std::flat_set<Key,Compare,KeyContainer>::insert

 

C++

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Named requirements

Feature test macros (C++20)

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Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

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Numerics library

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Filesystem library (C++17)

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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)

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Iterator invalidation

Member function table

Non-member function table

 

std::flat_set

Member types

Member functions

flat_set::flat_set flat_set::operator= Iterators flat_set::beginflat_set::cbegin flat_set::endflat_set::cend flat_set::rbeginflat_set::crbegin flat_set::rendflat_set::crend Capacity flat_set::size flat_set::max_size flat_set::empty Observers flat_set::key_comp flat_set::value_comp      Modifiers flat_set::clear flat_set::insert flat_set::insert_range flat_set::emplace flat_set::emplace_hint flat_set::erase flat_set::swap flat_set::extract flat_set::replace Lookup flat_set::count flat_set::find flat_set::contains flat_set::equal_range flat_set::lower_bound flat_set::upper_bound Non-member functions operator==operator<=> swap(std::flat_set) erase_if(std::flat_set)

Helper classes

uses_allocator<std::flat_set>

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 K > iterator insert( const_iterator pos, K&& x );	(5)	(since C++23)
template< class InputIt > void insert( InputIt first, InputIt last );	(6)	(since C++23)
template< class K > std::pair<iterator, bool> insert( K&& x );	(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));.

5,7) If *this already contains an element which transparently compares equivalent to x, does nothing. Otherwise, inserts a new element as if by:

• (5) emplace(pos, std::forward<K>(x)) (in the position as close as possible to the position just prior to pos);
• (7) emplace(std::forward<K>(x)).

The conversion from x into key_type must construct an object u, for which find(k) == find(u) is true. Otherwise, the behavior is undefined.

These overloads participate in overload resolution only if

• The qualified-id Compare::is_transparent is valid and denotes a type, and
• std::is_constructible_v<value_type, K> is true,

which together allows calling this function without constructing an instance of Key.

6) Equivalent to the sequence of operations:

1. Inserts elements from range [first, last) as if by c.insert(c.end(), first, last);.
2. Sorts the range of newly inserted elements with respect to compare.
3. Merges the resulting sorted range and the sorted range of pre-existing elements into a single sorted range. (Note: the merge operation may allocate memory).
4. Erases all but the first element from each group of consecutive equivalent elements.

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). Equivalent to insert(first, last);.

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	-	iterator to the position before which the new element will be inserted
value	-	element value to insert
first, last	-	range of elements to insert
ilist	-	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 compare) 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.

3-5) An iterator to the inserted element, or to the element that prevented the insertion.

6) (none)

7) 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.

8-10) (none)

Exceptions

1-5,7) If an exception is thrown by any operation, the insertion has no effect.

Complexity

1-5) Linear in size().

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

7) Linear in size().

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

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 (3-5) 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.

Example

Run this code

#include <cassert>
#include <flat_set>
#include <iostream>
 
int main()
{
    std::flat_set<int> set;
 
    auto result_1 = set.insert(3);
    assert(result_1.first != set.end()); // it is a valid iterator
    assert(*result_1.first == 3);
    if (result_1.second)
        std::cout << "insert done\n";
 
    auto result_2 = set.insert(3);
    assert(result_2.first == result_1.first); // the same iterator
    assert(*result_2.first == 3);
    if (!result_2.second)
        std::cout << "no insertion\n";
}

Output:

insert done
no insertion

See also

emplace	constructs element in-place (public member function)
emplace_hint	constructs elements in-place using a hint (public member function)
inserter	creates a std::insert_iterator of type inferred from the argument (function template)