\Header{is.language}{Is an Object a Language Object?}
\keyword{programming}{is.language}
\begin{Description}\relax
\code{is.language} returns \code{TRUE} if \code{x} is either a
variable \code{\Link{name}}, a \code{\Link{call}}, or an
\code{\Link{expression}}.\end{Description}
\begin{Usage}
\begin{verbatim}
is.language(x)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x}] object to be tested.
\end{ldescription}
\end{Arguments}
\begin{Examples}
\begin{ExampleCode}
ll <- list(a = expression(x^2 - 2*x + 1), b = as.name("Jim"),
           c = as.expression(exp(1)), d = call("sin", pi))
sapply(ll, typeof)
sapply(ll, mode)
stopifnot(sapply(ll, is.language))
\end{ExampleCode}
\end{Examples}

