deduction guides for std::set

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< cpp‎ | container‎ | set

C++
Containers library
std::set
Defined in header <set>
template <

class InputIt,
class Comp = std::less < typename std::iterator_traits <InputIt> :: value_type >,
class Alloc = std::allocator < typename std::iterator_traits <InputIt> :: value_type >>
set( InputIt, InputIt, Comp = Comp( ), Alloc = Alloc( ) )

- > set< typename std::iterator_traits <InputIt> :: value_type, Comp, Alloc> ;
(1) (since C++17)
template <

class Key, class Comp = std::less <Key>,
class Alloc = std::allocator <Key> >
set( std::initializer_list <Key>, Comp = Comp( ), Alloc = Alloc( ) )

- > set<Key, Comp, Alloc> ;
(2) (since C++17)
template < class InputIt, class Alloc >

set( InputIt, InputIt, Alloc )
- > set< typename std::iterator_traits <InputIt> :: value_type,

std::less < typename std::iterator_traits <InputIt> :: value_type >, Alloc> ;
(3) (since C++17)
template < class Key, class Alloc >

set( std::initializer_list <Key>, Alloc )

- > set<Key, std::less <Key>, Alloc> ;
(4) (since C++17)
template < ranges::input_range R, class Compare = less< ranges::range_value_t <R>>,

class Alloc = std::allocator < ranges::range_value_t <R>> >
set( std::from_range_t, R&&, Compare = Compare( ), Alloc = Alloc( ) )

- > set< ranges::range_value_t <R>, Compare, Alloc> ;
(5) (since C++23)
template < ranges::input_range R, class Alloc >

set( std::from_range_t, R&&, Alloc )

- > set< ranges::range_value_t <R>, std::less < ranges::range_value_t <R>>, Alloc> ;
(6) (since C++23)
1-4) These deduction guides are provided for set to allow deduction from an iterator range (overloads (1,3)) and std::initializer_list (overloads (2,4)
5,6) These deduction guides are provided for set to allow deduction from a std::from_range_t tag and an input_range

These overloads participate in overload resolution only if InputIt satisfies LegacyInputIterator, Alloc satisfies Allocator, and Comp does not satisfy Allocator

Note: the extent to which the library determines that a type does not satisfy LegacyInputIterator is unspecified, except that as a minimum integral types do not qualify as input iterators. Likewise, the extent to which it determines that a type does not satisfy Allocator is unspecified, except that as a minimum the member type Alloc::value_type must exist and the expression std::declval <Alloc& > ( ).allocate ( std::size_t { } )

Notes

Feature-test macro Value Std Feature
__cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion; overload (5,6)

Example

Run this code
#include <set>
 
int main()
{
    // guide #2 deduces std::set<int>
    std::set s = {1, 2, 3, 4};
 
    // guide #1 deduces std::set<int>
    std::set s2(s.begin(), s.end());
}
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