std::ranges...es::none_of(3)

🎀 std::ranges...es::none_of(3) — C++ Standard Libary 🎀

🌸 NAME 🌸

std::ranges::all_of,std::ranges::any_of,std::ranges::none_of — std::ranges::all_of, std::ranges::any_of, std::ranges::none_of. That's the trio, no cap. 💅

✨ Synopsis ✨

Defined in header <algorithm> — yes, that exact header. Call signature time:

template< std::input_iterator I, std::sentinel_for<I> S,

          class Proj = std::identity,
          std::indirect_unary_predicate<std::projected<I, Proj>>
(1) (since C++20)
Pred >
constexpr bool

    all_of( I first, S last, Pred pred, Proj proj = {} );
template< ranges::input_range R, class Proj = std::identity,

          std::indirect_unary_predicate<
              std::projected<ranges::iterator_t<R>,Proj>> Pred >
(2) (since C++20)
constexpr bool

    all_of( R&& r, Pred pred, Proj proj = {} );
template< std::input_iterator I, std::sentinel_for<I> S,

          class Proj = std::identity,
          std::indirect_unary_predicate<std::projected<I, Proj>>
(3) (since C++20)
Pred >
constexpr bool

    any_of( I first, S last, Pred pred, Proj proj = {} );
template< ranges::input_range R, class Proj = std::identity,

          std::indirect_unary_predicate<
              std::projected<ranges::iterator_t<R>,Proj>> Pred >
(4) (since C++20)
constexpr bool

    any_of( R&& r, Pred pred, Proj proj = {} );
template< std::input_iterator I, std::sentinel_for<I> S,

          class Proj = std::identity,
          std::indirect_unary_predicate<std::projected<I, Proj>>
(5) (since C++20)
Pred >
constexpr bool

    none_of( I first, S last, Pred pred, Proj proj = {} );
template< ranges::input_range R, class Proj = std::identity,

          std::indirect_unary_predicate<
              std::projected<ranges::iterator_t<R>,Proj>> Pred >
(6) (since C++20)
constexpr bool

    none_of( R&& r, Pred pred, Proj proj = {} );

• (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 cannot be specified when calling any of them.
• None of them are visible to argument-dependent lookup.
• When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

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 🎀

1. (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.
2. (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.
3. (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.

Also: see Notes below. 👀

🔥 Complexity 🔥

At most last - first applications of the predicate and the projection.

🧚 Possible implementation 🧚

🌟 all_of (1,2)

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;

🌟 any_of (3,4)

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;

🌟 none_of (5,6)

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 → (1,2) all_of: true; (3,4) any_of: true; (5,6) none_of: false
• input range contains some true, some false → (1,2) all_of: false; (3,4) any_of: true; (5,6) none_of: false
• input range contains none true, all false → (1,2) all_of: false; (3,4) any_of: false; (5,6) none_of: true
• input range contains none true, none false (empty range) → (1,2) all_of: true; (3,4) any_of: false; (5,6) none_of: true

🌈 Example 🌈

Run this code:

// Run this code

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

namespace ranges = std::ranges;

constexpr bool some_of(auto&& r, auto&& pred) // some but not all
{
    return not (ranges::all_of(r, pred) or ranges::none_of(r, pred));
}

constexpr auto w = {1, 2, 3};
static_assert(!some_of(w, [](int x) { return x < 1; }));
static_assert( some_of(w, [](int x) { return x < 2; }));
static_assert(!some_of(w, [](int x) { return x < 4; }));

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 👑

• all_of — checks if a predicate is true for all, any or none of the elements in a range. (C++11) (function template)
• any_of — checks if a predicate is true for all, any or none of the elements in a range. (C++11)
• none_of — checks if a predicate is true for all, any or none of the elements in a range. (C++11)

🫶 that's the whole page, bestie. source: http://cppreference.com · date/version: 2024.06.10 · page: std::ranges...es::none_of(3) — mwah 💋