[Rd] paste(character(0), collapse="", recycle0=FALSE) should be ""
Gabriel Becker
g@bembecker @end|ng |rom gm@||@com
Fri May 22 12:00:21 CEST 2020
Hi Martin et al,
On Thu, May 21, 2020 at 9:42 AM Martin Maechler <maechler using stat.math.ethz.ch>
wrote:
> >>>>> Hervé Pagès
> >>>>> on Fri, 15 May 2020 13:44:28 -0700 writes:
>
> > There is still the situation where **both** 'sep' and 'collapse' are
> > specified:
>
> >> paste(integer(0), "nth", sep="", collapse=",")
> > [1] "nth"
>
> > In that case 'recycle0' should **not** be ignored i.e.
>
> > paste(integer(0), "nth", sep="", collapse=",", recycle0=TRUE)
>
> > should return the empty string (and not character(0) like it does at
> the
> > moment).
>
> > In other words, 'recycle0' should only control the first operation
> (the
> > operation controlled by 'sep'). Which makes plenty of sense: the 1st
> > operation is binary (or n-ary) while the collapse operation is
> unary.
> > There is no concept of recycling in the context of unary operations.
>
> Interesting, ..., and sounding somewhat convincing.
>
> > On 5/15/20 11:25, Gabriel Becker wrote:
> >> Hi all,
> >>
> >> This makes sense to me, but I would think that recycle0 and
> collapse
> >> should actually be incompatible and paste should throw an error if
> >> recycle0 were TRUE and collapse were declared in the same call. I
> don't
> >> think the value of recycle0 should be silently ignored if it is
> actively
> >> specified.
> >>
> >> ~G
>
> Just to summarize what I think we should know and agree (or be
> be "disproven") and where this comes from ...
>
> 1) recycle0 is a new R 4.0.0 option in paste() / paste0() which by default
> (recycle0 = FALSE) should (and *does* AFAIK) not change anything,
> hence paste() / paste0() behave completely back-compatible
> if recycle0 is kept to FALSE.
>
> 2) recycle0 = TRUE is meant to give different behavior, notably
> 0-length arguments (among '...') should result in 0-length results.
>
> The above does not specify what this means in detail, see 3)
>
> 3) The current R 4.0.0 implementation (for which I'm primarily responsible)
> and help(paste) are in accordance.
> Notably the help page (Arguments -> 'recycle0' ; Details 1st para ;
> Examples)
> says and shows how the 4.0.0 implementation has been meant to work.
>
> 4) Several provenly smart members of the R community argue that
> both the implementation and the documentation of 'recycle0 =
> TRUE' should be changed to be more logical / coherent / sensical ..
>
> Is the above all correct in your view?
>
> Assuming yes, I read basically two proposals, both agreeing
> that recycle0 = TRUE should only ever apply to the action of 'sep'
> but not the action of 'collapse'.
>
> 1) Bill and Hervé (I think) propose that 'recycle0' should have
> no effect whenever 'collapse = <string>'
>
> 2) Gabe proposes that 'collapse = <string>' and 'recycle0 = TRUE'
> should be declared incompatible and error. If going in that
> direction, I could also see them to give a warning (and
> continue as if recycle = FALSE).
>
Herve makes a good point about when sep and collapse are both set. That
said, if the user explicitly sets recycle0, Personally, I don't think it
should be silently ignored under any configuration of other arguments.
If all of the arguments are to go into effect, the question then becomes
one of ordering, I think.
Consider
paste(c("a", "b"), NULL, c("c", "d"), sep = " ", collapse = ",",
recycle0=TRUE)
Currently that returns character(0), becuase the logic is essenttially (in
pseudo-code)
collapse(paste(c("a", "b"), NULL, c("c", "d"), sep = " ",
recycle0=TRUE), collapse = ", ", recycle0=TRUE)
-> collapse(character(0), collapse = ", " recycle0=TRUE)
-> character(0)
Now Bill Dunlap argued, fairly convincingly I think, that paste(...,
collapse=<string>) should *always* return a character vector of length
exactly one. With recycle0, though, it will return "" via the progression
paste(c("a", "b"), NULL, c("c", "d"), sep = " ", collapse = ",",
recycle0=TRUE)
-> collapse(character(0), collapse = ", ")
-> ""
because recycle0 is still applied to the sep-based operation which occurs
before collapse, thus leaving a vector of length 0 to collapse.
That is consistent but seems unlikely to be what the user wanted, imho. I
think if it does this there should be at least a warning when paste
collapses to "" this way, if it is allowed at all (ie if mixing
collapse=<string> and recycle0=TRUE is not simply made an error).
I would like to hear others' thoughts as well though. @Pages, Herve
<hpages using fredhutch.org> @William Dunlap <wdunlap using tibco.com> is "" what you
envision as thee desired and useful behavior there?
Best,
~G
> I have not yet my mind up but would tend to agree to "you guys",
> but I think that other R Core members should chime in, too.
>
> Martin
>
> >> On Fri, May 15, 2020 at 11:05 AM Hervé Pagès <hpages using fredhutch.org
> >> <mailto:hpages using fredhutch.org>> wrote:
> >>
> >> Totally agree with that.
> >>
> >> H.
> >>
> >> On 5/15/20 10:34, William Dunlap via R-devel wrote:
> >> > I agree: paste(collapse="something", ...) should always return a
> >> single
> >> > character string, regardless of the value of recycle0. This
> would be
> >> > similar to when there are no non-NULL arguments to paste;
> >> collapse="."
> >> > gives a single empty string and collapse=NULL gives a zero long
> >> character
> >> > vector.
> >> >> paste()
> >> > character(0)
> >> >> paste(collapse=", ")
> >> > [1] ""
> >> >
> >> > Bill Dunlap
> >> > TIBCO Software
> >> > wdunlap tibco.com
> >> <
> https://urldefense.proofpoint.com/v2/url?u=http-3A__tibco.com&d=DwMFaQ&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=cC2qctlVXd0qHMPvCyYvuVMqR8GU3DjTTqKJ0zjIFj8&s=rXIwWqf4U4HZS_bjUT3KfA9ARaV5YTb_kEcXWHnkt-c&e=
> >
> >> >
> >> >
> >> > On Thu, Apr 30, 2020 at 9:56 PM suharto_anggono--- via R-devel <
> >> > r-devel using r-project.org <mailto:r-devel using r-project.org>> wrote:
> >> >
> >> >> Without 'collapse', 'paste' pastes (concatenates) its arguments
> >> >> elementwise (separated by 'sep', " " by default). New in R devel
> >> and R
> >> >> patched, specifying recycle0 = FALSE makes mixing zero-length and
> >> >> nonzero-length arguments results in length zero. The result of
> >> paste(n,
> >> >> "th", sep = "", recycle0 = FALSE) always have the same length as
> >> 'n'.
> >> >> Previously, the result is still as long as the longest argument,
> >> with the
> >> >> zero-length argument like "". If all og the arguments have
> >> length zero,
> >> >> 'recycle0' doesn't matter.
> >> >>
> >> >> As far as I understand, 'paste' with 'collapse' as a character
> >> string is
> >> >> supposed to put together elements of a vector into a single
> >> character
> >> >> string. I think 'recycle0' shouldn't change it.
> >> >>
> >> >> In current R devel and R patched, paste(character(0), collapse =
> "",
> >> >> recycle0 = FALSE) is character(0). I think it should be "", like
> >> >> paste(character(0), collapse="").
> >> >>
> >> >> paste(c("4", "5"), "th", sep = "", collapse = ", ", recycle0 =
> >> FALSE)
> >> >> is
> >> >> "4th, 5th".
> >> >> paste(c("4" ), "th", sep = "", collapse = ", ", recycle0 =
> >> FALSE)
> >> >> is
> >> >> "4th".
> >> >> I think
> >> >> paste(c( ), "th", sep = "", collapse = ", ", recycle0 =
> >> FALSE)
> >> >> should be
> >> >> "",
> >> >> not character(0).
> >> >>
> >> >> ______________________________________________
> >> >> R-devel using r-project.org <mailto:R-devel using r-project.org> mailing
> list
> >> >>
> >>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=776IovW06eUHr1EDrabHLY7F47rU9CCUEItSDI96zc0&s=xN84DhkZeoxzn6SG0QTMpOGg2w_ThmjZmZymGUuD0Uw&e=
> >> >>
> >> >
> >> > [[alternative HTML version deleted]]
> >> >
> >> > ______________________________________________
> >> > R-devel using r-project.org <mailto:R-devel using r-project.org> mailing list
> >> >
> >>
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> >> >
> >>
> >> --
> >> Hervé Pagès
> >>
> >> Program in Computational Biology
> >> Division of Public Health Sciences
> >> Fred Hutchinson Cancer Research Center
> >> 1100 Fairview Ave. N, M1-B514
> >> P.O. Box 19024
> >> Seattle, WA 98109-1024
> >>
> >> E-mail: hpages using fredhutch.org <mailto:hpages using fredhutch.org>
> >> Phone: (206) 667-5791
> >> Fax: (206) 667-1319
> >>
> >> ______________________________________________
> >> R-devel using r-project.org <mailto:R-devel using r-project.org> mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >> <
> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel&d=DwMFaQ&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=cC2qctlVXd0qHMPvCyYvuVMqR8GU3DjTTqKJ0zjIFj8&s=COnDeGgHNnHJlLLZOznMlhcaFU1nIRlkaSbssvlrMvw&e=
> >
> >>
>
> > --
> > Hervé Pagès
>
> > Program in Computational Biology
> > Division of Public Health Sciences
> > Fred Hutchinson Cancer Research Center
> > 1100 Fairview Ave. N, M1-B514
> > P.O. Box 19024
> > Seattle, WA 98109-1024
>
> > E-mail: hpages using fredhutch.org
> > Phone: (206) 667-5791
> > Fax: (206) 667-1319
>
> > ______________________________________________
> > R-devel using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
>
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