addMod(_:modulus:)

Returns (self + other) % modulus.

iOS 18.0+
macCatalyst 18.0+
macOS 15.0+
tvOS 18.0+
visionOS 2.0+
watchOS 11.0+

func addMod(_ other: UInt256, modulus: UInt256) -> UInt256

Parameters

other: The value to add.
modulus: The modulus (must be ≥ 2).

Return Value

(self + other) mod modulus.

Discussion

Uses addingReportingOverflow to detect the 257-bit intermediate, then reduces modulo modulus via dividingFullWidth when overflow occurs or via a simple compare-and-subtract when it doesn’t.

Precondition

modulus >= 2.