[Rd] pairlist objects
simon.urbanek at r-project.org
Tue Oct 2 19:55:00 CEST 2007
On Oct 1, 2007, at 10:28 PM, hpages at fhcrc.org wrote:
> ?pairlist gives no explanation about what exactly is the difference
> between a pairlist and a list (except that a pairlist of length 0
> is 'NULL'). So, what's a pairlist?
I read "traditional _dotted pair_ lists (as in LISP)" there - c.f. also
>  "pairlist"
> Some strange things about the "pairlist" type:
> Error in getClass(Class) : "pairlist" is not a defined class
> Why the above doesn't work?
Because "pairlist" is not a formal class. Why should it?
> It works for "list":
> No Slots, prototype of class "list"
> Extends: "vector"
>  TRUE
>  FALSE
> This doesn't make sense! If 'x' is a list, then it should be
> considered a vector too.
Why? They are completely different objects. lists are generic
vectors, pairlists are not vectors (c.f. the docs above).
> Subsetting a pairlist with  doesn't produce a pairlist:
>  "list"
> Yes, this one is documented, but still...
As the docs say, on R level pairlists are usually converted to
vectors as the use of pairlists is deprecated.
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