R help - Aug 2006 - Backquote in R syntax

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 (? 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.

--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 07-Aug-06                                       Time: 10:25:31
------------------------------ XFMail ------------------------------

?Quote tells you all about quotes in R (and so does ?backquote in 
R-devel, but many people call it backtick and that is all 2.3.1 has).

On Mon, 7 Aug 2006, Ted.Harding at nessie.mcc.ac.uk wrote:
> 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 (? 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.
> 
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 07-Aug-06                                       Time: 10:25:31
> ------------------------------ XFMail ------------------------------
> 
> ______________________________________________
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> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

(Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> writes:
> 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 (? 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.
?Quotes should put you straight. (And help.search("`") gets you there,
as does help.search("backtick"), although not help.search("back
quote"))

-- 
   O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907