24 Ranges library [ranges]

24.7 Range adaptors [range.adaptors]

24.7.6 Take view [range.take]

24.7.6.1 Overview [range.take.overview]

take_­view produces a view of the first N elements from another view, or all the elements if the adapted view contains fewer than N.
The name views​::​take denotes a range adaptor object ([range.adaptor.object]).
Let E and F be expressions, let T be remove_­cvref_­t<decltype((E))>, and let D be range_­difference_­t<decltype((E))>.
If decltype((F)) does not model convertible_­to<D>, views​::​take(E, F) is ill-formed.
Otherwise, the expression views​::​take(E, F) is expression-equivalent to:
  • If T is a specialization of ranges​::​empty_­view ([range.empty.view]), then ((void) F, decay-copy(E)).
  • Otherwise, if T models random_­access_­range and sized_­range and is then T{ranges​::​begin(E), ranges​::​begin(E) + min<D>(ranges​::​size(E), F)}, except that E is evaluated only once.
  • Otherwise, ranges​::​take_­view{E, F}.
[Example:
vector<int> is{0,1,2,3,4,5,6,7,8,9};
take_view few{is, 5};
for (int i : few)
  cout << i << ' '; // prints: 0 1 2 3 4
— end example]