In place quicksort

I implemented my own sorting in VBA because it doesn't provide its own, and it's healthy to test yourself. It was surprisingly difficult and I ended up make a few tweaks that I didn't expect to make in order for it to sort.

Public Sub quicksort(ByRef arr As Variant, _
                     ByVal left As Integer, _
                     ByVal right As Integer)
    If right = p And l  r Then Call swap(arr(l), arr(r))
    Wend
    ' Don't swap the same thing
    If l <> right Then Call swap(arr(right), arr(l))
    Call quicksort(arr, left, l - 1) 
    Call quicksort(arr, l + 1, right)
End Sub

Few notes.

• All algorithms on ranges are much simpler if the range is considered semi-open (that is, right is just beyond the last interesting element.

• The `While l

• One more thing you want to do is to eliminate a last tail-recursive call to quicksort. It is very well possible that the compiler will do it for you; still it is better to be explicit.

StackExchange Code Review Q#47591, answer score: 7