[S] Q: stringFactor in tapply() and split()

[Vadim Ogranovich <vograno@arbitrade.com>]

Hi, I am writing a custom reader function that should read from a connection
and execute each line on the connection in a separate process. It turned out
to be quite simple, but I have problems to restore the standard reader back
when I am done.

Here are the details. I have a function myReader(con), which does nothing
but evaluates next line on a connection. When it encounters "q()" in the
input line it resets the connection back to the standardReader.

"myReader" <- 
function(con)
{
        x <- readLines(con)
        if(x == "q()") {
                setReader(con, standardReader)
        }
        else {
                print(eval(parse(text = x)))
                cat("my> ")     # custom prompt
        }
}

And here is a sample annotated session:

Version 5.1 Release 1 for Sun SPARC, SunOS 5.5 : 1999 
Working data will be in .Data 
> setReader(stdin(), myReader)
[1] 1
> showReaders()
 Tag Connection    Class   Action 
   1   /dev/tty terminal myReader
NULL
my> q()
# here I had to hit RETURN a couple of times before I got the prompt

> seq(1)
# notice that the output appears AFTER the prompt
> [1] 1
seq(1)
> [1] 1

My feeling that setting the stdin() to the standard reader did not go clean.
There are some other side effects that show up in S-mode under Emacs.

Any suggestion?

Thanks,
Vadim 


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