# scanHexDouble(_:) Scans for a double value from a hexadecimal representation, returning a found value by reference. ``` func scanHexDouble(_ result: UnsafeMutablePointer?) -> Bool ``` ## Parameters `result` Upon return, contains the scanned value. Contains `HUGE_VAL` or `–HUGE_VAL` on overflow, or `0.0` on underflow. ## Return Value if the receiver finds a valid double-point representation, otherwise . Overflow or underflow are both considered valid floating-point representations. ## Discussion This corresponds to `%a` or `%A` formatting. The hexadecimal double representation must be preceded by `0x` or `0X`. Skips past excess digits in the case of overflow, so the scanner’s position is past the entire floating-point representation. Invoke this method with `NULL` as `result` to simply scan past a hexadecimal double representation. --- 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)