[Rd] bug with OutDec option and deferred_string altrep object

[Tierney, Luke]

This is now fixed in R-devel. Will port to R_patched in due course.
R_inspect also now handles pairlists ending with dotted pairs.

Best,

luke

On Tue, 9 Oct 2018, Tierney, Luke wrote:

> Thanks for the report. The approach you outlines below should work --
> I'll look into it.
>
> Best,
>
> luke
>
> On Mon, 8 Oct 2018, Michael Sannella wrote:
>
>> While implementing R's new 'altrep' functionality in the TERR engine,
>> I discovered a bug in R's 'deferred_string' altrep object: it is not
>> using the correct value of the 'OutDec' option when it expands a
>> deferred_string.  See the following example:
>>
>> R 3.5.1: (same results in R 3.6.0 devel engine built 10/5)
>>     > options(scipen=0, OutDec=".")
>>     > as.character(123.456)
>>     [1] "123.456"
>>     > options(scipen=-5, OutDec=",")
>>     > as.character(123.456)
>>     [1] "1,23456e+02"
>>     > xx <- as.character(123.456)
>>     > options(scipen=0, OutDec=".")
>>     > xx
>>     [1] "1.23456e+02"
>>     >
>>
>> In the example above, the variable 'xx' is set to a deferred_string
>> while OutDec is ','.  However, when the string is actually formatted
>> (when xx is printed), it uses the current option value OutDec='.' to
>> format the string.  I think that deferred_string should use the value
>> OutDec=',' from when as.character was called.
>>
>> Note that the behavior is different with the 'scipen' option: The
>> deferred_string object records the scipen=-5 value when as.character
>> is called, and uses this value when xx is printed.  Looking at the
>> deferred_string object, it appears that CDR(R_altrep_data1(<obj>)) is
>> set to a scalar integer containing the scipen value at the time the
>> deferred_string was created.
>>
>> Ideally, the deferred_string object would save both the scipen and
>> OutDec option values.  I'd suggest saving these values as regular
>> pairlist values, say by setting the data1 field to pairlist(<source>,
>> scipen=-5L, OutDec=',') for the value of xx above.  To save space, you
>> could avoid saving these values in the common case where scipen=0L,
>> OutDec='.'.  It would also be better if the data1 field was a
>> well-formed pairlist; the current value of the data1 field causes
>> R_inspect to segfault.
>>
>> I understand that you probably wouldn't want to change the
>> deferred_string structure.  An alternative fix would be to avoid this
>> case by:
>>   1. Never create a deferred_string if OutDec is not '.'.
>>   2. When expanding an element of a deferred_string, temporarily set
>> OutDec to '.'.
>>
>>   ~~ Michael Sannella
>>
>>
>>
>
>

-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney using uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu