[Rd] paste(character(0), collapse="", recycle0=FALSE) should be ""

William Dunlap wdun|@p @end|ng |rom t|bco@com
Fri May 22 18:50:33 CEST 2020


I agree with Herve, processing collapse happens last so collapse=non-NULL
always leads to a single character string being returned, the same as
paste(collapse="").  See the altPaste function I posted yesterday.

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, May 22, 2020 at 9:12 AM Hervé Pagès <hpages using fredhutch.org> wrote:

> I think that
>
>     paste(c("a", "b"), NULL, c("c",  "d"),  sep = " ", collapse = ",",
> recycle0=TRUE)
>
> should just return an empty string and don't see why it needs to emit a
> warning or raise an error. To me it does exactly what the user is asking
> for, which is to change how the 3 arguments are recycled **before** the
> 'sep' operation.
>
> The 'recycle0' argument has no business in the 'collapse' operation
> (which comes after the 'sep' operation): this operation still behaves
> like it always had.
>
> That's all there is to it.
>
> H.
>
>
> On 5/22/20 03:00, Gabriel Becker wrote:
> > Hi Martin et al,
> >
> >
> >
> > On Thu, May 21, 2020 at 9:42 AM Martin Maechler
> > <maechler using stat.math.ethz.ch <mailto: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=TRUEis not simply made an error).
> >
> > I would like to hear others' thoughts as well though. @Pages, Herve
> > <mailto:hpages using fredhutch.org> @William Dunlap
> > <mailto: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>
> >          >> <mailto: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=q5ueyHReS5hHK6TZ0dJ1N7Ro8dx-rsLHys8GrCugOls&s=o9ozvxBK-kVvAUFro7U1RrI5w0U8EPb0uyjQwMvOpt8&e=
> >
> >          >>
> >     <
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> >
> >          >> >
> >          >> >
> >          >> > 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>
> >     <mailto: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>
> >     <mailto:R-devel using r-project.org <mailto:R-devel using r-project.org>>
> >     mailing list
> >          >> >>
> >          >>
> >
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> >          >> >>
> >          >> >
> >          >> >       [[alternative HTML version deleted]]
> >          >> >
> >          >> > ______________________________________________
> >          >> > R-devel using r-project.org <mailto:R-devel using r-project.org>
> >     <mailto: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>
> >     <mailto: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>
> >     <mailto:R-devel using r-project.org <mailto:R-devel using r-project.org>>
> >     mailing list
> >          >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >     <
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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
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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
> Phone:  (206) 667-5791
> Fax:    (206) 667-1319
>

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