std::ranges::includes() algorithm
- since C++20
- Simplified
- Detailed
// (1)
constexpr bool
includes( I1 first1, S1 last1, I2 first2, S2 last2,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )
// (2)
constexpr bool
includes( R1&& r1, R2&& r2, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} )
The type of arguments are generic and have the following constraints:
-
I1
,I2
-std::input_iterator
-
S1
,S2
-std::sentinel_for<I1>
,std::sentinel_for<I2>
-
R1
,R2
-std::ranges::input_range
-
O
-std::weakly_incrementable
-
Comp
:- (1) -
indirect_strict_weak_order<projected<I1, Proj1>, projected<I2, Proj2>>
- (2) -
indirect_strict_weak_order<projected<ranges::iterator_t<R1> Proj1>, projected<ranges::iterator_t<R2> Proj2>>
(The
std::
namespace was ommited here for readability) - (1) -
-
Proj1
,Proj2
- (none)
The Proj
and Comp
template arguments have the following default types: std::identity
, ranges::less
for all overloads.
(The std::
namespace was ommited here for readability)
// (1)
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 = {} )
// (2)
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 = {} )
-
(1) Returns
true
if the projections of the sorted range [first2
;last2
) is a subsequence of the projections of the sorted range [first1
;last1
).The ranges must be sorted with the given comparison function
comp
.A subsequence need not be contiguous.
-
(2) Same as (1), but uses
r1
as the first range andr2
as the second range, as if usingranges::begin(r1)
asfirst1
,ranges::end(r1)
aslast1
,ranges::begin(r2)
asfirst2
, andranges::end(r2)
aslast2
.
The function-like entities described on this page are niebloids.
Parameters
first1 last1 | The sorted range of elements to examine. |
r 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 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
Given N1
as ranges::distance(r1)
and N2
as ranges::distance(r2)
:
At most 2 * (N1 + N2 − 1) comparisons
Exceptions
(none)
Possible implementation
includes(1) and includes(2)
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 {};
Examples
#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);
}
{ 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
Hover to see the original license.