[alexandria-devel] Implementation of DELETE-FROM-PLIST

[Stas Boukarev]

Robert Smith <quad at symbo1ics.com> writes:

> Good style remarks, I suppose, which I can change.
>
> On Sat, Feb 23, 2013 at 8:08 AM, Stas Boukarev <stassats at gmail.com> wrote:
>> And I don't quite understand the purpose of
>> (unless (eq first plist)
>>         (setf (cddr plist)
>>               first))
>
> The point of that was for more DWIMness.
>
> Without it, we have:
>
> CL-USER> (let ((x (list :a 1 :b 2 :c 3 :d 4)))
>            (print (delete-from-plist x :a :b :c))
>            x)
>
> (:D 4)
> (:A 1 :B 2 :C 3 :D 4)
>
> And with it, we have:
>
> CL-USER> (let ((x (list :a 1 :b 2 :c 3 :d 4)))
>            (print (delete-from-plist x :a :b :c))
>            x)
>
> (:D 4)
> (:A 1 :D 4)
>
> If your typical mode of operation is to (setf x (delete-from...)),
> then of course either are fine. If your goal is to use
> DELETE-FROM-PLIST for its side effects, then I think the latter is
> more useful. In fact, for really simple and efficient imperative
> maintenance of a plist, just prepend (nil nil), and use the function
> purely for mutation.
I don't see how (:A 1 :D 4) is useful, it's less wrong, but it's still
wrong.

-- 
With best regards, Stas.