std::ranges::iota_view<W, Bound>::iota_view
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std::ranges::iota_view
iota_view::iota_view
iota_view() requires std::default_initializable <W> = default;
(1)
(since C++20)
constexpr explicit iota_view( W value );
(2)
(since C++20)
constexpr explicit iota_view( std::type_identity_t <W> value,
std::type_identity_t <Bound> bound );
(3)
(since C++20)
std::type_identity_t <Bound> bound );
constexpr explicit iota_view( /*iterator*/ first, /* see below */ last );
(4)
(since C++20)
Constructs an iota_view.
| Overload | Data members | |
|---|---|---|
value_
|
bound_
| |
| (1) | value-initialized | value-initialized |
| (2) | initialized with value | |
| (3) | initialized with bound | |
| (4) | initialized with first.value_
|
see below |
2,3) If any of the following conditions is satisfied, the behavior is undefined:
- Bound() is unreachable from value, unless
Bounddenotes std::unreachable_sentinel_t . -
WandBoundmodeltotally_ordered_with, and bool(value <= bound) is false.
4) If any of the following conditions is satisfied, the behavior is undefined:
- Bound() is unreachable from value, unless
Bounddenotes std::unreachable_sentinel_t . -
WandBoundmodeltotally_ordered_with, and bool(first.value_
The type of last and the method of initializing
bound_ are determined by the type Bound denotes:
The type Bound denotes
|
The type of last | bound_
|
|---|---|---|
W
|
iterator
|
initialized with last.value_
|
| std::unreachable_sentinel_t | Bound
|
initialized with last |
| any other type | sentinel
|
initialized with last.bound_
|
[edit] Parameters
value
-
the starting value
bound
-
the bound
first
-
the iterator denoting the starting value
last
-
the iterator or sentinel denoting the bound
[edit] Example
Run this code
#include <cassert> #include <iostream> #include <iterator> #include <ranges> int main() { const auto l = {1, 2, 3, 4}; auto i1 = std::ranges::iota_view <int, int>(); // overload (1) assert (i1.empty() and i1.size() == 0); auto i2 = std::ranges::iota_view (1); // overload (2) assert (not i2.empty() and i2.front() == 1); for (std::cout << "1) "; auto e : i2 | std::views::take (3)) std::cout << e << ' '; std::cout << '\n'; auto i3 = std::ranges::iota_view (std::begin (l)); // overload (2) assert (not i3.empty() and i3.front() == l.begin()); for (std::cout << "2) "; auto e : i3 | std::views::take (4)) std::cout << *e << ' '; std::cout << '\n'; auto i4 = std::ranges::iota_view (1, 8); // overload (3) assert (not i4.empty() and i4.front() == 1 and i4.back() == 7); for (std::cout << "3) "; auto e : i4) std::cout << e << ' '; std::cout << '\n'; auto i5 = std::ranges::iota_view (l.begin(), l.end()); // overload (4) for (std::cout << "4) "; auto e : i5) std::cout << *e << ' '; std::cout << '\n'; auto i6 = std::ranges::iota_view (l.begin(), std::unreachable_sentinel ); // (4) for (std::cout << "5) "; auto e : i6 | std::views::take (3)) std::cout << *e << ' '; std::cout << '\n'; }
Output:
1) 1 2 3 2) 1 2 3 4 3) 1 2 3 4 5 6 7 4) 1 2 3 4 5) 1 2 3
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3523 | C++20 | overload (4) might use wrong sentinel type | corrected |
| P2711R1 | C++20 | overloads (3,4) were not explicit | made explicit |