enumitemlistsspacing
The enumitem package documentation says:
\topsep,\itemsep,\partopsep,\parsep?
Ok, it doesn't quite say that, but it also doesn't illustrate what these dimensions mean. Can I get a diagram with what each of these means? And what's the equivalent of \bottomsep?
Perhaps the multienum package could be an option:
\documentclass[12pt]{article}
\usepackage{amssymb} %for \blacksquare
\usepackage{multienum}
\newcommand{\rsqr}{\raisebox{0.4ex}{\tiny $\blacksquare$}}
\newlength\myindent
\newlength\mylen
\renewcommand{\itemxx}[2]{%
\setlength\mylen{\remainxx}
\addtolength\mylen{-\myindent}
\hskip\myindent
\parbox[t]{\labelwidth}{\hfill\labelenumi}%
\hskip\labelsep
\parbox[t]{0.5\mylen}{\raggedright #1}%
\hfill\parbox[t]{\labelwidth}{\hfill\labelenumi}%
\hskip\labelsep
\parbox[t]{0.5\mylen}{\raggedright #2}\smallskip}
\newenvironment{listable}[1][0cm]
{\begin{multienumerate}
\setlength\myindent{#1}
\renewcommand\labelenumi{\rsqr}
\setlength\itemsep{-.5\baselineskip}
}
{\end{multienumerate}}
\begin{document}
\begin{listable}
\mitemxx{Lots and lots of text, oh my!}{More and more text}
\mitemxx{word}{All work and no play makes Jack a dull boy}
\end{listable}
\begin{listable}[4em]
\mitemxx{Lots and lots of text, oh my!}{More and more text}
\mitemxx{word}{All work and no play makes Jack a dull boy}
\end{listable}
\end{document}
The optional argument of the listable environment controls the indentation from the left margin (default value: 0cm).
Your problem is due to the fact that on one hand you use the enumitem package but then you also define your own lists via the list environment of LaTeX. The enumitem package doesn't know about your new list and gets confused.
Basically what happens is that the following code in \enit@preset makes the wrong choice:
\ifnum\@listdepth=\@ne
\enit@outerparindent\parindent
\else
\parindent\enit@outerparindent
\fi
The idea of this code is to save the outer \parindent value in \enit@outerparindent when we enter the first level of lists and if we enter a nested list reuse the saved value instead. Now unfortunately your new list doesn't know about this so nothing gets saved. But if the enumerate is entered it is in fact already on level 2 and therefore \parindent gets the current value of \enit@outerparindent which is, of course, still zero.
So either you simply give listparindent and explicit value when you call enumarate, e.g.
\begin{enumerate}[parsep=0pt,listparindent=15pt]
or, if you like this properly fixed you could set \enit@outerparindent in your definition of exercises if it exists (i.e., if enumitem was loaded), e.g.,
\makeatletter
\newenvironment{exercises}%
{\begin{list}{\exitem}{%
\@ifundefined{enit@outerparindent}{}% if this command exists set it, otherwise do nothing
{\ifnum\@listdepth=\@ne
\enit@outerparindent\parindent
\else
\parindent\enit@outerparindent
\fi
}%
\usecounter{exercise}%
\small%
\setlength{\itemindent}{\exlabelwidth}%
\addtolength{\itemindent}{\labelsep}%
\setlength{\labelwidth}{\exlabelwidth}%
\addtolength{\labelwidth}{\exsymbolwidth}%
\addtolength{\labelwidth}{\exlabelsep}%
\setlength{\leftmargin}{0.0cm}%
\setlength{\itemsep}{0.0cm}%
\setlength{\parsep}{0.0cm}%
\setlength{\listparindent}{\parindent}%
}%
}%
{\end{list}}
\makeatother
Because of the @ signs you need \makeatletter ...\makeatother.
Best Answer
The book by Leslie Lamport, LaTeX: a document preparation system (1994) has a figure like the one you asked for on page 113, which explains, among other things, that the vertical space at the bottom of a list is always the same as the space at the top. The latter depends on the circumstances, namely, on whether the list was or was not started in vertical mode.
This is the corresponding figure in “The LaTeX Companion”