23 Iterators library [iterators]

23.5 Iterator adaptors [predef.iterators]

constexpr counted_iterator& operator++();

Preconditions: length > 0.

Effects: Equivalent to:

++current;
--length;
return *this;

decltype(auto) operator++(int);

Preconditions: length > 0.

Effects: Equivalent to:

--length;
try { return current++; }
catch(...) { ++length; throw; }

constexpr counted_iterator operator++(int)
  requires forward_iterator<I>;

Effects: Equivalent to:

counted_iterator tmp = *this;
++*this;
return tmp;

  constexpr counted_iterator& operator--()
    requires bidirectional_iterator<I>;

Effects: Equivalent to:

--current;
++length;
return *this;

  constexpr counted_iterator operator--(int)
    requires bidirectional_iterator<I>;

Effects: Equivalent to:

counted_iterator tmp = *this;
--*this;
return tmp;

  constexpr counted_iterator operator+(iter_difference_t<I> n) const
    requires random_access_iterator<I>;

Effects: Equivalent to: return counted_iterator(current + n, length - n);

friend constexpr counted_iterator operator+(
  iter_difference_t<I> n, const counted_iterator& x)
    requires random_access_iterator<I>;

Effects: Equivalent to: return x + n;

  constexpr counted_iterator& operator+=(iter_difference_t<I> n)
    requires random_access_iterator<I>;

Preconditions: n <= length.

Effects: Equivalent to:

current += n;
length -= n;
return *this;

  constexpr counted_iterator operator-(iter_difference_t<I> n) const
    requires random_access_iterator<I>;

Effects: Equivalent to: return counted_iterator(current - n, length + n);

template<common_with<I> I2>
  friend constexpr iter_difference_t<I2> operator-(
    const counted_iterator& x, const counted_iterator<I2>& y);

Preconditions: x and y refer to elements of the same sequence ([counted.iterator]).

Effects: Equivalent to: return y.length - x.length;

friend constexpr iter_difference_t<I> operator-(
  const counted_iterator& x, default_sentinel_t);

Effects: Equivalent to: return -x.length;

friend constexpr iter_difference_t<I> operator-(
  default_sentinel_t, const counted_iterator& y);

Effects: Equivalent to: return y.length;

constexpr counted_iterator& operator-=(iter_difference_t<I> n)
  requires random_access_iterator<I>;

Preconditions: -n <= length.

Effects: Equivalent to:

current -= n;
length += n;
return *this;