I've run into an unpleasant oddity involving the interaction of
environments and generic functions. I want to check my diagnosis, and
see if there is a good way to avoid the problem.
Problem:
A library defines
"foo" <- function(object) 1
setMethod("foo", c("matrix"), function(object) 30)
After loading the library
foo(0) is 1
foo(matrix()) is 30
foo is a generic
The source the file with the code given above.
Now
foo(matrix()) is 1
foo is a function
(Also, there is no "creating generic function" message).
Diagnosis:
The library creates foo and related generics in package:libname.
The source for the initial definition puts the name and function
definition in .GlobalEnv.
The source'd setMethod finds the existing generic in package:libname and
updates it (I'm not sure about this last step).
foo then discovers the foo in .GlobalEnv, not the generic, so the
generic and the alternate methods are hidden.
In case you're wondering, I found this out because I was experimenting
with a library, changing the R and not the C code. I get sick of doing
R CMD INSTALL with each iteration, but needed to load the library to get
the .so file.
So, is my diagnosis correct?
Any suggestions about how to avoid this problem?
Maybe sys.source("file", 2)... Seems to work!
Ross Boylan wk: (415) 514-8146 185 Berry St #5700 ross at biostat.ucsf.edu Dept of Epidemiology and Biostatistics fax: (415) 514-8150 University of California, San Francisco San Francisco, CA 94107-1739 hm: (415) 550-1062