[Rd] print.<strorageMode>() not called when autoprinting

[Martin Maechler]

>>>>> William Dunlap 
>>>>>     on Tue, 21 May 2019 12:11:45 -0700 writes:

    > Letting a user supply the autoprint function would be nice also.  In a way
    > you can already do that, using addTaskCallback(), but that doesn't let you
    > suppress the standard autoprinting.

    > Having the default autoprinting do its own style of method dispatch doesn't
    > seem right.

I agree (if I understand correctly what you mean ... ;-)

    > Bill Dunlap
    > TIBCO Software
    > wdunlap tibco.com


    > On Tue, May 21, 2019 at 10:50 AM Lionel Henry <lionel using rstudio.com> wrote:

    >> FWIW it was the intention of the patch to make printing of unclassed
    >> functions consistent with other base types. This was documented in the
    >> "patch 3" section:
    >> 
    >> https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17398

I now vaguely remember.
OTOH,  tests/reg-tests-2.R  {the "output related" regression tests} 
*did* have an explicit test to ensure that print() and
auto-print do the same thing for functions:

    print.function <- function(x, ...) { str(x,...); invisible(x) }
    print.function
    f
    rm(print.function)
    ## auto-printing and printing differed up to R 2.9.x

so this was not
  "an undocumented consequence of an implementation detail"  ..

but you are right that it has not been documented explicitly.

    >> I think we need a general way to customise auto-printing for base types
    >> and even classed objects as that'd be useful for both users and IDEs.

Thank you, Lionel;  but I'm not convinced :

I'm pretty sure that all teaching and documentation about S and R 
has suggested that  print(f)  and auto-printing should result in
the same output _ AFAIR also for S4 objects
[unless  print() and show() methods were explicitly made to differ.. ? ]

    >> However S3 dispatch may not be optimal for this because it essentially
    >> requires polluting the global environment with print methods. Maybe
    >> it'd make sense to add getOption("autoprint") which should be set to
    >> a user- or environment- supplied function. That function would do the
    >> dispatch. I'd be happy to send a patch for this, if it makes sense.

    >> Best,
    >> Lionel

I'd rather we'd work towards the goal that auto printing
and print() should result in identical output :

1) for unclassed basic objects, i.e., what Bill meant with print.<storageMode>
   where maybe   print.<typeof>   would be a slightly better name;
2) for S3 classed objects;
3) for S4 classed objects with no print() method (but possibly a show() one).

Adding an option for autoprinting would render R even less
strictly functional, depending on yet another powerful global option,
and typical R usage would become more different from
'R --vanilla' even more --- really not a good direction to go in my view.

AFAICS, the above goal would need changes only for case '1)'

Martin

    >> > On 21 May 2019, at 13:38, William Dunlap via R-devel <
    >> r-devel using r-project.org> wrote:
    >> >
    >> > It also is a problem with storage.modes "integer" and "complex":
    >> >
    >> > 3.6.0> print.integer <- function(x,...) "integer vector"
    >> >                3.6.0> 1:10
    >> > [1]  1  2  3  4  5  6  7  8  9 10
    >> > 3.6.0> print(1:10)
    >> > [1] "integer vector"
    >> > 3.6.0>
    >> > 3.6.0> print.complex <- function(x, ...) "complex vector"
    >> > 3.6.0> 1+2i
    >> > [1] 1+2i
    >> > 3.6.0> print(1+2i)
    >> > [1] "complex vector"
    >> >
    >> > Bill Dunlap
    >> > TIBCO Software
    >> > wdunlap tibco.com
    >> >
    >> >
    >> > On Tue, May 21, 2019 at 9:31 AM Martin Maechler <
    >> maechler using stat.math.ethz.ch>
    >> > wrote:
    >> >
    >> >>>>>>> William Dunlap via R-devel
    >> >>>>>>>    on Thu, 16 May 2019 11:56:45 -0700 writes:
    >> >>
    >> >>> In R-3.6.0 autoprinting was changed so that print methods for the
    >> >> storage
    >> >>> modes are not called when there is no explicit class attribute.
    >> >> E.g.,
    >> >>
    >> >>> % R-3.6.0 --vanilla --quiet
    >> >>>> print.function <- function(x, ...) { cat("Function with argument
    >> >> list ");
    >> >>> cat(sep="\n    ", head(deparse(args(x)), -1)); invisible(x) }
    >> >>>> f <- function(x, ...) { sum( x * seq_along(x) ) }
    >> >>>> f
    >> >>> function(x, ...) { sum( x * seq_along(x) ) }
    >> >>>> print(f)
    >> >>> Function with argument list function (x, ...)
    >> >>
    >> >>> Previous to R-3.6.0 autoprinting did call such methods
    >> >>> % R-3.5.3 --vanilla --quiet
    >> >>>> print.function <- function(x, ...) { cat("Function with argument
    >> >> list ");
    >> >>> cat(sep="\n    ", head(deparse(args(x)), -1)); invisible(x) }
    >> >>>> f <- function(x, ...) { sum( x * seq_along(x) ) }
    >> >>>> f
    >> >>> Function with argument list function (x, ...)
    >> >>>> print(f)
    >> >>> Function with argument list function (x, ...)
    >> >>
    >> >>> Was this intentional?
    >> >>
    >> >> No, it was not.  ... and I've been the one committing the wrong change.
    >> >>
    >> >> ... Related to the NEWS entries which start
    >> >>
    >> >>     "Changes in print.*() ...."
    >> >>
    >> >> Thank you Bill, for reporting....
    >> >>
    >> >> It's amazing this has not been detected earlier by anybody.
    >> >>
    >> >> I think it is *only* for functions, not general
    >> >> print.<storagemode>() as you were suggesting - right?
    >> >>
    >> >> Martin
    >> >>
    >> >
    >> >       [[alternative HTML version deleted]]
    >> >
    >> > ______________________________________________
    >> > R-devel using r-project.org mailing list
    >> > https://stat.ethz.ch/mailman/listinfo/r-devel
    >> 
    >> 

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