From: Hans Hagen <j.hagen@xs4all.nl>
To: mailing list for ConTeXt users <ntg-context@ntg.nl>
Subject: Re: Checking existence of a macro (control sequence) by Lua
Date: Fri, 29 May 2020 09:36:25 +0200 [thread overview]
Message-ID: <6eb726fb-aae8-7750-0d29-860a8d48059a@xs4all.nl> (raw)
In-Reply-To: <263ba20f41f00d3da9433eaf9a66e5b7@vivaldi.net>
On 5/28/2020 11:24 PM, context@vivaldi.net wrote:
> Hello,
>
> one more question - why macros \Undefined and \DoNothing show "defined"
> although I (tried to) undefine them?
>
> ----
> \starttext
> \def\MyMacro{Ahoj}
> \def\MyMac#1#2{Something}
>
> \def\Undefined{}
> \let\Undefined\undefined
>
> \def\DoNothing{}
> \let\DoNothing\donothing
>
> \startluacode
> local str = { [true] = "defined", [false] = "undefined" }
>
> local function whatever(s)
> context.type("\\" .. s)
> context(" is " .. (tokens.defined(s) and "defined" or
> "undefined")) --% Hans' way
> context(" and is " .. str[token.is_defined(s)] .. ".") --%
> Henri's way
> context.par()
> end
>
> whatever("MyMacro")
> whatever("MyMacroD")
> whatever(" ")
> whatever("-")
> whatever("Undefined")
> whatever("DoNothing")
> \stopluacode
>
> %\Undefined % Causes "! Undefined control sequence"
> \stoptext
> ----
>
> Gives:
>
> "
> \MyMacro is defined and is defined.
> \MyMacroD is undefined and is undefined.
> \ is defined and is defined.
> \- is defined and is defined.
> \Undefined is defined and is defined.
> \DoNothing is defined and is defined.
> "
Because the macro actually *is* defined: as soon as tex sees
\foo
it reserves the name and gives it the meaning undefined, so even
\undefined is defined.
Anyway, that is why we have \ifdefined that does a different kind of
checking. In retrospect, that is a better one, so I'll adapt that in lmtx.
\starttext
\let\MyMacroA\undefined
\startluacode
local function whatever(s)
context.type("\\" .. s)
context(" is " .. (tokens.defined(s,true) and "defined" or
"undefined")) --% Hans' way
context(" and has meaning " .. (tokens.defined(s) and "defined"
or "undefined")) --% Hans' way
context.par()
end
whatever("MyMacroA")
whatever("MyMacroB")
\stopluacode
\stoptext
\MyMacroA is defined and has meaning undefined
\MyMacroB is undefined and has meaning undefined
You can do this in current luatex/mkiv:
if CONTEXTLMTXMODE == 0 then
local d = tokens.defined
local c = tokens.create
function tokens.defined(s,b)
if b then
return d(s)
else
return c(s).cmd_name == "undefined_cmd"
end
end
end
Hans
-----------------------------------------------------------------
Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage : http://www.pragma-ade.nl / http://context.aanhet.net
archive : https://bitbucket.org/phg/context-mirror/commits/
wiki : http://contextgarden.net
___________________________________________________________________________________
next prev parent reply other threads:[~2020-05-29 7:36 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 22:42 context
2020-05-27 22:49 ` luigi scarso
2020-05-28 7:56 ` Hans Hagen
2020-05-28 6:50 ` Henri Menke
2020-05-28 8:34 ` Hans Hagen
2020-05-28 11:24 ` context
2020-05-28 21:24 ` context
2020-05-29 7:36 ` Hans Hagen [this message]
2020-05-29 21:21 ` context
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6eb726fb-aae8-7750-0d29-860a8d48059a@xs4all.nl \
--to=j.hagen@xs4all.nl \
--cc=ntg-context@ntg.nl \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).