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(). John ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
