Re: [gobo-eiffel-develop] Comment in {DS_LINEAR}.after misleading?

[Colin A. <col...@ho...>]

>From: Stefan Sieber <sie...@st...>

>
>Hi,
>
>The description of {DS_LINEAR}.after fooled me this morning ;) Andreas 
>Leitner
>suggested to contact the gobo mailing list, so this is what I'll do now...
>
>Here's {DS_LINEAR}.after:
>
>	after: BOOLEAN is
>			-- Is there no valid position to right of internal cursor?
>		do
>			Result := cursor_after (internal_cursor)
>		end
>
>The description "Is there no valid position to right of internal cursor?" 
>made
>me think that 'after' is true whenever the cursor is on the _last_ item of
>the linear (and not beyond). I assumed that "no valid position to the 
>right"
>means that the next position will not point to an item of the container
>anymore.

That assumption is incorrect. The internal cursor has a valid position after 
the last item - the after-life sentinel (my (joke) terminiology).

The point is that when you are on the last item, it is still valid to call 
`forth'. This will move the cursor forward (hence it's name), and the cursor 
has to go somewhere. It goes to the after-sentinel position. Now there is no 
longer a valid position, so you may no longer call `forth'.

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