\name{is.language}
\title{Is an Object a Language Object?}
\usage{is.language(x)}
\alias{is.language}
\description{
  \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}}.
}
\examples{
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)
sapply(ll, is.language)# all TRUE
}
\keyword{programming}
