std::ranges::views::take_while, std::ranges::take_while_view
Defined in header <ranges> |
||
|---|---|---|
template< ranges::view V, class Pred >
requires ranges::input_range<V> &&
std::is_object_v<Pred> &&
std::indirect_unary_predicate<const Pred, ranges::iterator_t<V>>
class take_while_view : public ranges::view_interface<take_while_view<V, Pred>> |
(1) | (since C++20) |
namespace views {
inline constexpr /*unspecified*/ take_while = /*unspecified*/;
} |
(2) | (since C++20) |
| Call signature | ||
template< ranges::viewable_range R, class Pred >
requires /* see below */
constexpr ranges::view auto take_while( R&& r, Pred&& pred ); |
(since C++20) | |
template< class Pred > constexpr /*range adaptor closure*/ take_while( Pred&& pred ); |
(since C++20) |
1) A range adaptor that represents
view of the elements from an underlying sequence, starting at the beginning and ending at the first element for which the predicate returns false.
2)
Range adaptor object. The expression
views::take_while(e, f) is
expression-equivalent to
take_while_view(e, f) for any suitable subexpressions
e and
f.
take_while_view models the concepts contiguous_range, random_access_range, bidirectional_range, forward_range, and input_range when the underlying view V models respective concepts.
Expression-equivalent
Expression e is expression-equivalent to expression f, if.
-
eandfhave 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)).
Member functions
|
(C++20)
|
constructs a take_while_view (public member function) |
|
(C++20)
|
returns a copy of the underlying (adapted) view (public member function) |
|
(C++20)
|
returns a reference to the stored predicate (public member function) |
|
(C++20)
|
returns an iterator to the beginning (public member function) |
|
(C++20)
|
returns a sentinel representing the end (public member function) |
Inherited from |
|
|
(C++20)
|
Returns whether the derived view is empty. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>) |
|
(C++20)
|
Returns whether the derived view is not empty. Provided if ranges::empty is applicable to it. (public member function of std::ranges::view_interface<D>) |
|
(C++20)
|
Gets the address of derived view's data. Provided if its iterator type satisfies contiguous_iterator. (public member function of std::ranges::view_interface<D>) |
|
(C++20)
|
Returns the first element in the derived view. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>) |
|
(C++20)
|
Returns the nth element in the derived view. Provided if it satisfies random_access_range. (public member function of std::ranges::view_interface<D>) |
Deduction guides
Nested classes
| the sentinel type (exposition-only member class template) |
Example
#include <ranges>
#include <iostream>
int main()
{
for (int year : std::views::iota(2017)
| std::views::take_while([](int y) { return y <= 2020; })) {
std::cout << year << ' ';
}
std::cout << '\n';
const char idea[] {"Today is yesterday's tomorrow!.."};
for (char x : std::ranges::take_while_view(idea, [](char c) { return c != '.'; })) {
std::cout << x;
}
std::cout << '\n';
}
Output:
2017 2018 2019 2020 Today is yesterday's tomorrow!
See also
|
(C++20)
|
a view consisting of the first N elements of another view (class template) (range adaptor object) |
|
(C++20)
|
a view consisting of the elements of another view, skipping the initial subsequence of elements until the first element where the predicate returns false (class template) (range adaptor object) |
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