\HeaderA{is.object}{Is an Object ``internally classed''?}{is.object}
\keyword{methods}{is.object}
\keyword{classes}{is.object}
\begin{Description}\relax
A function rather for internal use.  It returns \code{TRUE} if the
object \code{x} has the \R{} internal \code{OBJECT} bit set, and
\code{FALSE} otherwise.  The \code{OBJECT} bit is set when a
\code{"class"} attribute is added and removed when that attribute is
removed, so this is a very efficient way to check if an object has a
class attribute.  (S4 objects always should.)
\end{Description}
\begin{Usage}
\begin{verbatim}
is.object(x)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x}] object to be tested.
\end{ldescription}
\end{Arguments}
\begin{SeeAlso}\relax
\code{\LinkA{class}{class}}, and \code{\LinkA{methods}{methods}}.

\code{\LinkA{isS4}{isS4}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
is.object(1) # FALSE
is.object(as.factor(1:3)) # TRUE
\end{ExampleCode}
\end{Examples}

