[Tex/LaTex] Swap definition of starred and non-starred command

Question

I don't like the fact that I am required to use \abs* when I want the vertical line of the absolute value to automatically re-size. I pretty much always want it to re-size, so would like to swap the definition of the two commands, but not sure how to do that. My attempt below is commented out as it does not compile.

I can't think of a case where I'd want to use the version that does not resize, but in case some corner case arises in the future I don't want to loose that. Or, is there a good reason to not to do this swap, and go and change all occurrences of \abs to \abs*.

\documentclass{article}

\usepackage{amsmath}
\usepackage{mathtools}

\DeclarePairedDelimiter\abs{\lvert}{\rvert}

%\let\oldabs{\abs}%
%\let\oldabs*{\abs*}%
%\let\abs{oldabs*}%
%\let\abs*{\oldabs}%

\begin{document}
Not sure why this is the default behavior, but it is:
\[\abs{\frac{1}{2}}\]

Would prefer to get this behavior using \textbackslash{abs},
instead of having to use \textbackslash{abs*}.
\[\abs*{\frac{1}{2}}\]
\end{document}

Answer 1

You can redefine \abs to call the opposite version of the original command:

\makeatletter
\let\oldabs\abs
\def\abs{\@ifstar{\oldabs}{\oldabs*}}
\makeatother

(The reason that your commented try doesn't work is that technically the * is not part of the macro name, but is read by the macro itself using \@ifstar, \@ifnextchar or similar commands.)