23 Iterators library [iterators]

23.5 Iterator adaptors [predef.iterators]

23.5.4 Common iterators [iterators.common]

23.5.4.6 Comparisons [common.iter.cmp]

template<class I2, sentinel_for<I> S2> requires sentinel_for<S, I2> friend bool operator==( const common_iterator& x, const common_iterator<I2, S2>& y);
Preconditions: x.v_­.valueless_­by_­exception() and y.v_­.valueless_­by_­exception() are each false.
Returns: true if i == j, and otherwise get<i>(x.v_­) == get<j>(y.v_­), where i is x.v_­.index() and j is y.v_­.index().
template<class I2, sentinel_for<I> S2> requires sentinel_for<S, I2> && equality_comparable_with<I, I2> friend bool operator==( const common_iterator& x, const common_iterator<I2, S2>& y);
Preconditions: x.v_­.valueless_­by_­exception() and y.v_­.valueless_­by_­exception() are each false.
Returns: true if i and j are each 1, and otherwise get<i>(x.v_­) == get<j>(y.v_­), where i is x.v_­.index() and j is y.v_­.index().
template<sized_sentinel_for<I> I2, sized_sentinel_for<I> S2> requires sized_sentinel_for<S, I2> friend iter_difference_t<I2> operator-( const common_iterator& x, const common_iterator<I2, S2>& y);
Preconditions: x.v_­.valueless_­by_­exception() and y.v_­.valueless_­by_­exception() are each false.
Returns: 0 if i and j are each 1, and otherwise get<i>(x.v_­) - get<j>(y.v_­), where i is x.v_­.index() and j is y.v_­.index().