[R] Change in behavior of compare statement

From: Tomas Andersson <tomas.andersson_at_spotfire.com>
Date: Tue 20 Sep 2005 - 00:46:33 EST


Dear all,  

I have come across some Windows Script code which calls the
"file.exists" function in R to check for the existence of a particular
file on an R server. This is what the code looks like:  

            do

            {

                        // some useful code

            }

            while (m_workspace.session.eval("file.exists(" + dataFile +

")") != "1");
 

It appears that the behavior of this code is different when used with R version 2.1.1 compared to R version 1.9.1. If the compare statement s is changed from  

            while (s != "1")

to

            while (s != "True")

or

            while !(s)  

the behavior of the code is the same with both versions of R.  

After reading the R documentation, I have not found any evidence that the original syntax (s != "1") is in any way recommended or supported (in version 2.1.1). Still, my questions are:  

  1. Is it possible that the syntax has been supported in older versions of R?
  2. Is the reason for the recent change in behavior known and documented anywhere?

I have been unable to find an answer to either question, so any information about this would be appreciated.  

Thanks,  

T. Andersson

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