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  legitimate slot names.
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  legitimate slot names.
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  Note that the \code{"@"} operators for extraction and (since \R 3.0.0)
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  Note that the \code{"@"} operators for extraction and (since \R 3.0.0)
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  replacement are primitive and actually reside in the \pkg{base}
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  replacement are primitive and actually reside in the \pkg{base}
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  package.
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  package.
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  The replacement versions of  \code{"@"} and \code{slot()} differ in
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  the computations done to coerce the right side of the assignment to
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  the declared class of the slot.  Both verify that the value provided
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  is from a subclass of the declared slot class.  The  \code{slot()}
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  version will go on to call the coerce method if there is one, in
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  effect doing the computation \code{as(value, slotClass, strict =
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    FALSE)}. The  \code{"@"} version just verifies the relation,
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  leaving any coerce to be done later (e.g., when a relevant method is
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  dispatched).
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  In most uses the result is equivalent, and the  \code{"@"} version
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  saves an extra function call, but if empirical evidence shows that a
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  conversion is needed, either call \code{as()} before the replacement
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  or use the replacement version of \code{slot()}.
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}
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}
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\references{
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\references{
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 Chambers, John M. (2008)
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 Chambers, John M. (2008)
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 \emph{Software for Data Analysis: Programming with R}
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 \emph{Software for Data Analysis: Programming with R}
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  Springer.  (For the R version.)
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  Springer.  (For the R version.)