I'd like to have a symbol that is the exact overlap between \top and \bot so that it looks like the roman number "Ⅰ". I have searched a particular symbol, but I found nothing. And overlapping techniques in this and other forums are a little confusing.
Can someone help me?
The following code implements \bottop that combines \bot and \top with respecting the current math style:
\documentclass{article}
\makeatletter
\newcommand*{\bottop}{%
\mathpalette\@bottop{}%
}
\newcommand*{\@bottop}[2]{%
% #1: math style
% #2: unused, but expected by \mathpalette
\rlap{$#1\bot\m@th$}% put \bot to the right without moving the current point
\top
}
\makeatother
\begin{document}
\[ \bottop \scriptstyle \bottop \scriptscriptstyle \bottop \]
\end{document}
From http://tug.ctan.org/info/symbols/comprehensive/symbols-a4.pdf here is a possible implementation:
\documentclass{article}
\def\topbotatom#1{\hbox{\hbox to 0pt{$#1\bot$\hss}$#1\top$}}
\newcommand*{\topbot}{\mathrel{\mathchoice{\topbotatom\displaystyle}
{\topbotatom\textstyle}
{\topbotatom\scriptstyle}
{\topbotatom\scriptscriptstyle}}}
\begin{document}
$\topbot$
\end{document}
\documentclass{article}
\usepackage{amsmath}
% see https://tex.stackexchange.com/a/22375/4427 for \ooalign
% see https://tex.stackexchange.com/a/34412/4427 for \mathpalette
\makeatletter
\newcommand{\topbot}{\mathord{\mathpalette\top@bot\relax}}
\newcommand{\top@bot}[2]{%
\ooalign{$\m@th#1\top$\cr$\m@th#1\bot$\cr}%
}
\makeatother
\begin{document}
$\top\topbot\bot$
$X_{\top\topbot\bot}$
\end{document}
I suggest to use romanabar package. Here a short example.
\documentclass[a4paper,12pt]{article}
\usepackage{romanbar}
\begin{document}
\Romanbar{1}, \Romanbar{2}, \Romanbar{3}, \Romanbar{50}
\end{document}
