Change in behavior of compare statement

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?

On 9/19/2005 12:25 PM, Tomas Andersson wrote:

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");

What is this function m_workspace.session.eval?  It's not a base 
function.  Perhaps its definition has changed?

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:

s != "1" is perfectly valid R code.  It will evaluate to TRUE in at 
least the following case:

as.character(s) is not an NA, but isn't "1".

s != "True" will evaluate to TRUE in most cases, unless s happens to 
contain that exact string.

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?

The syntax is fine, but it looks like a behaviour change in that 
function m_workspace.session.eval.  You'll need to ask the author of 
that function what is happening.

Duncan Murdoch

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch 
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Mihai Nica
Sent: Monday, September 19, 2005 4:07 PM
To: r-help at stat.math.ethz.ch
Subject: Re: [R] text editor TinR?

Greetings,

Please help me remember the name of the "tiny" text editor 
that works with R.... TinR maybe? I cannot find it at all, 
and cannot remember it, it is really frustrating...

Thanks,

Mihai Nica, ABD
Jackson State University
170 East Griffith Street G5
Jackson, MS 39201
601 914 0361

Greetings,

Please help me remember the name of the "tiny" text editor that works with 
R.... TinR maybe? I cannot find it at all, and cannot remember it, it is 
really frustrating...