File r37/doc/manual/rest.tex from the latest check-in

\subsection{ROOT\_VAL Operator}

The {\tt ROOT\_VAL} operator takes a single univariate polynomial as
argument, and returns a list of root values at system precision (or
greater if required to separate roots).  It is used with the syntax
\begin{verbatim}
	ROOT_VAL(EXPRN:univariate polynomial):list.
\end{verbatim}
For example, the sequence
\begin{verbatim}
        on rounded; root_val(x^3-x-1);
\end{verbatim}
gives the result
\begin{verbatim}
        {0.562279512062*I - 0.662358978622, - 0.562279512062*I

          - 0.662358978622,1.32471795724}
\end{verbatim}