class(x) <- error

I think this is an error in r-devel:

R : Copyright 2003, The R Development Core Team
Version 1.7.0 Under development (unstable) (2003-02-25)
...

 > x <- matrix(1:9,3,3)
 > class(x)<-c("a", "matrix")
 > class(x)

[1] "a"      "matrix"

 > class(x)<-class(x)[-1]
 > class(x)

[1] "a"      "matrix"  # should be "matrix"

 > class(x)<-"matrix"
 > class(x)

[1] "a"      "matrix"  # should be "matrix"

As of this minute I am seeing the correct behaviour under RedHat 7.3 Linux.

R : Copyright 2003, The R Development Core Team
Version 1.7.0 Under development (unstable) (2003-02-26)
...
 > x <- matrix(1:9,3,3)
 > class(x)<-c("a", "matrix")
 > class(x)
[1] "a"      "matrix"
 > class(x)<-class(x)[-1]
 > class(x)
[1] "matrix"
 > class(x)<-"matrix"
 > class(x)
[1] "matrix"

Have you redefined class<- somehow?

Ross Ihaka                         Email:  ihaka@stat.auckland.ac.nz
Department of Statistics           Phone:  (64-9) 373-7599 x 85054
University of Auckland             Fax:    (64-9) 373-7018
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New Zealand