Align list ignoring negative sign of the first number in items

Question

I am currently using enumitem and made an environment for my lists in a document. It is the following:

\newenvironment{alternativas}[1][0]
{
    \begin{enumerate}[label={\Alph*)}, itemsep=#1cm, topsep = 0.5cm, wide=0pt,labelwidth=.5cm,leftmargin=!]
}
{
    \end{enumerate}
}

I've been trying to align the items ignoring the negative sign, if the item starts with one. Images will explain it a lot better than me:

I've searched for similar questions and I've only found people with this problem on a table, and solutions usign align environments and stuff like that. I even searched for something to solve this in TeX books (and accidentally learned a lot while doing that haha) but I haven't been successful.

Many solutions for these similar problems also make use of some manual adjustment, like using a \phantom in the items without a minus sign so that the spacing looks equal (I produced the wanted result using \hspace with a negative number). But I have been searching for a solution that automatizes this for me, because I share the documents with less experienced people and want it to be easy for them to use. Thank you very much!

The same should happen with any-digit numbers, better if it works with fractions too. Align with the first non minus sign character — Blaz Korecic, Mar 26 '20 at 11:05
Are you sure you want a list for this? The advantages of a list is that the contents can break across pages and you can nest them. The main disadvantage is that the text after \item is NOT an argument and cannot be parsed easily. — John Kormylo, Mar 26 '20 at 13:46
I actually was looking for a way for my lists to not break across pages, so that may be really helpful too — Blaz Korecic, Mar 26 '20 at 22:49

Steven B. Segletes · Accepted Answer · 2020-03-26T22:41:43.353

5

What i do is to redefine \item inside the environment to examine the first token of \item (following an optional argument). If it is a - token, I \mathllap it and then continue, else I just typeset it directly.

\documentclass{article}
\usepackage{enumitem,mathtools}
\let\svitem\item
\newenvironment{alternativas}[1][0]
{
  \renewcommand\item[2][\relax]{%
    \ifx\relax##1\def\next{}\else\def\next{[##1]}\fi
    \ifx-##2\def\nnext{$\mathllap{##2}$}\else\def\nnext{##2}\fi
    \expandafter\svitem\next\nnext}
    \begin{enumerate}[label={\Alph*)}, itemsep=#1cm, topsep = 0.5cm, 
      wide=0pt, labelwidth=.5cm,leftmargin=!,labelsep=10pt]
}
{
    \end{enumerate}
}
\begin{document}
\begin{alternativas}
\item -1
\item 4
\item -5
\item 6
\end{alternativas}
\end{document}

ADDENDUM

OP clarified in comments that all numbers are entered in math mode (via leading $). However, not all items begin with math. So, some revisions were required:

\documentclass{article}
\usepackage{enumitem,mathtools}
\let\svitem\item
\newenvironment{alternativas}[1][0]
{
  \renewcommand\item[3][\relax]{%
    \ifx\relax##1\def\next{}\else\def\next{[##1]}\fi
    \ifx$##2\ifx-##3\def\nnext{##2\mathllap{##3}}\else\def\nnext{##2##3}\fi
      \else\def\nnext{##2##3}\fi
    \expandafter\svitem\next\nnext}
    \begin{enumerate}[label={\Alph*)}, itemsep=#1cm, topsep = 0.5cm, 
      wide=0pt, labelwidth=.5cm,leftmargin=!,labelsep=10pt]
}
{
    \end{enumerate}
}
\begin{document}
\begin{alternativas}
\item $-1$
\item $4$
\item $-\frac{5}{7}$
\item $\frac{6}{11}$
\item text
\end{alternativas}
\end{document}

edited Mar 26 '20 at 22:41

answered Mar 26 '20 at 10:35

Steven B. Segletes

237,551

Thanks a lot for you answer! I have a problem with it, though: when I insert numbers in math mode in an \item, it doesn't work (i.e \item $-13$ won't work) so if I need to use a fraction, it won't work because I have to put it in math mode – Blaz Korecic Mar 26 '20 at 22:21
Is it because if I insert math mode, the first token will be $ instead of -? Is it possible to make this work if the item starts with "$-"? – Blaz Korecic Mar 26 '20 at 22:29
1

@BlazKorecic So, sometimes the \item may begin with a number, other times with a minus, and still other times with a $-? – Steven B. Segletes Mar 26 '20 at 22:29
It will never start with a minus. All numbers will be in math mode, and if it starts with $- then the mathllap is needed – Blaz Korecic Mar 26 '20 at 22:30
1

@BlazKorecic An obvious workaround on your part is to place the minus before you enter math mode. However, my prior comment is an effort to nail to all possible uses. If there is some regularity, I might be able to develop something that works. But you need to tell me all the ways it could be used. – Steven B. Segletes Mar 26 '20 at 22:30
1

Sometimes there will be items without math mode. However, they will have no numbers and the mathllap will never be needed in that case – Blaz Korecic Mar 26 '20 at 22:33
1

@BlazKorecic Please see ADDENDUM – Steven B. Segletes Mar 26 '20 at 22:41

score 3 · Answer 2 · answered Mar 26 '20 at 11:10

You can load mathtools (needless to load amsmath in this case) to use its \mathllap command and slightly increase \labelsep:

\documentclass{article}

\usepackage{enumitem}
\usepackage{mathtools}
\newenvironment{alternativas}[1][0]
{
    \begin{enumerate}[label={\Alph*)}, itemsep=#1cm, topsep = 0.5cm, labelsep=6pt, wide=0pt,labelwidth=.5cm,leftmargin=!]
}
{
    \end{enumerate}
}

\begin{document}

 \begin{alternativas}
    \item $\mathllap{-}1 $
    \item $ 4 $
    \item $ \mathllap{-}5 $
    \item $ 6 $
    \end{alternativas}

\end{document}

Align list ignoring negative sign of the first number in items

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