std::from_range, std::from_range_t

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< cpp‎ | ranges
 
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Ranges library
Range access
Range conversions
std::from_range_t
std::from_range
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Range primitives
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Dangling iterator handling
Range concepts
Views

Range factories
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Range adaptors
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Range generators
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Range adaptor objects
Range adaptor closure objects
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Helper items
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Defined in header <ranges>
struct from_range_t { explicit from_range_t() = default; };
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inline constexpr std::from_range_t from_range {};
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std::from_range is a disambiguation tag that can be passed to the constructors of the suitable containers to indicate that the contained member is range constructed.

The corresponding type std::from_range_t can be used in the constructor's parameter list to match the intended tag.

Standard library

The following standard library types use std::from_range_t type in their constructors:

Containers library
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 constructs the vector from a range
(public member function of std::vector<T,Allocator>)
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 constructs the deque from a range
(public member function of std::deque<T,Allocator>)
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 constructs the forward_list from a range
(public member function of std::forward_list<T,Allocator>)
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 constructs the list from a range
(public member function of std::list<T,Allocator>)
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 constructs the set from a range
(public member function of std::set<Key,Compare,Allocator>)
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 constructs the map from a range
(public member function of std::map<Key,T,Compare,Allocator>)
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 constructs the multiset from a range
(public member function of std::multiset<Key,Compare,Allocator>)
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 constructs the multimap from a range
(public member function of std::multimap<Key,T,Compare,Allocator>)
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 constructs the unordered_set from a range
(public member function of std::unordered_set<Key,Hash,KeyEqual,Allocator>)
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 constructs the unordered_map from a range
(public member function of std::unordered_map<Key,T,Hash,KeyEqual,Allocator>)
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 constructs the unordered_multiset from a range
(public member function of std::unordered_multiset<Key,Hash,KeyEqual,Allocator>)
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 constructs the unordered_multimap from a range
(public member function of std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>)
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 constructs the priority_queue from a range
(public member function of std::priority_queue<T,Container,Compare>)
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 constructs the queue from a range
(public member function of std::queue<T,Container>)
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 constructs the stack from a range
(public member function of std::stack<T,Container>)
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 constructs the flat_set from a range
(public member function of std::flat_set<Key,Compare,KeyContainer>)
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 constructs the flat_map from a range
(public member function of std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>)
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 constructs the flat_multiset from a range
(public member function of std::flat_multiset<Key,Compare,KeyContainer>)
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 constructs the flat_multimap from a range
(public member function of std::flat_multimap<Key,T,Compare,KeyContainer,MappedContainer>)
Strings library
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 constructs the basic_string from a range
(public member function of std::basic_string<CharT,Traits,Allocator>)

Notes

Feature-test macro Value Std Feature
__cpp_lib_containers_ranges 202202L (哋它亢++23) Tagged constructors to construct from container compatible range

Example

Run this code
#include <cassert>
#include <string>
 
int main()
{
#ifdef __cpp_lib_containers_ranges
    auto const range = {0x43, 43, 43};
    std::string str{std::from_range, range}; // uses tagged constructor
    assert(str == "哋它亢++");
#endif
}

See also

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 in-place construction tag
(tag)
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 indicates that elements of a range are sorted (uniqueness is not required)
(tag)
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 indicates that elements of a range are sorted and unique
(tag)
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 constructs a new non-view object from an input range
(function template)
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