[R] [R-devel] Source Code for function

Fri Sep 6 22:07:02 CEST 2019

Thank you all for your reply. I should clarify, that I am looking to understand why the keyword function can take a logical argument (eg: x<4) and use that later inside the function's definition for logical evaluations.

Consider this example, which is a simplification of getAnywhere(subset.data.frame):
x = data.frame("Col1" = c(1, 2, 3, 4, 5), "Col2" = c(6, 7, 8, 9, 10))
test <- function(x, logic){
	e <- substitute(logic)
	r <- eval(e, x, parent.frame())
	r[r]
}

Shelby

On 9/6/19, 1:02 PM, "R-help on behalf of Richard M. Heiberger" <r-help-bounces using r-project.org on behalf of rmh using temple.edu> wrote:

    You might also want to look at the codetools package, for example the
    showTree function " Prints a Lisp-style representation of R
    expression."

    > library(codetools)

    > showTree(quote(x %*% x))
    (%*% x x)
    > showTree(quote(a+b))
    (+ a b)
    > showTree(quote(y ~ a+b))
    (~ y (+ a b))

    On Fri, Sep 6, 2019 at 2:30 PM Bert Gunter <bgunter.4567 using gmail.com> wrote:
    >
    > The following may be of use (it gives the parse tree of the text):
    >
    > > z <- as.list(parse(text = "function(x)x %*% x"))
    > > z[[1]]
    > function(x) x %*% x
    > > z[[c(1,1)]]
    > `function`
    > > z[[c(1,2)]]
    > $x
    > > z[[c(1,3)]]
    > x %*% x
    > > z[[c(1,3,1)]]
    > `%*%`
    > > z[[c(1,3,2)]]
    > x
    > > z[[c(1,3,3)]]
    > x
    >
    >
    > Bert Gunter
    >
    >
    >
    > On Fri, Sep 6, 2019 at 10:14 AM Wang Jiefei <szwjf08 using gmail.com> wrote:
    >
    > > If you are looking for an R code parser, I think the `parse` and `eval`
    > > function might be a good start point. See the example below.
    > >
    > > > parse(text="function(x)message(x)")
    > > expression(function(x)message(x))
    > > > eval(parse(text="function(x)message(x)"))
    > > function(x)message(x)
    > >
    > > Best,
    > > Jiefei
    > >
    > > On Fri, Sep 6, 2019 at 12:55 PM Golden, Shelby <GoldenS using njhealth.org>
    > > wrote:
    > >
    > >> Hello Bert,
    > >>
    > >> Thank you for the reply and your clarifications. Yes, it might be helpful
    > >> to look into R’s formal grammar to see how “function” parses input to
    > >> delegate correct syntax. Is that accessible online?
    > >>
    > >> Thank you,
    > >> Shelby
    > >>
    > >>
    > >> From: Bert Gunter <bgunter.4567 using gmail.com>
    > >> Date: Friday, September 6, 2019 at 10:44 AM
    > >> To: "Golden, Shelby" <GoldenS using NJHealth.org>
    > >> Cc: "r-help using R-project.org" <r-help using r-project.org>, "Gillenwater, Lucas" <
    > >> GILLENWATERL using NJHEALTH.ORG>
    > >> Subject: Re: [R] [R-devel] Source Code for function
    > >>
    > >> 1. This is a plain text list; all html is stripped. So there is no red
    > >> highlighting.
    > >>
    > >> 2. There is no "source code" for "function" -- it is a reserved keyword.
    > >> Or are you looking for R's formal grammar -- e.g. how it parses input to
    > >> determine correct syntax?
    > >>
    > >>
    > >>
    > >> Bert Gunter
    > >>
    > >> "The trouble with having an open mind is that people keep coming along
    > >> and sticking things into it."
    > >> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
    > >>
    > >>
    > >> On Fri, Sep 6, 2019 at 8:51 AM Golden, Shelby <GoldenS using njhealth.org
    > >> <mailto:GoldenS using njhealth.org>> wrote:
    > >> Hi all,
    > >>
    > >> I have been attempting to access the source code for the keyword
    > >> “function” to better understand how it assigns and stores logical inputs,
    > >> like in the subset() [base] function. Does anyone know how I can access the
    > >> source code for this?
    > >>
    > >> For example, if I have
    > >> norm <- function(x){
    > >>       sqrt(x%*%x))
    > >> }
    > >> I am looking for the source code for the “function” portion, highlighted
    > >> in red.
    > >>
    > >> Thank you for your time and assistance,
    > >> Shelby Golden
    > >> Lab Researcher Technician
    > >> Dr. Russell Bowler’s Lab
    > >> Department of Medicine
    > >> National Jewish Health in Denver, CO
    > >> Phone: (303) 270-2598
    > >>
    > >> NOTICE: This email message is for the sole use of the intended
    > >> recipient(s) and may contain confidential and privileged information. Any
    > >> unauthorized review, use, disclosure or distribution is prohibited. If you
    > >> are not the intended recipient, please contact the sender by reply email
    > >> and destroy all copies of the original message.
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    > >>
    > >> ______________________________________________
    > >> R-help using r-project.org<mailto:R-help using r-project.org> mailing list -- To
    > >> UNSUBSCRIBE and more, see
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    > >> http://mx2.njhealth.org:32224/?dmVyPTEuMDAxJiZmMWRiYmMxZjFmNmI5ZDBkMz01RDcyOEQwN18yMjk2OF8zOTk2XzEmJjljNzlmMDA4YWRmZTZjMz0xMjMzJiZ1cmw9aHR0cHMlM0ElMkYlMkZzdGF0JTJFZXRoeiUyRWNoJTJGbWFpbG1hbiUyRmxpc3RpbmZvJTJGci1oZWxw
    > >> >
    > >> PLEASE do read the posting guide
    > >> http://www.R-project.org/posting-guide.html<
    > >> http://mx2.njhealth.org:32224/?dmVyPTEuMDAxJiZlMTkwYmMwMzFlNjk4ZTAzNz01RDcyOEQwN18yMjk2OF8zOTk2XzEmJmFkYTkxMWRkMWRhZTFkNz0xMjMzJiZ1cmw9aHR0cCUzQSUyRiUyRnd3dyUyRVItcHJvamVjdCUyRW9yZyUyRnBvc3RpbmctZ3VpZGUlMkVodG1s
    > >> >
    > >> and provide commented, minimal, self-contained, reproducible code.
    > >>
    > >>         [[alternative HTML version deleted]]
    > >>
    > >> ______________________________________________
    > >> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
    > >> 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.
    > >>
    > >
    >
    >         [[alternative HTML version deleted]]
    >
    > ______________________________________________
    > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
    > 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 using r-project.org mailing list -- To UNSUBSCRIBE and more, see
    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.

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