[developers] dot.emacs redefinition of 'unless' and 'when'

[Michael Wayne Goodman]

Thanks, Stephan!

I've updated, re-enabled the LOGON-loading lines in my .emacs, and
confirmed that it no longer interferes with the other package.

On Tue, Jan 9, 2018 at 5:45 AM, Stephan Oepen <oe at ifi.uio.no> wrote:
> dear mike (and all),
>
> my apologies i did not get to look into this thread earlier!  but i am
> happy to report that i have just made a change in the LOGON tree to
> use private names for these convenience macros.  so, once you ‘svn
> update’ i hope you will no longer experience unwanted interactions
> with third-party emacs lisp code?
>
> for historical background (in case anyone cared): these used to not be
> re-definitions because emacs lisp (unlike common lisp) did not provide
> when() and unless() in the 1990s.  i appear to have added these
> convenience definitions to my personal emacs configuration in 1992 and
> had not noticed until now that they have become part of standard emacs
> lisp in the past few decades.
>
> i agree with your assessment that my macro definition of unless() is
> deficient in returning a non-nil value in case the condition is true.
> i apparently have never cared about the return values of my unless(),
> but i am sorry this property has caused you problems with other emacs
> lisp libraries!
>
> with my above patch, i would like to think there is no need to make
> changes to other files, e.g. ‘tdl-mode.el’, as entertained by dan.
> all should be (back to) good now, i hope, right?
>
> best wishes, oe
>
>
> On Tue, Dec 19, 2017 at 10:49 PM, Michael Wayne Goodman <goodmami at uw.edu> wrote:
>> Sorry, one more change to my original mail. I mistakenly assumed that
>> 'unless' was not returning the last value when the condition was false
>> (based on some symptoms I was seeing), but I didn't explicitly test this,
>> and my lisp is not good enough to deduce this by looking at the defmacro
>> expression in ${LOGONROOT]/dot.emacs. In fact, it *does* appear to return
>> the last value, but the difference from the default definition is that
>> LOGON-unless returns the value of the condition when it's non-nil, rather
>> than returning nil.
>>
>> ; standard unless
>> (unless nil 1 2 3)  ; returns: 3
>> (unless 'value 1 2 3)  ; returns: nil
>>
>> ; LOGON unless
>> (unless nil 1 2 3)  ; returns: 3
>> (unless 'value 1 2 3)  ; returns: value
>>
>> So when LOGON-unless is used in constructing a list, it will (I think)
>> append the value of the condition to the list instead of nothing.
>>
>>
>> On Tue, Dec 19, 2017 at 10:18 AM, Michael Wayne Goodman <goodmami at uw.edu>
>> wrote:
>>>
>>> On Tue, Dec 19, 2017 at 8:12 AM, Michael Wayne Goodman <goodmami at uw.edu>
>>> wrote:
>>>>
>>>> Hi Developers,
>>>>
>>>> Does anyone know why ${LOGONROOT}/dot.emacs redefines the 'unless' and
>>>> 'when' macros? It breaks some other Emacs packages I have that depend on the
>>>> return value of the 'unless', which should be the value of the last
>>>> argument. I'm aware that 'unless' and 'when' should be used when the return
>>>> value is *not* important (according to
>>>> https://www.emacswiki.org/emacs/WhenToUseIf), but do we have to enforce that
>>>> suggestion by redefining the macros so they don't return the last value?
>>>>
>>>> Also see
>>>> https://www.gnu.org/software/emacs/manual/html_node/elisp/Conditionals.html,
>>>> which says that 'unless' is equivalent to:
>>>>
>>>>     (if condition nil
>>>>        a b c)
>>>
>>>
>>> Er... I meant that the guide says `(unless condition a b c)' is equivalent
>>> to the above, not in the general case. And I think the expected return value
>>> of the 'unless' expression would be c if condition returns nil.
>>>
>>>>
>>>> Thanks
>>>>
>>>> --
>>>> Michael Wayne Goodman
>>>> Ph.D. Candidate, UW Linguistics
>>>
>>>
>>>
>>>
>>> --
>>> Michael Wayne Goodman
>>> Ph.D. Candidate, UW Linguistics
>>
>>
>>
>>
>> --
>> Michael Wayne Goodman
>> Ph.D. Candidate, UW Linguistics



-- 
Michael Wayne Goodman
Ph.D. Candidate, UW Linguistics