| Line 69... |
Line 69... |
| 69 |
%% --------------- grep -nw DispatchGroup src/*/*[ch]
|
69 |
%% --------------- grep -nw DispatchGroup src/*/*[ch]
|
| 70 |
|
70 |
|
| 71 |
There are four \emph{groups} for which S3 methods can be written,
|
71 |
There are four \emph{groups} for which S3 methods can be written,
|
| 72 |
namely the \code{"Math"}, \code{"Ops"}, \code{"Summary"} and
|
72 |
namely the \code{"Math"}, \code{"Ops"}, \code{"Summary"} and
|
| 73 |
\code{"Complex"} groups. These are not \R objects, but methods can be
|
73 |
\code{"Complex"} groups. These are not \R objects, but methods can be
|
| 74 |
supplied for them and base \R contains \code{\link{factor}} and
|
74 |
supplied for them and base \R contains \code{\link{factor}},
|
| 75 |
\code{\link{data.frame}} methods for the first three groups.
|
75 |
\code{\link{data.frame}} and \code{\link{difftime}} methods for
|
| - |
|
76 |
the first three groups.
|
| 76 |
(There is also a \code{\link{ordered}} method for \code{Ops}.)
|
77 |
(There are also a \code{\link{ordered}} method for \code{Ops},
|
| - |
|
78 |
\code{\link{POSIXt}} methods for \code{Math} and \code{Ops}, as well as a
|
| - |
|
79 |
\code{\link[stats]{ts}} method for \code{Ops} in package \pkg{stats}.)
|
| 77 |
|
80 |
|
| 78 |
% A function \emph{\code{f}} belonging to one of these groups must be
|
81 |
% A function \emph{\code{f}} belonging to one of these groups must be
|
| 79 |
% \code{\link{.Internal}} or \code{\link{.Primitive}} and will
|
82 |
% \code{\link{.Internal}} or \code{\link{.Primitive}} and will
|
| 80 |
% automatically be using \emph{\code{<grp>.<class> (ob)}} when
|
83 |
% automatically be using \emph{\code{<grp>.<class> (ob)}} when
|
| 81 |
% \emph{\code{f(<ob>)}} is called, \emph{\code{f}} belongs to group
|
84 |
% \emph{\code{f(<ob>)}} is called, \emph{\code{f}} belongs to group
|
| Line 145... |
Line 148... |
| 145 |
\item \code{Arg}, \code{Conj}, \code{Im}, \code{Mod}, \code{Re}
|
148 |
\item \code{Arg}, \code{Conj}, \code{Im}, \code{Mod}, \code{Re}
|
| 146 |
% do_cmathfuns() [complex.c:267]: if(DispatchGroup("Complex",...))
|
149 |
% do_cmathfuns() [complex.c:267]: if(DispatchGroup("Complex",...))
|
| 147 |
}
|
150 |
}
|
| 148 |
}
|
151 |
}
|
| 149 |
|
152 |
|
| - |
|
153 |
Note that a method will used for either one of these groups or one of
|
| - |
|
154 |
its members \emph{only} if it corresponds to a \code{"class"}
|
| - |
|
155 |
attribute, as the internal code dispatches on \code{\link{oldClass}}
|
| - |
|
156 |
and not on \code{\link{class}}. This is for efficiency: having to
|
| - |
|
157 |
dispatch on, say, \code{Ops.integer} would be too slow.
|
| - |
|
158 |
|
| 150 |
The number of arguments supplied for \code{"Math"} group generic
|
159 |
The number of arguments supplied for \code{"Math"} group generic
|
| 151 |
methods is not checked prior to dispatch. (Prior to \R 1.7.0, all
|
160 |
methods is not checked prior to dispatch. (Most have default methods
|
| 152 |
those whose default method has one argument were checked, but the
|
161 |
expecting one argument, but three expect two.)
|
| 153 |
others were not.)
|
- |
|
| 154 |
}
|
162 |
}
|
| 155 |
\section{S4 Group Dispatching}{
|
163 |
\section{S4 Group Dispatching}{
|
| 156 |
When package \pkg{methods} is attached, formal (S4) methods can be
|
164 |
When package \pkg{methods} is attached, formal (S4) methods can be
|
| 157 |
defined for groups.
|
165 |
defined for groups.
|
| 158 |
|
166 |
|
The R Project SVN
R