Difference between revisions of "cpp/algorithm/all any none of"

Revision as of 12:35, 22 January 2013

Template:ddcl list begin <tr class="t-dsc-header">

<td></td> <td></td> </tr> <tr class="t-dcl ">

<td > (1) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td > (2) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td > (3) </td> <td > (since C++11) </td> </tr> Template:ddcl list end

1) Checks if unary predicate p returns true for all elements in the range [first, last).

2) Checks if unary predicate p returns true for at least one element in the range [first, last).

3) Checks if unary predicate p returns true for no elements in the range [first, last).

Parameters

Return value

1) true if unary predicate returns true for all elements in the range, false otherwise. Returns true if the range is empty.

2) true if unary predicate returns true for at least one element in the range, false otherwise. Returns false if the range is empty.

3) true if unary predicate returns true for no elements in the range, false otherwise. Returns true if the range is empty.

Complexity

At most last - first applications of the predicate

Possible implementation

template< class InputIt, class UnaryPredicate >
bool all_of(InputIt first, InputIt last, UnaryPredicate p)
{
    for (; first != last; ++first) {
        if (!p(*first)) return false;
    }
    return true;
}

template< class InputIt, class UnaryPredicate >
bool any_of(InputIt first, InputIt last, UnaryPredicate p)
{
    for (; first != last; ++first) {
        if (p(*first)) return true;
    }
    return false;
}

template< class InputIt, class UnaryPredicate >
bool none_of(InputIt first, InputIt last, UnaryPredicate p)
{
    for (; first != last; ++first) {
        if (p(*first)) return false;
    }
    return true;
}

Example

#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";
    }
}

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