[Rd] is.vector(as.vector(x)) is FALSE

[Gabor Grothendieck]

The following, which was recently discussions on the rcom-l list,
is a situation where coercing x1mat to a vector using as.vector
results in an object that is.vector says is not a vector:

     R> x1mat<-matrix(list(1,1.1,1+1i,"a",NA,NaN), 3, 2)
     R> is.vector(as.vector(x1mat))
     [1] FALSE