std::ranges::views::all, std::ranges::views::all_t
Defined in header <ranges> |
||
---|---|---|
inline constexpr /* unspecified */ all = /* unspecified */; |
(1) | (since C++20) |
template <ranges::viewable_range R> using all_t = decltype(views::all(std::declval<R>())); |
(2) | (since C++20) |
view
that includes all elements of its
range
argument.
The expression views::all(e)
is expression-equivalent (has the same effect) to:
- Implicitly converting
e
to astd::decay_t<decltype((e))>
prvalue, if the result type modelsview
. - Otherwise,
std::ranges::ref_view{e}
if that expression is well-formed. - Otherwise,
std::ranges::owning_view{e}
.
Expression-equivalent
Expression e
is expression-equivalent to expression f
, if.
-
e
andf
have the same effects, and - either both are constant subexpressions or else neither is a constant subexpression, and
- either both are potentially-throwing or else neither is potentially-throwing (i.e.
noexcept(e) == noexcept(f)
).
Example
#include <ranges> #include <vector> #include <iostream> #include <type_traits> int main() { std::vector<int> v{0,1,2,3,4,5}; for(int n : std::views::all(v) | std::views::take(2) ) { std::cout << n << ' '; } static_assert(std::is_same< decltype(std::views::single(42)), std::ranges::single_view<int> >{}); static_assert(std::is_same< decltype(std::views::all(v)), std::ranges::ref_view<std::vector<int, std::allocator<int>>> >{}); int a[]{1,2,3,4}; static_assert(std::is_same< decltype(std::views::all(a)), std::ranges::ref_view<int [4]> >{}); static_assert(std::is_same< decltype(std::ranges::subrange{std::begin(a)+1, std::end(a)-1}), std::ranges::subrange<int*, int*, std::ranges::subrange_kind(1)> >{}); }
Output:
0 1
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
P2415R2 | C++20 | views::all returned a subrange for a non-view rvalue range |
returns a owning_view for it |
See also
(C++20)
|
an empty view with no elements (class template) (variable template) |
(C++20)
|
a view that contains a single element of a specified value (class template) (customization point object) |
(C++20)
|
a view with unique ownership of some range (class template) |
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