25 Ranges library [ranges]

25.5 Range utilities [range.utility]

25.5.3 View interface [view.interface]

25.5.3.2 Members [view.interface.members]

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constexpr decltype(auto) front() requires forward_range<D>; constexpr decltype(auto) front() const requires forward_range<const D>;
1
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Hardened preconditions: !empty() is true.
2
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Effects: Equivalent to: return *ranges​::​begin(derived());
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constexpr decltype(auto) back() requires bidirectional_range<D> && common_range<D>; constexpr decltype(auto) back() const requires bidirectional_range<const D> && common_range<const D>;
3
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Hardened preconditions: !empty() is true.
4
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Effects: Equivalent to: return *ranges​::​prev(ranges​::​end(derived()));
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template<random_access_range R = D> requires sized_range<R> constexpr decltype(auto) at(range_difference_t<R> n); template<random_access_range R = const D> requires sized_range<R> constexpr decltype(auto) at(range_difference_t<R> n) const;
5
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Returns: (*this)[n].
6
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Throws: out_of_range if n < 0 is true or n >= ranges​::​distance(derived()) is true.