std::ranges::view_interface<D>:: back
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(C++23)
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(C++23)
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back
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constexpr
decltype
(
auto
)
back
(
)
requires ranges:: bidirectional_range < D > && ranges:: common_range < D > ; |
(1) | (since C++20) |
|
constexpr
decltype
(
auto
)
back
(
)
const
requires ranges:: bidirectional_range < const D > && ranges:: common_range < const D > ; |
(2) | (since C++20) |
The default implementation of
back()
member function returns the last element in the view of the derived type. Whether the element is returned by value or by reference depends on the
operator
*
of the iterator type.
derived
be
static_cast
<
D
&
>
(
*
this
)
. Equivalent to
return
*
ranges::
prev
(
ranges::
end
(
derived
)
)
;
. The behavior is undefined if
empty()
is
true
(i.e. the beginning iterator compares equal to the sentinel), even if the iterator obtained in the same way is dereferenceable.
derived
is
static_cast
<
const
D
&
>
(
*
this
)
.
Parameters
(none)
Return value
The last element in the view.
Notes
In C++20, no type derived from
std::ranges::view_interface
in the standard library provides their own
back()
member function.
However, following derived types cannot use the default implementations, as they never satisfy neither
bidirectional_range
nor
common_range
:
- std::ranges::basic_istream_view
- std::ranges::lazy_split_view
- std::ranges::split_view
- std::ranges::take_while_view
The inherited
back()
member function is available for
std::ranges::empty_view
, but a call to it always results in undefined behavior.
Example
|
This section is incomplete
Reason: no example |
See also
|
(C++14)
|
returns a reverse iterator to the beginning of a container or array
(function template) |
|
(C++20)
|
returns a reverse iterator to a range
(customization point object) |
|
(C++20)
|
returns a reverse iterator to a read-only range
(customization point object) |