Possible bug in 'relist()' and/or 'as.relistable()'

Dear list,

I think I just stumbled across a bug in either 'relist()' and/or
'as.relistable()'. It seems that 'pairlists' can only be un- and relisted as
long as they're not nested:

Good:
a <- as.relistable(as.pairlist(list(a=1, b=2)))
a <- unlist(a)
relist(a)# Works

Bad:
a <- as.relistable(as.pairlist(list(a=1, b=2, c=list(c.1=1, c.2=2))))
Technically, you're not nesting pairlists - you' are putting a generic vector in a parilist ... (not that it matters here).
a <- unlist(a)
relist(a)

relist() has no method for pairlists - but you can actually use the "list" method as-is:
relist.pairlist <- utils:::relist.list
str(src <- as.pairlist(list(a=1, b=2, c=list(c.1=1, c.2=2))))
Dotted pair list of 3
 $ a: num 1
 $ b: num 2
 $ c:List of 2
  ..$ c.1: num 1
  ..$ c.2: num 2
str(relist(unlist(as.relistable(src))))
Dotted pair list of 3
 $ a: num 1
 $ b: num 2
 $ c:List of 2
  ..$ c.1: num 1
  ..$ c.2: num 2
 - attr(*, "class")= chr [1:2] "relistable" "pairlist"

and that will also support actual nested pairlists:
str(src <- pairlist(a=1, b=2, c=pairlist(c.1=1, c.2=2)))
Dotted pair list of 3
 $ a: num 1
 $ b: num 2
 $ c:Dotted pair list of 2
  ..$ c.1: num 1
  ..$ c.2: num 2
str(relist(unlist(as.relistable(src))))
Dotted pair list of 3
 $ a: num 1
 $ b: num 2
 $ c:Dotted pair list of 2
  ..$ c.1: num 1
  ..$ c.2: num 2
 - attr(*, "class")= chr [1:2] "relistable" "pairlist"

so I guess it should be easy to add relist.pairlist to utils ... I'm not sure about the implications, but it does sound appealing.

Cheers,
Simon
The help page didn't say anything about pairlists and I don't know if
they're at all relevant, but I'm using them whenever I want my functions to
recognize a clear 'name-value' structure (e.g. for batch assigning
variables) as opposed to standard list structures.

Cheers,
Janko

   sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: i386-pc-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252   
[3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C                   
[5] LC_TIME=German_Germany.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] codetools_0.2-8 tools_2.12.1

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Possible bug in 'relist()' and/or 'as.relistable()'

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