[Tex/LaTex] Arrow with plus/minus sign on top

symbols

Below you can see an arrow with a plus and a minus sign on top of it. How is this achievable in latex? Further possibilities: arrow with only plus and arrow with only minus sign on top. How can I do this?

enter image description here

Best Answer

`\stackrel`

LaTeX provides \stackrel to place something on a relational operator:

\documentclass{article}

\begin{document}
\[
  A \stackrel{+/-}\longrightarrow
  B \stackrel{+}\rightarrow
  C \stackrel{-}\rightarrow
  D
\]
\end{document}

$Result \stackrel$

However the arrow is too short for the first case with +/-.
The plus/minus signs are perfectly horizontally centered, but it does not look too good because of the arrow tip. The plus/minus signs should be moved to the left a little.

`\xrightarrow`

Package amsmath addresses the previous problems by providing extensible arrows:

\xrightarrow[<below>]{<above>}

The length of the arrow grows with width of the annotations below or above. The arrow tip is taken into account.

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\[ A \xrightarrow{+/-} B \xrightarrow{+} C \xrightarrow{-} D \]
\end{document}

$Result \xrightarrow$

But there is room for improvement:

The minus and plus sign start and end with a horizontal line, thus the extra space of the arrow to the left and right can be reduced a little.

\documentclass{article}
\usepackage{amsmath}

\newcommand*{\rightarrowpm}[1]{%
  \xrightarrow{\!#1\!}%
}

\begin{document}
\[
   A \rightarrowpm{+/-}
   B \rightarrowpm{+}
   C \rightarrowpm{-}
   D
\]
\end{document}

$Result \xrightarrow and !$

If the size of the plus and minus signs are too large, then \scriptscriptstyle can be added:

\documentclass{article}
\usepackage{amsmath}

\newcommand*{\rightarrowpm}[1]{%
  \xrightarrow{\scriptscriptstyle\!#1\!}%                     
}

\begin{document}
\[
   A \rightarrowpm{+/-}
   B \rightarrowpm{+}
   C \rightarrowpm{-}
   D
\]
\end{document}

$Result \xrightarrow + \, + \scriptscriptstyle$

Scalable `\xrightarrow`

\xrightarrow of amsmath does not resize automatically with different math styles. The last example redefines \ext@arrow for \rightarrowpm to make it scalable according to the current math style. A smaller style than \scriptscriptstyle is achieved by scaling to 90%.

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}

\makeatletter
\newcommand*{\rightarrowpm}[1]{%
  \begingroup
    \let\ext@arrow\ext@arrow@scalable
    \xrightarrow{\scriptscriptstyle\!#1\!}%
  \endgroup
}
\newcommand*{\ext@arrow@scalable}[7]{%
  \mathrel{%
    \mathpalette{\@ext@arrow@scalable{#1}{#2}{#3}{#4}{#5}{#6}{#7}}{}%
  }%
}
\newcommand*{\@ext@arrow@scalable}[8]{%
  \mathop{%
    \setbox\z@\hbox{#5#8}%
    \setbox\tw@\vbox{%
      \m@th
      \ifx#8\scriptscriptstyle
        \let\my@hbox\hbox@scriptscriptscaled
      \else
        \let\my@hbox\hbox@math
      \fi
      \my@hbox{%
        \ifx#8\scriptstyle\scriptscriptstyle\else\scriptstyle\fi
        \mkern#3mu{#6}\mkern#4mu%
      }%
      \my@hbox{%
        \ifx#8\scriptstyle\scriptscriptstyle\else\scriptstyle\fi
        \mkern#3mu{#7}\mkern#4mu%
      }%
      \copy\z@
    }%
    \hbox to\wd\tw@{\unhbox\z@}}%
  \limits
    \@ifnotempty{#7}{%
      ^{%
        \ifx#8\scriptscriptstyle
          \expandafter\hbox@scriptscriptscaled
        \else
          \expandafter\@firstofone
        \fi
        {%
          \if0#1\else\mkern#1mu\fi
          #7%
          \if0#2\else\mkern#2mu\fi
        }%
      }%
    }%
    \@ifnotempty{#6}{%
      _{%
        \ifx#8\scriptscriptstyle
          \expandafter\hbox@scriptscriptscaled
        \else
          \expandafter\@firstofone
        \fi
        {%
          \if0#1\else\mkern#1mu\fi
          #6%
          \if0#2\else\mkern#2mu\fi
        }%
      }%
    }%
}

\newcommand*{\hbox@scriptscriptscaled}[1]{%
  \hbox{%
    \scalebox{.9}{$\scriptscriptstyle#1\m@th$}%
  }%
}
\newcommand*{\hbox@math}[1]{%
  \hbox{$#1\m@th$}%
}
\makeatother

\begin{document}
\[ A \rightarrowpm{+/-} B^{A\rightarrowpm{+/-}B^{A\rightarrowpm{+/-}B}} \]
\end{document}

Related Solutions

[Tex/LaTex] different plus/minus within braket environment

I am not too sure what font to use for the internal + and -, so I just used \hbox{\texttt{+}}. In TeX, each character has a \mathcode, describing its behavious in maths. All of them lie between "0000 and "7FFF (in hexadecimal), except the special mathcode "8000, which makes the character act like an active character. Within the group which \bra, \ket and \braket define, I get + and - to be active and expand to \braket@inner@minus and \braket@inner@plus.

\documentclass{article}
\usepackage{braket}

\makeatletter
\newcommand{\braket@inner@minus}{\hbox{\texttt{-}}}
\newcommand{\braket@inner@plus}{\hbox{\texttt{+}}}
\begingroup
\catcode`\-=13\relax %active
\catcode`\+=13\relax %active
\@firstofone{\endgroup %end the local changes to catcodes.
  \newcommand\braket@inner@defs{%
    \edef\restore@mathcode{%
      \mathcode`\noexpand +=\the\mathcode`+%
      \mathcode`\noexpand -=\the\mathcode`-%
    }%
    \mathcode`\+="8000\relax
    \mathcode`\-="8000\relax
    \def+{\begingroup\restore@mathcode\braket@inner@plus\endgroup}%
    \def-{\begingroup\restore@mathcode\braket@inner@minus\endgroup}%
  }%
}
% old definition:
% \newcommand{\bra}[1]{\mathinner {\langle {#1}|}}
% new definition:
\renewcommand{\bra}[1]{\mathinner {\langle \braket@inner@defs {#1}|}}
\renewcommand{\ket}[1]{\mathinner {|\braket@inner@defs{#1}\rangle }}
\renewcommand{\braket}[1]{\mathinner {\langle \braket@inner@defs {#1}\rangle }}
\makeatother

\begin{document}
\[
\bra{++--}A^\dag A\ket{-+-+} = \braket{++--|A^\dag A|-+-+} = \cdots
\]
However, 
\[
\bra{++}(A+B)\ket{--} \neq \braket{++|(A+B)|--}
\]
\end{document}

[Tex/LaTex] plus-minus symbol with parenthesis around the minus sign

I once proposed the following definitions

\newcommand\varpm{\mathbin{\vcenter{\hbox{%
  \oalign{\hfil$\scriptstyle+$\hfil\cr
          \noalign{\kern-.3ex}
          $\scriptscriptstyle({-})$\cr}%
}}}}
\newcommand\varmp{\mathbin{\vcenter{\hbox{%
  \oalign{$\scriptstyle({+})$\cr
          \noalign{\kern-.3ex}
          \hfil$\scriptscriptstyle-$\hfil\cr}%
}}}}

Example

\documentclass{article}
\newcommand\varpm{\mathbin{\vcenter{\hbox{%
  \oalign{\hfil$\scriptstyle+$\hfil\cr
          \noalign{\kern-.3ex}
          $\scriptscriptstyle({-})$\cr}%
}}}}
\newcommand\varmp{\mathbin{\vcenter{\hbox{%
  \oalign{$\scriptstyle({+})$\cr
          \noalign{\kern-.3ex}
          \hfil$\scriptscriptstyle-$\hfil\cr}%
}}}}

\begin{document}
$a\varpm b\varmp c$
\end{document}

enter image description here

Best Answer

\stackrel

\xrightarrow

Scalable \xrightarrow