[Rd] Inherited Methods in r-devel (for package maintainers mainly)

From: John Chambers <jmc_at_r-project.org>
Date: Mon, 26 Jan 2009 18:01:28 -0800


A recently committed revison of R-devel (47740) has introduced a new mechanism for ordering superclasses consistently, with related changes for selecting inherited methods.

As part of the process, a function testInheritedMethods has been introduced that examines method selection for the relevant subclasses and reports ambiguities.

Maintainers of packages that have methods involving multiple arguments are encouraged to run testInheritedMethods for the relevant generic functions (e.g., the binary operators). The new method selection is unambiguous for single-argument selection.

It's preferable to find such ambiguities during package development or revision, rather than having users encounter ambiguous method selection later on. In that spirit, ambiguous method selection is no longer a warning, just a message.

The new mechanism for class ordering and method selection is described in a draft paper at http://stat.stanford.edu/~jmc4/classInheritance.pdf (later likely to be part of a submission to the R Journal).

John



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