Math & Science ⇒ Old code not working anymore

[svend_tveskaeg]

Hi all.

I found the following code some time ago and then it compiled without problems:

Code: Select all

\documentclass[a4paper,12pt]{article}

\usepackage{mathtools}

\makeatletter
 \newcommand*{\textupperscript}[2]{%
  \@textupperscript{\selectfont#1}{\selectfont#2}
 }
 \def\@textupperscript#1#2{%
  {\m@th\ensuremath{%
    ^{\mbox{\fontsize\sf@size\z@#1}}
    _{\mbox{\fontsize\sf@size\z@#2}}
  }}
 }
\def\@super{^}
\def\@sub{_}

\catcode`^\active
\catcode`_\active
  \def\@super@sub#1_#2{\textbothscript{#1}{#2}}
  \def\@sub@super#1^#2{\textbothscript{#2}{#1}}
    \def\@@super#1{\@ifnextchar_{\@super@sub{#1}}{\textsuperscript{#1}}}
    \def\@@sub#1{\@ifnextchar^{\@sub@super{#1}}{\textsubscript{#1}}}
      \def^{\let\@next\relax\ifmmode\@super\else\let\@next\@@super\fi\@next}
      \def_{\let\@next\relax\ifmmode\@sub\else\let\@next\@@sub\fi\@next}
\makeatother

\begin{document}

\noindent Something:
\begin{equation*}
  \Psi\textupperscript{Horse}{Fish}(x)
\end{equation*}

\end{document}

Now it does not compile and I have no idea what I have changed; the error I get is the following:

Code: Select all

! Extra \else.
\@next #1#2#3#4->\ifx #2\@empty #4\else 
                                        \expandafter \@xnext #2\@@ #1#2#3\fi 
l.25  \catcode`\noexpand\^^
                           A\the\catcode`\^^A\relax

Can anyone help my make the code wotk again? An explanation would be great but it is not necessary.

Thank you in advance!

[Stefan Kottwitz]

It's a compatibility issue with mathtools and those definitions. If you would just use amsmath, it would work fine.

Stefan

[svend_tveskaeg]

Thank you, Stefan.

It used to work with mathtools (if I am not mistaken).