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std::set::insert(3) C++ Standard Libary std::set::insert(3) NAME std::set::insert - std::set::insert Synopsis std::pair<iterator, bool> insert( const value_type& (1) value ); std::pair<iterator, bool> insert( value_type&& value (2) (since C++11) ); iterator insert( iterator pos, const value_type& (until C++11) value ); iterator insert( const_iterator pos, const (since C++11) value_type& value ); iterator insert( const_iterator pos, value_type&& (4) (since C++11) value ); template< class InputIt > (5) void insert( InputIt first, InputIt last ); void insert( std::initializer_list<value_type> ilist (3) (6) (since C++11) ); insert_return_type insert( node_type&& nh ); (7) (since C++17) iterator insert( const_iterator pos, node_type&& nh (8) (since C++17) ); template< class K > (9) (since C++23) std::pair<iterator, bool> insert( K&& x ); template< class K > (10) (since C++23) iterator insert( const_iterator pos, K&& x ); Inserts element(s) into the container, if the container doesn't al- ready contain an element with an equivalent key. 1,2) Inserts value. 3,4) Inserts value in the position as close as possible to the posi- tion just prior to pos. 5) Inserts elements from range [first, last). If multiple elements in the range have keys that compare equivalent, it is unspecified which element is in- serted (pending LWG2844). 6) Inserts elements from initializer list ilist. If multiple ele- ments in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844). 7) If nh is an empty node handle, does nothing. Otherwise, inserts the element owned by nh into the container , if the container doesn't already contain an element with a key equivalent to nh.key(). The behavior is undefined if nh is not empty and get_allocator() != nh.get_allocator(). 8) If nh is an empty node handle, does nothing and returns the end iterator. Otherwise, inserts the element owned by nh into the container, if the container doesn't already contain an element with a key equivalent to nh.key(), and returns the iterator pointing to the element with key equivalent to nh.key()(regardless of whether the insert succeeded or failed). If the insertion succeeds, nh is moved from, otherwise it retains ownership of the element. The element is inserted as close as possible to the position just prior to pos. The behavior is undefined if nh is not empty and get_allocator() != nh.get_allocator(). 9) If *this already contains an element which transparently compares equivalent to x, does nothing. Otherwise, constructs an object u of the value_type with std::forward<K>(x) and then inserts u into *this. If equal_range(u) == equal_range(x) is false, the behavior is undefined. The value_type must be EmplaceConstructible into set from std::forward<K>(x). This overload participates in overload resolution only if the qualified-id Compare::is_transparent is valid and denotes a type. It allows calling this function without constructing an instance of Key. 10) If *this already contains an element which transparently com- pares equivalent to x, does nothing. Otherwise, constructs an object u of the value_type with std::forward<K>(x) and then inserts u into *this in the position as close as possible to the position just prior to pos. If equal_range(u) == equal_range(x) is false, the behavior is undefined. The value_type must be EmplaceCon- structible into set from std::forward<K>(x). This overload participates in overload resolution only if: * std::is_convertible_v<K&&, const_iterator> and std::is_convert- ible_v<K&&, iterator> are both false, and * the qualified-id Compare::is_transparent is valid and denotes a type, which together allows calling this function without constructing an instance of Key. No iterators or references are invalidated. If the insertion is successful, pointers and references to the ele- ment obtained while it is held in the node handle are invalidated, and pointers and references obtained to that element before it was extracted become valid. (since C++17) 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 nh - a compatible node handle x - a value of any type that can be transparently compared with a key 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. 5,6) (none) 7) An object of insert_return_type with the members initialized as follows: * If nh is empty, inserted is false, position is end(), and node is empty. * Otherwise if the insertion took place, inserted is true, posi- tion points to the inserted element, and node is empty. * If the insertion failed, inserted is false, node has the previ- ous value of nh, and position points to an element with a key equivalent to nh.key(). 8) End iterator if nh was empty, iterator pointing to the inserted element if insertion took place, and iterator pointing to an element with a key equivalent to nh.key() if it failed. 9) 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. 10) An iterator to the inserted element, or to the element that pre- vented the insertion. Exceptions 1-4) If an exception is thrown by any operation, the insertion has no effect. This section is incomplete Reason: cases 5-8, 9, 10 Complexity 1,2) Logarithmic in the size of the container, O(log(size())). 3,4) Amortized constant if the insertion happens in the position just after (until C++11) before (since C++11) pos, logarithmic in the size of the container other- wise. 5,6) O(Nlog(size() + N)), where N is the number of elements to in- sert. 7) Logarithmic in the size of the container, O(log(size())). 8) Amortized constant if the insertion happens in the position just before pos, logarithmic in the size of the container otherwise. 9) Logarithmic in the size of the container, O(log(size())). 10) Amortized constant if the insertion happens in the position just before pos, logarithmic in the size of the container otherwise. Notes The hinted insert (3,4) does not return a boolean in order to be signature-compatible with positional insert on sequential contain- ers, such as std::vector::insert. This makes it possible to create generic in- serters such as std::inserter. One way to check success of a hinted insert is to compare size() before and after. The overloads (5,6) are often implemented as a loop that calls the overload (3) with end() as the hint; they are optimized for appending a sorted se- quence (such as another std::set) whose smallest element is greater than the last element in *this. Feature-test macro Value Std Feature Het- erogeneous over- loads for the re- maining member __cpp_lib_associative_heterogeneous_insertion 202311L (C++26) func- tions in ordered and unordered asso- ciative con- tainers. (9,10) Example // Run this code #include <cassert> #include <iostream> #include <set> int main() { std::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); // same iterator assert(*result_2.first == 3); if (!result_2.second) std::cout << "no insertion\n"; } Output: insert done no insertion Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Cor- rect behavior the inser- tion is required pos was just a hint, it could be to LWG 233 C++98 totally ignored be as close as possible to the position just prior to pos the complexity of overload (5) was removed the linear LWG 264 C++98 required to be linear if require- ment the range [first, last) is sorted in this special case according to Compare in the return value of overload (1), LWG 316 C++98 it was not specified success is which bool value indicates a indicated by true successful insertion See also emplace constructs element in-place (C++11) (public member function) emplace_hint constructs elements in-place using a hint (C++11) (public member function) inserter creates a std::insert_iterator of type inferred from the argument (function template) Category: * Todo with reason http://cppreference.com 2024.06.10 std::set::insert(3)
NAME | Synopsis | Parameters | Type requirements | Return value | Exceptions | Complexity | Notes | Example | Output: | See also | Category:
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