std::ranges::all_of, std::ranges::any_of, std::ranges::none_of
From cppreference.com
| Defined in header <algorithm>
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| Call signature |
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| template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(1) | (since C++20) |
| template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(2) | (since C++20) |
| template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(3) | (since C++20) |
| template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(4) | (since C++20) |
| template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(5) | (since C++20) |
| template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(6) | (since C++20) |
1) Checks if unary predicate
pred returns true for all elements in the range [first, last) (after projecting with the projection proj).3) Checks if unary predicate
pred returns true for at least one element in the range [first, last) (after projecting with the projection proj).5) Checks if unary predicate
pred returns true for no elements in the range [first, last) (after projecting with the projection proj).2,4,6) Same as (1,3,5), but uses
r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last.The function-like entities described on this page are niebloids, that is:
- Explicit template argument lists may not be specified when calling any of them.
- None of them is visible to argument-dependent lookup.
- When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup.
In practice, they may be implemented as function objects, or with special compiler extensions.
Parameters
| first, last | - | the range of the elements to examine |
| r | - | the range of the elements to examine |
| pred | - | predicate to apply to the projected elements |
| proj | - | projection to apply to the elements |
Return value
See also Notes below.
1-2) true if std::invoke(pred, std::invoke(proj, *i)) != false for every iterator
i in the range, false otherwise. Returns true if the range is empty.3-4) true if std::invoke(pred, std::invoke(proj, *i)) != false for at least one iterator
i in the range, false otherwise. Returns false if the range is empty.5-6) true if std::invoke(pred, std::invoke(proj, *i)) == false for every iterator
i in the range, false otherwise. Returns true if the range is empty.Complexity
At most last - first applications of the predicate and the projection.
Possible implementation
| First version |
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struct all_of_fn { template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_unary_predicate<std::projected<I, Proj>> Pred > constexpr bool operator()( I first, S last, Pred pred, Proj proj = {} ) const { return ranges::find_if_not(first, last, std::ref(pred), std::ref(proj)) == last; } template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< std::projected<ranges::iterator_t<R>,Proj>> Pred > constexpr bool operator()( R&& r, Pred pred, Proj proj = {} ) const { return operator()(ranges::begin(r), ranges::end(r), std::ref(pred), std::ref(proj)); } }; inline constexpr all_of_fn all_of; |
| Second version |
struct any_of_fn { template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_unary_predicate<std::projected<I, Proj>> Pred > constexpr bool operator()( I first, S last, Pred pred, Proj proj = {} ) const { return ranges::find_if(first, last, std::ref(pred), std::ref(proj)) != last; } template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< std::projected<ranges::iterator_t<R>,Proj>> Pred > constexpr bool operator()( R&& r, Pred pred, Proj proj = {} ) const { return operator()(ranges::begin(r), ranges::end(r), std::ref(pred), std::ref(proj)); } }; inline constexpr any_of_fn any_of; |
| Third version |
struct none_of_fn { template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_unary_predicate<std::projected<I, Proj>> Pred > constexpr bool operator()( I first, S last, Pred pred, Proj proj = {} ) const { return ranges::find_if(first, last, std::ref(pred), std::ref(proj)) == last; } template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< std::projected<ranges::iterator_t<R>,Proj>> Pred > constexpr bool operator()( R&& r, Pred pred, Proj proj = {} ) const { return operator()(ranges::begin(r), ranges::end(r), std::ref(pred), std::ref(proj)); } }; inline constexpr none_of_fn none_of; |
Notes
The return value represented in the form of the Truth table is:
| input range contains | ||||
|---|---|---|---|---|
| all true, none false |
some true, some false |
none true, all false |
none true, none false (empty range) | |
| 1–2) all_of | true | false | false | true |
| 3–4) any_of | true | true | false | false |
| 5–6) none_of | false | false | true | true |
Example
Run this code
#include <vector> #include <numeric> #include <algorithm> #include <iterator> #include <iostream> #include <functional> namespace ranges = std::ranges; int main() { std::vector<int> v(10, 2); std::partial_sum(v.cbegin(), v.cend(), v.begin()); std::cout << "Among the numbers: "; ranges::copy(v, std::ostream_iterator<int>(std::cout, " ")); std::cout << '\n'; if (ranges::all_of(v.cbegin(), v.cend(), [](int i){ return i % 2 == 0; })) { std::cout << "All numbers are even\n"; } if (ranges::none_of(v, std::bind(std::modulus<int>(), std::placeholders::_1, 2))) { std::cout << "None of them are odd\n"; } auto DivisibleBy = [](int d) { return [d](int m) { return m % d == 0; }; }; if (ranges::any_of(v, DivisibleBy(7))) { std::cout << "At least one number is divisible by 7\n"; } }
Output:
Among the numbers: 2 4 6 8 10 12 14 16 18 20 All numbers are even None of them are odd At least one number is divisible by 7
See also
| (C++11)(C++11)(C++11) |
checks if a predicate is true for all, any or none of the elements in a range (function template) |