# probsoln error: “undefined control sequence \repeat” in a loop

For context, I am using the probsoln package to create a list of problems and solutions. The problems and their solutions come from files in the same directory titled bank_lesson1.tex, bank_lesson2.tex, etc. There are 10 lessons.

For some reason, I'm getting the error "Undefined control sequence \repeat". I was under the impression that \loop and \repeat were built into TeX and were immediately usable.

\documentclass[11pt]{article}
\geometry{letterpaper}
\usepackage{graphicx}
\usepackage{amssymb, amsmath, commath}

\usepackage{probsoln}

\begin{document}

\newcounter{intA}
\setcounter{intA}{1}
\loop

\section{Lesson \theintA}

{
\begin{enumerate}
\foreachproblem[bank_lesson\theintA]{\item\thisproblem}
\end{enumerate}
}

\clearpage