std::all_of...td::none_of(3)

💖 std::all_of, std::any_of, std::none_of — C++ Standard Libary 💖

okay so bestie, this is the manual page std::all_of...td::none_of(3) from the C++ Standard Libary (yes, the typo is canon 💀). It's the all_of / any_of / none_of trio, and they are literally here to check a unary predicate over a range. 💅

🌸 NAME 🌸

std::all_of,std::any_of,std::none_of — std::all_of, std::any_of, std::none_of. That's the whole squad: three algorithms, one range, one predicate, no cap. 🫶

✨ Synopsis ✨

Defined in header <algorithm>.

template< class InputIt, class UnaryPred >               (1) (since C++11)
bool all_of( InputIt first, InputIt last, UnaryPred p ); (constexpr since C++20)

template< class ExecutionPolicy, class ForwardIt, class UnaryPred >  (2) (since C++17)
bool all_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, UnaryPred p );

template< class InputIt, class UnaryPred >               (3) (since C++11)
bool any_of( InputIt first, InputIt last, UnaryPred p ); (constexpr since C++20)

template< class ExecutionPolicy, class ForwardIt, class UnaryPred >  (4) (since C++17)
bool any_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, UnaryPred p );

template< class InputIt, class UnaryPred >               (5) (since C++11)
bool none_of( InputIt first, InputIt last, UnaryPred p ); (constexpr since C++20)

template< class ExecutionPolicy, class ForwardIt, class UnaryPred >  (6) (since C++17)
bool none_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, UnaryPred p );

Here's the tea on each overload, fr fr:

• 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 participate in overload resolution only if:

std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true.

(until C++20)

std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true.

(since C++20)

🧚 Parameters 🧚

• first, last — the range of elements to examine.
• policy — the execution policy to use. See execution policy for details.
• p — unary predicate. 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).

bestie, that VT& thing is not allowed — and VT is also not allowed unless for VT a move is equivalent to a copy (since C++11). iykyk 💅

🦋 Type requirements 🦋

• InputIt must meet the requirements of LegacyInputIterator.
• ForwardIt must meet the requirements of LegacyForwardIterator.
• UnaryPred must meet the requirements of Predicate.

🌈 Return value 🌈

highkey here's the return-value table translated into bullet form, because tables are not the vibe in this terminal:

• Has true element: Yes, has false element: Yes → all_of = false, any_of = true, none_of = false
• Has true element: Yes, has false element: No → all_of = true, any_of = true, none_of = false
• Has true element: No, has false element: Yes → all_of = false, any_of = false, none_of = true
• Has true element: No, has false element: No → all_of = true, any_of = false, none_of = true

⭐ Complexity ⭐

1-6) At most std::distance(first, last) applications of the predicate p. That's the whole budget, lowkey.

💀 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 🎀

See also the implementations of

• all_of in libstdc++ and libc++.
• any_of in libstdc++ and libc++.
• none_of in libstdc++ and libc++.

all_of

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

any_of

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

none_of

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

🍓 Example 🍓

// Run this code

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

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<>(),
                                                     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

🌸 See also 🌸

• ranges::all_of (C++20) (niebloid)
• ranges::any_of (C++20) (niebloid)
• ranges::none_of (C++20) (niebloid)

The trio checks if a predicate is true for all, any or none of the elements in a range. Obsessed. 🔥

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💖 source: http://cppreference.com · version/date: 2024.06.10 · page: std::all_of...td::none_of(3) — k bye bestie, go check those predicates and slay 💅✨