NAME¶

std::flat_map::flat_map - std::flat_map::flat_map

Synopsis¶

flat_map() (1) (since C++23)
: flat_map(key_compare()) { }
template< class Allocator > (2) (since C++23)
flat_map( const flat_map&, const Allocator& alloc );
template< class Allocator > (3) (since C++23)
flat_map( flat_map&&, const Allocator& alloc );
flat_map( key_container_type key_cont, mapped_container_type
mapped_cont, (4) (since C++23)
const key_compare& comp = key_compare() );
template< class Allocator >

flat_map( const key_container_type& key_cont, (5) (since C++23)
const mapped_container_type& mapped_cont,

const Allocator& alloc );
template< class Allocator >

flat_map( const key_container_type& key_cont, (6) (since C++23)
const mapped_container_type& mapped_cont,

const key_compare& comp, const Allocator& alloc );
flat_map( std::sorted_unique_t, key_container_type key_cont,

mapped_container_type mapped_cont, (7) (since C++23)

const key_compare& comp = key_compare() );
template< class Allocator >

flat_map( std::sorted_unique_t, const key_container_type&
key_cont, (8) (since C++23)

const mapped_container_type& mapped_cont, const
Allocator& alloc );
template< class Allocator >

flat_map( std::sorted_unique_t, const key_container_type&
key_cont, (9) (since C++23)
const mapped_container_type& mapped_cont,

const key_compare& comp, const Allocator& alloc );
explicit flat_map( const key_compare& comp ) (10) (since C++23)
: c(), compare(comp) { }
template< class Allocator > (11) (since C++23)
flat_map( const key_compare& comp, const Allocator& alloc );
template< class Allocator > (12) (since C++23)
explicit flat_map( const Allocator& alloc );
template< class InputIter >

flat_map( InputIter first, InputIter last, (13) (since C++23)
const key_compare& comp = key_compare() )

: c(), compare(comp);
template< class InputIter, class Allocator >

flat_map( InputIter first, InputIter last, (14) (since C++23)

const key_compare& comp, const Allocator& alloc );
template< class InputIter, class Allocator >
flat_map( InputIter first, InputIter last, const Allocator& alloc (15) (since C++23)
);
template< container-compatible-range<value_type> R >

flat_map( std::from_range_t, R&& rg, const key_compare& comp ) (16) (since C++23)

: flat_map(comp);
template< container-compatible-range<value_type> R >

flat_map( std::from_range_t fr, R&& rg ) (17) (since C++23)

: flat_map(fr, std::forward<R>(rg), key_compare()) { }
template< container-compatible-range<value_type> R, class
Allocator > (18) (since C++23)
flat_map( std::from_range_t, R&& rg, const Allocator& alloc );
template< container-compatible-range<value_type> R, class
Allocator >
(19) (since C++23)
flat_map( std::from_range_t, R&& rg, const key_compare& comp,

const Allocator& alloc );
template< class InputIter >

flat_map( std::sorted_unique_t s, InputIter first, InputIter
last, (20) (since C++23)
const key_compare& comp = key_compare() )

: c(), compare(comp);
template< class InputIter, class Allocator >

flat_map( std::sorted_unique_t s, InputIter first, InputIter (21) (since C++23)
last,

const key_compare& comp, const Allocator& alloc );
template< class InputIter, class Allocator >

flat_map( std::sorted_unique_t s, InputIter first, InputIter (22) (since C++23)
last,

const Allocator& alloc );
flat_map( std::initializer_list<value_type> init,

const key_compare& comp = key_compare() ) (23) (since C++23)

: flat_map(init.begin(), init.end(), comp) { }
template< class Allocator >

flat_map( std::initializer_list<value_type> init, const (24) (since C++23)
key_compare& comp,

const Allocator& alloc );
template< class Allocator >
flat_map( std::initializer_list<value_type> init, const (25) (since C++23)
Allocator& alloc );
flat_map( std::sorted_unique_t s,
std::initializer_list<value_type> init,
(26) (since C++23)
const key_compare& comp = key_compare() )

: flat_map(s, init.begin(), init.end(), comp) { }
template< class Allocator >

flat_map( std::sorted_unique_t s, (27) (since C++23)
std::initializer_list<value_type> init,

const key_compare& comp, const Allocator& alloc );
template< class Allocator >

flat_map( std::sorted_unique_t s, (28) (since C++23)
std::initializer_list<value_type> init,

const Allocator& alloc );

Constructs new container adaptor from a variety of data sources and optionally using
user supplied comparison function object comp and/or allocator alloc.

1) A default constructor. Constructs an empty container adaptor.
2) A copy constructor. Constructs c with the copy of the contents of other.c and
compare with other.compare. See allocator usage note below.
3) A move constructor. Constructs the container adaptor with the contents of other
using move semantics. See allocator usage note below.
4) First, initializes c.keys with std::move(key_cont), c.values with
std::move(mapped_cont), and compare with comp. Then sorts the underlying range
[begin(), end()) with respect to value_comp(). Finally, erases the duplicate
elements as if by:
auto zv = views::zip(c.keys, c.values);
auto it = ranges::unique(zv, key_equiv(compare)).begin();
auto dist = distance(zv.begin(), it);
c.keys.erase(c.keys.begin() + dist, c.keys.end());
c.values.erase(c.values.begin() + dist, c.values.end());.
5) Same as (4), equivalent to flat_map(key_cont, mapped_cont);. See allocator usage
note below.
6) Same as (4), equivalent to flat_map(key_cont, mapped_cont, comp);. See allocator
usage note below.
7) Initializes c.keys with std::move(key_cont), c.values with
std::move(mapped_cont), and compare with comp.
8) Same as (7), equivalent to flat_map(s, key_cont, mapped_cont);. See allocator
usage note below.
9) Same as (7), equivalent to flat_map(s, key_cont, mapped_cont, comp);. See
allocator usage note below.
10) Constructs an empty container adaptor.
11,12) Constructs an empty container adaptor. See allocator usage note below.
13) Constructs the container adaptor with the contents of the range [first, last),
equivalent to insert(first, last);.
14,15) Same as (13). See allocator usage note below.
16) Constructs the container adaptor with the contents of the range rg. First, uses
(10) as delegating constructor. Then initializes c with the contents of rg as if by
insert_range(std::forward<R>(rg));.
17) Same as (16) using it as delegating constructor.
18,19) Same as (16). See allocator usage note below.
20) Constructs the underlying containers with the contents of the range
[first, last) as if by insert(first, last).
21,22) Same as (20). See allocator usage note below.
23) An initializer-list constructor. Constructs the underlying container with the
contents of the initializer list init, using (13) as delegating constructor.
24,25) Same as (23). See allocator usage note below.
26) An initializer-list constructor. Constructs the underlying container with the
contents of the initializer list init, using (20) as delegating constructor.
27,28) Save as (26). See allocator usage note below.

Note for overloads (13-15,20-22): If [first, last) is not a valid range, the
behavior is undefined.

Note for overloads (4-6,13-19,23-25): If multiple elements in the range have keys
that compare equivalent, it is unspecified which element is inserted (pending
LWG2844).

Parameters¶

key_cont - a container to be used as source to initialize the underlying keys
container
mapped_cont - a container to be used as source to initialize the underlying values
container
other - another flat_map to be used as source to initialize the elements of
the underlying containers with
alloc - an allocator to use for all memory allocations of the underlying
containers
comp - a function object to be used for all comparisons of keys
first, last - a range to copy the elements from
init - an initializer list to initialize the elements of the underlying
containers with
a container compatible range (that is, an input_range whose elements
rg - are convertible to value_type) to be used as source to initialize the
underlying containers
fr - a disambiguation tag that indicates that the contained member should
be range constructed
s - a disambiguation tag that indicates that the input sequence is sorted
with respect to value_comp() and all its elements are unique

Type requirements¶

-
InputIt must meet the requirements of LegacyInputIterator.
-
Compare must meet the requirements of Compare.
-
Allocator must meet the requirements of Allocator.

Complexity¶

1) Constant.
2) Linear in size of other.
3) Same as the corresponding move-constructor of the wrapped container, i.e.
constant or linear in size of cont.
4-6) Linear in \(\scriptsize N\)N if cont is sorted with respect to value_comp(),
otherwise \(\scriptsize \mathcal{O}(N\cdot\log{(N)})\)𝓞(N·log(N)), where
\(\scriptsize N\)N is the value of key_cont.size() before this call.
7-9) Same as the corresponding move-constructor of the wrapped container, i.e.
constant or linear in size of cont.
10-12) Constant.
13-15) Linear in \(\scriptsize N\)N if the input range [first, last) is sorted with
respect to value_comp(), otherwise \(\scriptsize
\mathcal{O}(N\cdot\log{(N)})\)𝓞(N·log(N)), where \(\scriptsize N\)N is the value of
key_cont.size() before this call.
16-19) Linear in \(\scriptsize N\)N if the input range rg is sorted with respect to
value_comp(), otherwise \(\scriptsize \mathcal{O}(N\cdot\log{(N)})\)𝓞(N·log(N)),
where \(\scriptsize N\)N is the value of key_cont.size() before this call.
20-22) Linear in size of [first, last).
23-25) Linear in \(\scriptsize N\)N if the elements of init are sorted with respect
to value_comp(), otherwise \(\scriptsize \mathcal{O}(N\cdot\log{(N)})\)𝓞(N·log(N)),
where \(\scriptsize N\)N is the value of key_cont.size() before this call.
26-28) Linear in size of init.

Exceptions¶

Calls to Allocator::allocate may throw.

Notes¶

After container move construction (overload (3)), references, pointers, and
iterators (other than the end iterator) to other remain valid, but refer to elements
that are now in *this. The current standard makes this guarantee via the blanket
statement in [container.reqmts]/67, and a more direct guarantee is under
consideration via LWG issue 2321.

Example¶

This section is incomplete
Reason: no example

See also¶

operator= assigns values to the container adaptor
(public member function)

Category:¶

* Todo no example