R devel - Apr 2011 - 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))))
a <- unlist(a)
relist(a)

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

On Apr 14, 2011, at 5:13 PM, Janko Thyson wrote:
> 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
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
>