Extended \Mapsto with text above

Question

\documentclass{standalone}

\usepackage{centernot}
\usepackage{mathtools}
\usepackage{ stmaryrd }

\begin{document}
    $\xmapsto{sdfkjhsdf}$ % This is similar to what I want

    $\Mapsto$ % however I need this kind of arrow

    %$\xMapsto{sdfkjhsdf}$ % does not exist - results in error
\end{document}

Output of the first two:

xMapsto

I want an extensible mapsto with writing on top like the first, but with an arrow like the second. Is there a way to do this from the existing packages?

Very similar: math mode - \xRightarrow (text) - TeX - LaTeX Stack Exchange, symbols - Extending arrows with overset text - TeX - LaTeX Stack Exchange — user202729, Jan 31 '23 at 15:01

score 16 · Accepted Answer · edited Jun 12 '17 at 18:16

16

The mathtools package provides nearly everything you need to construct this, and stmaryrd has the extra pieces of symbols. Putting these together gives

Sample output

\documentclass{article}

\usepackage{centernot}
\usepackage{mathtools}
\usepackage{stmaryrd}

\makeatletter
\newcommand{\xMapsto}[2][]{\ext@arrow 0599{\Mapstofill@}{#1}{#2}}
\def\Mapstofill@{\arrowfill@{\Mapstochar\Relbar}\Relbar\Rightarrow}
\makeatother

\begin{document}
\begin{gather*}
   \mapsto \qquad \xmapsto[A]{sdfkjhsdf} \\
 \Mapsto \qquad \xMapsto[A]{sdfkjhsdf}
\end{gather*}
\end{document}

The parameters 0599 are for the placement of the labels and how much the arrow extends over them. I have use the same numbers as mathtools does for \xmapsto. \Mapstochar is the short bar at the beginning, from the stmaryrd package, \Relbar is the double line which fits with final \Rightarrow. The internal macros names include the @ character, so have to be included in a \makeatletter / \makeatother pair.

It might have been nice to use the extpfeil package for this, but unfortunately it loads stmaryrd with clashing options.

edited Jun 12 '17 at 18:16

Moriambar

11,466

answered Aug 13 '13 at 12:22

Andrew Swann

95,762

1

I was about to post the same answer. ;-) – egreg Aug 13 '13 at 12:50
why do i get an error saying that mathtools does not exists? MicTex 2.9 X64, Win7 X64. – Chen Stats Yu Oct 18 '14 at 15:12
@ChenStatsYu That sounds like a completely separate question. May be http://tex.stackexchange.com/q/187725/15925 helps. – Andrew Swann Oct 18 '14 at 18:01
when i type \xmapsto{A} then there is a normal rightarrow with a 7 at the start.. – Lillien Sabrina Gluch Jul 07 '18 at 13:21
@LillienSabrinaGluch I can not reproduce that; it works fine for me. Perhaps you could ask a separate question posting the code you try. – Andrew Swann Jul 10 '18 at 11:00

Steven B. Segletes · Answer 2 · 2013-08-13T12:17:51.457

The fp package is used to calculate the appropriate width of the arrow. The kerns will be important if you change fonts. It's set up to provide an arrow length of a certain minimum width, regardless of the over/underset. THen, as the over/underset grows, the arrow width will grow with it.

\documentclass{article} 
\usepackage{stackengine}
\usepackage{scalerel}
\usepackage{fp}
\def\clipeq{\kern -.65pt\mathrm{=}\kern -1pt}
\def\Lla{\rule[-.1ex]{.3pt}{1.3ex}}
\def\Lra{\kern -3.5pt\Longrightarrow}
\newcount\argwidth
\newcount\clipeqwidth
\savestack\tempstack{\stackon{$\clipeq$}{}}%
\clipeqwidth=\wd\tempstackcontent\relax
\newcommand\xMapsto[2]{%
  \savestack\tempstack{\stackon{$\scriptstyle#1$}{$\scriptstyle#2$}}%
  \argwidth=\wd\tempstackcontent\relax%
  \FPdiv\scalefactor{\the\argwidth}{\the\clipeqwidth}%
  \FPsub\scalefactor{\scalefactor}{1.5}% <---CAN PLAY WITH THIS VALUE
  \FPmax\scalefactor{\scalefactor}{.05}%
  \mathrel{%
  \stackunder[2pt]{\stackon[3pt]{$\Lla\hstretch{\scalefactor}{\clipeq}\Lra$}%
     {$\scriptstyle#1~$}}{$\scriptstyle#2~$}%
  }%
}
\parskip 1ex
\begin{document} 
$X \xMapsto{ABC}{defghi} Y$

$\xMapsto{}{}$

$\xMapsto{a}{}$

$\xMapsto{ab}{}$

$\xMapsto{abc}{}$

$\xMapsto{abcd}{}$

$\xMapsto{abcde}{}$
\end{document}

enter image description here

Extended \Mapsto with text above

2 Answers2