How can I make a math version of itemize, enumerate, and description environments?

Question

tabular is to array as itemize is to …?

I'd like to have a list like

\documentclass{article}
\begin{document}
\begin{eqlist}
\item E=mc^2
\item e^{i\pi}+1=0
\item \text{ducks} + \text{caffeine}
    = \text{\url{https://i.stack.imgur.com/GVksc.gif}}
\end{eqlist}
\end{document}

I'm already using enumitem, but I don't think that package will be of any help. Of course, any solution will work :)

Important variations:

• What about display math?
• What about the other list environments – like description and enumerate?

Use Case

The use-case is pretty trivial, actually – to have a list of equations. You could call this 'for fun', but I have in the past actually hacked something together for class notes that allowed me to do something like this (e.g. listing out and naming the properties of algebraic groups). I had thought the idea was limited to that so I never generalized my (terribly messy) solution, but I'm seeing the pattern pop-up more and more in various documents where it actually doesn't look absolutely awful as you'd expect. Conveniently, I don't have any solid examples except this newbie document that popped up on reddit.com/r/LaTeX.

Answer 1

Here is a solution (it doesn't use, but I hope it will be compatible with enumitem)

Note: I don't understand what the OP want to do with display math

Limitation: blank lines not supported (this code will not work)

\begin{mathitem}
\item E=mc^2

\item e^{i\pi}+1=0
\item \text{ducks} + \text{caffeine}
    = \text{\url{https://i.stack.imgur.com/GVksc.gif}}
\end{mathitem}

Complete code

\documentclass{article}
\usepackage{xpatch}

\usepackage{amsmath,url}
\usepackage{enumitem}


\makeatletter
\newcommand{\mtmathitem}{%
\xpatchcmd{\item}{\@inmatherr\item}{\relax\ifmmode$\fi}{}{\errmessage{Patching of \noexpand\item failed}}
\xapptocmd{\@item}{$}{}{\errmessage{appending to \noexpand\@item failed}}}
\makeatother

\newenvironment{mathitem}[1][]{%
\itemize[#1]\mtmathitem}{$\endlist}                    %$

\newenvironment{mathenum}[1][]{%
\enumerate[#1]\mtmathitem}{$\endlist}                  %$

\newenvironment{mathdesc}[1][]{%
\description[#1]\mtmathitem}{$\endlist}                %$


\begin{document}

\begin{mathitem}
\item E=mc^2
\item e^{i\pi}+1=0
\item \text{ducks} + \text{caffeine}
    = \text{\url{https://i.stack.imgur.com/GVksc.gif}}
\end{mathitem}


\begin{mathenum}
\item E=mc^2
\item e^{i\pi}+1=0
\item \text{ducks} + \text{caffeine}
    = \text{\url{https://i.stack.imgur.com/GVksc.gif}}
\end{mathenum}


\begin{mathenum}[label=\emph{\alph*})]
\item E=mc^2
\item e^{i\pi}+1=0
\item \text{ducks} + \text{caffeine}
    = \text{\url{https://i.stack.imgur.com/GVksc.gif}}
\end{mathenum}

\begin{mathdesc}
\item[some] E=mc^2
\item[thing] e^{i\pi}+1=0
\item[else] \text{ducks} + \text{caffeine}
    = \text{\url{https://i.stack.imgur.com/GVksc.gif}}
\end{mathdesc}

\end{document}

Answer 2

(Answer modified to (i) add a "MathDescription" environment and (ii) demonstrate compatibility with the enumitem package.)

Here's a LuaLaTeX-based solution. It defines three new environments called MathItemize, MathEnumerate, and MathDescription. The environments work just like the "ordinary" itemize, enumerate, and description environments, except that all material (other than the descriptive labels in the MathDescription environment) is typeset in math mode instead of text mode.

If need be, \displaystyle can be inserted after \item in order to render an item's contents in displaymath mode. Use

\item \displaystyle \hfill <formula> \hfill 

to center-set the display-math material.

The code appears to work very well with the enumitem package. To wit, the example below below loads the enumitem package and changes some of the default settings of the itemize and enumerate environments.

As the OP's write-up and comments do not seem to indicate a need for nested lists, the code works only for non-nested lists.

% !TEX TS-program = lualatex
\documentclass{article}
\usepackage{amsmath}      % for "\text" macro
\usepackage{url,hyperref} 
\hypersetup{colorlinks=true}

%% Check compatibility with "enumitem" package...
\usepackage{enumitem} 
\setlist{itemsep=1ex}
\setlist[itemize]{label=$\star$}
\setlist[enumerate]{label=\roman*), leftmargin=*, widest = iii}

\usepackage{luacode,luatexbase}
%% Lua-side code: Three Boolean variables, two new
%% functions, & calls to assign the new functions to 
%% the "process_input_buffer" callback
\begin{luacode}
env_type_1 = false
env_type_2 = false
first_list_item = true

function change_item_properties_itemenum ( line )
  if (env_type_1 == true) then
    if (first_list_item == true) then
        line = string.gsub( line, "\\item", "\\item $" )
        first_list_item = false
    else 
        line = string.gsub( line, "\\item", "$ \\item $" )
    end  
  end  
  return (line)
end

function change_item_properties_desc ( line )
  if (env_type_2 == true) then
    if (first_list_item == true) then
        line = string.gsub( line, "(\\item.-%[.-%])", "%0 $" )
        first_list_item = false
    else 
        line = string.gsub( line, "(\\item.-%[.-%])", "$ %0 $" )
    end  
  end  
  return (line)
end

luatexbase.add_to_callback ( "process_input_buffer",
        change_item_properties_itemenum, 
        "MathModeItemizeEnumerate" )
luatexbase.add_to_callback ( "process_input_buffer",
        change_item_properties_desc, 
        "MathModeDescription" )
\end{luacode}

%% TeX-side code -- Three new environments: 
%% MathItemize, MathEnumerate, MathDescription
\newenvironment{MathItemize}%
  {\directlua{ env_type_1 = true }
   \begin{itemize} }%
  {$\end{itemize}
   \directlua{ env_type_1 = false 
               first_list_item = true}}
\newenvironment{MathEnumerate}%
  {\directlua{ env_type_1 = true }
   \begin{enumerate}}%
  {$\end{enumerate}
   \directlua{ env_type_1 = false 
               first_list_item = true}}
\newenvironment{MathDescription}%
  {\directlua{ env_type_2 = true }
   \begin{description}}%
  {$\end{description}
   \directlua{ env_type_2 = false 
               first_list_item = true}}

\begin{document}

\noindent
A \verb+MathItemize+ list
\begin{MathItemize}
\item E=mc^2
\item e^{i\pi}+1=0
\item \text{ducks} + \text{caffeine}
    = \text{\url{https://i.stack.imgur.com/GVksc.gif}}
\end{MathItemize}

\bigskip\noindent
An ``ordinary'' \verb+itemize+ list
\begin{itemize}
\item Hello world.
\item Goodbye world.
\end{itemize}

\bigskip\noindent
A \verb+MathEnumerate+ list
\begin{MathEnumerate}
\item a^2+b^2=c^2
\item \displaystyle \hfill \sum_{k=1}^\infty \frac{1}{k^2} = \frac{\pi^2}{6} \hfill
\item 1+1=2
\end{MathEnumerate}

\bigskip\noindent
A \verb+MathDescription+ list
\begin{MathDescription}
\item [Einstein] \hfill  E=mc^2 \hfill 
\item[Euler] e^{i\pi}+1=0
\item  [Pythagoras] a^2+b^2=c^2
\end{MathDescription}

\bigskip\noindent
Finally, an ``ordinary'' \verb+enumerate+ list
\begin{enumerate}[widest=ii] 
\item abcdef, and
\item uvwxyz.
\end{enumerate}

\end{document}

Answer 3

Quick and dirty:

\documentclass{article}

\makeatletter
\newif\if@mathitemize
\newif\if@closemathitem
\let\orig@item=\item
\renewcommand{\item}{\if@closemathitem$\fi\orig@item\if@mathitemize\@closemathitemtrue$\fi}
\newenvironment{mathitemize}{\@mathitemizetrue\itemize\@closemathitemfalse}{$\enditemize}
\makeatother

\begin{document}

\begin{itemize}
\item test
\item test2
\end{itemize}

\begin{mathitemize}
\item E=mc^2
\end{mathitemize}

\end{document}