[Rd] 1. Performance fix in as(); 2. low-level access functions

[John Chambers]

1.  A bug was found & fixed in the as() function that prevented it from
caching methods; in some examples there would be a big performance
penalty (found in investigating slow performance of the R DBI package). 
The fix has been committed to r-patched and r-devel.

Thanks to David James for pointing out the problem.

2.  A number of low-level access functions are being phased out. They
were inconsistent and seemed to cause some confusion. For internal use,
they have been replaced with direct access to slots in the class
definition.

The more useful of the properties have higher-level versions that work
better (users were getting confused, e.g., between the high-level
extends() and low-level getExtends()).  All the low-level functions are
equivalent to slot access, some with out-of-date names, going back to
the early work on the methods package.

See ?getExtends in the r-devel version for a list of the functions and
the corresponding slots. Barring protests, the functions will be
deprecated shortly.

John


---
John M. Chambers                  jmc at bell-labs.com
Bell Labs, Lucent Technologies    office: (908)582-2681
700 Mountain Avenue, Room 2C-282  fax:    (908)582-3340
Murray Hill, NJ  07974            web: http://www.cs.bell-labs.com/~jmc