Assert that an object is a single value of a given type

Each function checks that x has length exactly 1, is of the named type, and is not NA. (A single value that is secretly NA is almost always a bug, so it is rejected here; use the plain vector checks such as assert_character() if you want to allow NA.) On success the input is returned invisibly so checks can be stacked; on failure an error is raised against the calling function.

Usage

assert_scalar_character(
  x,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

assert_scalar_numeric(
  x,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

assert_scalar_integer(
  x,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

assert_scalar_double(
  x,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

assert_scalar_logical(
  x,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

assert_scalar_complex(
  x,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

assert_scalar_factor(
  x,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

assert_scalar_raw(
  x,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

Arguments

x

Object to check.

null_ok

Single logical. If TRUE, a NULL value passes the check without error. Use this for optional arguments that default to NULL. Defaults to FALSE, so NULL is rejected unless you opt in.

arg

Name used to refer to x in error messages. Defaults to the name of the expression passed as x.

call

Environment used as the error's call context. Defaults to the calling function, so errors point at the user's code.

Value

The input x, invisibly.

Examples

assert_scalar_character("hello")
assert_scalar_numeric(42)
assert_scalar_logical(TRUE)

# Optional argument that defaults to NULL:
assert_scalar_numeric(NULL, null_ok = TRUE)