[R] Example for Roxygen @eval tag?

[Duncan Murdoch]

On 22/04/2019 2:40 a.m., Boris Steipe wrote:
> I see .. you mean code that extends Roxygen. I was thinking something simple like an .Rmd chunk. But just creating an existing tag doesn't do much either:
> 
>    #' @eval sprintf("@section Time: %s", Sys.time() )
> 
> Renders as...
> 
>    @eval sprintf("@section Time:
> 
>   ... in the .Rd - more than before, but not what I though
> 
> An actual example would be most enlightening.

If you look in the Roxygen2 code you'll find some, e.g. in R/rd.R, which 
displays in ?rd_roclet.

I'd guess the percent sign is messing things up.  It's a comment in Rd 
files, and perhaps also in roxygen.

Doing the search through the source code also turned up @evalRd and 
@evalNamespace, which might be worth exploring.

Duncan Murdoch


> Thanks Jeff,
> Boris
> 
> 
> 
>> On 2019-04-22, at 02:25, Jeff Newmiller <jdnewmil using dcn.davis.ca.us> wrote:
>>
>> What tag are you creating with the eval? Your example wouldn't create valid roxygen code... as I said, it looks rather meta....
>>
>> On April 21, 2019 10:40:27 PM PDT, Boris Steipe <boris.steipe using utoronto.ca> wrote:
>>> Yes, that's where I started -  the vignette says:
>>>
>>>    ... Run arbtirary R code with @eval.
>>>
>>>    ... the @eval tag. It evaluates code and treats the result as if it
>>>    was a literal roxygen tags. This makes it possible to eliminate
>>>    duplication by writing functions.
>>>
>>> The first thing I noticed was that it does not say anything about
>>> delimiters. By trial and error it seems to consider everything up to
>>> the next @... tag in the header. Things that are not R code create an
>>> error during devtools::document() processing. It seems the output is
>>> captured and processed, i.e. System.time() creates a not-a-string
>>> error, but as.character(System.time()) passes ... but then nothing
>>> appears in the .Rd - and I haven't been able to find a single example
>>> of @eval in use in the wild.
>>>
>>> No joy.
>>>
>>>
>>>
>>>
>>>> On 2019-04-22, at 01:29, Jeff Newmiller <jdnewmil using dcn.davis.ca.us>
>>> wrote:
>>>>
>>>> I have not used it... but did you read the vignette [1]? It sounds
>>> like it is a bit more meta than you think it is...
>>>>
>>>> [1]
>>> https://cran.r-project.org/web/packages/roxygen2/vignettes/rd.html
>>>>
>>>> On April 21, 2019 7:44:17 PM PDT, Boris Steipe
>>> <boris.steipe using utoronto.ca> wrote:
>>>>> Playing with Roxygen features, but can't get @eval to work. E.g. ...
>>>>>
>>>>> #' @eval sprintf("%s", Sys.time())
>>>>>
>>>>> ... does not do what I thought it would (i.e. substitute the tag and
>>>>> the expression with the string). Instead I see nothing in the .RD
>>> file.
>>>>>
>>>>> Any working examples out there?
>>>>> Thanks!
>>>>> Boris
>>>>>
>>>>> ______________________________________________
>>>>> 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.
>>>>
>>>> -- 
>>>> Sent from my phone. Please excuse my brevity.
>>
>> -- 
>> Sent from my phone. Please excuse my brevity.
> 
> ______________________________________________
> 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.
>