Does a vector start with the same values as another vector

starts-with.R

truncate_len <- function(x, n) {
  if (length(x) < n) {
    stop("Can't truncate vector to the given length because it is already shorter")
  }
  x[seq_len(n)]
}
truncate_along <- function(x, y) {
  truncate_len(x, length(y))
}
starts_with <- function(x, y) {
  x <- truncate_along(x, y)
  all(x == y)
}

short <- setNames(1:10, letters[1:10])
long <- setNames(1:26, letters)
wrong <- rev(long)

truncate_along(long, short)
#>  a  b  c  d  e  f  g  h  i  j 
#>  1  2  3  4  5  6  7  8  9 10
truncate_along(short, long)
#> Error in truncate_len(x, length(y)): Can't truncate vector to the given length because it is already shorter

starts_with(long, short)
#> [1] TRUE
starts_with(short, long)
#> Error in truncate_len(x, length(y)): Can't truncate vector to the given length because it is already shorter
starts_with(wrong, short)
#> [1] FALSE

starts_with(names(long), names(short))
#> [1] TRUE
starts_with(names(wrong), names(short))
#> [1] FALSE
starts_with(names(short), names(long))
#> Error in truncate_len(x, length(y)): Can't truncate vector to the given length because it is already shorter

Created on 2019-04-09 by the reprex package (v0.2.1.9000)

I guess starts_with() should return FALSE instead of failing when length is shorter.