Re: Instead of pcase

[Lynn Winebarger <owinebar@gmail.com>]

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On Mon, Nov 20, 2023, 9:42 PM Richard Stallman <rms@gnu.org> wrote:

>
>   > > They contain code that looks like Lisp but does not have the same
>   > > semantic rules as Lisp.
>
>   > Yes: it's a domain-specific language.
>
> THat is why pcase adds to the total complexity of Emacs Lisp: because
> it incorporates a domain-specific language.  (I called it a "little
> lajguage".)
>
>   > To interpret those backquotes and commas, one can imagine that the
> they
>   > do the inverse of the usual.
>
> I uderstand that when you say it, but when I saw the line
>
> >          > (`(,hookfun . (,start ,end ,collection . ,plist))
>
> I was not sure which part of the line that rule applies to.
>
> In particular, what is the reason for the period and inner
> parenthsses?  Why doesn't the code say this?


> >          > (`(,hookfun ,start ,end ,collection . ,plist)
>
> Would that be equiva;ent?
>
> I could not assume the inner parenthsses were unnecessary.  Maybe
> there was a conventiob by which they change the meaning.
> I did not know.


I haven't seen anyone point this out yet, but they have to be equivalent.
The reader constructs the same data structure for those concrete
expressions (text) before the pcase macro is ever evaluated.

I would think the author is simply emphasizing that they are parsing an
entity in an association list for which hookfun is a key.

Lynn

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