[R] [Rd] Semantics of sequences in R

[Wacek Kusnierczyk]

Stefan Evert wrote:
> Dear vQ,
>
>> vectors (can-be-considered-lists),
>
> can you please stop repeating this nonsense?  I don't think anybody
> ever claimed that vectors can be considered list.  

yes, it is nonsense.  yes, there is one person who repeatedly made this
claim.  please read the archives; specifically, [1]. note this statement:

	"Note that any vector can be considered to be a list."


[1] https://stat.ethz.ch/pipermail/r-help/2009-February/186932.html

when you're talking about nonsense, please attribute it to the right person.


> It's rather the other way round: lists can also be seen as vectors to
> R (possibly they are implemented as such, but I don't much about the
> internals of R).

not *all* lists are vectors;  pairlists are not, though they are lists.

>
> > a <- as.list(1:10)
> > b <- 1:10
> > is.vector(a)
> [1] TRUE
> > is.list(a)
> [1] TRUE
> > is.vector(b)
> [1] TRUE
> > is.list(b)
> [1] FALSE
>
> Hence the confusion about
>
> > mode(as.vector(a))
> [1] "list"

but
   
    mode(unlist(a))
    # "numeric"
    class(unlist(a))
    # integer


>
> which prompted the original comment that you are taking so much
> exception to.

which original comment?

>
>> as to "it could only work in very specific circumstances" -- no, it
>> would work for any list whatsoever, provided the user has a correctly
>> implemented comparator.  for example, i'd like to sort a list of vectors
>> by the vectors' length -- is this a very exotic idea?
>
> Honestly, I can't think of a situation where I would want to do than
> in R.  In a Perl script, quite likely; but this is a kind of data
> manipulation that R wasn't really designed for IMHO.

irrespectively of how exotic sorting lists of vectors can be in a system
for the manipulation of a comprehensive range of sorts of data, having a
procedure called 'sort.list' complain about being called on a list is a
sure source of confusion. 

how much is it likely that people will want to sort complex numbers in a
system where complex numbers are incomparable?

best,
vQ

>
> Not that I'd mind having sort() operate properly on lists; it just
> isn't something I miss in the language.
>
> Best,
> Stefan