list of valid characters in object names

Dear all,
Could someone please point me to the definitive list of valid
characters that are allowed in object names in R? I believe that the
following list covers them:
_.abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789

but I would like to make sure.

Your question is a little ambiguous.  All characters are allowed in 
object names, but the parser will only recognize some of them if they 
are quoted in backticks.

The ones it recognizes without the backticks are ones that the C 
isalnum() (or iswalnum()) function declares to be alphanumeric, plus . 
and _.  Your list above are all allowed, but locales are allowed to 
declare other characters to be alpha.  I wouldn't recommend using 
anything else, because your code won't be recognized in other locales.

The definitive reference for this is the source code, specifically 
src/main/gram.y.  There's some discussion in the Intro to R manual, 
section 1.8.

Duncan Murdoch