template<ranges::random_access_range R = D>
constexpr decltype(auto) operator[]( ranges::range_difference_t<R> n );
(1) (since C++20)
template<ranges::random_access_range R = const D>
constexpr decltype(auto) operator[]( ranges::range_difference_t<R> n ) const;
(2) (since C++20)

The default implementation of operator[] member function obtains the element at the specified offset relative to the beginning iterator, reusing the operator[] of the iterator type.

1) Let derived be static_cast<D&>(*this). Equivalent to return ranges::begin(derived)[n];.
2) Same as (1), except that derived is static_cast<const D&>(*this).


n - position of the element to return

Return value

The element at offset n relative to the beginning iterator.


In C++20, no type derived from std::ranges::view_interface in the standard library provides their own operator[] member function.

However, following derived types cannot use the default implementations, as they never satisfy random_access_range:

The inherited operator[] member function is available for std::ranges::empty_view, but a call to it always results in undefined behavior.


© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.