Clarify non-exact length in the Iterator::take documentation

library/core/src/iter/traits/iterator.rs

@@ -1228,7 +1228,11 @@ pub trait Iterator {
 
  /// Creates an iterator that skips the first `n` elements.
  ///
- /// After they have been consumed, the rest of the elements are yielded.
+ /// `skip(n)` skips elements until `n` elements are skipped or the end of the
+ /// iterator is reached (whichever happens first). After that, all the remaining
+ /// elements are yielded. In particular, if the original iterator is too short,
+ /// then the returned iterator is empty.
+ ///
  /// Rather than overriding this method directly, instead override the `nth` method.
  ///
  /// # Examples
@@ -1252,7 +1256,14 @@ pub trait Iterator {
  Skip::new(self, n)
  }
 
- /// Creates an iterator that yields its first `n` elements.
+ /// Creates an iterator that yields the first `n` elements, or fewer
+ /// if the underlying iterator ends sooner.
+ ///
+ /// `take(n)` yields elements until `n` elements are yielded or the end of
+ /// the iterator is reached (whichever happens first).
+ /// The returned iterator is a prefix of length `n` if the original iterator
+ /// contains at least `n` elements, otherwise it contains all of the
+ /// (fewer than `n`) elements of the original iterator.
  ///
  /// # Examples
  ///