Assert that two bounds form a range

Checks that lower and upper form a sensible (non-inverted) range. By default equal bounds are allowed (lower <= upper, a point range); set allow_equal = FALSE to require them strictly ordered (lower < upper), rejecting lower == upper — handy for half-open windows like start < end. Works for any comparable type: numbers, dates, date-times, strings. If either bound is NULL the range is treated as open-ended on that side and the check passes — handy for optional start / end arguments.

Usage

assert_range(
  lower,
  upper,
  allow_equal = TRUE,
  arg_lower = rlang::caller_arg(lower),
  arg_upper = rlang::caller_arg(upper),
  call = rlang::caller_env()
)

Arguments

lower

The lower bound, or NULL for unbounded below.

upper

The upper bound, or NULL for unbounded above.

allow_equal

Single logical. If TRUE (default) the bounds may be equal (lower <= upper); if FALSE they must be strictly ordered (lower < upper), so equal bounds fail.

arg_lower

Name used to refer to lower in error messages.

arg_upper

Name used to refer to upper in error messages.

call

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

Value

NULL, invisibly.

Examples

assert_range(0, 10)
assert_range(5, 5) # equal bounds: passes by default
assert_range(5, 6, allow_equal = FALSE) # strict ordering required
assert_range(as.Date("2026-01-01"), as.Date("2026-12-31"))
assert_range(NULL, 10) # open-ended below: passes