std::ranges::includes - cppreference.com (original) (raw)

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 algorithm function objects (informally known as 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.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Possible implementation
• 5 Example
• 6 See also

[edit] Parameters

[edit] Return value

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

[edit] Complexity

At most \(\scriptsize 2 \cdot (N_1+N_2-1)\)2·(N1+N2-1) comparisons, where \(\scriptsize N_1\)N1 is ranges::distance(r1) and \(\scriptsize N_2\)N2 is ranges::distance(r2).

[edit] Possible implementation

struct includes_fn { template<std::input_iterator I1, std::sentinel_for S1, std::input_iterator I2, std::sentinel_for 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, Proj1>, std::projected<ranges::iterator_t, 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 {};

[edit] Example

#include #include #include #include #include #include #include   template std::ostream& operator<<(std::ostream& os, std::initializer_list const& list) { for (os << "{ "; auto const& elem : list) os << elem << ' '; return os << "} "; }   struct true_false : std::numpunct { 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

[edit] See also