Re: Errors in interactive commands

[David Kastrup <dak@gnu.org>]

Andreas Röhler <andreas.roehler@online.de> writes:

> Am 03.08.2011 09:28, schrieb Stephen J. Turnbull:
>> Andreas Röhler writes:
>>
>>   >  A move-forward at the end of the buffer isn't a wrong command as such,
>>   >  just will not be successful.
>>   >
>>   >  Therefor it should not be raised an error, just nil returned.
>>
>> This is problematic, IMO.  Suppose you have a buffer which is supposed
>> to have an even number of objects in it, and you want to delete every
>> second then.  Then
>>
>> (progn
>>    (goto (point-min))
>>    (while (not (eobp))
>>      (forward-object 2)
>>      (delete-object -1)))
>>
>> DTRTs, including detecting the "incorrect state" of an odd number of
>> objects, and not deleting the first object on an incomplete last line.

[...]

> Nonetheless think arguments are wrong here, mixing up two levels of
> execution.
>
> To get what you want, it's a state-of-affairs variable to introduce
> pointing at the action.
>
> Ie 'Delete-every-second' is the matter at stake, whilst "forward-"
> below resp. inside.
>
> With a little bit pseudo-code introduced:
>
>  (progn
>     (goto (point-min))
>     (while (and (QUERY Delete-every-second-state)(not (eobp)))
>       (forward-object 2)
>       (delete-object -1)
>       (UPDATE Delete-every-second-state)))
>
> Useful return values of "forward-" is important for a wide range of
> things, not just to serve several specific cases.
>
> Sorting execution levels might be the term at stake.
> Would like to read another term from experts. Pretty sure exists some
> in informatics.

I consider it likely that most experts would take the term
"befuddlement" into close consideration.  I consistently fail to
recognize a logical connection between your postings and what they are
supposed to be a reply to.

-- 
David Kastrup