You have set up your criteria for success to be that your user has full freedom
to specify code in strings to evaluate. Then you ask how to achieve this goal
without evaluating that code. Are you thinking objectively at all about your
question?
The advice to not use eval has a number of justifications that you should be
able to find yourself online (unnecessary obfuscation and program security are
two). Implementing an interpreter is not where this advice applies.
At the core of this problem, as long as you accept that your user is working
within the R interpreter then they can provide your code with functions that
access data on their own. You don't need to assume so much responsibility as
your question assumes you have to.
"Doctor, my head hurts!"
"Then stop banging it against the wall."
---------------------------------------------------------------------------
Jeff Newmiller The ..... ..... Go Live...
DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go...
Live: OO#.. Dead: OO#.. Playing
Research Engineer (Solar/Batteries O.O#. #.O#. with
/Software/Embedded Controllers) .OO#. .OO#. rocks...1k
---------------------------------------------------------------------------
Sent from my phone. Please excuse my brevity.
On February 1, 2014 8:40:47 AM PST, Hai Qian <hq...@gopivotal.com> wrote:
>I know using eval is not optimal and maybe bad, but how to avoid using
>eval
>in the following example
>
>func1 <- function(dat, eval.this) {
> eval(parse(text = paste0("with(dat, ", eval.this, ")")))
>}
>
>dat <- data.frame(x = 1:2, y = 2:3)
>
>func1(dat, "x*2+y")
>
>func1(dat, "sin(x)*cos(y)")
>
>Here eval.this is a string that contains whatever the user wants to
>evaluate. I wonder whether there is a neat way to avoid using eval in
>this
>case? So far I have not figured out a way to do this.
>
> [[alternative HTML version deleted]]
>
>______________________________________________
>R-help@r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
