std::from_range, std::from_range_t

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

Range primitives
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

Range concepts
range borrowed_range    sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	constant_range (C++23)

Views
view_interface	subrange

Range factories
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while concat_viewviews::concat (C++26)(C++26)	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)

Range generators std::generator (C++23)

Range adaptor closure objects range_adaptor_closure (C++23)

Range adaptor objects

Helper items
copyable-box movable-box (until C++23)  (C++23)	simple-view non-propagating-cache

 

Defined in header <ranges>
struct from_range_t { explicit from_range_t() = default; };		(since C++23)
inline constexpr std::from_range_t from_range {};		(since C++23)

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
(constructor) (C++23)	constructs the vector from a range (public member function of std::vector<T,Allocator>)
(constructor) (C++26)	constructs the inplace_vector from a range (public member function of std::inplace_vector<T,N>)
(constructor) (C++23)	constructs the deque from a range (public member function of std::deque<T,Allocator>)
(constructor) (C++23)	constructs the forward_list from a range (public member function of std::forward_list<T,Allocator>)
(constructor) (C++23)	constructs the list from a range (public member function of std::list<T,Allocator>)
(constructor) (C++23)	constructs the set from a range (public member function of std::set<Key,Compare,Allocator>)
(constructor) (C++23)	constructs the map from a range (public member function of std::map<Key,T,Compare,Allocator>)
(constructor) (C++23)	constructs the multiset from a range (public member function of std::multiset<Key,Compare,Allocator>)
(constructor) (C++23)	constructs the multimap from a range (public member function of std::multimap<Key,T,Compare,Allocator>)
(constructor) (C++23)	constructs the unordered_set from a range (public member function of std::unordered_set<Key,Hash,KeyEqual,Allocator>)
(constructor) (C++23)	constructs the unordered_map from a range (public member function of std::unordered_map<Key,T,Hash,KeyEqual,Allocator>)
(constructor) (C++23)	constructs the unordered_multiset from a range (public member function of std::unordered_multiset<Key,Hash,KeyEqual,Allocator>)
(constructor) (C++23)	constructs the unordered_multimap from a range (public member function of std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>)
(constructor) (C++23)	constructs the priority_queue from a range (public member function of std::priority_queue<T,Container,Compare>)
(constructor) (C++23)	constructs the queue from a range (public member function of std::queue<T,Container>)
(constructor) (C++23)	constructs the stack from a range (public member function of std::stack<T,Container>)
(constructor) (C++23)	constructs the flat_set from a range (public member function of std::flat_set<Key,Compare,KeyContainer>)
(constructor) (C++23)	constructs the flat_map from a range (public member function of std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>)
(constructor) (C++23)	constructs the flat_multiset from a range (public member function of std::flat_multiset<Key,Compare,KeyContainer>)
(constructor) (C++23)	constructs the flat_multimap from a range (public member function of std::flat_multimap<Key,T,Compare,KeyContainer,MappedContainer>)
Strings library
(constructor) (C++23)	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	(C++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 == "C++");
#endif
}

See also

in_placein_place_typein_place_indexin_place_tin_place_type_tin_place_index_t (C++17)	in-place construction tag (tag)
sorted_equivalentsorted_equivalent_t (C++23)	indicates that elements of a range are sorted (uniqueness is not required) (tag)
sorted_uniquesorted_unique_t (C++23)	indicates that elements of a range are sorted and unique (tag)
ranges::to (C++23)	constructs a new non-view object from an input range (function template)