[Rd] should base R have a piping operator ?

[John Mount]

Many of those issues can be dealt with by introducing curly braces:

	compose <- function(f, g) { function(x) g(f(x)) }
	plus1 <- function(x) x + 1
	plus2 <- { plus1 ->.; compose(., plus1) }
	plus2(5)
	# [1] 7

And a lot of that is a point to note: we may not all agree on what cases are corner cases, and which ones should be handled in a given way.

> On Oct 5, 2019, at 8:48 AM, Ant F <antoine.fabri using gmail.com> wrote:
> 
> Hi John,
> 
> Thanks, but the Bizzaro pipe comes with many flaws though :
> * It's not a single operator
> * It has a different precedence
> * It cannot be used in a subcall
> * The variable assigned to must be on the right
> * It doesn't trigger indentation when going to the line
> * It creates/overwrite a `.` variable in the worksace. 
> 
> And it doesn't deal gracefully with some lazy evaluation edge cases such as : 
> 
> compose <- function(f, g) { function(x) g(f(x)) }
> plus1   <- function(x) x + 1
> 
> plus2 <- plus1 %.% compose(.,plus1)
> plus2(5)
> #> [1] 7
> 
> plus1 ->.; compose(.,plus1) -> .; . -> plus2
> plus2(5)
> #> Error: C stack usage  15923776 is too close to the limit
> 
> What I propose on the other hand can always substitute any existing proper pipe in their standard feature, as long as the dot is made explicit.
> 
> Best regards,
> 
> Antoine
> 
> 
> 
> Le sam. 5 oct. 2019 à 16:59, John Mount <jmount using win-vector.com <mailto:jmount using win-vector.com>> a écrit :
> Actually, base R already has a pipe fairly close to the one you describe: ->.;
> 
> 	iris ->.; head(.) ->.; dim(.)
> 	# [1] 6 5
> 
> I've called it the Bizarro pipe ( http://www.win-vector.com/blog/2016/12/magrittrs-doppelganger/ <http://www.win-vector.com/blog/2016/12/magrittrs-doppelganger/> ), and for some reason we chickened out and didn't spend time on it in the dot pipe paper ( https://journal.r-project.org/archive/2018/RJ-2018-042/index.html <https://journal.r-project.org/archive/2018/RJ-2018-042/index.html> ).
> 
> For documentation Bizarro pipe has the advantage that one can work out how it works from the application itself, with out reference to a defining function.
> 
>> On Oct 5, 2019, at 7:34 AM, Ant F <antoine.fabri using gmail.com <mailto:antoine.fabri using gmail.com>> wrote:
>> 
>> Dear R-devel,
>> 
>> The most popular piping operator sits in the package `magrittr` and is used
>> by a huge amount of users, and imported /reexported by more and more
>> packages too.
>> 
>> Many workflows don't even make much sense without pipes nowadays, so the
>> examples in the doc will use pipes, as do the README, vignettes etc. I
>> believe base R could have a piping operator so packages can use a pipe in
>> their code or doc and stay dependency free.
>> 
>> I don't suggest an operator based on complex heuristics, instead I suggest
>> a very simple and fast one (>10 times than magrittr in my tests) :
>> 
>> `%.%` <- function (e1, e2) {
>>  eval(substitute(e2), envir = list(. = e1), enclos = parent.frame())
>> }
>> 
>> iris %.% head(.) %.% dim(.)
>> #> [1] 6 5
>> 
>> The difference with magrittr is that the dots must all be explicit (which
>> sits with the choice of the name), and that special magrittr features such
>> as assignment in place and building functions with `. %>% head() %>% dim()`
>> are not supported.
>> 
>> Edge cases are not surprising:
>> 
>> ```
>> x <- "a"
>> x %.% quote(.)
>> #> .
>> x %.% substitute(.)
>> #> [1] "a"
>> 
>> f1 <- function(y) function() eval(quote(y))
>> f2 <- x %.% f1(.)
>> f2()
>> #> [1] "a"
>> ```
>> 
>> Looking forward for your thoughts on this,
>> 
>> Antoine
>> 
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>> 
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> 
> ---------------
> John Mount
> http://www.win-vector.com/ <http://www.win-vector.com/> 
> Our book: Practical Data Science with R https://www.manning.com/books/practical-data-science-with-r-second-edition <http://www.manning.com/zumel/>
> 
> 
> 
> 

---------------
John Mount
http://www.win-vector.com/ <http://www.win-vector.com/> 
Our book: Practical Data Science with R https://www.manning.com/books/practical-data-science-with-r-second-edition <http://www.manning.com/zumel/>





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