mathsetup.sty

\usepackage{xspace}
\usepackage{amsmath}
\usepackage{amssymb}
% includes proof env
\usepackage{amsthm}
% provides \mathscr font
\usepackage{mathrsfs}
% provides IEEEeqnarray environment
% included in the texlive-publishers apt-get package
\usepackage[retainorgcmds]{IEEEtrantools}
% labels and refs for enumerate environment
\usepackage{enumitem}
% in the texlive-science apt-get package
% provides the \lightning (contraction) symbol
\usepackage{stmaryrd}

\newtheorem{thm}{Theorem}[chapter]
\newtheorem{prop}[thm]{Proposition}
\newtheorem{lem}[thm]{Lemma}
\newtheorem{cor}[thm]{Corollary}
\newtheorem*{axiom}{Axiom}
\newtheorem*{defn}{Definition}
\newtheorem*{nota}{Notation}
\newtheorem*{rem*}{\remarknumber}
\providecommand{\remarknumber}{}
\newtheorem*{Ex*}{\exercisenumber}
\providecommand{\exercisenumber}{}
\newtheorem*{exa}{Example}
\newtheorem*{fact}{Fact}

%% ---- RedeclareMathOperator ----
% https://tex.stackexchange.com/questions/175251/how-to-redefine-a-command-using-declaremathoperator
\newcommand\RedeclareMathOperator{%
  \@ifstar{\def\rmo@s{m}\rmo@redeclare}{\def\rmo@s{o}\rmo@redeclare}%
}
% this is taken from \renew@command
\newcommand\rmo@redeclare[2]{%
  \begingroup \escapechar\m@ne\xdef\@gtempa{{\string#1}}\endgroup
  \expandafter\@ifundefined\@gtempa
     {\@latex@error{\noexpand#1undefined}\@ehc}%
     \relax
  \expandafter\rmo@declmathop\rmo@s{#1}{#2}}
% This is just \@declmathop without \@ifdefinable
\newcommand\rmo@declmathop[3]{%
  \DeclareRobustCommand{#2}{\qopname\newmcodes@#1{#3}}%
}
\@onlypreamble\RedeclareMathOperator
%% ----


\DeclareMathOperator{\st}{\,st.}
\DeclareMathOperator{\iffa}{\Leftrightarrow}
\RedeclareMathOperator{\iff}{\ iff\ }
\DeclareMathOperator{\Ima}{Im}
\DeclareMathOperator{\Int}{Int}
\DeclareMathOperator{\card}{card}
\DeclareMathOperator{\diam}{diam}
\DeclareMathOperator{\nbhd}{nbhd}
\DeclareMathOperator{\subspc}{subspc}
\DeclareMathOperator{\bdry}{\partial}
\DeclareMathOperator{\acc}{acc}
\DeclareMathOperator{\topo}{\tau}
\newcommand{\setcomp}[1]{{#1}^{\mathsf{c}}}
\newcommand{\setint}[1]{{#1}^{\circ}}
% https://tex.stackexchange.com/questions/22252/how-to-typeset-function-restrictions
\newcommand{\restr}[2]{{% we make the whole thing an ordinary symbol
  \left.\kern-\nulldelimiterspace % automatically resize the bar with \right
  #1 % the function
  \vphantom{\big|} % pretend it's a little taller at normal size
  \right|_{#2} % this is the delimiter
}}
\newcommand{\loopy}{\circledast}
\newcommand{\attn}{\bigstar}

% as in
% https://tex.stackexchange.com/questions/167030/numbering-of-assumptions
% allow custom labels via \begin{rem}{<label>} of remarks
\newenvironment{rem}[1]{%
  %% todo: omit space when #1 undefined, possibly with ifthenelse pkg
  \renewcommand{\remarknumber}{Remark #1}%
  \begin{rem*}%
    \protected@edef\@currentlabel{#1}%
}{%
  \end{rem*}
}
\newenvironment{Ex}[1]{%
  %% todo: omit space when #1 undefined, possibly with ifthenelse pkg
  \renewcommand{\exercisenumber}{Exercise #1}%
  \begin{Ex*}%
    \protected@edef\@currentlabel{#1}%
}{%
  \end{Ex*}
}

% https://tex.stackexchange.com/questions/147812/customizing-equation-numbering-labeling-in-ieeeeqnarray
% ... avoiding pulling in the geometry package for now
\newenvironment{IEEEeqnarraytagged}[2]{%
  \begin{equation}
    \tag{#2}
    \begin{minipage}{\linewidth}
      \begin{IEEEeqnarray*}{#1}
}{%
      \end{IEEEeqnarray*}
    \end{minipage}
  \end{equation}
}

\newenvironment{addcomment}{\begin{quote}$\circledast$}{$\circledast$\end{quote}}

\newcommand{\sketch}[1]{
  \begin{quote}
    \texttt{#1}
  \end{quote}
}

%%% https://emacs.stackexchange.com/questions/14971/how-can-i-write-0-1-in-latex-mode-without-breaking-indentation
\newcommand{\openhalf}[2]{\ensuremath{(#1,#2]}}
\newcommand{\halfopen}[2]{\ensuremath{[#1,#2)}}