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bug#20784: 25.0.50; pcase documentation on t and nil
From: |
Michael Heerdegen |
Subject: |
bug#20784: 25.0.50; pcase documentation on t and nil |
Date: |
Fri, 12 Jun 2015 19:31:10 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) |
Stefan Monnier <monnier@iro.umontreal.ca> writes:
> We currently don't have a special "fail" pattern which simply never
> matches. Of course, you can make one up (e.g. (guard nil)).
(or) would also do it, but raises (error "Please avoid it") (BTW
(or _) raises that error, too). Why are those (error "Please avoid it")
calls useful?
> I think making nil such a pattern would probably lead to more
> errors/confusion than anything, since it's extremely rare to need such
> a pattern.
Agreed.
> That's pretty much what SELFQUOTING is. IF you think renaming it to
> ATOM would help, then we could do that.
I would prefer that over SELFQUOTING because
SELFQUOTING is a shorthand for 'SELFQUOTING.
sounds like a tautology.
> As explained the use of `eq' is supposed to be a pure optimization with
> no semantics effect.
I see. Then I guess it would make sense to merge these two lines in the
` doc?
STRING matches if the object is ‘equal’ to STRING.
ATOM matches if the object is ‘eq’ to ATOM.
into
ATOM matches if the object is ‘equal’ to ATOM.
Regards,
Michael.