I apologize if this issue has been raised before.
I really like object oriented S3 programming.
However, there's one feature of object oriented S3 programming that I
don't
like.
Generic functions can have arguments other than dots.
Lets say you have an R package with something like:
print.myfunction (f, ...)
{ dosomething (f, ...)
}
Noting that I use function objects a lot.
R CMD check will generate a warning because you've named your object f
rather than x.
I don't want to name my object x.
I want to name my object f.
Naming the object x makes the program unreadable.
Especially if f contains an attribute or an argument named x.
There's a work around.
You can redefine the print function, using something like:
print = function (...) base::print (...)
However, you have to export and document the function.
I think that it would be better if generic functions didn't have any
arguments except for dots.
[[alternative HTML version deleted]]
A generic function is not simply a way to name two functions (methods) the same. It has a particular purpose, and the argument names are aligned with and convey that purpose. The methods only implement polymorphism; they don't change the purpose. Changing the purpose would make code unreadable. Michael On Thu, Aug 9, 2018 at 2:45 PM, Abs Spurdle <spurdle.a at gmail.com> wrote:> I apologize if this issue has been raised before. > > I really like object oriented S3 programming. > However, there's one feature of object oriented S3 programming that I don't > like. > Generic functions can have arguments other than dots. > > Lets say you have an R package with something like: > > print.myfunction (f, ...) > { dosomething (f, ...) > } > > Noting that I use function objects a lot. > > R CMD check will generate a warning because you've named your object f > rather than x. > > I don't want to name my object x. > I want to name my object f. > Naming the object x makes the program unreadable. > Especially if f contains an attribute or an argument named x. > > There's a work around. > You can redefine the print function, using something like: > > print = function (...) base::print (...) > > However, you have to export and document the function. > > I think that it would be better if generic functions didn't have any > arguments except for dots. > > [[alternative HTML version deleted]] > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel >
On 09/08/2018 5:45 PM, Abs Spurdle wrote:> I apologize if this issue has been raised before. > > I really like object oriented S3 programming. > However, there's one feature of object oriented S3 programming that I don't > like. > Generic functions can have arguments other than dots. > > Lets say you have an R package with something like: > > print.myfunction (f, ...) > { dosomething (f, ...) > } > > Noting that I use function objects a lot. > > R CMD check will generate a warning because you've named your object f > rather than x. > > I don't want to name my object x. > I want to name my object f.There are reasons for this requirement. Suppose I have an object of class myfunction named myobj. However, being a 3rd party, I have no idea what class myfunction is about. Then I might say print(x = myobj) That would not work with your method, because the x would be absorbed into ..., it would not bind to f.> Naming the object x makes the program unreadable. > Especially if f contains an attribute or an argument named x.That's nonsense. You don't need to name your object the same as an argument. You name your object something readable (e.g. myobj), then pass it to print(), which binds it to x. If x is not a sensible name within the print.myfunction() method, then there's a one line fix: print.myfunction <- function(x, ...) { f <- x dosomething(f) }> > There's a work around. > You can redefine the print function, using something like: > > print = function (...) base::print (...) > > However, you have to export and document the function.That's a really, really bad idea. If there are two generics named the same, how are your users going to know which one they are getting when they just say print(myobj)?> > I think that it would be better if generic functions didn't have any > arguments except for dots.That makes argument checking much harder. If a generic always needs two arguments, why not name them, so R can complain when a user calls it with just one? Duncan Murdoch
> If x is not a sensible name within the print.myfunction() method, thenthere's a one line fix:> > print.myfunction <- function(x, ...) { > f <- x > dosomething(f) > }Naming the argument x is not an option.>> print = function (...) base::print (...)> That's a really, really bad idea. If there are two generics named thesame, how are your users going to know which one they are getting when they just say print(myobj)? If redefining the generics is "a really, really bad idea" then an alternative would be to define a new generic and two methods, one of which acts as a kind of bridging function, using something like: myprint = function (...) UseMethod ("myprint") myprint.myfunction = function (f, ...) {dosomething (f, ...)} print.myfunction = function (x, ...) myprint (x, ...)> If a generic always needs two arguments, why not name them, so R cancomplain when a user calls it with just one? We can apply that principle to the methods rather than the generic. On Fri, Aug 10, 2018 at 10:20 AM, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:> On 09/08/2018 5:45 PM, Abs Spurdle wrote: > >> I apologize if this issue has been raised before. >> >> I really like object oriented S3 programming. >> However, there's one feature of object oriented S3 programming that I >> don't >> like. >> Generic functions can have arguments other than dots. >> >> Lets say you have an R package with something like: >> >> print.myfunction (f, ...) >> { dosomething (f, ...) >> } >> >> Noting that I use function objects a lot. >> >> R CMD check will generate a warning because you've named your object f >> rather than x. >> >> I don't want to name my object x. >> I want to name my object f. >> > > There are reasons for this requirement. Suppose I have an object of class > myfunction named myobj. However, being a 3rd party, I have no idea what > class myfunction is about. Then I might say > > print(x = myobj) > > That would not work with your method, because the x would be absorbed into > ..., it would not bind to f. > > > Naming the object x makes the program unreadable. >> Especially if f contains an attribute or an argument named x. >> > > That's nonsense. You don't need to name your object the same as an > argument. You name your object something readable (e.g. myobj), then pass > it to print(), which binds it to x. > > If x is not a sensible name within the print.myfunction() method, then > there's a one line fix: > > print.myfunction <- function(x, ...) { > f <- x > dosomething(f) > } > >> >> There's a work around. >> You can redefine the print function, using something like: >> >> print = function (...) base::print (...) >> >> However, you have to export and document the function. >> > > That's a really, really bad idea. If there are two generics named the > same, how are your users going to know which one they are getting when they > just say print(myobj)? > > >> I think that it would be better if generic functions didn't have any >> arguments except for dots. >> > > That makes argument checking much harder. If a generic always needs two > arguments, why not name them, so R can complain when a user calls it with > just one? > > Duncan Murdoch >[[alternative HTML version deleted]]