[R] Change in behavior of compare statement

[Tomas Andersson]

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