From hb@maths.lth.se  Mon Oct 14 00:34:46 2002
From: hb@maths.lth.se (hb@maths.lth.se)
Date: Mon, 14 Oct 2002 01:34:46 +0200 (MET DST)
Subject: The class attribute on an environment seems buggy (PR#2159)
Message-ID: <200210132334.BAA05124@pubhealth.ku.dk>

Full_Name: Henrik Bengtsson
Version: 1.6.0, 1.5.1
OS: WinXP Pro
Submission from: (NULL) (128.250.252.82)


The following example, which I tested on both R v1.5.1 and R v1.6.0 on WinXP
Pro, shows the problem I encountered when trying to use the class attribute of
an environment:

# Define method print() for class Environment
C

print(e)
# gives:
# [1] "An Environment!"

# Exit [R]
q(save="yes")

When restarting [R] and loading the previous workspace something goes wrong(?):
% R

print(e)
# gives:
# <environment: 01BE52F4>
# attr(,"class")
# [1] "Environment"

print(class(e))
# gives: 
# [1] "Environment"

print(unclass(e))
# gives:
# <environment: 01BE52F4>
# attr(,"class")
# [1] "Environment"

str(e)
# gives because of the malfunctioning unclass():
# Class 'Environment' Class 'Environment' Class 'Environment' Class
'Environment' 
# Class 'Environment' Class 'Environment' Class 'Environment' Class
'Environment' 
# Class 'Environment' Class 'Environment' Class 'Environment' ...

Note how unclass(e) does not work properly. More importantly, it the
S3/UseMethod() method dispatching get confused and won't recognize the class
attribute. 

Cheers

Henrik Bengtsson

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The class attribute on an environment seems buggy (PR#2159)
hb@maths.lth.se