NAME

std::ranges::includes - std::ranges::includes

Synopsis

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< (1) (since C++20)
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 = {} )
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>, (2) (since C++20)
std::projected<ranges::iterator_t<R2>, Proj2>> Comp = ranges::less
>
constexpr bool includes( R1&& r1, R2&& r2, Comp comp = {},

Proj1 proj1 = {}, Proj2 proj2 = {} )

1) Returns true if the projections of the sorted range [first2, last2) is a
subsequence of the projections of the sorted range [first1, last1).
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:

* Explicit template argument lists may not be specified when calling any of them.
* None of them is visible to argument-dependent lookup.
* When one of them is found by normal unqualified lookup for the name to the left
of the function-call operator, it inhibits argument-dependent lookup.

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

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 [first2, last2) is a subsequence of [first1, last1); otherwise false.

Complexity

At most \(\scriptsize 2 \cdot (N_1+N_2-1)\)2·(N[1]+N[2]-1) comparisons, where
\(\scriptsize N_1\)N[1] is ranges::distance(r1) and \(\scriptsize N_2\)N[2] is
ranges::distance(r2).

Possible implementation

struct includes_fn {
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 operator()(I1 first1, S1 last1, I2 first2, S2 last2,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) const
{
for (; first2 != last2; ++first1)
{
if (first1 == last1 && comp(*first2, *first1))
return false;
if (!comp(*first1, *first2))
++first2;
}
return true;
}

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 operator()(R1&& r1, R2&& r2, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {}) const
{
return (*this)(ranges::begin(r1), ranges::end(r1),
ranges::begin(r2), ranges::end(r2),
std::ref(comp), std::ref(proj1), std::ref(proj2));
}
};

inline constexpr auto includes = includes_fn{};

Example

// Run this code

#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