///
/// assert_eq!(None, iter.next());
/// ```
+ ///
+ /// If the string is empty or all whitespace, the iterator yields no string slices:
+ /// ```
+ /// assert_eq!("".split_whitespace().next(), None);
+ /// assert_eq!(" ".split_whitespace().next(), None);
+ /// ```
#[must_use = "this returns the split string as an iterator, \
without modifying the original"]
#[stable(feature = "split_whitespace", since = "1.1.0")]
///
/// assert_eq!(None, iter.next());
/// ```
+ ///
+ /// If the string is empty or all ASCII whitespace, the iterator yields no string slices:
+ /// ```
+ /// assert_eq!("".split_ascii_whitespace().next(), None);
+ /// assert_eq!(" ".split_ascii_whitespace().next(), None);
+ /// ```
#[must_use = "this returns the split string as an iterator, \
without modifying the original"]
#[stable(feature = "split_ascii_whitespace", since = "1.34.0")]