parameter description with long descriptions and long lists -- possibility of page break?

Question

I have a series of equations with following parameter description. Some of those descriptions are relatively long, meaning that I nead a line break. I use so far table, and to accomodate the long lines I use tabularx

\begin{tabularx}{\textwidth}{@{}lX}
where: & $a$ -- long text long text long text long text long text long text long text long text ,\\
 & $b$ -- long text long text long text long text long text long text long text long text ,\\
 & $c$ -- text,\\
 & $d$ -- text, and\\
 & $e$ -- text.
\end{tabularx}

As the list is relatively long and there are several such equations with list, this leads to ugly spacing between parameters. I would therefore like to allow page breakes within the table. I found the possibility of using ltxtable and longtable, but don't really understand how it would need to be implemented. Is a table even the best solution or are there other and better option where I can have long descriptions and long lists with page breaks?

Answer 1

Something like this, but modify parameters to suit (or use the enumitem interface)

\documentclass{article}
\setlength\textwidth{10cm}

\newenvironment{plist}{%
\list{}{\labelwidth0pt
\def\makelabel##1{\makebox[2cm][r]{##1 -- }}%
\itemsep 0pt
\advance\leftmargin2cm
\itemindent-2cm
}}
{\endlist}

\begin{document}

\noindent X\dotfill X
\begin{plist}
\item[where\hfill $a$]
long text long text long text long text long text long text long text long text,
long text long text long text long text long text long text long text long text,
\item[$b$]long text long text long text long text long text long text long text long text,
\item[$c$]text,
\item[$d$]text, and
\item[$e$]text.
\end{plist}

\end{document}

---

or

\documentclass{article}
\setlength\textwidth{10cm}

\newenvironment{plist}{%
\list{}{\labelwidth0pt
\def\makelabel##1{\makebox[1.5cm][r]{##1}}%
\parsep 0pt
\itemsep 0pt
\advance\leftmargin1.5cm
\itemindent-1.5cm
}}
{\endlist}

\begin{document}

\noindent X\dotfill X
\begin{plist}
\item[where\hfill $a$]--
long text long text long text long text long text long text long text long text,
long text long text long text long text long text long text long text long text,
\item[$b$]-- long text long text long text long text long text long text long text long text,
\item[$c$]-- text,
\item[$d$]-- text, and
\item[$e$]-- text.
\item[$C_{ox}$]${}=23$nF -- gate capacitance,
\item[$\mu$]-- mobility in the semiconductor [cm$^2$/Vs], and
\item[$V_{g,th}$]-- threshold voltage.
\end{plist}

\end{document}

---

or (one last time:-) another variant (in this one I made the indent an optional parameter to the environment, defaulting to 1.5cmand as requested set where flush left.):

\documentclass{article}
\setlength\textwidth{10cm}

\newenvironment{plist}[1][1.5cm]{%
\list{}{
\def\makelabel##1{##1\hfill}%
\parsep 0pt
\itemsep 0pt
\labelsep0pt
\labelwidth#1\relax
\leftmargin\labelwidth
\itemindent0pt
}}
{\endlist}

\begin{document}

\noindent X\dotfill X
\begin{plist}
\item[where] $a$ --
long text long text long text long text long text long text long text long text,
long text long text long text long text long text long text long text long text,
\item $b$ -- long text long text long text long text long text long text long text long text,
\item $c$ -- text,
\item $d$ -- text, and
\item $e$ -- text.
\item $C_{ox}=23$nF -- gate capacitance,
\item $\mu$ -- mobility in the semiconductor [cm$^2$/Vs], and
\item $V_{g,th}$ -- threshold voltage.
\end{plist}

\end{document}