The R Project SVN R

\name{class}
\title{Object Classes}
\usage{
class(x)
class(x) <- names
unclass(x)
inherits(x, name)
}
\alias{class}
\alias{class<-}
\alias{unclass}
\alias{inherits}
\description{
R possesses a simple generic function mechanism
which can be used for an object-oriented style of programming.
Method despatch takes place based on the class of the first argument
to the generic function.

An R ``object'' is a data object which has a \code{class} attribute.
A class attribute is a vector of character strings giving the
names of the classes which the object ``inherits'' from.
When a generic function \code{fun} is applied to an object 
with class attribute c("first","second"), the system searches
for a function called \code{fun.first} and, if it finds it,
applied it to the object.  If no such function is found
a function called \code{fun.second} is tried.
If no class name produces a suitable function, the function
\code{fun.default} is used.

The function \code{class} prints the vector of names of classes
which an object inherits from.
Correspondingly, \code{class<-} sets the classes
which an object inherits from.
\code{unclass} returns (a copy of) its argument
with its class information removed.
\code{inherits} indicates whether its first argument inherits
from a class with name equal to its second argument.
}
\seealso{
\code{\link{UseMethod}}, \code{\link{NextMethod}}.
}