\documentclass[draft]{article}
\sloppy

\usepackage{amsmath}
\usepackage{amssymb}

\usepackage{lipsum}

\usepackage{todos}

\include{catprog}

\makeatletter

\def\show@monad@names#1{\ifx#1\show@monad@names\else\csname BB#1\endcsname\expandafter\show@monad@names@\fi}
\def\show@monad@names@#1{\ifx#1\show@monad@names\else\comma\csname BB#1\endcsname\expandafter\show@monad@names@\fi}
%
\def\show@cat@names#1{\ifx#1\show@cat@names\else\csname BB#1\endcsname\expandafter\show@cat@names@\fi}
\def\show@cat@names@#1{\ifx#1\show@cat@names\else\comma\csname B#1\endcsname\expandafter\show@cat@names@\fi}

\begin{document}

Categories: $\show@cat@names ABCDEFGHIJKLMNOPQRSTUVWXYZ\show@cat@names$

Monads: $\show@monad@names ABCDEFGHIJKLMNOPQRSTUVWXYZ\show@monad@names$

\todo{This is a use of the todo-command}

$-\dfrac{\hslash^2}{2m} \, \dfrac{\mathrm{d}^2 \psi}{\mathrm{d} x^2} \todo{It can be used like this}$
%
\begin{flalign*}
E = mc^2 &&\by{\todo{or like this}} 
\end{flalign*}


\todo*{This is a use of the todo-command with a star

- starts a new line

- no indentation (initially)

- suitable for large chunks of text

\bigskip
\lipsum[1]


}

\end{document}