slice.md
In vctrs: Vector Helpers

vec_slice throws error with non-vector subscripts

Code
  (expect_error(vec_slice(1:3, Sys.Date()), class = "vctrs_error_subscript_type"))
Output
  <error/vctrs_error_subscript_type>
  Error in `vec_slice()`:
  ! Can't subset elements with `i`.
  x `i` must be logical, numeric, or character, not a <Date> object.
Code
  (expect_error(vec_slice(1:3, matrix(TRUE, nrow = 1)), class = "vctrs_error_subscript_type")
  )
Output
  <error/vctrs_error_subscript_type>
  Error in `vec_slice()`:
  ! Can't subset elements with `i`.
  x Subscript `i` must be a simple vector, not a matrix.

can't index beyond the end of a vector

Code
  (expect_error(vec_slice(1:2, 3L), class = "vctrs_error_subscript_oob"))
Output
  <error/vctrs_error_subscript_oob>
  Error in `vec_slice()`:
  ! Can't subset elements past the end.
  i Location 3 doesn't exist.
  i There are only 2 elements.
Code
  (expect_error(vec_slice(1:2, -3L), class = "vctrs_error_subscript_oob"))
Output
  <error/vctrs_error_subscript_oob>
  Error in `vec_slice()`:
  ! Can't negate elements past the end.
  i Location 3 doesn't exist.
  i There are only 2 elements.

can slice with double indices

Code
  (expect_error(vec_as_location(2^31, 3L), class = "vctrs_error_subscript_type"))
Output
  <error/vctrs_error_subscript_type>
  Error:
  ! Can't subset elements with `2^31`.
  x Can't convert from `2^31` <double> to <integer> due to loss of precision.

Unnamed vector with character subscript is caught

Code
  vec_slice(1:3, letters[1])
Condition
  Error in `vec_slice()`:
  ! Can't use character names to index an unnamed vector.

Negative subscripts are checked

Code
  vec_slice(1:3, -c(1L, NA))
Condition
  Error in `vec_slice()`:
  ! Can't subset elements with `i`.
  x Negative locations can't have missing values.
  i Subscript `i` has a missing value at location 2.

Code
  vec_slice(1:3, c(-1L, 1L))
Condition
  Error in `vec_slice()`:
  ! Can't subset elements with `i`.
  x Negative and positive locations can't be mixed.
  i Subscript `i` has a positive value at location 2.

oob error messages are properly constructed

Code
  vec_slice(c(bar = 1), "foo")
Condition
  Error in `vec_slice()`:
  ! Can't subset elements that don't exist.
  x Element `foo` doesn't exist.

Code
  vec_slice(letters, c(100, 1000))
Condition
  Error in `vec_slice()`:
  ! Can't subset elements past the end.
  i Locations 100 and 1000 don't exist.
  i There are only 26 elements.

Code
  vec_slice(letters, c(1, 100:103, 2, 104:110))
Condition
  Error in `vec_slice()`:
  ! Can't subset elements past the end.
  i Locations 100, 101, 102, ..., 109, and 110 don't exist.
  i There are only 26 elements.

Code
  vec_slice(set_names(letters), c("foo", "bar"))
Condition
  Error in `vec_slice()`:
  ! Can't subset elements that don't exist.
  x Elements `foo` and `bar` don't exist.

Code
  vec_slice(set_names(letters), toupper(letters))
Condition
  Error in `vec_slice()`:
  ! Can't subset elements that don't exist.
  x Elements `A`, `B`, `C`, `D`, `E`, etc. don't exist.

vec_init() validates `n`

Code
  (expect_error(vec_init(1L, 1.5)))
Output
  <error/rlang_error>
  Error in `vec_init()`:
  ! `n` must be a whole number, not a fractional number.
Code
  (expect_error(vec_init(1L, c(1, 2))))
Output
  <error/rlang_error>
  Error in `vec_init()`:
  ! `n` must be a single number, not a double vector.
Code
  (expect_error(vec_init(1L, -1L)))
Output
  <error/rlang_error>
  Error in `vec_init()`:
  ! `n` must be a positive number or zero.
Code
  (expect_error(vec_init(1L, NA)))
Output
  <error/rlang_error>
  Error in `vec_init()`:
  ! `n` must be a single number, not `NA`.
Code
  (expect_error(vec_init(1L, NA_integer_)))
Output
  <error/rlang_error>
  Error in `vec_init()`:
  ! `n` must be a single number, not an integer `NA`.