[Rd] anomalies with call objects (PR#412)

[p.dalgaard@biostat.ku.dk]

Call objects don't always behave as you'd expect. They're mostly
list-like, but with exceptions:

> f<-function(x,y,...)match.call(expand.dots=FALSE)
> xx <- f(y=1,2,z=3,4)
> dd <- xx$...
> xx$... <- NULL
> c(xx,dd)
[[1]]
f(x = 2, y = 1)

$z
[1] 3

[[3]]
[1] 4

> as.call(c(as.list(xx),dd))
f(x = 2, y = 1, z = 3, 4)

(Splus has this rather differently, since dd becomes a call to list()
rather than a list of promises:

S> c(xx,dd)
f(x = 2, y = 1, list, z = 3, 4)
S> as.call(c(as.list(xx),dd))
f(x = 2, y = 1, list, z = 3, 4)

..but at least gives the same in both cases)

Also, the names of arguments added with [[<- is getting dropped if a
new element is required:

> xx[["abc"]]<-123
> xx
f(x = 2, y = 1, 123)

S has what I'd expect there:

S> xx[["abc"]]<-123
S> xx
f(x = 2, y = 1, abc = 123)

[R-0.99.0 prerelease on RedHat6.1, but this is likely not a new thing.]

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907

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