4

Please help me with the anti-circulant square matrix notation. It looks like the vector notation but has a double line arrow. \xRightarrow from mathtools wouldn't work because the arrow is in the middle of the line.

enter image description here

Thruston
  • 42,268
rimrim
  • 43
  • Welcome to TeX.SX! Please help us to help you and add a minimal working example (MWE) that illustrates your problem. It will be much easier for us to recommend the best way to get the double arrow over the v when we see compilable code, starting with \documentclass{...} and ending with \end{document}. – Thruston Mar 27 '15 at 11:59
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    \xRightarrow it not meant to be used as a vector margin, but rather as a \Rightarrow with comment. I've never seen vectors (or what ever it is) written with a double stemmed arrow. Do you have any examples from literature or articles from e.g. arxiv which uses this notation? – daleif Mar 27 '15 at 12:02
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    You might find this useful. – Thruston Mar 27 '15 at 12:03

2 Answers2

6

Here are several ways to make double arrows over symbols.

enter image description here

\documentclass{article}
\usepackage{amssymb}
\usepackage{accents}
\makeatletter
\def\Rightarrowfill{$\m@th\mathord= \mkern-6mu
    \cleaders\hbox{$\mkern-2mu\mathord= \mkern-2mu$}\hfill
    \mkern-6mu \mathord\Rightarrow$}
\def\Overrightarrow#1{\vbox{\m@th\ialign{##\crcr
    \Rightarrowfill\crcr\noalign{\kern.4pt\nointerlineskip}
    $\hfil\displaystyle{#1}\hfil$\crcr}}}
\makeatother
\newcommand{\vect}[1]{\accentset{\Rightarrow}{#1}}
\newcommand{\vectt}[1]{\accentset{\Longrightarrow}{#1}}

\begin{document}
Here is the usual \texttt{vec} command and my suggested \texttt{vect} for
comparison.
\[ \vec{v}\in\mathbb{Z}^{N\times N} \qquad \vect{v}\in\mathbb{Z}^{N\times N}\]

One way to deal with a wide argument is just to put the accent on the $C$.
\[ \vect{C}_\mathit{Mi}\in\mathbb{Z}^{N\times N}\]

Another way is to define \texttt{vectt} with \texttt{Longrightarrow}.
\[ \vectt{C_{\mathit{Mi}}}\in\mathbb{Z}^{N\times N}\]

A third way is to create a new stretchy macro like \texttt{overrightarrow}.
\[ \overrightarrow{C_\mathit{Mi}}\in\mathbb{Z}^{N\times N} \qquad 
   \Overrightarrow{C_\mathit{Mi}}\in\mathbb{Z}^{N\times N}\]
\end{document}

Note that \mathit{Mi} looks slightly better than {Mi} in the subcript.

Original solution

\documentclass{article}
\usepackage{amssymb}
\usepackage{accents}
\newcommand{\vect}[1]{\accentset{\Rightarrow}{#1}}
\begin{document}
\[ \vec{v}\in\mathbb{Z}^{N\times N}\]
\[ \vect{v}\in\mathbb{Z}^{N\times N}\]
\end{document}

enter image description here

Thruston
  • 42,268
  • Many thanks for this, please advise how to make it work for a longer symbol, say, \vect{C_{Mi}}? (the little arrow is currently covering only half of the C character :).. – rimrim Mar 30 '15 at 11:52
  • @rimrim - I offer you no fewer that three ways to do this! See updated answer. – Thruston Mar 30 '15 at 15:00
3

Maybe a stack? The use of \useanchorwidth in the true condition means that the size of the overset does not affect the underlying math spacing.

\documentclass{article}
\usepackage{stackengine,amsfonts}
\stackMath
\def\useanchorwidth{T}
\begin{document}
\[
\stackon[1pt]{v}{\,\scriptscriptstyle\Rightarrow} \in \mathbb{Z}^{N\times N}
\]
\end{document}

enter image description here

Steven B. Segletes
  • 237,551