Auto adjust item separation for equal spacing

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}
}

(though I don't think it matters that much for the question)

and I've been searching for a way to auto-adjust itemsep to have equal space between all items. This is what I don't want to happen:

Because of the fraction using more height, the spacing between A-B-C is different from the spacing between C-D-E, and it looks odd for me. My current fix is to use the optional parameter in the environment to manually adjust the itemsep parameter and get it to look like this:

However, it is slow to manually adjust and I need some less-experienced people to use this environment. Is there a way for itemsep to be automatically set to the biggest separation between items? I searched a lot and couldn't find it (maybe my bad english didn't help). Thanks!

Answer 1

My proposed solution is to measure the height and depth of each item, so to get the maximum height and depth. If necessary, the baseline skip is set to the maximum height plus the maximum depth plus 2pt.

\documentclass{article}
\usepackage{xparse,enumitem,amsmath}

\ExplSyntaxOn

\NewDocumentCommand{\alternatives}{m}
 {
  \blaz_alternativas:n { #1 }
 }

\seq_new:N \l__blaz_alternativas_seq
\box_new:N \l__blaz_alternativas_item_box
\dim_new:N \l__blaz_alternativas_height_dim
\dim_new:N \l__blaz_alternativas_depth_dim

\cs_new_protected:Nn \blaz_alternativas:n
 {
  % first populate the sequence of items
  \seq_set_split:Nnn \l__blaz_alternativas_seq { \\ } { #1 }
  % now measure the heights and depths
  \dim_zero:N \l__blaz_alternativas_height_dim
  \dim_zero:N \l__blaz_alternativas_depth_dim
  \seq_indexed_map_inline:Nn \l__blaz_alternativas_seq
   {
    % set the box to the current item
    \hbox_set:Nn \l__blaz_alternativas_item_box { ##2 }
    % measure the height if not the first item
    \int_compare:nT { ##1 > 1 }
     {
      \dim_set:Nn \l__blaz_alternativas_height_dim
       {
        \dim_max:nn { \l__blaz_alternativas_height_dim }
                    { \box_ht:N \l__blaz_alternativas_item_box }
       }
     }
    % measure the depth if not the last item
    \int_compare:nT { ##1 < \seq_count:N \l__blaz_alternativas_seq }
     {
      \dim_set:Nn \l__blaz_alternativas_depth_dim
       {
        \dim_max:nn { \l__blaz_alternativas_depth_dim }
                    { \box_dp:N \l__blaz_alternativas_item_box }
       }
     }
   }
   \begin{enumerate}[label={\Alph*)},wide=0pt,labelwidth=.5cm,leftmargin=!,itemsep=0pt]
   % set the baselineskip
   \skip_set:Nn \baselineskip
    {
     \dim_max:nn { \baselineskip }
                 { \l__blaz_alternativas_height_dim + \l__blaz_alternativas_depth_dim }
     + 2pt
    }
   % deliver the items
   \seq_map_inline:Nn \l__blaz_alternativas_seq { \item ##1 }
   \end{enumerate}
 }

\ExplSyntaxOff

\begin{document}

\alternatives{ $1$ \\ $2$ \\ $3$ \\ $4$ \\ $5$ }

\alternatives{
  $1$ \\
  $\dfrac{3}{2}$ \\
  $\dfrac{3}{4}$ \\
  $4$ \\
  $5$
}

\end{document}

Here's a version that adds \hphantom{$-$} in front of each item that doesn't start with $-, provided at least one does.

\documentclass{article}
\usepackage{xparse,enumitem,amsmath}

\ExplSyntaxOn

\NewDocumentCommand{\alternatives}{m}
 {
  \blaz_alternativas:n { #1 }
 }

\seq_new:N \l__blaz_alternativas_seq
\box_new:N \l__blaz_alternativas_item_box
\dim_new:N \l__blaz_alternativas_height_dim
\dim_new:N \l__blaz_alternativas_depth_dim

\cs_new_protected:Nn \blaz_alternativas:n
 {
  % first populate the sequence of items
  \seq_set_split:Nnn \l__blaz_alternativas_seq { \\ } { #1 }
  % now measure the heights and depths
  \dim_zero:N \l__blaz_alternativas_height_dim
  \dim_zero:N \l__blaz_alternativas_depth_dim
  \seq_indexed_map_inline:Nn \l__blaz_alternativas_seq
   {
    % set the box to the current item
    \hbox_set:Nn \l__blaz_alternativas_item_box { ##2 }
    % measure the height if not the first item
    \int_compare:nT { ##1 > 1 }
     {
      \dim_set:Nn \l__blaz_alternativas_height_dim
       {
        \dim_max:nn { \l__blaz_alternativas_height_dim }
                    { \box_ht:N \l__blaz_alternativas_item_box }
       }
     }
    % measure the depth if not the last item
    \int_compare:nT { ##1 < \seq_count:N \l__blaz_alternativas_seq }
     {
      \dim_set:Nn \l__blaz_alternativas_depth_dim
       {
        \dim_max:nn { \l__blaz_alternativas_depth_dim }
                    { \box_dp:N \l__blaz_alternativas_item_box }
       }
     }
   }
   \begin{enumerate}[label={\Alph*)},wide=0pt,labelwidth=.5cm,leftmargin=!,itemsep=0pt]
   % set the baselineskip
   \skip_set:Nn \baselineskip
    {
     \dim_max:nn { \baselineskip }
                 { \l__blaz_alternativas_height_dim + \l__blaz_alternativas_depth_dim }
     + 2pt
    }
   % check whether some items start with $-
   \cs_set_protected:Nn \__blaz_alternativas_minus:n {##1} % do nothing by default
   \seq_map_inline:Nn \l__blaz_alternativas_seq
    {
     \regex_match:nnT { \A \$\- } { ##1 }
      {
       \seq_map_break:n
        {
         \cs_set_eq:NN \__blaz_alternativas_minus:n \__blaz_alternativas_addminus:n
        }
      }
    }
   % deliver the items
   \seq_map_inline:Nn \l__blaz_alternativas_seq { \item \__blaz_alternativas_minus:n {##1} }
   \end{enumerate}
 }
\cs_new_protected:Nn \__blaz_alternativas_addminus:n
 {
  \regex_match:nnF { \A \$\- } { #1 } { \hphantom{$-$} } #1
 }

\ExplSyntaxOff

\begin{document}

\alternatives{ $1$ \\ $2$ \\ $3$ \\ $4$ \\ $5$ }

\alternatives{
  $-1$ \\
  $-\dfrac{3}{2}$ \\
  $\dfrac{3}{4}$ \\
  $4$ \\
  $5$
}

\end{document}

Answer 2

Here is an entirely different approach based on a tabular. I have used a sligthly adapted version of the automaic table row numbering in combination with the cellspace package for the spacing around the entries. Since I right aligned the column, this also seems to solve your follow-up question:

\documentclass{article}
\usepackage[column=0]{cellspace}
\setlength\cellspacetoplimit{6pt}
\setlength\cellspacebottomlimit{\cellspacetoplimit}

\usepackage{array,etoolbox}
\preto\tabular{\setcounter{magicrownumbers}{0}}
\newcounter{magicrownumbers}
\newcommand\rownumber{\stepcounter{magicrownumbers}\Alph{magicrownumbers}}
\usepackage{amsmath}

\newenvironment{myalternatives}[1][0]
{\begin{tabular}{@{\makebox[3em][r]{\rownumber)~}}  >{$}0r<{$}}}
{\end{tabular}}

\begin{document}

\begin{myalternatives}
  1 \\
  \dfrac{3}{2} \\
  \dfrac{3}{4} \\
  4 \\
  5 \\
  -6\\
\end{myalternatives}

\end{document}