\section{nan --- Not-a-Number Value}
\label{fn:nan}
\index{nan()}
\index{not-a-number value}
\begin{rail}
NotANumber : 'nan' '(' ')' ;
\end{rail}

\verb+nan+ returns a scalar encoded with the IEEE-754 NaN (Not a 
Number) value. You should be able to use this value as an argument to
just about any operation or function, with a result of NaN.


\paragraph{Example}
\index{example of nan()}
\index{nan()!example}
\begin{verbatim}
> nan()
      NaN
> nan() - nan()
      NaN
> nan() + nan()
      NaN
> exp(nan())
      NaN
\end{verbatim}

See also: Page~\pageref{fn:inf} \verb+inf()+,
Page~\pageref{fn:isnan} \verb+isnan()+.

\newpage



