Use \item as a string in comparison

Question

I wish to design a convenience command \lazycmd that works like this (simplified version):

\newcommand{\lazycmd}[1]{%
  ...
}

% Use case 1.
\lazycmd{
  \item one
  \item two
}

% Use case 2.
\lazycmd{
  custom
}

\lazycmd is expected to:

Add \begin{itemize} and \end{itemize} in the front and the back of #1, if the argument begins with \item (with leading spaces skipped). This is my "normal case".
Otherwise, copy #1. This is my "special case", as the argument will provides its own format.

The problems are, how to use "\item" as a string in the comparison, and how to skip any potential leading spaces? Thanks a lot!

Manuel · Accepted Answer · 2015-12-31T08:56:40.043

Option one.

\newcommand\lazycmd[1]{\begingroup
  \let\saveditem\item
  \let\auxend\relax
  \def\item{\let\item\saveditem\def\auxend{\end{itemize}}\begin{itemize}\item}%
  #1%
  \auxend\endgroup
}

Option two.

\newcommand\lazycmd[1]{\dolazycmd#1\endlazycmd}
\def\dolazycmd#1\endlazycmd
  {\@ifnextchar\item{\def\auxend{\end{itemize}}\begin{itemize}}{\let\auxend\relax}#1\auxend}

Third option.

\newcommand\lazycmd[1]{\dolazycmd#1\endlazycmd}
\def\dolazycmd#1#2\endlazycmd
  {\ifx\item#1
     \begin{itemize}#1#2\end{itemize}%
   \else
     #1#2%
   \fi}

score 1 · Answer 2 · answered Dec 31 '15 at 12:30

You may be interested in an expl3 based solution:

\documentclass{article}

\usepackage{xparse}

\ExplSyntaxOn
\NewDocumentCommand{\lazycmd}{O{\use:n} m}
 {
  \seq_set_split:Nnn \l_wdscxsj_lazycmd_seq { \item } { #2 }
  \int_compare:nTF { \seq_count:N \l_wdscxsj_lazycmd_seq > 1 }
   { % more than one item, there was \item
    \begin{itemize}
    \seq_use:Nn \l_wdscxsj_lazycmd_seq { \item }
    \end{itemize}
   }
   {
    #1 { \tl_trim_spaces:n { #2 } }
   }
 }
\seq_new:N \l_wdscxsj_lazycmd_seq
\ExplSyntaxOff

\begin{document}

Here is some text followed by the command
\lazycmd{
  \item one
  \item two
}
and the same without any item
\lazycmd{
  single
}
that can also be typeset in a different way
\lazycmd[\textbf]{
  single
}

\end{document}

Use \item as a string in comparison

2 Answers2