\documentclass{amsart}
\usepackage{enumitem}
\begin{document}
\begin{enumerate}[label=\arabic*, ref=(\arabic*)]
  \item \label{samesign1} They are of the same sign.
  \end{enumerate}
\ref{samesign1} is bad.
\end{document}

\begin{tikzpicture}
\coordinate (first)  at (0,0);
\coordinate (second) at  (1,0);

\node at (first) {$\circ$};
\node at (second) {$\circ$};

\node [below] at (first) {$s_1$};
\node [below] at (second) {$s_2$};

edge [-] (first)
edge [-] (second);
\end{tikzpicture}

\documentclass[tikz]{standalone}
\tikzset{dots/.style={shape=circle,draw,inner sep=1pt}}
\begin{document}
\begin{tikzpicture}
\node[dots, label=below:$s_1$] (first)   at (0,0) {};
\node[dots, label=below:$s_2$] (second)  at (1,0) {};
\path (first) edge (second);
\end{tikzpicture}
\end{document}

\documentclass[tikz]{standalone}
\tikzset{
	dots/.style={shape=circle,draw,inner sep=1pt,label=#1},
	dynkin/.style={shorten >=6\pgflinewidth,shorten <=6\pgflinewidth}
}
\begin{document}
\begin{tikzpicture}
\node[dots=below:$s_1$] (first)   at (0,0) {};
\node[dots=below:$s_2$] (second)  at (1,0) {};
\path[dynkin] (first) edge (second);
\end{tikzpicture}
\end{document}

\documentclass[tikz]{standalone}
\tikzset{
	dots/.style={shape=circle,draw,inner sep=1pt,label=#1,outer sep=2pt},
}
\begin{document}
\begin{tikzpicture}
\node[dots=below:$s_1$] (first)   at (0,0) {};
\node[dots=below:$s_2$] (second)  at (1,0) {};
\draw (first) -- (second);
\end{tikzpicture}
\end{document}

\documentclass[tikz]{standalone}
\tikzset{
	dots/.style={shape=circle,draw,inner sep=1pt,label=#1,outer sep=2pt},
    dynkin/.style={shorten >=6\pgflinewidth,shorten <=6\pgflinewidth}
}
\begin{document}
\begin{tikzpicture}[>=stealth]
\node[dots=below:$s_1$] (first)   at (0,0) {};
\node[dots=below:$s_2$] (second)  at (1,0) {};
\path (first) edge[ultra thick,<->,bend left] (second);
\path (first) edge[ultra thick,dynkin,<->,bend right] (second);
\end{tikzpicture}
\end{document}

\documentclass[tikz,convert=false]{standalone}
\usetikzlibrary{shapes.geometric}
\begin{document}
\begin{tikzpicture}
\tikzstyle{every node}=[trapezium, draw]
\tikzset{every trapezium node/.append style={minimum width=3cm,trapezium left angle=120, trapezium right angle=60}}

\node[trapezium stretches body] at (0,0) {A};
\node[rotate=-30] at (0,1.5) {A rotate $-30^\circ$};

\node[minimum height=1cm] at (3,0) {B};

\node[minimum height=1cm,rotate=-30] at (3,1.8) {B rotate $-30^\circ$};
\end{tikzpicture}

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pstricks}

\begin{document}
% starred
\begin{pspicture}[showgrid=top](4,4)
\psframe*[linecolor=red](1,1)(3,3)
\end{pspicture}

% dimen=middle
\begin{pspicture}[showgrid=top](4,4)
\psframe[fillstyle=solid,fillcolor=red,linestyle=none,dimen=middle](1,1)(3,3)
\end{pspicture}

% linewidth=0
\begin{pspicture}[showgrid=top](4,4)
\psframe[fillstyle=solid,fillcolor=red,linestyle=none,linewidth=0](1,1)(3,3)
\end{pspicture}
\end{document}

\def\solid@star{%
  \if@star
    \pslinewidth=\z@
    \psdoublelinefalse
    \def\pslinestyle{none}%
    \def\psk@fillstyle{\psfs@solid}%
    \let\psfillcolor\pslinecolor
  \fi}

\def\solid@star{%
  \if@star
    \pslinewidth=\z@
    \psdoublelinefalse
    \def\pslinestyle{none}%
    \def\psk@fillstyle{\psfs@solid}%
    \let\psfillcolor\pslinecolor
  \fi}

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage{expl3}
\usepackage{xparse}

\ExplSyntaxOn

\int_new:N \fm_counter_int

\NewDocumentCommand{\happybirthday} { } {
	\int_set:Nn \fm_counter_int { 1 }
	\fp_do_until:nn { \fm_counter_int = 5} {
		Zum ~ Geburtstag \int_compare:nNnTF \fm_counter_int = 3 {  , ~ liebe ~ Frank } { ~ viel ~ Glück } ! \par
		\int_incr:N \fm_counter_int
	}
}

\ExplSyntaxOff

\begin{document}

\happybirthday

\end{document}

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}


\usepackage{expl3}
\usepackage{xparse}

\ExplSyntaxOn

\int_new:N \fm_counter_int

\NewDocumentCommand{\happybirthday} { } {
	\int_set:Nn \fm_counter_int { 1 }
	\fp_do_until:nn { \fm_counter_int = 5} {
		Zum ~ Geburtstag \int_compare:nNnTF \fm_counter_int = 3
		{ , ~ lieber ~ Frank }
		{ ~ viel ~ Glück }
		! \par
		\int_incr:N \fm_counter_int
	}
}

\ExplSyntaxOff

\begin{document}

\happybirthday

\end{document}

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\happybirthday} { }
 {
  \int_step_inline:nnnn { 1 } { 1 } { 4 }
   {
    Zum ~ Geburtstag
     \int_compare:nTF { ##1 = 3 }
      { , ~ liebe ~ Frank }
      { ~ viel ~ Gl\"uck }
    ! \par
   }
 }
\ExplSyntaxOff

\begin{document}

\happybirthday

\end{document}

Psmith, the TeX bot, in fixed font mode: Here's the output from texdef:

\newpage:
macro:->\if@noskipsec \ifx \@nodocument \relax \leavevmode \global \@noskipsecfalse \fi \fi \if@inlabel \leavevmode \global \@inlabelfalse \fi \if@nobreak \@nobreakfalse \everypar {}\fi \par \vfil \penalty -\@M


\newline:
macro:->\protect \newline


\newline :
\long macro:->\@normalcr \relax

\documentclass{standalone}
\usepackage{amsmath}
\newenvironment{caser}{%
  \left\lbrace
  \def\arraystretch{1.2}%
  \array{@{}r@{\quad}l@{}}%
}{%
  \endarray\right.%
}
\begin{document}
\(
	\begin{caser}
		 0 & \text{if something} \\
		-1 & \text{otherwise}
	\end{caser}
\)
\end{document}

\documentclass{article}
\usepackage{amsmath}
\makeatletter
\renewenvironment{cases}[1][l]{\matrix@check\cases\env@cases{#1}}{\endarray\right.}
\def\env@cases#1{%
  \let\@ifnextchar\new@ifnextchar
  \left\lbrace\def\arraystretch{1.2}%
  \array{@{}#1@{\quad}l@{}}}
\makeatother
\begin{document}
\[\begin{cases}
		 0 & \text{if something} \\
		-1 & \text{otherwise}
	\end{cases} = \begin{cases}[r]
		 0 & \text{if something} \\
		-1 & \text{otherwise}
	\end{cases} \]
\end{document}