On 30 Aug 2019, at 11:56, Ben Coman <btc@openinworld.com> wrote:

On Fri, 30 Aug 2019 at 15:34, Julien <julien.delplanque@inria.fr> wrote:

Hello,

I opened that issue: https://github.com/pharo-project/pharo/issues/4442

And I think to fix it we need to actually discuss about what we want.

#allButFirst: behaves differently depending on the actual type of sequenceable collection when argument is greater than collection size.

For instance:

#(1 2) allButFirst: 3.  "PrimitiveFailed signaled"

(LinkedList with: 1 with: 2) allButFirst: 3. "PrimitiveFailed signaled"

(OrderedCollection with: 1 with: 2) allButFirst: 3.  "an OrderedCollection() ��

The question is then, who is right?

Its worthwhile to at least survey other Smalltalks.  

For Visualworks...

      #(1 2) allButFirst: 3.  "==> #()"

      (OrderedCollection with: 1 with: 2) allButFirst: 3.   "==> OrderedCollection ()"

      (LinkedList with: Link new with: Link new ) allButFirst: 3.  "raises an error Subscription out of bounds error"

and also...

      (LinkedList with: Link new with: Link new ) allButFirst: 2.  "raises an error Subscription out of bounds error"

I feel that proceeding-without-iterating is nicer than showing-an-application-error.

It provides the opportunity to not-check the number elements or wrapping error handling around it - i.e. less code if its not important.

If its important not to exceed the number of elements, then that check can be explicitly coded.

cheers -ben