[Rd] is.vector(...) <-> is(..., "vector")

[Matthias.Kohl at uni-bayreuth.de]

Hello,

Is it intended that is.vector(...) and is(..., "vector")
do not always give identical results?

is.vector() works as documented ('is.vector' returns
'FALSE' if 'x' has any attributes except names.)
Thus,

A <- array(1:2, 1:2)
M <- diag(2)

is.vector(M) # FALSE, as documented
# and
is.vector(A) # FALSE, as documented

# however
is(M, "vector") # TRUE
is(A, "vector") # TRUE

# which is also correct, since
extends("matrix", "vector")
extends("array", "vector")

I'm working with R Version 2.0.1 Patched (2004-12-09)
on Windows 2000.

Thanks, for any comments!
Matthias