Problems with \begin{enumerate}[1.3.i]

Question

I should have searched more for this subject before posting, I'm sure, but I got frustrated with the amount of interesting items of clothing made from latex, so please forgive me if this has already been answered. I'm trying to make a list of examples like:

1.3.i bla bla
1.3.ii and so on
...

I feel I should be able to use \begin{enumerate}[1.3.i], but it comes out as:

i.3.i bla bla
ii.3.ii and so on
...

I suppose it makes sense, since '1' is one of the characters that get interpreted, but isn't there a way to protect the number, when you just want it to be a static part of the label?

Answer 1

You have to hide the fixed part (which contains a 1 that would otherwise be mistaken for a counter denotation):

\documentclass{article}
\usepackage{enumerate}

\begin{document}

\section{Title}
\setcounter{subsection}{2} % faking two subsections

\subsection{Title}

\begin{enumerate}[{1.3}.i]
\item bla bla
\item and so on
\end{enumerate}

\end{document}

It's easier with enumitem that is much recommended over enumerate:

\documentclass{article}
\usepackage{enumitem}

\begin{document}

\section{Title}
\setcounter{subsection}{2} % faking two subsections

\subsection{Title}

\begin{enumerate}[label=1.3.\roman*]
\item bla bla
\item and so on
\end{enumerate}

\end{document}

However, both solutions suffer from the hardcoded 1.3; also, the labels will be poorly aligned. Here's my suggestion:

\documentclass{article}
\usepackage{enumitem}

\begin{document}

\section{Title}
\setcounter{subsection}{2} % faking two subsections

\subsection{Title}\label{ssec:xyz}

\begin{enumerate}[label=\ref{ssec:xyz}.\roman*,align=left]
\item bla bla
\item and so on
\end{enumerate}

\end{document}

Using \label and \ref will ensure the enumeration will have the correct label, independently on possible changes in the material.

Answer 2

You can 'hide' the 1.3 from enumerate's parser by putting it into a macro

\documentclass{article}
\usepackage{enumerate}

\newcommand*{\enumprefix}{1.3}
\begin{document}
\begin{enumerate}[\enumprefix.i]
\item Lorem
\item Ipsum
\end{enumerate}
\end{document}

If the "1.3" is not a random number, but stands in relation with other counters in the document, you may be able to get rid of the \newcommand. If it is the number of the current subsection, you would use

\documentclass{article}
\usepackage{enumerate}

\begin{document}
\section{Foo}
\subsection{Bar}
\begin{enumerate}[\thesubsection.i]
\item Lorem
\item Ipsum
\end{enumerate}
\end{document}

But you could also use the enumitem package, which has a slightly more verbose syntax here, but offers many additional options. Plus, you can hide the more verbose settings in your own macro definitions or apply the globally.

\documentclass{article}
\usepackage{enumitem}

\begin{document}
\section{Foo}
\subsection{Bar}
\begin{enumerate}[label=\thesubsection.\roman*]
\item Lorem
\item Ipsum
\end{enumerate}
\end{document}