Using parameters in \newenvironment

Question

Is there any way to use parameters of the structure \newenvironment{example}[]{}{} after the text between the \begin{example} and the \end{example}. For example, how do I write a new environment that takes as a parameter the author of a text and write it AFTER the text written in the environment?

Welcome to TeX.SX! Could you provide some example how you would like to format this? Should the author name be in a new line, right-aligned perhaps? Should the environment be formatted in a special way? — Jasper Habicht, Mar 17 '21 at 14:59
let's say: text=italics, footnotesized, centered. Author: in a new line, small caps, footnotesized, right aligned — cento18, Mar 17 '21 at 15:01
Related: Why can't the end code of an environment contain an argument? — Werner, Mar 17 '21 at 15:58
Possible duplicate: Passing \newenvironment parameters to the end block? — Werner, Mar 17 '21 at 15:59

Skillmon · Answer 1 · 2021-03-17T15:11:13.093

EDIT: changed the formatting to match specification from comment.

There are two ways to do this, either, with the command \newenvironment you can store the argument inside a temporary macro (using \def or \renewcommand, but initialising it beforehand with \newcommand in either case). Or you use \NewDocumentEnvironment, in which you can refer to the parameters in the \end-part:

\documentclass[]{article}
\newcommand*\exampleARG{}% to assert the name is free
\newenvironment{example}[1]
  {%
    \par\medskip
    \def\exampleARG{#1}%
    \begingroup
      \centering
      \itshape
      \footnotesize
  }
  {%
      \par
    \endgroup
    \leavevmode\hfill\mbox{\textsc{\exampleARG}}\par
    \medskip
  }
\NewDocumentEnvironment{Example}{m}
  {%
    \par\medskip
    \begingroup
      \centering
      \itshape
      \footnotesize
  }
  {%
      \par
    \endgroup
    \leavevmode\hfill\mbox{\textsc{#1}}\par
    \medskip
  }
\usepackage[]{duckuments}
\begin{document}
\begin{example}{a wise duck}
  \blindduck
\end{example}
\begin{Example}{a wise duck}
  \blindduck
\end{Example}
\end{document}

thank you very much, this really solved my problem. I'm really new to LaTeX so I had some trouble understanding everything but I somehow figured it out. However it seems overly complicated to do such thing. — cento18, Mar 17 '21 at 15:34
@cento18 not really, imho. The complication is just for formatting, the key point of using the parameter in the end part is just the \def\exampleARG{#1} thingy (or in the \NewDocumentEnvironment case straight forward #1). The rest in the begin-part is only formatting (with \begingroup so it doesn't affect the author), the end part could be done differently (\begingroup\raggedleft\scshape\exampleARG\par\endgroup), but that's no big difference, imho (though that would also work for authors needing more than a single line...). — Skillmon, Mar 17 '21 at 15:40

Using parameters in \newenvironment

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