[Rd] documentation omission in Extract.Rd?

[Tony Plate]

The help file for "[<-" (and "[[<-" doesn't contain those functions in 
it's usage section ( .../src/library/base/man/Extract.Rd ).  Although 
that file lists "[<-" and "[[<-" as aliases, it doesn't document them in 
a formal manner (consequently, the "value" argument is not described in 
the "arguments" section.)

Is this an oversight, or are those documented elsewhere?  In contrast, 
src/library/base/man/Extract.factor.Rd does contain the replacement 
forms in its usage section (as does Extract.data.frame.Rd)

Also, Extract.Rd uses forms like "x[i, j, \dots , drop = TRUE]" in the 
usage section, while Extract.factor.Rd uses the "method" syntax: 
"\method{[}{factor}(x, \dots, drop = FALSE)".  Is this because the 
"method" syntax is not appropriate for the default methods that are 
documented in Extract.Rd, or is the source of the docs not up-to-date 
with the latest Rd syntax?  I ask because I was looking for examples of 
how to write documentation for extraction and replacement functions.

This is based on looking at the source code at 
http://svn.r-project.org/R/trunk/src/library/base/man/Extract.Rd and I 
see the same in R-2.10.0 for Linux.

-- Tony Plate