--- Begin Message ---
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Subject: |
28.0.50; Why `bound-and-true-p' is not working in lexical binding? |
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Date: |
Sat, 19 Jun 2021 14:39:54 +0300 |
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
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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
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european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
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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)
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(intervals 56 201 0)
(buffers 992 11))
--
Thanks,
Jean Louis
Take action in Free Software Foundation campaigns:
https://www.fsf.org/campaigns
--- End Message ---
--- Begin Message ---
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Subject: |
Re: bug#49116: 28.0.50; Why `bound-and-true-p' is not working in lexical binding? |
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Date: |
Sun, 20 Jun 2021 00:49:14 +1200 |
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User-agent: |
Orcon Webmail |
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
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