cppdraft_translate/cppdraft/range/drop/overview.md

[range.drop.overview]

25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.12 Drop view [range.drop]

25.7.12.1 Overview [range.drop.overview]

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drop_view produces a view excluding the first N elements from another view, or an empty range if the adapted view contains fewer than N elements.

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The name views​::​drop 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 modelconvertible_to,views​::​drop(E, F) is ill-formed.

Otherwise, the expression views​::​drop(E, F) is expression-equivalent to:

• (2.1)

  If T is a specialization ofempty_view ([range.empty.view]), then ((void)F, decay-copy(E)), except that the evaluations of E and F are indeterminately sequenced.

• (2.2)

  Otherwise, if T modelsrandom_access_range and sized_range and is

  • (2.2.1)

a specialization of span ([views.span]),

• (2.2.2)

a specialization of basic_string_view ([string.view]),

• (2.2.3)

a specialization of iota_view ([range.iota.view]), or

• (2.2.4)

a specialization of subrange ([range.subrange]) where T​::​StoreSize is false,

then U(ranges​::​begin(E) + std​::​min(ranges​::​distance(E), F), ranges​::​end(E)), except that E is evaluated only once, where U is span<typename T​::​element_type> if T is a specialization of span and T otherwise.

• (2.3)

  Otherwise, if T is a specialization of subrange that models random_access_range and sized_range, thenT(ranges​::​begin(E) + std​::​min(ranges​::​distance(E), F), ranges​::​end(E),to-unsigned-like(ranges​::​distance(E) - std​::​min(ranges​::​distance(E), F))), except that E and F are each evaluated only once.

• (2.4)

  Otherwise, if T is a specialization of repeat_view ([range.repeat.view]):

  • (2.4.1)

if T models sized_range, thenviews::repeat(*E.value_, ranges::distance(E) - std::min(ranges::distance(E), F)) except that E is evaluated only once;

• (2.4.2)

otherwise, ((void)F, decay-copy(E)), except that the evaluations of E and F are indeterminately sequenced.

• (2.5)

  Otherwise, drop_view(E, F).

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[Example 1: auto ints = views::iota(0) | views::take(10);for (auto i : ints | views::drop(5)) { cout << i << ' '; // prints 5 6 7 8 9} — end example]