[Rd] sprintf behavior (PR#9250)

[Bill Dunlap]

On Mon, 25 Sep 2006 ripley at stats.ox.ac.uk wrote:

> On Mon, 25 Sep 2006, michael.bauer at lo-res.org wrote:
> ...
> > sprintf("\p") doesn't show the backslash, this occurs with all strings that
> > start with certain letters. There is however no explanation to this behavior.
>
> There is: see ?Quote (and C behaves in the same way).
>
> > And there seems to be no way to get a guaranteed backslash in sprintf.
>
> "\\", see the FAQ 7.8 for example.

Splus's parser emits a warning when it sees a backslash
outside of the recognized backslash sequence.  E.g.,

  > nchar("\Backslashed?")
  [1] 12
  Warning messages:
    The initial backslash is ignored in \B -- not a recognized escape sequence.
          Use \\ to make a backslash

You might want to add that warning to R's parser.  I've
seen the error in several R packages.  E.g.,

  bayesmix/R/JAGScontrol.R:  text[4] <- "-inits.R\"\n\initialize\n"
  SciViews/svDialogs/R/fixedDlg.wxPython.R:        if (length(grep("[\.]", basename(res))) == 0)

The warning is mostly emitted when the error is benign, but it
might help get people to think about what they are typing.

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Bill Dunlap
Insightful Corporation
bill at insightful dot com
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