[Tex/LaTex] Plus sign and minus sign as superscripts in bmatrix

Question

As the title says I am trying to write a plus or minus as superscripts for various particle names in a bmatrix, but it does not work. I have searched for solutions, but only came up with one, which should work, but doesn't. Now it really bothers why LaTeX does not have this feature built in, that seems really silly, but maybe there is a good reason.

My code is:

%various packages
\newcommand{\minus}[1]{{#1}^{\scalebox{0.8}{-}}}
\newcommand{\plus}[1]{{#1}^{\scalebox{0.6}{\!+}}}
\begin{document}
\begin{bmatrix}
   \pi^{\plus} & 0 & 0 \\
   0 & 0 & 0 \\
   0 & 0 & 0
\end{bmatrix}
\end{document}

the error i get is "Argument of \plus has an extra }. \par \pi^{\plus} and the error repeats in my log – maybe 50 of the same errors but only on the same line.

Thank you for your time.

Answer 1

You should define \plus and \minus to not take an argument:

\documentclass{article}

\usepackage{amsmath,graphicx}

\newcommand{\minus}{\scalebox{0.8}{$-$}}
\newcommand{\plus}{\scalebox{0.6}{$+$}}

\begin{document}

\[\begin{bmatrix}
  \pi^{\plus} & 0 & 0 \\
  0 & \pi^{\minus} & 0 \\
  0 & 0 & \pi^{\plus}
\end{bmatrix}\]

\end{document}

I've updated the definition slightly, ensuring that + and - are taken as math binary operators.