[Rd] Internal flag for S4 objects
jmc at r-project.org
Sun Sep 3 17:53:46 CEST 2006
A recent revision (svn version 39077) has introduced an internal flag (a
bit in the C structure) that is turned on by the code that generates
objects from an S4 class.
There are corresponding tests for an S4 object, isS4() in R and
IS_S4_OBJECT() in C. These are fast and reliable, and should replace
any heuristic tests previously used.
The tests are not currently used widely, but in the future could be
combined with some of the other recent changes to improve reliability
and efficiency of computations with S4 objects. Most such changes are
more likely for 2.5.x than 2.4.0.
S4 objects in saved sessions and other binary files will not have the
bit set, so they should be regenerated. A likely symptom that you have
not done so is that the objects will not print automatically with the
standard S4 method, because the internal code now checks for an S4
object before dispatching show().
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