From: Phil Sainty <psainty@orcon.net.nz>
To: Jean Louis <bugs@gnu.support>
Cc: 49116-done@debbugs.gnu.org
Subject: bug#49116: 28.0.50; Why `bound-and-true-p' is not working in lexical binding?
Date: Sun, 20 Jun 2021 00:49:14 +1200 [thread overview]
Message-ID: <3157c274e97fc9db7ceb345ba020f74b@webmail.orcon.net.nz> (raw)
In-Reply-To: <861r8yozg5.fsf@protected.rcdrun.com>
On 2021-06-19 23:39, Jean Louis wrote:
> When I evaluate following it is not detecting variable `direction'
> under lexical bindings:
>
> (defun verify-direction (timestamp &optional direction)
> (cond ((bound-and-true-p direction) (message "OK"))))
>
> (verify-direction "10:00" t) ⇒ nil
>
> I would like to understand if it is intended to be so?
>
> Or is this possible bug?
This is expected / not a bug (and so I'm closing it).
(bound-and-true-p VAR) is syntactic sugar for (and (boundp 'VAR) VAR)
which means that it works only for dynamic variables (i.e. variables
stored in the value slot of a symbol).
Under lexical binding, function arguments are lexical variables, which
means they are not stored in the symbol of that name, and hence cannot
be detected with `boundp'.
In your case there's no need to be checking whether `direction' is
"bound" -- whether it's lexical or dynamic, you already *know* that
it exists because it's an argument for the function in which you're
checking it. All you want is the "true-p" part, which is implicit
in every value (either nil or non-nil).
Instead of "(bound-and-true-p direction)" just use "direction".
-Phil
next prev parent reply other threads:[~2021-06-19 12:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-19 11:39 bug#49116: 28.0.50; Why `bound-and-true-p' is not working in lexical binding? Jean Louis
2021-06-19 12:49 ` Phil Sainty [this message]
2021-06-19 12:54 ` Eli Zaretskii
2021-06-19 13:01 ` Lars Ingebrigtsen
2021-06-19 13:13 ` Phil Sainty
2021-06-19 13:21 ` Lars Ingebrigtsen
2021-06-21 17:00 ` Michael Heerdegen
2021-06-22 12:59 ` Lars Ingebrigtsen
2021-06-22 23:00 ` Michael Heerdegen
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