std::all_of,std::any_of,std::none_of (3) - Linux Manuals

std::all_of,std::any_of,std::none_of: std::all_of,std::any_of,std::none_of

NAME

std::all_of,std::any_of,std::none_of - std::all_of,std::any_of,std::none_of

Synopsis

Defined in header <algorithm>
template< class InputIt, class UnaryPredicate > (since C++11)
bool all_of( InputIt first, InputIt last, UnaryPredicate p ); (until C++20)
template< class InputIt, class UnaryPredicate > (since C++20)
constexpr bool all_of( InputIt first, InputIt last, UnaryPredicate p );
template< class ExecutionPolicy, class ForwardIt, class UnaryPredicate > (2) (since C++17)
bool all_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, UnaryPredicate p );
template< class InputIt, class UnaryPredicate > (since C++11)
bool any_of( InputIt first, InputIt last, UnaryPredicate p ); (until C++20)
template< class InputIt, class UnaryPredicate > (1) (since C++20)
constexpr bool any_of( InputIt first, InputIt last, UnaryPredicate p );
template< class ExecutionPolicy, class ForwardIt, class UnaryPredicate > (4) (since C++17)
bool any_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, UnaryPredicate p ); (3)
template< class InputIt, class UnaryPredicate > (since C++11)
bool none_of( InputIt first, InputIt last, UnaryPredicate p ); (until C++20)
template< class InputIt, class UnaryPredicate > (5) (since C++20)
constexpr bool none_of( InputIt first, InputIt last, UnaryPredicate p );
template< class ExecutionPolicy, class ForwardIt, class UnaryPredicate > (6) (since C++17)
bool none_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, UnaryPredicate p );

1) Checks if unary predicate p returns true for all elements in the range [first, last).
3) Checks if unary predicate p returns true for at least one element in the range [first, last).
5) Checks if unary predicate p returns true for no elements in the range [first, last).
2,4,6) Same as (1,3,5), but executed according to policy. These overloads do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Parameters

first, last - the range of elements to examine
policy - the execution policy to use. See execution_policy for details.
              unary predicate .
p - The expression p(v) must be convertible to bool for every argument v of type (possibly const) VT, where VT is the value type of InputIt, regardless of value_category, and must not modify v. Thus, a parameter type of VT&is not allowed
              , nor is VT unless for VT a move is equivalent to a copy
              (since C++11).

Type requirements

-
InputIt must meet the requirements of LegacyInputIterator.
-
ForwardIt must meet the requirements of LegacyForwardIterator.
-
UnaryPredicate must meet the requirements of Predicate.

Return value

1-2) true if unary predicate returns true for all elements in the range, false otherwise. Returns true if the range is empty.
3-4) true if unary predicate returns true for at least one element in the range, false otherwise. Returns false if the range is empty.
5-6) true if unary predicate returns true for no elements in the range, false otherwise. Returns true if the range is empty.

Complexity

1,3,5) At most last - first applications of the predicate
2,4,6) O(last-first) applications of the predicate

Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

* If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard_policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
* If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

First version

  template< class InputIt, class UnaryPredicate >
  constexpr bool all_of(InputIt first, InputIt last, UnaryPredicate p)
  {
      return std::find_if_not(first, last, p) == last;
  }

Second version

  template< class InputIt, class UnaryPredicate >
  constexpr bool any_of(InputIt first, InputIt last, UnaryPredicate p)
  {
      return std::find_if(first, last, p) != last;
  }

Third version

  template< class InputIt, class UnaryPredicate >
  constexpr bool none_of(InputIt first, InputIt last, UnaryPredicate p)
  {
      return std::find_if(first, last, p) == last;
  }

Example

// Run this code

  #include <vector>
  #include <numeric>
  #include <algorithm>
  #include <iterator>
  #include <iostream>
  #include <functional>

  int main()
  {
      std::vector<int> v(10, 2);
      std::partial_sum(v.cbegin(), v.cend(), v.begin());
      std::cout << "Among the numbers: ";
      std::copy(v.cbegin(), v.cend(), std::ostream_iterator<int>(std::cout, " "));
      std::cout << '\n';

      if (std::all_of(v.cbegin(), v.cend(), [](int i){ return i % 2 == 0; })) {
          std::cout << "All numbers are even\n";
      }
      if (std::none_of(v.cbegin(), v.cend(), std::bind(std::modulus<int>(),
                                                       std::placeholders::_1, 2))) {
          std::cout << "None of them are odd\n";
      }
      struct DivisibleBy
      {
          const int d;
          DivisibleBy(int n) : d(n) {}
          bool operator()(int n) const { return n % d == 0; }
      };

      if (std::any_of(v.cbegin(), v.cend(), 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