A comparison againsttrue orfalse is never needed,ary.isEmpty == false is more concisely expressed as!ary.isEmpty.

Here I would not use aguard statement at all. That statement was introduced to get rid of the “if-let pyramid of doom,” to unwrap a variable without introducing another scope/indentation level. But I would not use aguard statement for every “early return” situation, in particular not if it makes the statement look like a double negation.

if ary.isEmpty {    return ary}

is shorter and clearer in my opinion. Alternatively one can use optional binding

if let last = ary.last {    // ...} else {    return ary}

to test for a non-empty arrayand get the last element in one step, that allows to get rid of the ugly forced unwrapcopy[0] = last! in your code.

As already mentioned in the comment, arrayslicing methods can be used instead of copying all elements to their new place:

if let last = ary.last {    return [last] + ary.dropLast()} else {    return ary}

Another option is to concatenate two array slices, this can easily be generalized to shifting array elements by more than one position to the right or left:

if ary.isEmpty {    return ary}let frontIndex = ary.count - 1return Array(ary[frontIndex...]) + ary[0..<frontIndex]

Naming: The parameter nameary reminds my of unary/binary/arity and is not significantly shorter thanarray. My suggestion is to usearray with an empty argument label:

func rotateRight(_ array: [Int]) -> [Int] {    // ...    }var array1 = [1, 2, 3]print(rotateRight(array1)) // [3, 1, 2]

Of course, if you don't want to reinvent the wheel then you can simply use therotate(toStartAt:) method of theswift-algorithms package.

• algorithm
• array
• swift