I am trying to define some new commands starting with the word end and I found that it is impossible in TeX. For example, the following code does not work. My question is: Is it possible to define new commands starting with \end... in (La)TeX?
\documentclass{article}
\usepackage{amsthm,amssymb}
\newcommand{\endofproof}{\rule{0.7em}{0.7em}}
\begin{document}
\begin{proof}
Clear. \hfill \endofproof
\end{proof}
\end{document}
\endofproof
command: if you prefer a black tombstone, redefine\qedsymbol
.