std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>::insert

 

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

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

inplace_vector (C++26)

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Tables

Iterator invalidation

Member function table

Non-member function table

 

std::flat_map

Member types

Member functions

flat_map::flat_map flat_map::operator= Element access flat_map::at flat_map::operator[] Iterators flat_map::beginflat_map::cbegin flat_map::endflat_map::cend flat_map::rbeginflat_map::crbegin flat_map::rendflat_map::crend Lookup flat_map::count flat_map::find flat_map::contains flat_map::equal_range    flat_map::lower_bound flat_map::upper_bound Capacity flat_map::size flat_map::max_size flat_map::empty Modifiers flat_map::clear flat_map::erase flat_map::swap flat_map::emplace flat_map::extract flat_map::replace flat_map::insert flat_map::insert_range flat_map::insert_or_assign flat_map::emplace_hint flat_map::try_emplace Observers flat_map::key_comp flat_map::keys flat_map::value_comp flat_map::values

Non-member functions

operator==operator<=>         swap(std::flat_map) erase_if(std::flat_map)

Helper classes

uses_allocator<std::flat_map>

Tags

sorted_unique       sorted_unique_t

Deduction guides

 

std::pair<iterator, bool> insert( const value_type& value );	(1)	(since C++23)
std::pair<iterator, bool> insert( value_type&& value );	(2)	(since C++23)
iterator insert( const_iterator pos, const value_type& value );	(3)	(since C++23)
iterator insert( const_iterator pos, value_type&& value );	(4)	(since C++23)
template< class P > std::pair<iterator, bool> insert( P&& x );	(5)	(since C++23)
template< class P > iterator insert( const_iterator pos, P&& x );	(6)	(since C++23)
template< class InputIt > void insert( InputIt first, InputIt last );	(7)	(since C++23)
template< class InputIt > void insert( std::sorted_unique_t, InputIt first, InputIt last );	(8)	(since C++23)
void insert( std::initializer_list<key_type> ilist );	(9)	(since C++23)
void insert( std::sorted_unique_t s, std::initializer_list<key_type> ilist );	(10)	(since C++23)

Inserts element(s) into the container, if the container does not already contain an element with an equivalent key.

1) Inserts value. Equivalent to return emplace(value);.

2) Inserts value. Equivalent to return emplace(std::move(value));.

3) Inserts value in the position as close as possible to the position just prior to pos. Equivalent to return emplace_hint(pos, value);.

4) Inserts value in the position as close as possible to the position just prior to pos. Equivalent to return emplace_hint(pos, std::move(value));.

5) If *this already contains an element which transparently compares equivalent to x, does nothing. Otherwise, inserts x into *this as if by emplace(std::forward<P>(x));. This overload participates in overload resolution only if std::is_constructible_v<pair<key_type, mapped_type>, P> is true.

6) If *this already contains an element which transparently compares equivalent to x, does nothing. Otherwise, inserts x into *this in the position as close as possible to the position just prior to pos. Equivalent to return emplace_hint(position, std::forward<P>(x));. This overload participates in overload resolution only if std::is_constructible_v<pair<key_type, mapped_type>, P> is true.

7) Inserts elements from range [first, last) as if performing the following operations sequentially:

1. Adds elements to c as if by
   for (; first != last; ++first)
   {
       value_type value = *first;
       c.keys.insert(c.keys.end(), std::move(value.first));
       c.values.insert(c.values.end(), std::move(value.second));
   }
2. Sorts the range of newly inserted elements with respect to value_comp.
3. Merges the resulting sorted range and the sorted range of pre-existing elements into a single sorted range.
4. Erases the duplicate elements as if by:
   auto zv = std::views::zip(c.keys, c.values);
   auto it = ranges::unique(zv, key_equiv(compare)).begin();
   auto dist = std::distance(zv.begin(), it);
   c.keys.erase(c.keys.begin() + dist, c.keys.end());
   c.values.erase(c.values.begin() + dist, c.values.end());

May allocate memory during the in-place merge operation.

If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).

8) Inserts elements from range [first, last) as if performing the following operations sequentially:

1. Adds elements to c as if by
   for (; first != last; ++first)
   {
       value_type value = *first;
       c.keys.insert(c.keys.end(), std::move(value.first));
       c.values.insert(c.values.end(), std::move(value.second));
   }
2. Merges the sorted range of newly added elements and the sorted range of pre-existing elements into a single sorted range.
3. Erases the duplicate elements as if by:
   auto zv = std::views::zip(c.keys, c.values);
   auto it = ranges::unique(zv, key_equiv(compare)).begin();
   auto dist = std::distance(zv.begin(), it);
   c.keys.erase(c.keys.begin() + dist, c.keys.end());
   c.values.erase(c.values.begin() + dist, c.values.end());

May allocate memory during the in-place merge operation.

If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).

9) Inserts elements from initializer list ilist. Equivalent to insert(ilist.begin(), ilist.end());.

If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).

10) Inserts elements from initializer list ilist. Equivalent to insert(s, ilist.begin(), ilist.end());.

If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).

Parameters

pos	-	an iterator to the position before which the new element will be inserted
value	-	an element value to insert
first, last	-	a range of elements to insert
ilist	-	an initializer list to insert the values from
x	-	a value of any type that can be transparently compared with a key
s	-	a disambiguation tag indicating that the input sequence is sorted (with respect to value_comp()) and contains only unique elements
Type requirements
- InputIt must meet the requirements of LegacyInputIterator.

Return value

1,2) A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool value set to true if and only if the insertion took place.

3,4) An iterator to the inserted element, or to the element that prevented the insertion.

5) A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool value set to true if and only if the insertion took place.

6) An iterator to the inserted element, or to the element that prevented the insertion.

7-10) (none)

Exceptions

1-6) If an exception is thrown by any operation, the insertion has no effect.

Complexity

1-6) Linear in size().

7) N + M·log(M), where N is the size() before the operation and M is std::distance(first, last).

8) Linear in size().

9) N + M·log(M), where N is the size() before the operation and M is ilist.size().

10) Linear in N, where N is size() after the operation.

Notes

The hinted insert (3,4,6) does not return a boolean in order to be signature-compatible with positional insert on sequential containers, such as std::vector::insert. This makes it possible to create generic inserters such as std::inserter. One way to check success of a hinted insert is to compare size() before and after.

See also

emplace	constructs element in-place (public member function)
emplace_hint	constructs elements in-place using a hint (public member function)
insert_or_assign	inserts an element or assigns to the current element if the key already exists (public member function)
inserter	creates a std::insert_iterator of type inferred from the argument (function template)