How to write a character overlapping another character

Question

How can I write two characters in the same place?

In particular, I want to write an arrow $\rightarrow$, and then write a letter such that the arrow strikes through the letter. I found some similar questions (Range symbol over character, Substitute a character by another one (Lualatex), etc.) but they are not exactly the same question.

Answer 1

Not clear if you want it in text or math...

\documentclass{article}
\usepackage{stackengine}
\begin{document}
In te\stackengine{0pt}{x}{$\rightarrow$}{O}{c}{F}{T}{L}t...

$\ensurestackMath{\stackengine{0pt}{y}{\rightarrow}{O}{c}{F}{T}{L}} = mx + b$
\end{document}

Also, it is not clear if you want the arrow's width to be accounted for:

\documentclass{article}
\usepackage{stackengine}
\begin{document}
In te\stackengine{0pt}{x}{$\rightarrow$}{O}{c}{F}{F}{L}t...

$\ensurestackMath{\stackengine{0pt}{y}{\rightarrow\!}{O}{c}{F}{F}{L}} = mx + b$
\end{document}

Other things that can be easily adjusted above include horizontal alignment (currently centered) as well as vertical height of arrow placement (currently placed at its natural height).

Once the specifics are decided on the use case, this can be easily encapsulated in a macro.

Below, keeping up with the egregs, I implement a macro version (\overarrow) for math that preserves the math style:

\documentclass{article}
\usepackage{stackengine,scalerel}
\newcommand\overarrow[1]{\ThisStyle{\ensurestackMath{%
  \stackengine{0pt}{\SavedStyle#1}{\SavedStyle\rightarrow\!}{O}{c}{F}{F}{L}}}}
\begin{document}
$\overarrow{y} = mx_{\overarrow{z}} + b$
\end{document}

Answer 2

A simple \makebox[0pt]{..} can achieve this. Depending on your real use case, this may require a bit of tuning.

\documentclass[12pt,a4paper]{article}    
\begin{document}

$\makebox[0pt][l]{$\rightarrow$}A$

\end{document}

Answer 3

Here's for text in two versions:

\documentclass{article}

\DeclareRobustCommand{\asA}[1]{% arrow strike
  \leavevmode\begingroup
  \vphantom{#1}%
  \ooalign{\hidewidth$\mathsurround0pt\rightarrow$\hidewidth\cr#1\cr}%
  \endgroup
}
\DeclareRobustCommand{\asB}[1]{% arrow strike
  \leavevmode\begingroup
  \vphantom{#1}%
  \ooalign{$\mathsurround0pt\rightarrow$\cr\hidewidth#1\hidewidth\cr}%
  \endgroup
}

\begin{document}

st\asA{r}uck

st\asB{r}uck

\end{document}

For math:

\documentclass{article}

\makeatletter
\DeclareRobustCommand{\as}[1]{% arrow strike
  {\vphantom{#1}\mathpalette\erel@as{#1}}%
}

\newcommand{\erel@as}[2]{%
  \ooalign{\hfil$\m@th#1\rightarrow$\hfil\cr\hfil$\m@th#1#2$\hfil\cr}%
}
\makeatother

\begin{document}

$a+\as{b}+c_{\as{x}}$

\end{document}

Answer 4

In case you want a bit of flexibility and the arrow to adjust to the width of the stuff it is running through, you may want to use tikzmark.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{tikzmark}
\newcounter{atm}
\newcommand{\arrowthrough}[2][]{\stepcounter{atm}\tikzmarknode[path picture={
\draw[->,#1] (path picture bounding box.west) --
(path picture bounding box.east);}]{atm-\theatm}{#2}}
\begin{document}
 \arrowthrough{x}
 \[ E=\arrowthrough{m}c^2\]
 \arrowthrough[red,-latex]{Hello} \arrowthrough[latex-,thick,blue]{World!}
\end{document}