Subject: bug#49116: closed (Re: bug#49116: 28.0.50; Why `bound-and-true-p' is not working in lexical binding?)

From: [email-masked] (GNU bug Tracking System)
Date: Sat, 19 Jun 2021 12:50:02 +0000

Your bug report

#49116: 28.0.50; Why `bound-and-true-p' is not working in lexical binding?

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
49116: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=49116
GNU Bug Tracking System
Contact [email-masked] with problems

Subject: Re: bug#49116: 28.0.50; Why `bound-and-true-p' is not working in lexical binding?
From: Phil Sainty <[email-masked]>
To: Jean Louis <[email-masked]>
Cc: [email-masked]
Date: Sun, 20 Jun 2021 00:49:14 +1200
List-Id: <debbugs-submit.debbugs.gnu.org>

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

Subject: 28.0.50; Why `bound-and-true-p' is not working in lexical binding?
From: Jean Louis <[email-masked]>
To: [email-masked]
Date: Sat, 19 Jun 2021 14:39:54 +0300
List-Id: <debbugs-submit.debbugs.gnu.org>

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?

In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.29, cairo version 1.17.4)
 of 2021-06-02 built on protected.rcdrun.com
Repository revision: 09081ca119c3debcc72159a46d3bafabfd7519bb
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Parabola GNU/Linux-libre

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY
PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE
XIM XPM GTK3 ZLIB

Important settings:
  value of $LC_ALL: en_US.UTF-8
  value of $LANG: de_DE.UTF-8
  value of $XMODIFIERS: @im=exwm-xim
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map text-property-search time-date
subr-x seq byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
iso-transl tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice button loaddefs faces cus-face macroexp files
window text-properties overlay sha1 md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote threads dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
cairo move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 53041 4440)
 (symbols 48 7128 3)
 (strings 32 19321 1728)
 (string-bytes 1 630312)
 (vectors 16 13239)
 (vector-slots 8 175206 9539)
 (floats 8 21 34)
 (intervals 56 201 0)
 (buffers 992 11))

-- 
Thanks,
Jean Louis

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