R devel - May 2020 - paste(character(0), collapse="", recycle0=FALSE) should be ""

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-Herv?-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
> 
-- 
Herv? Pag?s

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

>>>>> Herv? Pag?s 
>>>>>     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-Herv?-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...

>>>>> Martin Maechler 
>>>>>     on Wed, 27 May 2020 13:35:44 +0200 writes:
>>>>> Herv? Pag?s 
>>>>>     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=<string> always gives a string
     (also w/ `recycle0=TRUE`)

Best regards,
Martin