is.environment, as.environment, and NULL
The r-devel (1.4) code has C implementations now of the class and class<- functions in package methods, and also of as.environment. The last brings up a question (it shows up in the isas-tests test suite). as.environment(NULL) is NULL. Seems like it has to be, since NULL is the environment associated with package:base. But is.environment(NULL) is FALSE, which is also fairly natural, if we think of testing the type of the argument. The inconsistency causes a related test in isas-tests.R to produce a FALSE (where generally they should either evaluate to TRUE or generate an error). Looking at the uses of is.environment in the R source itself, most of them seem to hedge their bets on whether is.environment(NULL) is TRUE or FALSE. There isn't a completely consistent solution, given the use of NULL as an environment. For the moment it seemed best to live with that one anomalous result in the tests. John
John M. Chambers jmc@bell-labs.com Bell Labs, Lucent Technologies office: (908)582-2681 700 Mountain Avenue, Room 2C-282 fax: (908)582-3340 Murray Hill, NJ 07974 web: http://www.cs.bell-labs.com/~jmc -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._