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
[[alternative HTML version deleted]]
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
