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std::ranges::includes

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< cpp‎ | algorithm‎ | ranges
Revision as of 10:38, 18 July 2023 by Lhamot (Talk | contribs)

 
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
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(C++17)
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(C++11)                (C++11)(C++11)

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(C++11)
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(until C++17)(C++11)
(C++20)(C++20)
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(C++17)

Sorting and related operations
Partitioning operations
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(on partitioned ranges)
Set operations (on sorted ranges)
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(C++11)
(C++17)
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C library
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Constrained algorithms
All names in this menu belong to namespace std::ranges
Non-modifying sequence operations
Modifying sequence operations
Partitioning operations
Sorting operations
Binary search operations (on sorted ranges)
       
       
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
       
       
Permutation operations
Fold operations
Numeric operations
(C++23)            
Operations on uninitialized storage
Return types
 
Defined in header <algorithm>
Call signature
template< std::input_iterator I1, std::sentinel_for<I1> S1,

          std::input_iterator I2, std::sentinel_for<I2> S2,
          class Proj1 = std::identity, class Proj2 = std::identity,
          std::indirect_strict_weak_order<
              std::projected<I1, Proj1>,
              std::projected<I2, Proj2>> Comp = ranges::less >
constexpr bool
    includes( I1 first1, S1 last1, I2 first2, S2 last2,

              Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )
(1) (since C++20)
template< ranges::input_range R1, ranges::input_range R2,

          class Proj1 = std::identity, class Proj2 = std::identity,
          std::indirect_strict_weak_order<
              std::projected<ranges::iterator_t<R1>, Proj1>,
              std::projected<ranges::iterator_t<R2>, Proj2>> Comp = ranges::less >
constexpr bool

    includes( R1&& r1, R2&& r2, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )
(2) (since C++20)
1) Returns true if the projections of the sorted range [first2last2) is a subsequence of the projections of the sorted range [first1last1).
2) Same as (1), but uses r1 and r2 as the source ranges, as if by using ranges::begin(r1) and ranges::begin(r2) as first1 and first2 respectively, and ranges::end(r1) and ranges::end(r2) as last1 and last2 respectively.

Both ranges must be sorted with the given comparison function comp. A subsequence need not be contiguous.

The function-like entities described on this page are niebloids, that is:

In practice, they may be implemented as function objects, or with special compiler extensions.

Contents

Parameters

first1, last1 - the sorted range of elements to examine
r1 - the sorted range of elements to examine
first2, last2 - the sorted range of elements to search for
r2 - the sorted range of elements to search for
comp - comparison function to apply to the projected elements
proj1 - projection to apply to the elements in the first range
proj2 - projection to apply to the elements in the second range

Return value

true if [first2last2) is a subsequence of [first1last1); otherwise false.

Complexity

At most 2·(N1+N2-1) comparisons, where N1 is ranges::distance(r1) and N2 is ranges::distance(r2).

Possible implementation

Example

#include <algorithm>
#include <cctype>
#include <initializer_list>
#include <iomanip>
#include <iostream>
#include <locale>
#include <string>
 
template<class T>
std::ostream& operator<<(std::ostream& os, std::initializer_list<T> const& list)
{
    for (os << "{ "; auto const& elem : list)
        os << elem << ' ';
    return os << "} ";
}
 
struct true_false : std::numpunct<char>
{
    std::string do_truename() const { return "? Yes\n"; }
    std::string do_falsename() const { return "? No\n"; }
};
 
int main()
{
    std::cout.imbue(std::locale(std::cout.getloc(), new true_false));
 
    auto ignore_case = [](char a, char b) { return std::tolower(a) < std::tolower(b); };
 
    const auto
        a = {'a', 'b', 'c'},
        b = {'a', 'c'},
        c = {'a', 'a', 'b'},
        d = {'g'},
        e = {'a', 'c', 'g'},
        f = {'A', 'B', 'C'},
        z = {'a', 'b', 'c', 'f', 'h', 'x'};
 
    std::cout
        << z << "includes\n" << std::boolalpha
        << a << std::ranges::includes(z.begin(), z.end(), a.begin(), a.end())
        << b << std::ranges::includes(z, b)
        << c << std::ranges::includes(z, c)
        << d << std::ranges::includes(z, d)
        << e << std::ranges::includes(z, e)
        << f << std::ranges::includes(z, f, ignore_case);
}

Output:

{ a b c f h x } includes
{ a b c } ? Yes
{ a c } ? Yes
{ a a b } ? No
{ g } ? No
{ a c g } ? No
{ A B C } ? Yes

See also

computes the difference between two sets
(niebloid)[edit]
searches for the first occurrence of a range of elements
(niebloid)[edit]
checks if the range contains the given element or subrange
(niebloid)[edit]
returns true if one sequence is a subsequence of another
(function template) [edit]