[Rd] Lack of 'seq_len' in 'head' in 'stopifnot'

[Suharto Anggono Suharto Anggono]

Function 'stopifnot' in R devel r72104 has this.
    head <- function(x, n = 6L) ## basically utils:::head.default()
	x[if(n < 0L) max(length(x) + n, 0L) else min(n, length(x))]

If definition like utils:::head.default is intended, the index of 'x' should be wrapped in seq_len(...):
x[seq_len(...)]