntegralTowardZero` operation defined by the [IEEE 754 specification](http://ieeexplore.ieee.org/servlet/opac?punumber=4610933). --- 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)