[Rd] rbind() on zero row matrices is inconsistent

[Duncan Murdoch]

The help for cbind() and rbind() says

"For cbind (rbind), vectors of zero length (including NULL) are ignored 
unless the result would have zero rows (columns), for S compatibility. 
(Zero-extent matrices do not occur in S3 and are not ignored in R.)"

This leads to an inconsistency.


   M <- matrix(NA, 0, 0)  # Make a 0x0 matrix
   N <- matrix(NA, 0, 1)  # Make a 0x1 matrix


   dim(rbind(M, NULL, NULL)) # adds 2 rows to M
   #> [1] 2 0
   dim(rbind(N, NULL, NULL)) # leaves N unchanged
   #> [1] 0 1


You get an extra row on the 0x0 matrix for each NULL value that is bound 
to it, but the 0xn matrix is unchanged for n > 0.

Clearly from the help this is intentional, but is it desirable? 
Wouldn't it make more sense for NULL to be ignored by rbind() and cbind()?

Duncan Murdoch