The methods package has methods for group generic "Ops" for S4 classes
that extend "array", "structure" or "vector". The
methods mainly try to
produce a consistent result when structures and vectors are combined.
See class?structure, section "Methods".
In the development version of R committed today (r47924), these methods
will be activated by loading any package with such classes. This was
always the intention, but up to version 2.8.1, the methods were not
activated UNLESS the package also defined some relevant methods itself.
(Fixing this turned out to need a whole new mechanism, to indicate that
the package needed the methods in question.)
Note to package maintainers: if you have a package that defines such
classes and does not define methods for operators, method selection may
change for objects from these classes. In some cases, the new methods
will be stricter (returning a vector result instead of mixing up
attributes, for example, as the base code sometimes does). I haven't
encountered examples, but please rerun CMD check if you think your
package fits the description.
John
