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A general description is here.
pretty() is now generic, with new methods for "Date" and
"POSIXt" classes (based on code contributed by Felix Andrews).
In the 'methods' package, the MethodsList metadata objects which had been superseded by hash tables (environments) since R 2.8.0 are being phased out. At the present stage stub objectObjects of this class are generated and a warning issued if these are accessed: shortly none will be generatedno longer assigned or used as metadata by the package.
getMethods() is now deprecated, with its internal use replaced by findMethods() and other changes. Creating objects from the MethodsList class is also deprecated.