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bug#30749: 26.0.91; (cl-)case is confused when a nil atom is used instea
From: |
Alex Bennée |
Subject: |
bug#30749: 26.0.91; (cl-)case is confused when a nil atom is used instead of a keylist |
Date: |
Thu, 08 Mar 2018 11:34:59 +0000 |
User-agent: |
mu4e 1.1.0; emacs 26.0.91 |
Noam Postavsky <npostavs@gmail.com> writes:
> Alex Bennée <alex.bennee@linaro.org> writes:
>
>> I got confused why my case statement was failing as I'd used the second
>> form assuming that having nil as an atom would work. I'm not sure why
>> the quoting fixed it but it's certainly a confusing inconsistency.
>
> 'nil is the same as (quote nil)
Ahh so ends up as a list containing nil?
>
>> I think this is probably fixable with just making the docstring clearer
>> as the results of handling the duel atom/list of nil might have
>> unexpected results.
>
> So just add a "non-nil" perhaps?
>
> --- i/lisp/emacs-lisp/cl-macs.el
> +++ w/lisp/emacs-lisp/cl-macs.el
> @@ -763,7 +763,7 @@ cl-case
> "Eval EXPR and choose among clauses on that value.
> Each clause looks like (KEYLIST BODY...). EXPR is evaluated and compared
> against each key in each KEYLIST; the corresponding BODY is evaluated.
> -If no clause succeeds, cl-case returns nil. A single atom may be used in
> +If no clause succeeds, cl-case returns nil. A single non-nil atom may be
> used in
> place of a KEYLIST of one atom. A KEYLIST of t or `otherwise' is
> allowed only in the final clause, and matches if no other keys match.
> Key values are compared by `eql'.
Works for me.
--
Alex Bennée