From ironholds at gmail.com  Thu Sep  8 03:59:00 2016
From: ironholds at gmail.com (Oliver Keyes)
Date: Wed, 7 Sep 2016 18:59:00 -0700
Subject: [Rd] R (development) changes in arith, logic,
 relop with (0-extent) arrays
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References: <22469.52585.935914.336374@aragorn.wu.ac.at>
	<22470.37902.198447.925212@stat.math.ethz.ch>
	<22470.38100.993865.828495@aragorn.wu.ac.at>
	<22473.36759.791968.814130@stat.math.ethz.ch>
	<22473.38325.834026.658339@stat.math.ethz.ch>
	<22474.35836.489860.992765@aragorn.wu.ac.at>
	<CAPRP4-eKdb1AKGt73P-+khNXFAWm_4q2PZr69Q7BAjWcXKpSzA@mail.gmail.com>
	<CAPRP4-e4fL=j2xUVMjO-kdmeTfvF=+=9AKrU9+981Xvhwc2MPA@mail.gmail.com>
	<22477.32999.558832.601073@stat.math.ethz.ch>
	<22479.9847.747220.924128@stat.math.ethz.ch>
	<22479.58007.358121.626142@stat.math.ethz.ch>
	<CAHHjBM6yvrgwOFiFAtM+w8BGmdwn114Z6gfyjMEsLQDLV8mA5A@mail.gmail.com>
Message-ID: <CADRwj9-XVd+g7aKYNh3EF8tXK=fCgygCWgk=KOssXQhcZC55Zw@mail.gmail.com>

+1. Very grateful; more consistency is always great :)

On Wednesday, 7 September 2016, robin hankin <hankin.robin at gmail.com> wrote:

> Martin
>
> I'd like to make a comment; I think that R's behaviour on 'edge' cases like
> this is an important thing and it's great that you are working on it.
>
> I make heavy use of zero-extent arrays, chiefly because the dimnames are an
> efficient and logical way to keep track of certain types of information.
>
> If I have, for example,
>
>  a <- array(0,c(2,0,2))
>  dimnames(a) <- list(name=c('Mike','Kevin'),NULL,item=c("hat","scarf"))
>
>
> Then in R-3.3.1, 70800 I get
>
> > a>0
> logical(0)
> >
>
> But in 71219 I get
>
> > a>0
> , , item = hat
>
>
> name
>   Mike
>   Kevin
>
> , , item = scarf
>
>
> name
>   Mike
>   Kevin
>
> (which is an empty logical array that holds the names of the people and
> their clothes). I find the behaviour of 71219 very much preferable because
> there is no reason to discard the information in the dimnames.
>
>
> Best wishes
>
> Robin
>
>
>
>
> On Wed, Sep 7, 2016 at 9:49 PM, Martin Maechler <
> maechler at stat.math.ethz.ch <javascript:;>>
> wrote:
>
> > >>>>> Martin Maechler <maechler at stat.math.ethz.ch <javascript:;>>
> > >>>>>     on Tue, 6 Sep 2016 22:26:31 +0200 writes:
> >
> >     > Yesterday, changes to R's development version were committed,
> > relating
> >     > to arithmetic, logic ('&' and '|') and
> >     > comparison/relational ('<', '==') binary operators
> >     > which in NEWS are described as
> >
> >     > SIGNIFICANT USER-VISIBLE CHANGES:
> >
> >     > [.............]
> >
> >     > ? Arithmetic, logic (?&?, ?|?) and comparison (aka
> >     > ?relational?, e.g., ?<?, ?==?) operations with arrays now
> >     > behave consistently, notably for arrays of length zero.
> >
> >     > Arithmetic between length-1 arrays and longer non-arrays had
> >     > silently dropped the array attributes and recycled.  This
> >     > now gives a warning and will signal an error in the future,
> >     > as it has always for logic and comparison operations in
> >     > these cases (e.g., compare ?matrix(1,1) + 2:3? and
> >     > ?matrix(1,1) < 2:3?).
> >
> >     > As the above "visually suggests" one could think of the changes
> >     > falling mainly two groups,
> >     > 1) <0-extent array>  (op)     <non-array>
> >     > 2) <1-extent array>  (arith)  <non-array of length != 1>
> >
> >     > These changes are partly non-back compatible and may break
> >     > existing code.  We believe that the internal consistency gained
> >     > from the changes is worth the few places with problems.
> >
> >     > We expect some package maintainers (10-20, or even more?) need
> >     > to adapt their code.
> >
> >     > Case '2)' above mainly results in a new warning, e.g.,
> >
> >     >> matrix(1,1) + 1:2
> >     > [1] 2 3
> >     > Warning message:
> >     > In matrix(1, 1) + 1:2 :
> >     > dropping dim() of array of length one.  Will become ERROR
> >     >>
> >
> >     > whereas '1)' gives errors in cases the result silently was a
> >     > vector of length zero, or also keeps array (dim & dimnames) in
> >     > cases these were silently dropped.
> >
> >     > The following is a "heavily" commented  R script showing (all ?)
> >     > the important cases with changes :
> >
> >     > ------------------------------------------------------------
> > ----------------
> >
> >     > (m <- cbind(a=1[0], b=2[0]))
> >     > Lm <- m; storage.mode(Lm) <- "logical"
> >     > Im <- m; storage.mode(Im) <- "integer"
> >
> >     > ## 1. -------------------------
> >     > try( m & NULL ) # in R <= 3.3.x :
> >     > ## Error in m & NULL :
> >     > ##  operations are possible only for numeric, logical or complex
> > types
> >     > ##
> >     > ## gives 'Lm' in R >= 3.4.0
> >
> >     > ## 2. -------------------------
> >     > m + 2:3 ## gave numeric(0), now remains matrix identical to  m
> >     > Im + 2:3 ## gave integer(0), now remains matrix identical to Im
> > (integer)
> >
> >     > m > 1      ## gave logical(0), now remains matrix identical to Lm
> > (logical)
> >     > m > 0.1[0] ##  ditto
> >     > m > NULL   ##  ditto
> >
> >     > ## 3. -------------------------
> >     > mm <- m[,c(1:2,2:1,2)]
> >     > try( m == mm ) ## now gives error   "non-conformable arrays",
> >     > ## but gave logical(0) in R <= 3.3.x
> >
> >     > ## 4. -------------------------
> >     > str( Im + NULL)  ## gave "num", now gives "int"
> >
> >     > ## 5. -------------------------
> >     > ## special case for arithmetic w/ length-1 array
> >     > (m1 <- matrix(1,1,1, dimnames=list("Ro","col")))
> >     > (m2 <- matrix(1,2,1, dimnames=list(c("A","B"),"col")))
> >
> >     > m1 + 1:2  # ->  2:3  but now with warning to  "become ERROR"
> >     > tools::assertError(m1 & 1:2)# ERR: dims [product 1] do not match
> the
> > length of object [2]
> >     > tools::assertError(m1 < 1:2)# ERR:                  (ditto)
> >     > ##
> >     > ## non-0-length arrays combined with {NULL or double() or ...}
> *fail*
> >
> >     > ### Length-1 arrays:  Arithmetic with |vectors| > 1  treated array
> > as scalar
> >     > m1 + NULL # gave  numeric(0) in R <= 3.3.x --- still, *but* w/
> > warning to "be ERROR"
> >     > try(m1 > NULL)    # gave  logical(0) in R <= 3.3.x --- an *error*
> > now in R >= 3.4.0
> >     > tools::assertError(m1 & NULL)    # gave and gives error
> >     > tools::assertError(m1 | double())# ditto
> >     > ## m2 was slightly different:
> >     > tools::assertError(m2 + NULL)
> >     > tools::assertError(m2 & NULL)
> >     > try(m2 == NULL) ## was logical(0) in R <= 3.3.x; now error as
> above!
> >
> >     > ------------------------------------------------------------
> > ----------------
> >
> >
> >     > Note that in R's own  'nls'  sources, there was one case of
> >     > situation '2)' above, i.e. a  1x1-matrix was used as a "scalar".
> >
> >     > In such cases, you should explicitly coerce it to a vector,
> >     > either ("self-explainingly") by  as.vector(.), or as I did in
> >     > the nls case  by  c(.) :  The latter is much less
> >     > self-explaining, but nicer to read in mathematical formulae, and
> >     > currently also more efficient because it is a .Primitive.
> >
> >     > Please use R-devel with your code, and let us know if you see
> >     > effects that seem adverse.
> >
> > I've been slightly surprised (or even "frustrated") by the empty
> > reaction on our R-devel list to this post.
> >
> > I would have expected some critique, may be even some praise,
> > ... in any case some sign people are "thinking along" (as we say
> > in German).
> >
> > In the mean time, I've actually thought along the one case which
> > is last above:  The <op>  (binary operation) between a
> > non-0-length array and a 0-length vector (and NULL which should
> > be treated like a 0-length vector):
> >
> > R <= 3.3.1  *is* quite inconsistent with these:
> >
> >
> > and my proposal above (implemented in R-devel, since Sep.5) would give an
> > error for all these, but instead, R really could be more lenient here:
> > A 0-length result is ok, and it should *not* inherit the array
> > (dim, dimnames), since the array is not of length 0. So instead
> > of the above [for the very last part only!!], we would aim for
> > the following. These *all* give an error in current R-devel,
> > with the exception of 'm1 + NULL' which "only" gives a "bad
> > warning" :
> >
> > ------------------------
> >
> > m1 <- matrix(1,1)
> > m2 <- matrix(1,2)
> >
> > m1 + NULL #    numeric(0) in R <= 3.3.x ---> OK ?!
> > m1 > NULL #    logical(0) in R <= 3.3.x ---> OK ?!
> > try(m1 & NULL)    # ERROR in R <= 3.3.x ---> change to logical(0)  ?!
> > try(m1 | double())# ERROR in R <= 3.3.x ---> change to logical(0)  ?!
> > ## m2 slightly different:
> > try(m2 + NULL)  # ERROR in R <= 3.3.x ---> change to double(0)  ?!
> > try(m2 & NULL)  # ERROR in R <= 3.3.x ---> change to logical(0)  ?!
> > m2 == NULL # logical(0) in R <= 3.3.x ---> OK ?!
> >
> > ------------------------
> >
> > This would be slightly more back-compatible than the currently
> > implemented proposal. Everything else I said remains true, and
> > I'm pretty sure most changes needed in packages would remain to be done.
> >
> > Opinions ?
> >
> >
> >
> >     > In some case where R-devel now gives an error but did not
> >     > previously, we could contemplate giving another  "warning
> >     > .... 'to become ERROR'" if there was too much breakage,  though
> >     > I don't expect that.
> >
> >
> >     > For the R Core Team,
> >
> >     > Martin Maechler,
> >     > ETH Zurich
> >
> > ______________________________________________
> > R-devel at r-project.org <javascript:;> mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
>
>
>
> --
> Robin Hankin
> Neutral theorist
> hankin.robin at gmail.com <javascript:;>
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at r-project.org <javascript:;> mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

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[Rd] R (development) changes in arith, logic, relop with (0-extent) arrays
Oliver Keyes