* Why is ,. (comma-dot) treated specially?
@ 2015-01-21 23:58 Artur Malabarba
2015-01-22 13:54 ` Stefan Monnier
0 siblings, 1 reply; 2+ messages in thread
From: Artur Malabarba @ 2015-01-21 23:58 UTC (permalink / raw)
To: emacs-devel
I ran into a problem the other day where writing
`(message ,.some-var)
unexpectedly split the .some-var symbol without evaluating anything:
(message (\,\. some-var))
Meanwhile, adding a space after the comma:
`(message , .some-var)
yielded the expected result:
(message [value of .some-var])
Upon inspecting `lread.c', I see that indeed ",." is treated specially
(look for references to Qcomma_dot), similarly to how ",@" is special.
On the other hand, I can find no mention of this "comma-dot" anywhere
inside backquote.el.
Is this a feature that was planned but is not yet finished? Why is the
dot handled specially after a comma if we don't do anything with it?
Cheers
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Why is ,. (comma-dot) treated specially?
2015-01-21 23:58 Why is ,. (comma-dot) treated specially? Artur Malabarba
@ 2015-01-22 13:54 ` Stefan Monnier
0 siblings, 0 replies; 2+ messages in thread
From: Stefan Monnier @ 2015-01-22 13:54 UTC (permalink / raw)
To: Artur Malabarba; +Cc: emacs-devel
> Is this a feature that was planned but is not yet finished? Why is the
> dot handled specially after a comma if we don't do anything with it?
Using special characters (like dot) in symbols is risky. Always has
been always will be.
> I ran into a problem the other day where writing
> `(message ,.some-var)
> unexpectedly split the .some-var symbol without evaluating anything:
> (message (\,\. some-var))
I'm not surprised it doesn't do what you expected, but I'm admittedly
surprised of the actual behavior. In any case, this looks like
a plain bug.
Stefan
^ permalink raw reply [flat|nested] 2+ messages in thread
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2015-01-21 23:58 Why is ,. (comma-dot) treated specially? Artur Malabarba
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