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In birational geometry, we often use dashed arrows to insist on the fact that our maps are not defined everywhere. I wonder how can we produce:

  1. a mapsto dashed arrow joining \mapsto and \dashrightarrow;
  2. a circle dashed arrow like \circlearrowleft?
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1 Answer 1

up vote 7 down vote accepted

The first one is easy

 \def\dashmapsto{\mapstochar\dashrightarrow}

The second one if you mean the dashes go round the circle really needs a font with that character, that I don't know.

If you can't find a font, then there is always a gross hack available, you may want to tweak the rule widths a bit but...

enter image description here

\documentclass{article}
\usepackage{amssymb,color}

   \def\dashmapsto{\mathrel{\mapstochar\dashrightarrow}}
   \def\dashcirclearrowleft{\mathrel{\circlearrowleft\llap{{\color{white}%
\vrule height 0.2em width 0.3em depth 0em
\vrule width 0.2em  height 0.7em depth -.3em
\vrule width 0.3em  height 0em depth .2em
\vrule height 0.3em width 0.4em depth -.1em
}}}}

\begin{document}

\[a \mapsto  b \]
\[a \dashmapsto  b \]
\[a \circlearrowleft b\]
\[a \dashcirclearrowleft b\]

\end{document}
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Thank you very much for your complete answer ! –  Frédéric Mangolte Mar 2 '12 at 14:00

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