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Possible Duplicate:
How to look up a math symbol?

I there a version of \mapsto going from right to left (i.e a "\leftmapsto"? Is there an easy way of creating such a symbol?

Community
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Anonymous
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  • If one doesn't exist, you could make one with the graphicx package and \reflectbox{\mapsto} – Seamus Aug 25 '11 at 12:05
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    Welcome to TeX-SX! For questions like this, there are some very good resources that are in the question linked in Jake's comment above. To help others find these resources quickly, we'll probably close this question as a duplicate of that one. This is just to ensure that other people find their way to that "canonical question" as easily as possible. – Andrew Stacey Aug 25 '11 at 12:34
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    As far as I can see there is no link to the other question that this is allegedly a duplicate of, and this question occurs first when I search for this topic. Is this a compatibility issue or a flaw in the design of the site? – j0equ1nn Jan 29 '15 at 13:09
  • @Seamus This code didn't compile for me, and the error message seems like garbage. Compiles perfectly without. – Richard Birkett Jan 30 '20 at 02:19
  • I was looking for a \mapsfrom or \leftmapsto, and not being able to access either of the required packages from MathJax, I resorted to \newcommand{\mapsfrom}{\mathrel{\unicode{x21a4}}} – robjohn Aug 06 '20 at 18:59

3 Answers3

22

\mapsfrom from the stmaryrd package.

You can look up such symbols using Detexify

Jake
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  • I tried Detexify but this one didn't come up when I inputted by handwriting (although it does come up when looking up its name). – Benjamin Wang Sep 22 '22 at 22:44
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  • MnSymbol provides \leftmapsto
  • stmaryrd provides \mapsfrom
  • with graphicx you can create one: \newcommand\mapsfrom{\mathrel{\reflectbox{\ensuremath{\mapsto}}}}
Seamus
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    Your command \mapsfrom gives the wrong spacing as it is defined. – Gonzalo Medina Aug 25 '11 at 12:17
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    That's easily fixed: Just define the command as \newcommand{\mapsfrom}{\mathrel{\reflectbox{\ensuremath{\mapsto}}}}. The \mathrel command tells (La)TeX to treat \mapsfrom as a relational operator. – Mico Aug 25 '11 at 13:00
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    Fix'd (I hope). Thanks for pointing that out. – Seamus Aug 25 '11 at 13:26
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The symbols document gives you \mapsfrom from the stmaryrd package or \leftmapsto to from the MnSymbol package:

\documentclass{article}
\usepackage{stmaryrd}
\usepackage{MnSymbol}
\begin{document}

%requires stmaryrd
\[ a\mapsfrom x \]

% requires MnSymbol
\[ a\leftmapsto x \]

\end{document}

enter image description here

Gonzalo Medina
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