[R] Backquote in R syntax

[(Ted Harding)]

Hi Folks,
Can someone satisfy my curiosity (well, at least about
the following query!)

Reading the draft proofs of an article I've been asked
to look through, I find the typesetter has set what
would normally be entered as

  source("xyz.R")   or   source('xyz.R')

as

  source(`xyz.R')

i.e. it has come out with an opening backquote, then
xyz.R, then a closing forward quote. I suspect the
intervention of "intelligent" software (à la Word's
"clever quotes").

Well, the cure is clear and I'm not asking about that.
But I got curious about what role the backquote might
play in R syntax (if any). As a start I tried typing
that in as it stands:

   source(`xyz.R')
## and then you get the "continuation +" as if it were
##   incomplete, so I tried a closing parenthesis:
+ )
Error: unprotect_ptr: pointer not found

So it wasn't a mere syntax error (which would have caused
an error message saying just that) -- using the backquote
caused R to try to do something.

So now I'm wondering what the effect of "`" is, in R.

Statutory Declaration: I have performed an R Site Search
for "backquote" obtaining 9 hits none of which seems to
address this question.

Best wishes to all,
Ted.

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E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
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Date: 07-Aug-06                                       Time: 10:25:31
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