[R] Lost backslashes in parse()

[Prof Brian Ripley]

On Thu, 1 Nov 2001, David Brahm wrote:

> I'm comparing R-1.3.0 on Solaris 2.6 to R-1.3.1 on WindowsNT.  The following
> 5-line script returns TRUE on Unix but FALSE on NT:
>
> fnam <- tempfile()
> file.create(fnam)
> txt <- paste("file.exists(\"", fnam, "\")", sep="")
> expr <- parse(text=txt)
> eval(expr)
>
> The issue seems to be that backslashes get lost in the parsing.  A workaround
> is to change the 3rd line to the rather ugly:
>   txt <- paste("file.exists(\"", gsub("\\\\","\\\\\\\\",fnam), "\")", sep="")
>
> Do you think this is something parse() should handle better?  If not, would it
> be preferable for tempfile() to return a forward-slash filename on NT?  How

No!  It should be a name that Windows utilities can make use of, as it is
often used in conjunction with system or shell.  If you want a
forward-slash version, that is easy to do in R (and you will see examples
throughout the code).

> else could you make this script return TRUE on NT?  Thanks!

It seems to me that you just want file.exists(fam).


-- 
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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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