`RangeReplaceableCollection.rotated(by:)` attempt w/ proper modulus.

rr_rotated_by_second_attempt.swift

infix operator %%: MultiplicationPrecedence // To match `%`’s precedence
// (https://developer.apple.com/documentation/swift/swift_standard_library/operator_declarations#2881142).
func %%<T: BinaryInteger>(_ lhs: T, _ rhs: T) -> T {
	let remainder = lhs % rhs
	guard remainder < 0 else { return remainder }

	return rhs > 0 ? // Note, while it seems like this ternary can be reduced down to either
		// `return remainder + abs(rhs)` or `return remainder + rhs.magnitude`, that‘d require `T`
		// to conform to `SignedNumeric` or for `T.Magnitude == T` and I figured we could keep generality.
		remainder + rhs :
		remainder - rhs
}


extension RangeReplaceableCollection where Index: BinaryInteger { // To allow for `%%`ing on `Index`.
	func rotated(by offset: Index) -> SubSequence {
		guard !isEmpty else { return .init() }
		let shiftPoint = offset %% endIndex // Updating the implementation to use `%%`.
		return self[shiftPoint...] + self[..<shiftPoint]
	}
}