[Rd] str and class
Dr Heather Turner
Heather.Turner at warwick.ac.uk
Fri May 9 19:00:37 CEST 2008
In previous versions of the gnm package, the terms component of "gnm"
objects had a "classID" attribute. This caused problems when used with
str as the following simple example illustrates:
> x <- 1
> attr(x, "classID") <- "type1"
Class 'type1' Class 'type1' Class 'type1' Class 'type1' Class 'type1'
Error: evaluation nested too deeply: infinite recursion /
The problem is that for S3 objects, str saves attr(object, "class") then
recalls str on unclass(object) -- any "class" attribute is removed, but
then the "classID" attribute is recursively picked up by attr(object,
"class") due to partial matching.
Obviously the solution is to use more sensibly named attributes, but str
could be made more foolproof by using
attr(object, "class", exact = TRUE)
Dr H Turner
Dept. of Statistics
The University of Warwick
Tel: 024 76575870
Fax: 024 76524532
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