Um... Let's get the concepts straight: The "function" function doesn't evaluate anything. It just takes the list of formal arguments (including default expressions), the function body, and the current evaluation environment, and stiches them together into a function object, known as a "closure". The action happens when a function is _called_. Then the actual arguments are combined with the formals, and the body expression is evaluated. You will find the source code for this in src/main/eval.c. It is a pretty complex beast, but the essential point for the present discussion is that actual arguments in function calls are passed in the form of so-called promises. These contain the expression passed, so that substitute() can extract it. It also enables lazy evaluation: putting off argument evaluation until the value is actually needed (possibly never). -pd> On 6 Sep 2019, at 23:10 , David Winsemius <dwinsemius at comcast.net> wrote: > > > On 9/6/19 1:07 PM, Golden, Shelby wrote: >> 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] >> } > > x<4 is not really a logical argument in that context. It is rather an expression and will remain an expression until it needs to be evaluated. See this even simpler example: > > > test <- function(x, logic, ... ){ > e <- deparse( substitute(logic)) > #r <- eval(e, x, parent.frame()) > e > } > test(4, x<4) > #[1] "x < 4" > > > test(4, is.logical(x < 4) ) > [1] "is.logical(x < 4)" > > > Some of this you have already been told, but appears necessary to repeat. Expressions given to `function` are not necessarily evaluated. They will be evaluated if assigned names. > > > test(4, zed = is.logical(x < 4) ) > #[1] "" > > The function()-function will parse the contents of the parentheses for number of arguments and for parse()-ability. It will evaluate named arguments created with "=". In the context of parsing the formals of a function the "=" operator is different than the "<-" function. > > The substitute function will not evaluate (since in the language of R operations it is "special"), but rather checks that the expression can be parsed by R's rules, i.e. is a valid parse tree. `deparse` returns the original character representation. > > -- > > David > > >> >> Shelby >> >> ?On 9/6/19, 1:02 PM, "R-help on behalf of Richard M. Heiberger" <r-help-bounces at r-project.org on behalf of rmh at 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 at 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 at 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 at 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 at gmail.com> >> > >> Date: Friday, September 6, 2019 at 10:44 AM >> > >> To: "Golden, Shelby" <GoldenS at NJHealth.org> >> > >> Cc: "r-help at R-project.org" <r-help at r-project.org>, "Gillenwater, Lucas" < >> > >> GILLENWATERL at 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 at njhealth.org >> > >> <mailto:GoldenS at 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. >> > >> [[alternative HTML version deleted]] >> > >> >> > >> ______________________________________________ >> > >> R-help at r-project.org<mailto:R-help at r-project.org> mailing list -- To >> > >> UNSUBSCRIBE and more, see >> > >> https://stat.ethz.ch/mailman/listinfo/r-help< >> > >> 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 at 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 at 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 at 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. >> >> >> 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. >> ______________________________________________ >> R-help at 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 at 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.-- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com
Afternoon, Peter,
Thank you for your concise but informative reply, and for a link to the source
code. These complex concepts do answer my question spot on, so thank you for
taking the time to put them all together and summarizing them for me.
Is the standard nomenclature for arguments in function calls
"promises"? I would like to look into this concept further. If there
are other concepts you think I should look into further too, I would be happy to
include those as well.
Regards,
Shelby
?On 9/6/19, 4:02 PM, "peter dalgaard" <pdalgd at gmail.com>
wrote:
Um... Let's get the concepts straight:
The "function" function doesn't evaluate anything. It just
takes the list of formal arguments (including default expressions), the function
body, and the current evaluation environment, and stiches them together into a
function object, known as a "closure".
The action happens when a function is _called_. Then the actual arguments
are combined with the formals, and the body expression is evaluated. You will
find the source code for this in src/main/eval.c. It is a pretty complex beast,
but the essential point for the present discussion is that actual arguments in
function calls are passed in the form of so-called promises. These contain the
expression passed, so that substitute() can extract it. It also enables lazy
evaluation: putting off argument evaluation until the value is actually needed
(possibly never).
-pd
> On 6 Sep 2019, at 23:10 , David Winsemius <dwinsemius at
comcast.net> wrote:
>
>
> On 9/6/19 1:07 PM, Golden, Shelby wrote:
>> 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]
>> }
>
> x<4 is not really a logical argument in that context. It is rather
an expression and will remain an expression until it needs to be evaluated. See
this even simpler example:
>
>
> test <- function(x, logic, ... ){
> e <- deparse( substitute(logic))
> #r <- eval(e, x, parent.frame())
> e
> }
> test(4, x<4)
> #[1] "x < 4"
>
>
> test(4, is.logical(x < 4) )
> [1] "is.logical(x < 4)"
>
>
> Some of this you have already been told, but appears necessary to
repeat. Expressions given to `function` are not necessarily evaluated. They will
be evaluated if assigned names.
>
>
> test(4, zed = is.logical(x < 4) )
> #[1] ""
>
> The function()-function will parse the contents of the parentheses for
number of arguments and for parse()-ability. It will evaluate named arguments
created with "=". In the context of parsing the formals of a function
the "=" operator is different than the "<-" function.
>
> The substitute function will not evaluate (since in the language of R
operations it is "special"), but rather checks that the expression can
be parsed by R's rules, i.e. is a valid parse tree. `deparse` returns the
original character representation.
>
> --
>
> David
>
>
>>
>> Shelby
>>
>> On 9/6/19, 1:02 PM, "R-help on behalf of Richard M.
Heiberger" <r-help-bounces at r-project.org on behalf of rmh at
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 at 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 at
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 at 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 at
gmail.com>
>> > >> Date: Friday, September 6, 2019 at 10:44 AM
>> > >> To: "Golden, Shelby" <GoldenS at
NJHealth.org>
>> > >> Cc: "r-help at R-project.org"
<r-help at r-project.org>, "Gillenwater, Lucas" <
>> > >> GILLENWATERL at 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 at njhealth.org
>> > >> <mailto:GoldenS at 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.
>> > >> [[alternative HTML version deleted]]
>> > >>
>> > >> ______________________________________________
>> > >> R-help at r-project.org<mailto:R-help at
r-project.org> mailing list -- To
>> > >> UNSUBSCRIBE and more, see
>> > >> https://stat.ethz.ch/mailman/listinfo/r-help<
>> > >>
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 at 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 at 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 at 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.
>>
>>
>> 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.
>> ______________________________________________
>> R-help at 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 at 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.
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com
It is time to end these queries and start your homework by consulting the references you have already been given. Wickham's goes into all of this; the R Language Definition that ships with R covers all of your questions and more in detail; and numerous online references and tutorials -- A search on "what is a promise in R" brings up numerous resources, for example -- are available. This list is for help. It is not a substitute for studying on your own. Cheers, Bert On Fri, Sep 6, 2019 at 3:15 PM Golden, Shelby <GoldenS at njhealth.org> wrote:> Afternoon, Peter, > > Thank you for your concise but informative reply, and for a link to the > source code. These complex concepts do answer my question spot on, so thank > you for taking the time to put them all together and summarizing them for > me. > > Is the standard nomenclature for arguments in function calls "promises"? I > would like to look into this concept further. If there are other concepts > you think I should look into further too, I would be happy to include those > as well. > > Regards, > Shelby > > > ?On 9/6/19, 4:02 PM, "peter dalgaard" <pdalgd at gmail.com> wrote: > > Um... Let's get the concepts straight: > > The "function" function doesn't evaluate anything. It just takes the > list of formal arguments (including default expressions), the function > body, and the current evaluation environment, and stiches them together > into a function object, known as a "closure". > > The action happens when a function is _called_. Then the actual > arguments are combined with the formals, and the body expression is > evaluated. You will find the source code for this in src/main/eval.c. It is > a pretty complex beast, but the essential point for the present discussion > is that actual arguments in function calls are passed in the form of > so-called promises. These contain the expression passed, so that > substitute() can extract it. It also enables lazy evaluation: putting off > argument evaluation until the value is actually needed (possibly never). > > -pd > > > On 6 Sep 2019, at 23:10 , David Winsemius <dwinsemius at comcast.net> > wrote: > > > > > > On 9/6/19 1:07 PM, Golden, Shelby wrote: > >> 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] > >> } > > > > x<4 is not really a logical argument in that context. It is rather > an expression and will remain an expression until it needs to be evaluated. > See this even simpler example: > > > > > > test <- function(x, logic, ... ){ > > e <- deparse( substitute(logic)) > > #r <- eval(e, x, parent.frame()) > > e > > } > > test(4, x<4) > > #[1] "x < 4" > > > > > > test(4, is.logical(x < 4) ) > > [1] "is.logical(x < 4)" > > > > > > Some of this you have already been told, but appears necessary to > repeat. Expressions given to `function` are not necessarily evaluated. They > will be evaluated if assigned names. > > > > > > test(4, zed = is.logical(x < 4) ) > > #[1] "" > > > > The function()-function will parse the contents of the parentheses > for number of arguments and for parse()-ability. It will evaluate named > arguments created with "=". In the context of parsing the formals of a > function the "=" operator is different than the "<-" function. > > > > The substitute function will not evaluate (since in the language of > R operations it is "special"), but rather checks that the expression can be > parsed by R's rules, i.e. is a valid parse tree. `deparse` returns the > original character representation. > > > > -- > > > > David > > > > > >> > >> Shelby > >> > >> On 9/6/19, 1:02 PM, "R-help on behalf of Richard M. Heiberger" < > r-help-bounces at r-project.org on behalf of rmh at 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 at 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 at 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 at 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 at gmail.com> > >> > >> Date: Friday, September 6, 2019 at 10:44 AM > >> > >> To: "Golden, Shelby" <GoldenS at NJHealth.org> > >> > >> Cc: "r-help at R-project.org" <r-help at r-project.org>, > "Gillenwater, Lucas" < > >> > >> GILLENWATERL at 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 at njhealth.org > >> > >> <mailto:GoldenS at 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. > >> > >> [[alternative HTML version deleted]] > >> > >> > >> > >> ______________________________________________ > >> > >> R-help at r-project.org<mailto:R-help at r-project.org> mailing > list -- To > >> > >> UNSUBSCRIBE and more, see > >> > >> https://stat.ethz.ch/mailman/listinfo/r-help< > >> > >> > 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 at 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 at 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 at 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. > >> > >> > >> 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. > >> ______________________________________________ > >> R-help at 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 at 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. > > -- > Peter Dalgaard, Professor, > Center for Statistics, Copenhagen Business School > Solbjerg Plads 3, 2000 Frederiksberg, Denmark > Phone: (+45)38153501 > Office: A 4.23 > Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com > > > > > > > > > > > >[[alternative HTML version deleted]]