我想在关系上放置一个符号，而不改变上标的位置。
\documentclass{article}
\usepackage{mathtools}
\usepackage{amssymb}
\usepackage{accents}
\newcommand{\rel}{\rhd}
\newcommand{\symb}{\text{I}}
\newcommand{\testmyrel}[1]{%
\begin{center}%
\begin{minipage}{\linewidth/2}%
\noindent Text text text\\%
$\text{T} #1^* \text{U}$\\%
$\text{T} \rel^* \text{U}$\\%
\end{minipage}%
\end{center}%
}%
\begin{document}
My goal is to place a symbol (e.g. $\symb$) over a rel (e.g. $\rel$) that can be used in text without overlapping with text above, and handles superscripts as if it did not have a symbol:
\begin{center}%
\begin{minipage}{\linewidth/2}%
\noindent Text text text\\%
$\text{T} \mathrel{\overset{\symb}{\rel}\vphantom{\rel}^*} \text{U}$\\%
$\text{T} \rel^* \text{U}$\\%
\end{minipage}%
\end{center}%
However, I do not want the superscript to be an argument of the command, which rules out the code above.
\begin{itemize}
\item Using overset makes the star too high:%
\testmyrel{%
\mathrel{%
\overset{%
\symb%
}{%
\mathord{\rel}%
}%
}%
}%
%
\item Smashing the rel makes it go over the text:%
\testmyrel{%
\mathrel{%
\smash{
\overset{\symb}{\mathord{\rel}}%
}%
}%
}%
%
\item Smashing the symbol makes it go over the text:%
\testmyrel{%
\mathrel{%
\overset{%
\smash{\symb}%
}{%
\mathord{\rel}%
}%
}%
}%
%
\item Adding a vphantom inside mathrel leads to the star being too high:%
\testmyrel{%
\mathrel{%
\overset{\symb}{\mathord{\rel}}%
\vphantom{\symb}%
}%
}%
%
\item Adding a vphantom after mathrel leads to the star being misplaced to the right:%
\testmyrel{%
\mathrel{%
\overset{\symb}{\mathord{\rel}}%
}%
\vphantom{\symb}%
}%
\item Accentset without mathrel does not have the spacing due to mathrel:
\testmyrel{%
\accentset{\symb}{\mathord{\rel}}%
}%
\item Accentset with mathrel puts the star too high:
\testmyrel{%
\mathrel{\accentset{\symb}{\mathord{\rel}}}%
}%
\end{itemize}
\end{document}
答案1
不要\text在数学中用它以直立类型排版，它通常不起作用；使用\mathrm。
也是\rhd不是一个关系符号，但做到这一点并不难。
\documentclass{article}
\usepackage{amsmath,amssymb,accents}
% \rhd is not a relation symbol
\mathchardef\rel=\numexpr\rhd+"1000
\newcommand{\overrel}[2]{%
\mathrel{\accentset{#1}{#2}}%
\mathrel{\vphantom{#2}}%
}
\begin{document}
\begin{center}
Text text text\\
$T \overrel{\mathrm{I}}{\rel}^* U$\\
$T \rel^* U$
\end{center}
\end{document}
或者，使用\overset：
\newcommand{\overrel}[2]{%
\overset{#1}{#2}%
\mathrel{\vphantom{#2}}%
}
诀窍在于，TeX 不会在连续的关系原子之间添加空格，也不会添加换行点。因此，我们可以将下标/上标添加到幻影关系中。