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From: eijkhout@s41.csrd.uiuc.edu (Victor Eijkhout)
Newsgroups: comp.text.tex
Subject: Re: How to include unbalanced brackets `}' in macro substitution?
Message-ID: <1991Feb5.174501.10666@csrd.uiuc.edu>
Date: 5 Feb 91 17:45:01 GMT
References: <1991Feb5.023920.20619@cs.ucla.edu>
Sender: news@csrd.uiuc.edu (news)
Organization: UIUC Center for Supercomputing Research and Development
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kirkaas@oahu.cs.ucla.edu (paul kirkaas) writes:

>I want to define macros that end a group, doing a few cleanup chores in
>the process --- for example, a \beginvcenter \endvcenter pair to center
>text vertically in a page.

>I would like to find a way to either:
>1) Include a closing brace `}' as part of the macro substitution
>    or
>2) Figure out how to properly use \begingroup & \endgroup to achieve the
>same end.

Boxes can be opened/closed by braces or by `implicit braces':
tokens that are \let to a brace.
Because of the definitions \let\bgroup{ \let\egroup}
(l)plain.tex, you can write \hbox\bgroup ... \egroup,
and you can do that with macros:
\def\beginbox{\hbox\bgroup}
\def\endbox{\egroup}

The \begingroup/\endgroup commands cannot be interchanged
with {} or \bgroup/\egroup. But they do define a group
in which changes are local. You can use them therefore
as some sort of runtime error checking:
they will not be matched accidentally with braces
or \bgroup/\egroup tokens appearing.

Victor.