Latex 中 mathmode 內的表達式上的十字標記

Question

如何使用乳膠在數學模式內的表達式上放置十字標記，如下所示？

Answer 1

也許這有點矯枉過正，但你可以用\timesoverlaid\longrightarrow來建立運算符

\documentclass[]{article}

\def\longxrightarrow{\mathrel{%
    \mathchoice{\LongXRightArrow}{\LongXRightArrow}{\scriptsize\LongXRightArrow}{\tiny\LongXRightArrow}%
}}
\def\LongXRightArrow{{%
    \setbox0\hbox{\ensuremath{\longrightarrow}}%
    \rlap{\hbox to \wd0{\ensuremath{\hss\times\hss}}}\box0
}}



\begin{document}

$   a^b  \longxrightarrow c^d $

\end{document}

出現為

Answer 2

\nrightarrow+ 鏡像\nrightarrow

也許十字架有點小，至少十字的大小和位置來自字體設計師，因為範例覆蓋了\nrightarrow它的鏡像版本：

\documentclass{article}

\usepackage{amssymb}
\usepackage{graphicx}

\makeatletter
\newcommand*{\crossrightarrow}{%
  \mathrel{%
    \mathpalette\@crossrightarrow{}%
  }%
}
\newcommand*{\@crossrightarrow}[2]{%
  % #1: math style
  % #2: unused
  \sbox0{$#1\nrightarrow\m@th$}%
  \sbox2{$#1\vcenter{}$}%
  \sbox2{\raisebox{\ht2}{\scalebox{1}[-1]{\raisebox{-\ht2}{\copy0}}}}%
  \ht2=\ht0 %
  \dp2=\dp2 %
  \rlap{\unhcopy2}%
  \copy0 %
}
\makeatother

\begin{document}
\[
  a^b \crossrightarrow a^c
\]
\end{document}

\rightarrow+ \setminus+ 鏡像\setminus

具有更大十字架的變體（就我的口味而言太大了）：

\documentclass{article}

\usepackage{graphicx}

\makeatletter
\newcommand*{\crossrightarrow}{%
  \mathrel{%
    \mathpalette\@crossrightarrow{}%
  }%
}
\newcommand*{\@crossrightarrow}[2]{%
  \sbox0{$#1\rightarrow\m@th$}%
  \sbox2{$#1\setminus\m@th$}%
  \copy0 %
  \kern-\wd0 %
  \hbox to \wd0{%
    \hspace{0pt plus 1fil}%
    \rlap{\scalebox{-1}[1]{\copy2}}%
    \copy2 %
    \hspace{0pt plus 1.5fil}%                                           
    % the factor for `fil' controls the horizontal position of the cross
  }%
}
\makeatother

\begin{document}
\[
  a^b \crossrightarrow a^c
\]
\end{document}

評論：

• \mathpalette用於使符號採用四種數學樣式。

Answer 3

\times重疊長右箭頭的更簡單方法：

\documentclass{article}

\makeatletter
\newcommand{\longxarrow}[1]{%
  \mathrel{\vphantom{\to}\mathpalette\longx@rrow{#1}}% arrows are bigger than \times
}
\newcommand{\longx@rrow}[2]{%
  \ooalign{\hidewidth$#1\times\m@th$\hidewidth\cr$#1#2\m@th$\cr}%
}
\makeatother

\newcommand{\longxrightarrow}{\longxarrow{\longrightarrow}}
\newcommand{\longxleftarrow}{\longxarrow{\longleftarrow}}

\begin{document}

$A\longxrightarrow B_{\longxrightarrow}$

$A\longxleftarrow B_{\longxleftarrow}$

\end{document}

Answer 4

\documentclass{article}
\usepackage{stackengine}
\usepackage{graphicx}
\usepackage{xcolor}
\begin{document}
$a^b 
  \mathrel{\stackengine{-1.3pt}{$\rightarrow$}%
    {\color{red}\scalebox{1.6}{$\times$}\kern3pt}{O}{c}{F}{T}{L}} 
a^c$
\end{document}