R/S indexing difference

Is this intentional?

R:

x <- 1:7
x[c(1, NA, 3)] <- -(4:6)
x

[1] -4  2 -6  4  5  6  7

so NAs are treated as FALSE

S+6.1:

x <- 1:7
x[c(1, NA, 3)] <- -(4:6)

Warning messages:
  Replacement length not a multiple of number of elements to
	replace in: x[c(1, NA, 3)] <-  - (4:6)

x

[1] -4  2 -5  4  5  6  7

and NAs are ignored.

ripley@stats.ox.ac.uk writes:

Is this intentional?

R:

x <- 1:7
x[c(1, NA, 3)] <- -(4:6)
x

[1] -4  2 -6  4  5  6  7

so NAs are treated as FALSE

S+6.1:

x <- 1:7
x[c(1, NA, 3)] <- -(4:6)

Warning messages:
  Replacement length not a multiple of number of elements to
	replace in: x[c(1, NA, 3)] <-  - (4:6)

x

[1] -4  2 -5  4  5  6  7

and NAs are ignored.

Hmm. Neither of the options look too safe to me...

A 3rd bit of logic would say that you should get a vector of
7 NAs since you're asking to put the -5 into an unknown location...