Proposed resolution:

This wording is relative to N5001 plus additions from P3471R4.

1. Modify [range.take.overview] as indicated:

   -2- 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:

   1. (2.?) — Hardened preconditions: static_cast<D>(F) >= 0 is true.

   2. (2.1) — if T is a specialization of empty_view ([range.empty.view]), then ((void)F, decay-copy(E)), except that the evaluations of E and F are indeterminately sequenced.

2. Modify [range.drop.overview] as indicated:

   -2- 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 model convertible_to<D>, views::drop(E, F) is ill-formed. Otherwise, the expression views::drop(E, F) is expression-equivalent to:

   1. (2.?) — Hardened preconditions: static_cast<D>(F) >= 0 is true.

   2. (2.1) — if T is a specialization of empty_view ([range.empty.view]), then ((void)F, decay-copy(E)), except that the evaluations of E and F are indeterminately sequenced.

[ 2025-02-24 ]

Upon reflector discussion many preferred to use instead the new Hardened preconditions: element which have been introduced by the recently voted in P3471R4.

The take/drop adaptor does not explicitly require N to be non-negative (although the view class does), which makes it possible for some specialized cases to be well-defined when N is negative, since no Preconditions are violated:

auto e = std::views::empty<int> 
       | std::views::take(-1);   // []
auto i = std::views::iota(1, 5)
       | std::views::drop(-1);   // [0, 1, 2, 3, 4]
auto r = std::views::repeat('a', 2)
       | std::views::drop(-1);   // ['a', 'a', 'a']

This is not the intention, we should ban these cases.