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

[Hervé Pagès]

Excellent! Thanks Martin.

H.

On 5/28/20 00:39, Martin Maechler wrote:

Martin Maechler
 on Wed, 27 May 2020 13:35:44 +0200 writes:



Hervé Pagès
 on Tue, 26 May 2020 12:38:13 -0700 writes:


 >> Hi Martin, On 5/26/20 06:24, Martin Maechler wrote: ...
 >>>
 >>> What about remaining back-compatible, not only to R 3.y.z
 >>> with default recycle0=FALSE, but also to R 4.0.0 with
 >>> recycle0=TRUE

 >> What back-compatibility with R 4.0.0 are we talking about?
 >> The 'recycle0' arg was added **after** the R 4.0.0 release
 >> and has never been part of an official release yet.

 > Yes, of course.  It was *planned* for R 4.0.0 and finally was
 > too late (feature freeze etc)... I'm sorry I was wrong and
 > misleading above.

 >> This is the time to fix it.

 > Well, R 4.0.1 is already in 'beta' and does contain it too.
 > So the "fix" should happen really really fast, or we (R core)
 > take it out from there entirely.

Well, in the end your repeated good reasoning has prevailed:
I've committed a change (to R-devel; most probably in
time to be ported to 4.0.1 beta).
I think this implements the   recycle0 = TRUE   behavior you
have been advocating for,
in svn r78591  (2020-05-27 19:45:07 +0200)   with message

  paste(), paste0(): collapse= always gives a string
  (also w/ `recycle0=TRUE`)

Best regards,
Martin



--
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: hpa...@fredhutch.org
Phone:  (206) 667-5791
Fax:(206) 667-1319

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

[Martin Maechler]

> Martin Maechler 
> on Wed, 27 May 2020 13:35:44 +0200 writes:

> Hervé Pagès 
> on Tue, 26 May 2020 12:38:13 -0700 writes:

>> Hi Martin, On 5/26/20 06:24, Martin Maechler wrote: ...
>>> 
>>> What about remaining back-compatible, not only to R 3.y.z
>>> with default recycle0=FALSE, but also to R 4.0.0 with
>>> recycle0=TRUE

>> What back-compatibility with R 4.0.0 are we talking about?
>> The 'recycle0' arg was added **after** the R 4.0.0 release
>> and has never been part of an official release yet. 

> Yes, of course.  It was *planned* for R 4.0.0 and finally was
> too late (feature freeze etc)... I'm sorry I was wrong and
> misleading above.

>> This is the time to fix it.

> Well, R 4.0.1 is already in 'beta' and does contain it too.
> So the "fix" should happen really really fast, or we (R core)
> take it out from there entirely.

Well, in the end your repeated good reasoning has prevailed:
I've committed a change (to R-devel; most probably in
time to be ported to 4.0.1 beta).
I think this implements the   recycle0 = TRUE   behavior you
have been advocating for, 
in svn r78591  (2020-05-27 19:45:07 +0200)   with message

 paste(), paste0(): collapse= always gives a string
 (also w/ `recycle0=TRUE`)

Best regards,
Martin

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

[Martin Maechler]

> Hervé Pagès 
> on Tue, 26 May 2020 12:38:13 -0700 writes:

> Hi Martin, On 5/26/20 06:24, Martin Maechler wrote: ...
>> 
>> What about remaining back-compatible, not only to R 3.y.z
>> with default recycle0=FALSE, but also to R 4.0.0 with
>> recycle0=TRUE

> What back-compatibility with R 4.0.0 are we talking about?
> The 'recycle0' arg was added **after** the R 4.0.0 release
> and has never been part of an official release yet. 

Yes, of course.  It was *planned* for R 4.0.0 and finally was
too late (feature freeze etc)... I'm sorry I was wrong and
misleading above.

> This is the time to fix it.

Well, R 4.0.1 is already in 'beta' and does contain it too.
So the "fix" should happen really really fast, or we (R core)
take it out from there entirely.

>> *and* add a new option for the Suharto-Bill-Hervé-Gabe
>> behavior, e.g., recycle0="sep.only" or just
>> recycle0="sep" ?

> OMG!

>> As (for back-compatibility reasons) you have to specify
>> 'recycle0 = ..'  anyway, you would get what makes most
>> sense to you by using such a third option.
>> 
>> ? (WDYT ?)

> Don't bother. I'd rather use

>paste(paste(x, y, z, sep="#", recycle0=TRUE), collapse=",")

> i.e. explicitly break down the 2 operations (sep and
> collapse). Might be slightly less efficient but I find it
> way more readable than

>paste(x, y, z, sep="#", collapse=",", recycle0="sep.only")

> BTW I appreciate you trying to accomodate everybody's
> taste. That doesn't sound like an easy task ;-)


> I'll just reiterate my earlier comment that controlling
> the collapse operation via an argument named 'recycle0'
> doesn't make sense (collapse involves NO recycling). So I
> don't know if the current 'recyle0=TRUE' behavior is "the
> correct one" but at the very least the name of the
> argument is a misnomer and misleading.

> More generally speaking using the same argument to control
> 2 distinct operations is not good API design. A better
> design is to use 2 arguments. Then the 2 arguments can
> generally be made orthogonal (like in this case) i.e. all
> possible combinations are valid (4 combinations in this case).

I don't disagree about the principle...

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

[Hervé Pagès]

Hi Martin,

On 5/26/20 06:24, Martin Maechler wrote:
...


What about remaining back-compatible, not only to R 3.y.z with
default recycle0=FALSE, but also to R 4.0.0 with recycle0=TRUE


What back-compatibility with R 4.0.0 are we talking about? The 
'recycle0' arg was added **after** the R 4.0.0 release and has never 
been part of an official release yet. This is the time to fix it.



*and* add a new option for the Suharto-Bill-Hervé-Gabe behavior,
e.g., recycle0="sep.only" or just  recycle0="sep" ?


OMG!



As (for back-compatibility reasons) you have to specify
'recycle0 = ..'  anyway, you would get what makes most sense to
you by using such a third option.

? (WDYT ?)


Don't bother. I'd rather use

  paste(paste(x, y, z, sep="#", recycle0=TRUE), collapse=",")

i.e. explicitly break down the 2 operations (sep and collapse). Might be 
slightly less efficient but I find it way more readable than


  paste(x, y, z, sep="#", collapse=",", recycle0="sep.only")

BTW I appreciate you trying to accomodate everybody's taste. That 
doesn't sound like an easy task ;-)


I'll just reiterate my earlier comment that controlling the collapse 
operation via an argument named 'recycle0' doesn't make sense (collapse 
involves NO recycling). So I don't know if the current 'recyle0=TRUE' 
behavior is "the correct one" but at the very least the name of the 
argument is a misnomer and misleading.


More generally speaking using the same argument to control 2 distinct 
operations is not good API design. A better design is to use 2 
arguments. Then the 2 arguments can generally be made orthogonal (like 
in this case) i.e. all possible combinations are valid (4 combinations 
in this case).


Thanks,
H.




Martin

 > Switching to scheme (3) or to a new custom scheme
 > would be a completely different proposal.

 >>
 >> At least I'm consistent right?

 > Yes :-)

 > Anyway discussing recycling schemes is interesting but not directly
 > related with what the OP brought up (behavior of the 'collapse' 
operation).

 > Cheers,
 > H.

 >>
 >> ~G



--
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: hpa...@fredhutch.org
Phone:  (206) 667-5791
Fax:(206) 667-1319

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

[Martin Maechler]

> Hervé Pagès 
> on Sun, 24 May 2020 14:22:37 -0700 writes:

> On 5/24/20 00:26, Gabriel Becker wrote:
>> 
>> 
>> On Sat, May 23, 2020 at 9:59 PM Hervé Pagès > > wrote:
>> 
>> On 5/23/20 17:45, Gabriel Becker wrote:
>> > Maybe my intuition is just
>> > different but when I collapse multiple character vectors together, I
>> > expect all the characters from each of those vectors to be in the
>> > resulting collapsed one.
>> 
>> Yes I'd expect that too. But the **collapse** operation in paste() has
>> never been about collapsing **multiple** character vectors together.
>> What it does is collapse the **single** character vector that comes out
>> of the 'sep' operation.
>> 
>> 
>> I understand what it does, I broke ti down the same way in my post 
>> earlier in the thread. the fact remains is that it is a single function 
>> which significantly muddies the waters. so you can say
>> 
>> paste0(x,y, collapse=",", recycle0=TRUE)
>> 
>> is not a collapse operation on multiple vectors, and of course there's a 
>> sense in which you're not wrong (again I understand what these functions 
>> do), but it sure looks like one in the invocation, doesn't it?
>> 
>> Honestly the thing that this whole discussion has shown me most clearly 
>> is that, imho, collapse (accepting ONLY one data vector) and 
>> paste(accepting multiple) should never have been a single function to 
>> begin with.  But that ship sailed long long ago.

> Yes :-(

>> 
>> So
>> 
>>    paste(x, y, z, sep="", collapse=",")
>> 
>> is analogous to
>> 
>>    sum(x + y + z)
>> 
>> 
>> Honestly, I'd be significantly more comfortable if
>> 
>> 1:10 + integer(0) + 5
>> 
>> were an error too.

> This is actually the recycling scheme used by mapply():

>> mapply(function(x, y, z) c(x, y, z), 1:10, integer(0), 5)
> Error in mapply(FUN = FUN, ...) :
> zero-length inputs cannot be mixed with those of non-zero length

> AFAIK base R uses 3 different recycling schemes for n-ary operations:

> (1) The recycling scheme used by arithmetic and comparison operations
> (Arith, Compare, Logic group generics).

> (2) The recycling scheme used by classic paste().

> (3) The recycling scheme used by mapply().

> Having such a core mechanism like recycling being inconsistent across 
> base R is sad. It makes it really hard to predict how a given n-ary 
> function will recycle its arguments unless you spend some time trying it 
> yourself with several combinations of vector lengths. It is of course 
> the source of numerous latent bugs. I wish there was only one but that's 
> just a dream.

> None of these 3 recycling schemes is perfect. IMO (2) is by far the 
> worst. (3) is too restrictive and would need to be refined if we wanted 
> to make it a good universal recycling scheme.

> Anyway I don't think it makes sense to introduce a 4th recycling scheme 
> at this point even though it would be a nice item to put on the wish 
> list for R 7.0.0 with the ultimate goal that it will universally adopted 
> in R 11.0.0 ;-)

> So if we have to do with what we have IMO (1) is the scheme that makes 
> most sense although I agree that it can do some surprising things for 
> some unusual combinations of vector lengths. It's the scheme I adhere to 
> in my own binary operations e.g. in S4Vector::pcompare().

> The modest proposal of the 'recycle0' argument is only to let the user 
> switch from recycling scheme (2) to (1) if they're not happy with scheme 
> (2) (I'm one of them).

Yes, indeed.  This was the purpose of introducing  'recycle0'.

Now, with collapse = ,  {in R "string" := character vector of length 1}.
we clearly see different interpretations on what is desirable
for  recycle0 = TRUE,
all of you (Suharto, Bill, Hervé, Gabe) assert that the behavior
should be different than now, and should either error (possibly,
by Gabe), or return a single string  (possibly with a warning),
i.e., collapse =   behavior should not be influenced (or
possibly be conflicting with) by recycle0=TRUE.

Within R core, some believe the current recyle0=TRUE behavior to
be the correct one.  Personally, I see
reasons for both..

What about remaining back-compatible, not only to R 3.y.z with
default recycle0=FALSE, but also to R 4.0.0 with recycle0=TRUE
*and* add a new option for the Suharto-Bill-Hervé-Gabe behavior,
e.g., recycle0="sep.only" or just  recycle0="sep" ?

As (for back-compatibility reasons) you have to specify
'recycle0 = ..'  anyway, you would get what makes most sense to
you by using such a third option.

? (WDYT ?)

Martin

> Switching to scheme (3) or to a new custom scheme 
> would be a completely different proposal.

>> 
>> At least 

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

[Hervé Pagès]

On 5/24/20 00:26, Gabriel Becker wrote:



On Sat, May 23, 2020 at 9:59 PM Hervé Pagès > wrote:


On 5/23/20 17:45, Gabriel Becker wrote:
 > Maybe my intuition is just
 > different but when I collapse multiple character vectors together, I
 > expect all the characters from each of those vectors to be in the
 > resulting collapsed one.

Yes I'd expect that too. But the **collapse** operation in paste() has
never been about collapsing **multiple** character vectors together.
What it does is collapse the **single** character vector that comes out
of the 'sep' operation.


I understand what it does, I broke ti down the same way in my post 
earlier in the thread. the fact remains is that it is a single function 
which significantly muddies the waters. so you can say


paste0(x,y, collapse=",", recycle0=TRUE)

is not a collapse operation on multiple vectors, and of course there's a 
sense in which you're not wrong (again I understand what these functions 
do), but it sure looks like one in the invocation, doesn't it?


Honestly the thing that this whole discussion has shown me most clearly 
is that, imho, collapse (accepting ONLY one data vector) and 
paste(accepting multiple) should never have been a single function to 
begin with.  But that ship sailed long long ago.


Yes :-(



So

    paste(x, y, z, sep="", collapse=",")

is analogous to

    sum(x + y + z)


Honestly, I'd be significantly more comfortable if

1:10 + integer(0) + 5

were an error too.


This is actually the recycling scheme used by mapply():

  > mapply(function(x, y, z) c(x, y, z), 1:10, integer(0), 5)
  Error in mapply(FUN = FUN, ...) :
zero-length inputs cannot be mixed with those of non-zero length

AFAIK base R uses 3 different recycling schemes for n-ary operations:

(1) The recycling scheme used by arithmetic and comparison operations
(Arith, Compare, Logic group generics).

(2) The recycling scheme used by classic paste().

(3) The recycling scheme used by mapply().

Having such a core mechanism like recycling being inconsistent across 
base R is sad. It makes it really hard to predict how a given n-ary 
function will recycle its arguments unless you spend some time trying it 
yourself with several combinations of vector lengths. It is of course 
the source of numerous latent bugs. I wish there was only one but that's 
just a dream.


None of these 3 recycling schemes is perfect. IMO (2) is by far the 
worst. (3) is too restrictive and would need to be refined if we wanted 
to make it a good universal recycling scheme.


Anyway I don't think it makes sense to introduce a 4th recycling scheme 
at this point even though it would be a nice item to put on the wish 
list for R 7.0.0 with the ultimate goal that it will universally adopted 
in R 11.0.0 ;-)


So if we have to do with what we have IMO (1) is the scheme that makes 
most sense although I agree that it can do some surprising things for 
some unusual combinations of vector lengths. It's the scheme I adhere to 
in my own binary operations e.g. in S4Vector::pcompare().


The modest proposal of the 'recycle0' argument is only to let the user 
switch from recycling scheme (2) to (1) if they're not happy with scheme 
(2) (I'm one of them). Switching to scheme (3) or to a new custom scheme 
would be a completely different proposal.




At least I'm consistent right?


Yes :-)

Anyway discussing recycling schemes is interesting but not directly 
related with what the OP brought up (behavior of the 'collapse' operation).


Cheers,
H.



~G


--
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: hpa...@fredhutch.org
Phone:  (206) 667-5791
Fax:(206) 667-1319

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

[Gabriel Becker]

On Sat, May 23, 2020 at 9:59 PM Hervé Pagès  wrote:

> On 5/23/20 17:45, Gabriel Becker wrote:
> > Maybe my intuition is just
> > different but when I collapse multiple character vectors together, I
> > expect all the characters from each of those vectors to be in the
> > resulting collapsed one.
>
> Yes I'd expect that too. But the **collapse** operation in paste() has
> never been about collapsing **multiple** character vectors together.
> What it does is collapse the **single** character vector that comes out
> of the 'sep' operation.
>

I understand what it does, I broke ti down the same way in my post earlier
in the thread. the fact remains is that it is a single function which
significantly muddies the waters. so you can say

paste0(x,y, collapse=",", recycle0=TRUE)

is not a collapse operation on multiple vectors, and of course there's a
sense in which you're not wrong (again I understand what these functions
do), but it sure looks like one in the invocation, doesn't it?

Honestly the thing that this whole discussion has shown me most clearly is
that, imho, collapse (accepting ONLY one data vector) and paste(accepting
multiple) should never have been a single function to begin with.  But that
ship sailed long long ago.




> So
>
>paste(x, y, z, sep="", collapse=",")
>
> is analogous to
>
>sum(x + y + z)
>

Honestly, I'd be significantly more comfortable if

1:10 + integer(0) + 5

were an error too.

At least I'm consistent right?

~G

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

[Hervé Pagès]

On 5/23/20 17:45, Gabriel Becker wrote:
Maybe my intuition is just 
different but when I collapse multiple character vectors together, I 
expect all the characters from each of those vectors to be in the 
resulting collapsed one.


Yes I'd expect that too. But the **collapse** operation in paste() has 
never been about collapsing **multiple** character vectors together. 
What it does is collapse the **single** character vector that comes out 
of the 'sep' operation.


So

  paste(x, y, z, sep="", collapse=",")

is analogous to

  sum(x + y + z)

The element-wise addition is analog to the 'sep' operation.
The sum() operation is analog to the 'collapse' operation.

H.

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

[Gabriel Becker]

Brodie,

A good point, but more analogous to what I'm concerned with is

> sum(5, numeric(0))

[1] 5


Not 0 (the analogu of Herve's desired behavior).

Best,
~G

PS Brodie sorry for the double.

On Fri, May 22, 2020 at 6:12 PM brodie gaslam 
wrote:

> > On Friday, May 22, 2020, 6:16:45 PM EDT, Hervé Pagès <
> hpa...@fredhutch.org> wrote:
> >
> > Gabe,
> >
> > It's the current behavior of paste() that is a major source of bugs:
> >
> >   ## Add "rs" prefix to SNP ids and collapse them in a
> >   ## comma-separated string.
> >   collapse_snp_ids <- function(snp_ids)
> >   paste("rs", snp_ids, sep="", collapse=",")
> >
> >   snp_groups <- list(
> > group1=c(55, 22, 200),
> > group2=integer(0),
> > group3=c(99, 550)
> >   )
> >
> >   vapply(snp_groups, collapse_snp_ids, character(1))
> >   #group1group2group3
> >   # "rs55,rs22,rs200"  "rs"  "rs99,rs550"
> >
> > This has hit me so many times!
> >
> > Now with 'collapse0=TRUE', we finally have the opportunity to make it do
> > the right thing. Let's not miss that opportunity.
> >
> > Cheers,
> > H.
>
> FWIW what convinces me is consistency with other aggregating functions
> applied
> to zero length inputs:
>
> sum(numeric(0))
> ## [1] 0
>
> >
> >
> > On 5/22/20 11:26, Gabriel Becker wrote:
> > > I understand that this is consistent but it also strikes me as an
> > > enormous 'gotcha' of a magnitude that 'we' are trying to avoid/smooth
> > > over at this point in user-facing R space.
> > >
> > > For the record I'm not suggesting it should return something other than
> > > "", and in particular I'm not arguing that any call to paste /that does
> > > not return an error/ with non-NULL collapse should return a character
> > > vector of length one.
>

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

[Gabriel Becker]

Herve (et al.),

On Fri, May 22, 2020 at 3:16 PM Hervé Pagès  wrote:

> Gabe,
>
> It's the current behavior of paste() that is a major source of bugs:
>
>## Add "rs" prefix to SNP ids and collapse them in a
>## comma-separated string.
>collapse_snp_ids <- function(snp_ids)
>paste("rs", snp_ids, sep="", collapse=",")
>
>snp_groups <- list(
>  group1=c(55, 22, 200),
>  group2=integer(0),
>  group3=c(99, 550)
>)
>
>vapply(snp_groups, collapse_snp_ids, character(1))
>#group1group2group3
># "rs55,rs22,rs200"  "rs"  "rs99,rs550"
>
> This has hit me so many times!
>
> Now with 'collapse0=TRUE', we finally have the opportunity to make it do
> the right thing. Let's not miss that opportunity.
>

I see what you're saying, but I don' know. Maybe my intuition is just
different but when I collapse multiple character vectors together, I
expect all the characters from each of those vectors to be in the resulting
collapsed one. In your example its a string literal tot be added
elementwise to the prefix, but what if it is another vector of length > 1.
Wouldn't it be strange that all those values are wiped and absent from the
resulting string? Maybe it's just me. like for paste(x,y,z, sep ="",
collapse = ", ", recycle0=TRUE) if length(y) is 0, it literally makes no
difference when x and z are.

I seem to be being largely outvoted anyway though, so we will see what
Martin and others who may pop up might think, but I raised the points I
wanted to raise so we'll see where things ultimately fall.

~G



>
> Cheers,
> H.
>
>
> On 5/22/20 11:26, Gabriel Becker wrote:
> > I understand that this is consistent but it also strikes me as an
> > enormous 'gotcha' of a magnitude that 'we' are trying to avoid/smooth
> > over at this point in user-facing R space.
> >
> > For the record I'm not suggesting it should return something other than
> > "", and in particular I'm not arguing that any call to paste /that does
> > not return an error/ with non-NULL collapse should return a character
> > vector of length one.
> >
> > Rather I'm pointing out that it could (perhaps should, imo) simply be an
> > error, which is also consistent, in the strict sense, with
> > previous behavior in that it is the developer simply declining to extend
> > the recycle0 argument to the full parameter space (there is no rule that
> > says we must do so, arguments whose use is incompatible with other
> > arguments can be reasonable and called for).
> >
> > I don't feel feel super strongly that reeturning "" in this and similar
> > cases horrible and should never happen, but i'd bet dollars to donuts
> > that to the extent that behavior occurs it will be a disproportionately
> > major source of bugs, and i think thats at least worth considering in
> > addition to pure consistency.
> >
> > ~G
> >
> > On Fri, May 22, 2020 at 9:50 AM William Dunlap  > > wrote:
> >
> > 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
> > <
> https://urldefense.proofpoint.com/v2/url?u=http-3A__tibco.com=DwMFaQ=eRAMFD45gAfqt84VtBcfhQ=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA=Z1o-HO3_OqxOR9LaRguGvnG7X4vF_z1_q13I7zmjcfY=7ZT1IjmexPqsDBhrV3NspPTr8M8XiMweEwJWErgAlqw=
> >
> >
> >
> > On Fri, May 22, 2020 at 9:12 AM Hervé Pagès  > > 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
> >  >  > 
> >  > >> wrote:
> >  >
> >  >  > Hervé Pagès
> >  >  > on Fri, 15 May 2020 13:44:28 -0700 writes:
> >  >
> >  >  > There is still the situation where **both** 'sep'
> and
> >

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

[Hervé Pagès]

On 5/22/20 18:12, brodie gaslam wrote:


FWIW what convinces me is consistency with other aggregating functions applied
to zero length inputs:

sum(numeric(0))
## [1] 0


Right.

And 1 is the identity element of multiplication:

> prod(numeric(0))
[1] 1

And the empty string is the identity element of string aggregation by 
concatenation.


H.

__
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel

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

[brodie gaslam via R-devel]

> On Friday, May 22, 2020, 6:16:45 PM EDT, Hervé Pagès  
> wrote:
>
> Gabe,
>
> It's the current behavior of paste() that is a major source of bugs:
>
>   ## Add "rs" prefix to SNP ids and collapse them in a
>   ## comma-separated string.
>   collapse_snp_ids <- function(snp_ids)
>   paste("rs", snp_ids, sep="", collapse=",")
>
>   snp_groups <- list(
> group1=c(55, 22, 200),
> group2=integer(0),
> group3=c(99, 550)
>   )
>
>   vapply(snp_groups, collapse_snp_ids, character(1))
>   #    group1    group2    group3
>   # "rs55,rs22,rs200"  "rs"  "rs99,rs550"
>
> This has hit me so many times!
>
> Now with 'collapse0=TRUE', we finally have the opportunity to make it do
> the right thing. Let's not miss that opportunity.
>
> Cheers,
> H.

FWIW what convinces me is consistency with other aggregating functions applied
to zero length inputs:

sum(numeric(0))
## [1] 0

>
>
> On 5/22/20 11:26, Gabriel Becker wrote:
> > I understand that this is consistent but it also strikes me as an
> > enormous 'gotcha' of a magnitude that 'we' are trying to avoid/smooth
> > over at this point in user-facing R space.
> >
> > For the record I'm not suggesting it should return something other than
> > "", and in particular I'm not arguing that any call to paste /that does
> > not return an error/ with non-NULL collapse should return a character
> > vector of length one.

__
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel

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

[Hervé Pagès]

Gabe,

It's the current behavior of paste() that is a major source of bugs:

  ## Add "rs" prefix to SNP ids and collapse them in a
  ## comma-separated string.
  collapse_snp_ids <- function(snp_ids)
  paste("rs", snp_ids, sep="", collapse=",")

  snp_groups <- list(
group1=c(55, 22, 200),
group2=integer(0),
group3=c(99, 550)
  )

  vapply(snp_groups, collapse_snp_ids, character(1))
  #group1group2group3
  # "rs55,rs22,rs200"  "rs"  "rs99,rs550"

This has hit me so many times!

Now with 'collapse0=TRUE', we finally have the opportunity to make it do 
the right thing. Let's not miss that opportunity.


Cheers,
H.


On 5/22/20 11:26, Gabriel Becker wrote:
I understand that this is consistent but it also strikes me as an 
enormous 'gotcha' of a magnitude that 'we' are trying to avoid/smooth 
over at this point in user-facing R space.


For the record I'm not suggesting it should return something other than 
"", and in particular I'm not arguing that any call to paste /that does 
not return an error/ with non-NULL collapse should return a character 
vector of length one.


Rather I'm pointing out that it could (perhaps should, imo) simply be an 
error, which is also consistent, in the strict sense, with 
previous behavior in that it is the developer simply declining to extend 
the recycle0 argument to the full parameter space (there is no rule that 
says we must do so, arguments whose use is incompatible with other 
arguments can be reasonable and called for).


I don't feel feel super strongly that reeturning "" in this and similar 
cases horrible and should never happen, but i'd bet dollars to donuts 
that to the extent that behavior occurs it will be a disproportionately 
major source of bugs, and i think thats at least worth considering in 
addition to pure consistency.


~G

On Fri, May 22, 2020 at 9:50 AM William Dunlap > wrote:


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 mailto:hpa...@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
 > mailto:maech...@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 

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

[Gabriel Becker]

I understand that this is consistent but it also strikes me as an enormous
'gotcha' of a magnitude that 'we' are trying to avoid/smooth over at this
point in user-facing R space.

For the record I'm not suggesting it should return something other than "",
and in particular I'm not arguing that any call to paste *that does not
return an error* with non-NULL collapse should return a character vector of
length one.

Rather I'm pointing out that it could (perhaps should, imo) simply be an
error, which is also consistent, in the strict sense, with
previous behavior in that it is the developer simply declining to extend
the recycle0 argument to the full parameter space (there is no rule that
says we must do so, arguments whose use is incompatible with other
arguments can be reasonable and called for).

I don't feel feel super strongly that reeturning "" in this and similar
cases horrible and should never happen, but i'd bet dollars to donuts that
to the extent that behavior occurs it will be a disproportionately major
source of bugs, and i think thats at least worth considering in addition to
pure consistency.

~G

On Fri, May 22, 2020 at 9:50 AM William Dunlap  wrote:

> 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  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
>> > mailto:maech...@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 

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

[William Dunlap via R-devel]

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  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
> > mailto:maech...@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 = '
> >
> > 2) Gabe proposes that 'collapse = ' 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 

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

[Hervé Pagès]

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 
mailto:maech...@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 = '

2) Gabe proposes that 'collapse = ' 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=) 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 

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

[Gabriel Becker]

Hi Martin et al,



On Thu, May 21, 2020 at 9:42 AM Martin Maechler 
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 = '
>
> 2) Gabe proposes that 'collapse = ' 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=) 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= and recycle0=TRUE is not simply made an error).

I would like to hear others' thoughts as well though. @Pages, Herve
 @William Dunlap  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  >> > wrote:
> >>
> >> Totally agree with that.
> >>
> >> H.
> >>
> >> On 5/15/20 10:34, William Dunlap via R-devel wrote:
> >> > I agree: 

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

[William Dunlap via R-devel]

> 1) Bill and Hervé (I think) propose that 'recycle0' should have
>   no effect whenever  'collapse = '

I think that collapse= should make paste() return a single string,
regardless of the value of recycle0.  E.g., I would like to see

> paste0("X",seq_len(3),collapse=", ", recycle0=TRUE)
[1] "X1, X2, X3"
> paste0("X",seq_len(0),collapse=", ", recycle0=TRUE)
[1] ""

Currently the latter gives character(0).

paste's collapse argument has traditionally acted after all the other
arguments were dealt with, as in the following not extensively tested
function.

altPaste <- function (..., collapse = NULL) {
tmp <- paste(...)
if (!is.null(collapse)) {
paste(tmp, collapse=collapse)
} else {
tmp
}
}

E.g., in post-R-4.0.0 R-devel
> altPaste("X", seq_len(3), sep="", collapse=", ")
[1] "X1, X2, X3"
> altPaste("X", seq_len(0), sep="", collapse=", ")
[1] "X"
> altPaste("X", seq_len(0), sep="", collapse=", ", recycle0=TRUE)
[1] ""

I think it would be good if the above function continued to act the same as
paste itself.

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Thu, May 21, 2020 at 9:42 AM Martin Maechler 
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 = '
>
> 2) Gabe proposes that 'collapse = ' 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).
>
> 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  >> > 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
> >> > 

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

[Martin Maechler]

> 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 = '

2) Gabe proposes that 'collapse = ' 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). 

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 > > 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
>> 

>> >
>> >
>> > On Thu, Apr 30, 2020 at 9:56 PM suharto_anggono--- via R-devel <
>> > r-devel@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 

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

[Hervé Pagès]

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.


H.

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

On Fri, May 15, 2020 at 11:05 AM Hervé Pagès > 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


 >
 >
 > On Thu, Apr 30, 2020 at 9:56 PM suharto_anggono--- via R-devel <
 > r-devel@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@r-project.org  mailing list
 >>

https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel=DwICAg=eRAMFD45gAfqt84VtBcfhQ=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA=776IovW06eUHr1EDrabHLY7F47rU9CCUEItSDI96zc0=xN84DhkZeoxzn6SG0QTMpOGg2w_ThmjZmZymGUuD0Uw=
 >>
 >
 >       [[alternative HTML version deleted]]
 >
 > __
 > R-devel@r-project.org  mailing list
 >

https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel=DwICAg=eRAMFD45gAfqt84VtBcfhQ=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA=776IovW06eUHr1EDrabHLY7F47rU9CCUEItSDI96zc0=xN84DhkZeoxzn6SG0QTMpOGg2w_ThmjZmZymGUuD0Uw=
 >

-- 
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: hpa...@fredhutch.org 
Phone:  (206) 667-5791
Fax:    (206) 667-1319

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

[Gabriel Becker]

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

On Fri, May 15, 2020 at 11:05 AM Hervé Pagès  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
> >
> >
> > On Thu, Apr 30, 2020 at 9:56 PM suharto_anggono--- via R-devel <
> > r-devel@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@r-project.org mailing list
> >>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel=DwICAg=eRAMFD45gAfqt84VtBcfhQ=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA=776IovW06eUHr1EDrabHLY7F47rU9CCUEItSDI96zc0=xN84DhkZeoxzn6SG0QTMpOGg2w_ThmjZmZymGUuD0Uw=
> >>
> >
> >   [[alternative HTML version deleted]]
> >
> > __
> > R-devel@r-project.org mailing list
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel=DwICAg=eRAMFD45gAfqt84VtBcfhQ=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA=776IovW06eUHr1EDrabHLY7F47rU9CCUEItSDI96zc0=xN84DhkZeoxzn6SG0QTMpOGg2w_ThmjZmZymGUuD0Uw=
> >
>
> --
> 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: hpa...@fredhutch.org
> Phone:  (206) 667-5791
> Fax:(206) 667-1319
>
> __
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

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

[Hervé Pagès]

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


On Thu, Apr 30, 2020 at 9:56 PM suharto_anggono--- via R-devel <
r-devel@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).

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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: hpa...@fredhutch.org
Phone:  (206) 667-5791
Fax:(206) 667-1319

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

[William Dunlap via R-devel]

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


On Thu, Apr 30, 2020 at 9:56 PM suharto_anggono--- via R-devel <
r-devel@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).
>
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Re: [Rd] paste(character(0), collapse="", recycle0=FALSE) should be ""

[suharto_anggono--- via R-devel]

 I was wrong, as I didn't actually try and didn't read the documentation 
carefully. I thought that ' zero-length arguments being recycled to "" ' 
happens when recycle0 = TRUE. It is actually the opposite.

Everywhere in my previous message, recycle0 = FALSE should be recycle0 = TRUE.

I really think that 'paste' with 'collapse' specified (as a character string) 
should always result in a single character string, no matter what value of 
'recycle0'.

paste(character(0), collapse = "", recycle0 = TRUE) # character(0), but should 
be ""

paste(character(0), recycle0 = FALSE)
is the same as
paste(character(0), recycle0 = TRUE) .
'recycle0' doesn't matter there.
Why should
paste(character(0), collapse = "", recycle0 = FALSE)
be different from
paste(character(0), collapse = "", recycle0 = TRUE) ?

paste(c("4", "5"), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # "4th, 
5th"
paste(c("4"    ), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # "4th"
paste(c(        ), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # 
character(0), but should be ""


On Saturday, 2 May 2020, 10:09:21 pm GMT+7, Martin Maechler 
 wrote:


> suharto anggono--- via R-devel 
>    on Fri, 1 May 2020 03:05:37 + (UTC) writes:

    > 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. 

That's not intended.
(It's what should only happen with the new (non-default) recycle0=TRUE )

> 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.

Well, not quite:  only  'recycle0=FALSE'  shouldn't change it
.. maybe this is what you meant anyway.

    > 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="").

Definitely:  The intent of the new 'recycle0' argument is to 
provide a non-default possibility for paste(, recycle0=TRUE) to behave more
like "arithmetic" functions where the recycling rules ensure that
if one argument has length 0 then the result has length 0:
i.e.,  paste(a,b,c,d,  recycle0=TRUE)      should recycle the same as
              a+b+c+d                      does recycle

Indeed, the default 'recycle0=FALSE'  should correspond to previous (R <= 4.0.0)
behavior entirely.

BUT from all I see, R-devel and R-patched's version of paste()
do behave as they should.  Also what you clim here is not true :

    > 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).

Rather, what I see is what the comments of the following code
lines claim (according to the intention of 'recycle0', contrary
some of your claims above) :


paste(character(0), collapse = "", recycle0 = FALSE) # is "", like
paste(character(0), collapse = "")
paste(character(0), collapse = "", recycle0 =  TRUE) # is character(0)


paste(c("4", "5"), "th", sep = "", collapse = ", ", recycle0 = FALSE) # is 
"4th, 5th"
paste(c("4"    ), "th", sep = "", collapse = ", ", recycle0 = FALSE) # is "4th"

paste(c(        ), "th", sep = "", collapse = ", ", recycle0 = FALSE) # is "th"
##
paste(c("4", "5"), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # is 
"4th, 5th"
paste(c("4"    ), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # is "4th"
paste(c(        ), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # is 
character(0)


There must be a lapsus / misunderstanding somewhere.
I don't see any problem in the new behavior for now.

Best regards,
Martin  
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Re: [Rd] paste(character(0), collapse="", recycle0=FALSE) should be ""

[Martin Maechler]

> suharto anggono--- via R-devel 
> on Fri, 1 May 2020 03:05:37 + (UTC) writes:

> 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. 

That's not intended.
(It's what should only happen with the new (non-default) recycle0=TRUE )

> 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.

Well, not quite:  only  'recycle0=FALSE'  shouldn't change it
.. maybe this is what you meant anyway.

> 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="").

Definitely:  The intent of the new 'recycle0' argument is to 
provide a non-default possibility for paste(, recycle0=TRUE) to behave more
like "arithmetic" functions where the recycling rules ensure that
if one argument has length 0 then the result has length 0:
i.e.,   paste(a,b,c,d,  recycle0=TRUE)  should recycle the same as
  a+b+c+d   does recycle

Indeed, the default 'recycle0=FALSE'  should correspond to previous (R <= 4.0.0)
behavior entirely.

BUT from all I see, R-devel and R-patched's version of paste()
do behave as they should.  Also what you clim here is not true :

> 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).

Rather, what I see is what the comments of the following code
lines claim (according to the intention of 'recycle0', contrary
some of your claims above) :


paste(character(0), collapse = "", recycle0 = FALSE) # is "", like
paste(character(0), collapse = "")
paste(character(0), collapse = "", recycle0 =  TRUE) # is character(0)

paste(c("4", "5"), "th", sep = "", collapse = ", ", recycle0 = FALSE) # is 
"4th, 5th"
paste(c("4" ), "th", sep = "", collapse = ", ", recycle0 = FALSE) # is "4th"
paste(c(), "th", sep = "", collapse = ", ", recycle0 = FALSE) # is "th"
##
paste(c("4", "5"), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # is 
"4th, 5th"
paste(c("4" ), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # is "4th"
paste(c(), "th", sep = "", collapse = ", ", recycle0 =  TRUE) # is 
character(0)


There must be a lapsus / misunderstanding somewhere.
I don't see any problem in the new behavior for now.

Best regards,
Martin

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

[suharto_anggono--- via R-devel]

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).

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