1. Edit 23.3.4.4 [iterator.concept.winc], as indicated:

[ Drafting note: Because integer-class type is only used in this subclause (the rest of the standard uses integer-like), I did not rename it. Cf. enum class. ]

[ Editor's note: [P2321R2] § 5.4 also contains edits to this subclause. The wording below subsumes those edits and should be applied instead if both papers are adopted. ]

2 A type I is an integer-class type if it is in a set of implementation-defined class types that behave as integer types do, as defined below. [ Note ?: An integer-class type is not necessarily a class type. — end note ]

3 The range of representable values of an integer-class type is the continuous set of values over which it is defined. The values 0 and 1 are part of the range of every integer-class type. If any negative numbers are part of the range, the type is a signed-integer-class type; otherwise, it is an unsigned-integer-class type. For any integer-class type, its range of representable values is either -2^N-1 to 2^N-1-1 (inclusive) for some integer N, in which case it is a signed-integer-class type, or 0 to 2^N-1 (inclusive) for some integer N, in which case it is an unsigned-integer-class type. In both cases, N is called the width of the integer-class type. The width of an integer-class type is greater than that of every integral type of the same signedness.

[ Editor's note: Move paragraph 11 here to make integer-like available for use in subsequent wording. ]

11 A type I other than cv bool is integer-like if it models integral<I> or if it is an integer-class type. An integer-like type I is signed-integer-like if it models signed_integral<I> or if it is a signed-integer-class type. An integer-like type I is unsigned-integer-like if it models unsigned_integral<I> or if it is an unsigned-integer-class type.

[ Drafting note: The unique addition ensures that even if an implementation decides to provide two integer-class types of the same signedness and width, the result of binary operators are still well-defined. ]

4 For every integer-class type I, let B(I) be a unique hypothetical extended integer type of the same signedness with the same width (6.8.2 [basic.fundamental]) as I the smallest width (6.8.2 [basic.fundamental]) capable of representing the same range of values. The width of I is equal to the width of B(I). [ Note ?: The corresponding hypothetical specialization numeric_limits<B(I)> meets the requirements on numeric_limits specializations for integral types (17.3.5 [numeric.limits]). — end note ] For every integral type J, let B(J) be the same type as J.

[ Editor's note: Reorder paragraph 6 before 5. ]

6 Expressions of integer-class type are explicitly convertible to any integer-likeintegral type, and implicitly convertible to any integer-class type of equal or greater width and the same signedness. Expressions of integral type are both implicitly and explicitly convertible to any integer-class type. Conversions between integral and integer-class types and between two integer-class types do not exit via an exception. The result of such a conversion is the unique value of the destination type that is congruent to the source modulo 2^N, where N is the width of the destination type.

5 Let a and b be an objectobjects of integer-class type I, let b be an object of integer-like type I2 such that the expression b is implicitly convertible to I, let x and y be respectively objects of type B(I) and B(I2) as described above that represent the same values as a and b respectively, and let c be an lvalue of any integral type.

• (5.?) The expressions a++ and a-- shall be prvalues of type I whose values are equal to that of a prior to the evaluation of the expressions. The expression a++ shall modify the value of a by adding 1 to it. The expression a-- shall modify the value of a by subtracting 1 from it.
• (5.?) The expressions ++a, --a, and &a shall be expression-equivalent to a += 1, a -= 1, and addressof(a), respectively.

[ Drafting note: The grammar term unary-operator includes * & + - ! ~. ]

• (5.1) For every unary-operatorunary operator @ other than & for which the expression @x is well-formed, @a shall also be well-formed and have the same value, effects, and value category as @x provided that value is representable by I. If @x has type bool, so too does @a; if @x has type B(I), then @a has type I.
• (5.2) For every assignment operator @= for which c @= x is well-formed, c @= a shall also be well-formed and shall have the same value and effects as c @= x. The expression c @= a shall be an lvalue referring to c.
• (5.?) For every assignment operator @= for which x @= y is well-formed, a @= b shall also be well-formed and shall have the same effects as x @= y, except that the value that would be stored into x is stored into a. The expression a @= b shall be an lvalue referring to a.
• (5.3) For every non-assignment binary operator @ for which x @ y and y @ x areis well-formed, a @ b and b @ a shall also be well-formed and shall have the same value, effects, and value category as x @ y and y @ x respectivelyprovided that value is representable by I. If x @ y has type bool, so too does a @ b; if x @ y or y @ x has type B(I), then a @ b or b @ a, respectively, has type I; if x @ y or y @ x has type B(I2), then a @ b or b @ a, respectively, has type I2; if x @ y or y @ x has any other type, then a @ b or b @ a, respectively, has that type.

7 An expression E of integer-class type I is contextually convertible to bool as if by bool(E != I(0)).

8 All integer-class types model regular (18.6 [concepts.object]) and three_way_comparable<strong_ordering> (17.11.4 [cmp.concept])totally_ordered (18.5.4 [concept.totallyordered]).

9 A value-initialized object of integer-class type has value 0.

[ Drafting note: There are some issues with the numeric_limit specialization: digits is defined in terms of radix, so it doesn’t make sense to define the former but not the latter, and the definition of digits is also incorrect for signed types. Instead of trying to fix this piecemeal and maintain an ever-growing list, we can simply specify this in terms of B(I). ]

10 For every (possibly cv-qualified) integer-class type I, numeric_limits<I> is specialized such that each static data member m has the same value as numeric_limits<B(I)>::m, and each static member function f returns I(numeric_limits<B(I)>::f()).:

• (10.1) numeric_limits<I>::is_specialized is true,
• (10.2) numeric_limits<I>::is_signed is true if and only if I is a signed-integer-class type,
• (10.3) numeric_limits<I>::is_integer is true,
• (10.4) numeric_limits<I>::is_exact is true,
• (10.5) numeric_limits<I>::digits is equal to the width of the integer-class type,
• (10.6) numeric_limits<I>::digits10 is equal to static_cast<int>(digits * log10(2)), and
• (10.7) numeric_limits<I>::min() and numeric_limits<I>::max() return the lowest and highest representable values of I, respectively, and numeric_limits<I>::lowest() returns numeric_limits<I>::min().

? For any two integer-like types I1 and I2, at least one of which is an integer-class type, common_type_t<I1, I2> denotes an integer-class type whose width is not less than that of I1 or I2. If both I1 and I2 are signed-integer-like types, then common_type_t<I1, I2> is also a signed-integer-like type.

12 is-integer-like<I> is true if and only if I is an integer-like type. is-signed-integer-like<I> is true if and only if I is a signed-integer-like type.

2. Edit 24.5.4.2 [range.subrange.ctor] p6 as indicated:

template<not-same-as<subrange> R>
  requires borrowed_range<R> &&
           convertible-to-non-slicing<iterator_t<R>, I> &&
           convertible_to<sentinel_t<R>, S>
constexpr subrange(R&& r) requires (!StoreSize || sized_range<R>);

6 Effects: Equivalent to:

• (6.1) If StoreSize is true, subrange(r, static_cast<decltype(size_­)>(ranges::size(r))).
• (6.2) Otherwise, subrange(ranges::begin(r), ranges::end(r)).

3. Edit 24.7.8.1 [range.take.overview] p2 as indicated:

2 The name views::take denotes a range adaptor object (24.7.2 [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:

• (2.1) If T is a specialization of ranges::empty_view (24.6.2.2 [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 models random_access_range and sized_range and is

  • (2.2.1) […]

  then T(ranges::begin(E), ranges::begin(E) + std::min<D>(ranges::distancesize(E), F)), except that E is evaluated only once.

• (2.3) Otherwise, ranges::take_view(E, F).

4. Edit 24.7.8.2 [range.take.view] as indicated:

namespace std::ranges {
  template<view V>
  class take_view : public view_interface<take_view<V>> {

    // [...]

    constexpr auto begin() requires (!simple-view<V>) {
      if constexpr (sized_range<V>) {
        if constexpr (random_access_range<V>)
          return ranges::begin(base_);
        else {
          auto sz = range_difference_t<V>(size());
          return counted_iterator((ranges::begin(base_), sz);
        }
      } else
        return counted_iterator(ranges::begin(base_), count_);
    }

    constexpr auto begin() const requires range<const V> {
      if constexpr (sized_range<const V>) {
        if constexpr (random_access_range<const V>)
          return ranges::begin(base_);
        else {
          auto sz = range_difference_t<const V>(size());
          return counted_iterator(ranges::begin(base_), sz);
        }
      } else
        return counted_iterator(ranges::begin(base_), count_);
    }

    constexpr auto end() requires (!simple-view<V>) {
      if constexpr (sized_range<V>) {
        if constexpr (random_access_range<V>)
          return ranges::begin(base_) + range_difference_t<V>(size());
        else
          return default_sentinel;
      } else
        return sentinel<false>{ranges::end(base_)};
    }

    constexpr auto end() const requires range<const V> {
      if constexpr (sized_range<const V>) {
        if constexpr (random_access_range<const V>)
          return ranges::begin(base_) + range_difference_t<const V>(size());
        else
          return default_sentinel;
      } else
        return sentinel<true>{ranges::end(base_)};
    }
    // [...]
  };

  template<class R>
    take_view(R&&, range_difference_t<R>)
      -> take_view<views::all_t<R>>;
}

5. Edit 24.7.10.1 [range.drop.overview] p2 as indicated:

2 The name views::drop denotes a range adaptor object (24.7.2 [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:

• (2.1) If T is a specialization of ranges::empty_view (24.6.2.2 [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 models random_access_range and sized_range and is

  • (2.2.1) […]

  then T(ranges::begin(E) + std::min<D>(ranges::distancesize(E), F), ranges::end(E)), except that E is evaluated only once.

• (2.3) Otherwise, ranges::drop_view(E, F).

6. Edit 24.7.15 [range.counted] p2 as indicated:

2 The name views::counted denotes a customization point object (16.3.3.3.6 [customization.point.object]). Let E and F be expressions, let T be decay_t<decltype((E))>, and let D be iter_difference_t<T>. If decltype((F)) does not model convertible_to<D>, views::counted(E, F) is ill-formed.

[ Note 1: This case can result in substitution failure when views::counted(E, F) appears in the immediate context of a template instantiation. — end note ]

Otherwise, views::counted(E, F) is expression-equivalent to:

• (2.1) If T models contiguous_iterator, then span(to_address(E), static_cast<size_t>(static_cast<D>(F))).
• (2.2) Otherwise, if T models random_access_iterator, then subrange(E, E + static_cast<D>(F)), except that E is evaluated only once.
• (2.3) Otherwise, subrange(counted_iterator(E, F), default_sentinel).

7. Add the following to 25.2 [algorithms.requirements] after p12:

? In the description of the algorithms, given an iterator a whose difference type is D, and an expression n of integer-like type other than cv D, the semantics of a + n and a - n are, respectively, those of a + D(n) and a - D(n).