math_config.sty

\usepackage{amsmath}
\usepackage{amsthm}       
\usepackage{amssymb}

\usepackage{bm}
\usepackage{nicefrac}

\newcommand{\E}{\operatorname{\mathbf{E}}}
\newcommand{\Var}{\operatorname{\mathbf{Var}}}

% ------------------- Theoremstyles --------------------- %

% count within "chapter" for 2.1,2.2,.. numbering
% switch to "section" for 2.1.1, 2.1.2.. 
% see http://tex.stackexchange.com/questions/13831

\theoremstyle{definition}
\newtheorem{definition}{Definition}[section]
\newtheorem*{definition*}{Definition}
\theoremstyle{theorem}
\newtheorem{theorem}[definition]{Theorem}           % sharing
\newtheorem*{theorem*}{Theorem}           % sharing
\newtheorem{proposition}[definition]{Proposition}   % counter
\newtheorem*{theorem_w}{Proposition}   % counter
\newtheorem{lemma}[definition]{Lemma}               % with   
\newtheorem{corollary}[definition]{Corollary}       % definition
\newtheorem{algorithm}[definition]{Algorithm}


\theoremstyle{remark}
% \newtheorem{remark}[definition]{Remark}  % numbered remarks
\newtheorem*{remark}{Remark}               % unnumbered remarks
%\newtheorem{example}[definition]{Remark}

% \newenvironment{example}[1][Example]{\begin{trivlist}
%  \item[\hskip \labelsep {\bfseries #1}]}{\end{trivlist}}
% \newenvironment{remark}[1][Remark]{\begin{trivlist}
% \item[\hskip \labelsep {\bfseries #1}]}{\end{trivlist}}



% ------------------ Theorem Spacing -------------------- %

% make spacing compatible with KOMA scirpt parskip=full
% http://tex.stackexchange.com/a/167608/4912
\begingroup
    \makeatletter
    \@for\theoremstyle:=definition,remark,plain\do{%
        \expandafter\g@addto@macro\csname th@\theoremstyle\endcsname{%
            \setlength\thm@preskip\parskip
            \setlength\thm@postskip{0pt}
            }%
        }
\endgroup

% adjust proof environment
% http://tex.stackexchange.com/a/59769/4912
\makeatletter
\renewenvironment{proof}[1][\proofname]{\par
  \vspace{-\topsep}% remove the space after the theorem
  \pushQED{\qed}%
  \normalfont
  \topsep0pt \partopsep0pt % controls space before
  \trivlist
  \item[\hskip\labelsep
        \itshape
    #1\@addpunct{.}]\ignorespaces
}{%
  \popQED\endtrivlist\@endpefalse
  \addvspace{0pt} % controls space after
}
\makeatother


% -------------- Norm || - || and Abs |-|  -------------- %

% defines \norm{} and \abs to automatically resize
% see http://tex.stackexchange.com/a/43009/4912
\usepackage{mathtools}
\DeclarePairedDelimiter\abs{\lvert}{\rvert}%
\DeclarePairedDelimiter\norm{\lVert}{\rVert}%

% Swap the definition of \abs* and \norm*, so that \abs
% and \norm resizes the size of the brackets, and the 
% starred version does not.
\makeatletter
\let\oldabs\abs
\def\abs{\@ifstar{\oldabs}{\oldabs*}}
%
\let\oldnorm\norm
\def\norm{\@ifstar{\oldnorm}{\oldnorm*}}
\makeatother