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\name{duck-typing}
\alias{\%isa\%}
\alias{\%hasa\%}
\alias{\%hasall\%}
\title{Functions for duck typing}
\description{Duck typing is a way to emulate type checking by virtue of an
object's characteristics as opposed to strong typing.}
\usage{
argument \%isa\% type
argument \%hasa\% property
argument \%hasall\% property
}
\arguments{
\item{argument}{An object to inspect}
\item{type}{A type name}
\item{property}{A property of an object}
}
\details{
These operators provide a convenient method for testing for specific
properties of an object.
\code{\%isa\%} checks if an object is of the given type.
\code{\%hasa\%} checks if an object has a given property. This can
be any named element of a list or data.frame.
}
\value{
Boolean value indicating whether the specific test is true or not.
}
\author{ Brian Lee Yung Rowe }
\seealso{
\code{\link{\%as\%}}
}
\examples{
5 \%isa\% numeric
Point(r,theta, 'polar') \%as\% {
o <- list(r=r,theta=theta)
o@system <- 'polar'
o
}
p <- Point(5, pi/2, 'polar')
p %hasa% theta
}
\keyword{ methods }
\keyword{ programming }
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