One of my recent assignments to first-year programming students was to model Left-Center-Right (https://en.wikipedia.org/wiki/LCR_(dice_game))��where they needed to do just what you are trying to do.

| size stream |

size := 10.

stream := WriteStream on: String new.

1 to: size do: [:i |��

stream

print: i; tab;

print: i \\ size + 1; tab;

print: i + size - 2 \\ size + 1; tab;

cr.

].

stream contents

On Mar 28, 2019, at 8:12 AM, Tim Mackinnon <tim@testit.works> wrote:

Hey guys - I���m wondering if someone might have a nice way of selecting the previous value in a list - but wrapping around to the last value if you are at the front.

Essentially I have an exercise with some values in a collection like:

list := ��#($a $e $o $u).

And I have an index into the list, and want to loop around from index 1, back to 4 when I hit the beginning of the list.

While moving forwards is pretty easy with mod - e.g.

^list at: (index \\ list size + 1)

I���m struggling with the cleanest way to do this backwards - as the following is unreadable to me (assuming index = 1)

^list at: (index - 2 \\ list size + 1)

And then I tried (which isn't bad - but still not quite right).

^list before: (list at: index) ifAbsent: [ids last].


I���m sure there is a better way to do this - but it���s alluding me?

Tim