Why does assq fail when getting quoted value from a property list?

Why does assq fail when getting quoted value from a property list?

[Cody Goodman]

This returns (urgent . 2) as I'd expect:

(assq 'urgent '((urgent . 2)))

Why does this not return the same?

(let ((lookup (plist-get '(:severity (quote urgent)) :severity)))
              (assq lookup '((urgent . 2))))

Thanks,

Cody

Re: Why does assq fail when getting quoted value from a property list?

[tomas]

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On Sun, Aug 05, 2018 at 10:55:05PM -0500, Cody Goodman wrote:
> This returns (urgent . 2) as I'd expect:
> 
> (assq 'urgent '((urgent . 2)))
> 
> Why does this not return the same?
> 
> (let ((lookup (plist-get '(:severity (quote urgent)) :severity)))
>               (assq lookup '((urgent . 2))))

Because the value of (plist-get '(:severity (quote urgent) :severity)
is the symbol 'urgent (and not the symbol urgent, as you probably expect).

IOW, '(:severity (quote urgent) :severity) is quoting the 'urgent twice,
so to speak (one is the outer '(...), the other is the inner, explicit
(quote ...)

HTH
- -- tomás
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Re: Why does assq fail when getting quoted value from a property list?

[Noam Postavsky]

On 6 August 2018 at 03:29,  <tomas@tuxteam.de> wrote:

>> (let ((lookup (plist-get '(:severity (quote urgent)) :severity)))
>>               (assq lookup '((urgent . 2))))
>
> Because the value of (plist-get '(:severity (quote urgent) :severity)
> is the symbol 'urgent

You mean the list of two symbols `quote' and `urgent'.

    (equal (list 'quote 'urgent)
           (plist-get '(:severity (quote urgent)) :severity))
    ;=> t

Re: Why does assq fail when getting quoted value from a property list?

[tomas]

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On Mon, Aug 06, 2018 at 07:53:51AM -0400, Noam Postavsky wrote:
> On 6 August 2018 at 03:29,  <tomas@tuxteam.de> wrote:
> 
> >> (let ((lookup (plist-get '(:severity (quote urgent)) :severity)))
> >>               (assq lookup '((urgent . 2))))
> >
> > Because the value of (plist-get '(:severity (quote urgent) :severity)
> > is the symbol 'urgent
> 
> You mean the list of two symbols `quote' and `urgent'.

Hmpf. You're right. "Evaluation" of quote happens later...

Cheers
- -- t
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