The label of an enumerate list on its own line using enumitem

Question

I would like to use the enumitem package to define a custom enumerate list such that the label occupies its own line. An example would be:

\documentclass{article}

\usepackage[shortlabels]{enumitem}

\setlength{\parindent}{0pt}
\setlength{\parskip}{1ex}

\begin{document}

\begin{center}
{\Large\sc Assignment 1}\\[2ex]
\end{center}

\begin{enumerate}[label={\large\bf Problem \arabic*.},wide]

\item

\begin{enumerate}[(a)]
    \item First question.
    \item Second question.
\end{enumerate}

\item

\begin{enumerate}[(a)]
    \item First question.
    \item Second question.
\end{enumerate}

\end{enumerate}

\end{document}

I would like the labels (Problem 1., Problem 2.) to appear on their own line, i.e., to force a line break right after the label.

According to this post putting \mbox{}\\ after \item works, but I thought it could be possible to avoid that using features of enumitem.

Answer 1

I haven't found anything like this at the enumitem documentation and I would also suggest daleif's answer using theorems.

But I was able to answer your question by redefining \item before a 1st level enumerate environment and redefining it back to it's original definition after the environment. It also works with a simple ~, you don't need a \mbox{} (maybe a \mbox{} has some advantages?).

I know this solution is bit dirty, but it leads to the desired result. Keep in mind that it affects all 1st level enumerations! Alternatively you could create a new list (see enumitem documentation).

\documentclass{article}

\usepackage[shortlabels]{enumitem}

\setlength{\parindent}{0pt}
\setlength{\parskip}{1ex}

\let\itemorig\item    % Create a copy of the original \item

\setlist[enumerate, 1]{%
  before=\renewcommand{\item}{\itemorig~},    % Append '~' to \item
  after=\renewcommand{\item}{\itemorig}       % Restore original \item
}

\begin{document}

\begin{center}
{\Large\sc Assignment 1}\\[2ex]
\end{center}

\begin{enumerate}[label={\large\bf Problem \arabic*.},wide]

\item

\begin{enumerate}[(a)]
    \item First question.
    \item Second question.
\end{enumerate}

\item

\begin{enumerate}[(a)]
    \item First question.
    \item Second question.
\end{enumerate}

\end{enumerate}

\end{document}

Answer 2

I think it might be better not to make the Problem ... lists, but rather theorems. Then you do not have to add those "empty" items.

Using ntheorem we can also build the list configuration into the surrounding env:

\documentclass[a4paper]{memoir}
\usepackage{enumitem}
\usepackage{ntheorem}
\theoremstyle{break}
\theorembodyfont{\normalfont}
\theoremseparator{.}
\theoremprework{
  \setlist*[enumerate]{label=(\alph*)} 
}
\newtheorem{problem}{Problem}


\begin{document}

\begin{problem}
  \begin{enumerate}
  \item First question.
  \item Second question.
  \end{enumerate}
\end{problem}

\begin{problem}
  \begin{enumerate}
  \item First question.
  \item Second question.
  \end{enumerate}
\end{problem}


\end{document}

Answer 3

Here is a solution using enumitem and etoolbox. I also changed the centred ‘Assignment’s, manually numbered, to sections, automatically numbered and referable, with the titlesec package.

\documentclass{article}

\usepackage[shortlabels]{enumitem}

\setlength{\parindent}{0pt}
\setlength{\parskip}{1ex}

\usepackage{etoolbox}
\newenvironment{problems}{%
\apptocmd{\item}{\mbox{}}{}{}
\setlist[enumerate, 2]{wide}
%\vspace{0.5\baselineskip}
\AtEndEnvironment{enumerate}{\vskip 1\baselineskip}
\begin{enumerate}[label={\large\bf Problem \arabic*.},wide]}%
{\end{enumerate}}

\usepackage[explicit]{titlesec}

\titleformat{\section}[block]{\filcenter\Large\scshape}{Assignment~\thesection}{0em}{\ifstrempty{#1}{}{: #1}}
\titlespacing{\section}{0pt}{2\baselineskip}{2.5\baselineskip}%{}

\begin{document}

\section{}
\begin{problems}

\item

\begin{enumerate}
    \item First question.
    \item Second question.
\end{enumerate}

\item

\begin{enumerate}
    \item First question.
    \item Second question.
\end{enumerate}

\end{problems}

\section{}

\begin{problems}

\item

\begin{enumerate}
    \item First question.
    \item Second question.
\end{enumerate}

\item

\begin{enumerate}
    \item First question.
    \item Second question.
\end{enumerate}

\end{problems}

\end{document} 

Answer 4

Start the second level lists with a empty item \item[] ([] is very important) or define a new list that do this like

\newenvironment{mylist}[1][]{\begin{enumerate}[#1]\item[]}{\end{enumerate}}

Thus, the normal space of the lists does not change and the options of the enumitem package can be used.

\begin{mylist}[<enumitem options>]
    \item First question.
    \item Second question.
\end{mylist}

My code

\documentclass{article}

\usepackage[shortlabels]{enumitem}

\setlength{\parindent}{0pt}
\setlength{\parskip}{1ex}

\begin{document}
\newenvironment{mylist}[1][]{\begin{enumerate}[#1]\item[]}{\end{enumerate}}
\begin{enumerate}[label={\large\bf Problem \arabic*.},wide]
\item
\begin{mylist}[(i)]
    \item First question.
    \item Second question.
\end{mylist}
\end{enumerate}
\end{document}

generates