[Rd] "\088" is legal syntax?

[William Dunlap]

The CRAN package svMisc misuses it, using "\8" instead of "\10" or "\b":
 ./svMisc/R/progress.R:          backspaces <- paste(rep("\8", l3), collapse = "")

I noticed it when S+ emitted a warning when parsing that file:
  > p <- parse("svMisc/R/progress.R")
  Warning messages:
    The initial backslash is ignored in \8 -- not a recognized escape sequence.
          Use \\ to make a backslash in: parse("svMisc/R/progress.R")
(S+ parses the "\8" as "8", as the warning obliquly implies.)

I grepped through other CRAN sources for "\\0*8" and also found
  ./mvbutils/R/mvbutils.R:  rep.percent <- '\008'
S+ emits no warning for that but parses it as "", because it
considers the octal escape to stop at the first non-octal digit.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 

> -----Original Message-----
> From: Duncan Murdoch [mailto:murdoch.duncan at gmail.com]
> Sent: Thursday, September 01, 2011 5:30 PM
> To: William Dunlap
> Cc: r-devel at r-project.org
> Subject: Re: [Rd] "\088" is legal syntax?
> 
> On 11-09-01 5:43 PM, William Dunlap wrote:
> > Is it intentional that the digit 8 is allowed
> > in octal escape sequences in character literals?
> >
> >    >  "\110" == "\088"
> >    [1] TRUE
> >    >  "\8" == "\b"
> >    [1] TRUE
> >
> > 9's are rejected, so I'd expected 8's to be illegal as well.
> 
> It is documented that way in the R-lang manual, but I imagine it's just
> a thinko.  It's been like that since octal escapes were added in 1998.
> I wonder how much will break if I fix it?
> 
> Duncan Murdoch
> 
> >
> >    >  "\9"
> >    Error: '\9' is an unrecognized escape in character string starting "\9"
> >    >  "\091")
> >    Error: embedded nul in string: '\091'
> >
> > Bill Dunlap
> > Spotfire, TIBCO Software
> > wdunlap tibco.com
> >
> >> sessionInfo()
> > R version 2.13.1 (2011-07-08)
> > Platform: x86_64-unknown-linux-gnu (64-bit)
> >
> > locale:
> >   [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
> >   [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
> >   [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
> >   [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
> >   [9] LC_ADDRESS=C               LC_TELEPHONE=C
> > [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
> >
> > attached base packages:
> > [1] stats     graphics  grDevices utils     datasets  methods   base
> >
> > ______________________________________________
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