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I would like to create a symbol for \implies and \impliedby where they are enclosed in a rotated lidless box as shown in the picture. Can anybody tell me how I could achieve this?

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4 Answers 4

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8

Welcome! You do not need any packages for that.

\documentclass{article}
\newcommand{\RightArrowInBox}{\begingroup
\renewcommand{\arraystretch}{0.6}\begin{array}{@{}c@{}|}\hline 
\raisebox{-0.2ex}{$\Rightarrow$}\\ \hline\end{array}\endgroup}
\newcommand{\LeftArrowInBox}{\begingroup
\renewcommand{\arraystretch}{0.6}\begin{array}{@{}c@{}|}\hline 
\raisebox{-0.2ex}{$\Leftarrow$}\\ \hline\end{array}\endgroup}
\begin{document}
$\RightArrowInBox~\LeftArrowInBox$
\end{document}

enter image description here

Of course you can modify the padding etc.

A version without cutting corners with major input by barbara beeton. 

\documentclass{article}
\newcommand{\RightArrowInBox}{\begingroup
\renewcommand{\arraystretch}{0.6}\begin{array}{@{}c@{\rule[-3pt]{0.4pt}{0.85em}}}\hline 
\raisebox{-0.28ex}{$\Rightarrow$}\\ \hline\end{array}\endgroup}
\newcommand{\LeftArrowInBox}{\begingroup
\renewcommand{\arraystretch}{0.6}\begin{array}{@{}c@{\rule[-3pt]{0.4pt}{0.85em}}}\hline 
\raisebox{-0.28ex}{$\Leftarrow$}\\ \hline\end{array}\endgroup}
\begin{document}
$\RightArrowInBox~\LeftArrowInBox$
\end{document}

enter image description here

Or with trimclip.

\documentclass{article}
\usepackage{trimclip}
\newcommand{\RightArrowInBox}{\begingroup
\clipbox{0.5ex 0em 0em 0em}{\fbox{$\Rightarrow\!$}}\endgroup}
\newcommand{\LeftArrowInBox}{\begingroup
\clipbox{0.5ex 0em 0em 0em}{\fbox{$\Rightarrow\!$}}\endgroup}

\begin{document}
$\RightArrowInBox~\LeftArrowInBox$
\end{document}

enter image description here

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4
  • 2
    The corners aren't closed. Maybe add to the vertical two times the thickness of the rules.
    – barbara beeton
    Mar 30, 2020 at 1:13
  • 2
    @barbarabeeton Thanks! Yes, I know, we cats are famously good at cutting the corners. ;-)
    – user194703
    Mar 30, 2020 at 1:14
  • Hmm. Somehow, when adding corners, a little too much extra space got added below the arrows. (Nit picking.) The corners do look nice though.
    – barbara beeton
    Mar 30, 2020 at 2:47
  • @barbarabeeton This is entirely controlled by the height of the rule. If the requirement is to make it symmetric, then you can either make the rule higher, or raise the box a bit lower, or a combination of those. For instance, \raisebox{-0.275ex}{$\Rightarrow$} leads to a very symmetric positioning. I just am not sure if this is what the OP wants.
    – user194703
    Mar 30, 2020 at 2:51
5

Here's a solution which places \implies and \impliedby into a modified version of \fbox. 

\documentclass{article}
\usepackage{amsmath}
\makeatletter
\def\@rframeb@x#1{%
  \@tempdima\fboxrule
  %\advance\@tempdima\fboxsep
  \advance\@tempdima\dp\@tempboxa
  \hbox{%
    \lower\@tempdima\hbox{%
      \vbox{%
        \hrule\@height\fboxrule
        \hbox{%
          %\vrule\@width\fboxrule
          #1%
          \vbox{%
            \vskip.7\fboxsep
            \box\@tempboxa
            \vskip.3\fboxsep}%
          #1%
          \vrule\@width\fboxrule}%
        \hrule\@height\fboxrule}%
                          }%
        }%
}
\DeclareRobustCommand\rfbox[1]{%
  \leavevmode
  \setbox\@tempboxa\hbox{%
    \color@begingroup
      \kern.2\fboxsep{#1}\kern.2\fboxsep
    \color@endgroup}%
  \@rframeb@x\relax}
\makeatother
\newcommand{\boximplies}{%
    \mathrel{\:\rfbox{$\Longrightarrow$}\:}%
}
\newcommand{\boximpliedby}{%
    \mathrel{\:\rfbox{$\Longleftarrow$}\:}%
}
\begin{document}
\( A \implies B \)

\( A \boximplies B \)

\( A \impliedby B \)

\( A \boximpliedby B \)
\end{document}
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5

Only array (that's a required package in every distribution):

\documentclass{article}
\usepackage{array}

\newcommand{\bimplies}{\mathrel{\bimpl{c|}{\Rightarrow}}}
\newcommand{\bimpliedby}{\mathrel{\bimpl{|c}{\Leftarrow}}}
\newcommand{\bimpl}[2]{%
  \begingroup
  \setlength{\arraycolsep}{0pt}%
  \renewcommand{\arraystretch}{0}%
  \begin{array}{#1}\hline{#2}\vphantom{+}\\\hline\end{array}%
  \endgroup
}

\begin{document}

$A\bimplies B\bimpliedby C$

\end{document}

enter image description here

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2

Try this overlay of two symbols. Too bad there is no big square left/right, so it requires rotation.

\usepackage{graphicx}
\usepackage{amssymb}

\newcommand\RightArrowInBox{%
 \rotatebox[origin=c]{90}{\ooalign{%
  \hfil$\Downarrow$\hfil\cr\noalign{\kern0.4pt}%
  \hfil$\bigsqcup$\hfil\cr}}}
\newcommand\LeftArrowInBox{%
 \rotatebox[origin=c]{-90}{\ooalign{%
  \hfil$\Downarrow$\hfil\cr\noalign{\kern0.4pt}%
  \hfil$\bigsqcup$\hfil\cr}}}

Other symbol collections like basic LaTeX or stmaryrd work better when inserting \displaystyle with the square or \scriptstyle with the arrow because the \bigsqcup is smaller than the version from amssymb.

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