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std::vector<T,Allocator>::insert

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< cpp‎ | container‎ | vector
 
 
 
std::vector
Member types
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Non-member functions
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides (C++17)
 
iterator insert( const_iterator pos, const T& value );
(1) (constexpr since C++20)
iterator insert( const_iterator pos, T&& value );
(2) (since C++11)
(constexpr since C++20)
iterator insert( const_iterator pos,
                 size_type count, const T& value );
(3) (constexpr since C++20)
template< class InputIt >
iterator insert( const_iterator pos, InputIt first, InputIt last );
(4) (constexpr since C++20)
iterator insert( const_iterator pos, std::initializer_list <T> ilist );
(5) (since C++11)
(constexpr since C++20)

Inserts elements at the specified location in the container.

1) Inserts a copy of value before pos.
If any of the following conditions is satisfied, the behavior is undefined:
(since C++11)
2) Inserts value before pos, possibly using move semantics.
If any of the following conditions is satisfied, the behavior is undefined:
3) Inserts count copies of the value before pos.
If any of the following conditions is satisfied, the behavior is undefined:
(since C++11)
4) Inserts elements from range [first, last) before pos.

This overload has the same effect as overload (3) if InputIt is an integral type.

(until C++11)

This overload participates in overload resolution only if InputIt satisfies the requirements of LegacyInputIterator.

(since C++11)
If any of the following conditions is satisfied, the behavior is undefined:
(since C++11)
  • first or last are iterators into *this.
5) Inserts elements from initializer list ilist before pos.
Equivalent to insert(pos, ilist.begin(), ilist.end()).


If after the operation the new size() is greater than old capacity() a reallocation takes place, in which case all iterators (including the end() iterator) and all references to the elements are invalidated. Otherwise, only the iterators and references before the insertion point remain valid.

Contents

[edit] Parameters

pos - iterator before which the content will be inserted
value - element value to insert
count - number of elements to insert
first, last - the pair of iterators defining the range of elements to insert
ilist - std::initializer_list to insert the values from

[edit] Return value

1,2) Iterator pointing to the inserted value.
3-5) Iterator pointing to the first element inserted, or pos if no element is inserted.

[edit] Complexity

If reallocation happens, linear in the number of elements of the vector after insertion; otherwise, linear in the number of elements inserted plus std::distance (pos, end()).

[edit] Exceptions

If an exception is thrown other than by

  • the copy constructor of T,
  • the move constructor of T,
(since C++11)
  • the copy assignment operator of T,
  • the move assignment operator of T,
(since C++11)
  • any InputIt operation,

these functions have no effect (strong exception safety guarantee).

If an exception is thrown when inserting a single element at the end, and T is CopyInsertable into *this or std::is_nothrow_move_constructible <T>::value is true, this function has no effect (strong exception guarantee). Otherwise, if an exception is thrown by the move constructor of a non-CopyInsertable T, the effects are unspecified.

(since C++11)

[edit] Example

Run this code
#include <iostream>
#include <iterator>
#include <string_view>
#include <vector>
 
namespace stq
{
 void println(std::string_view rem, const std::vector <int>& container)
 {
 std::cout << rem.substr(0, rem.size() - 2) << '[';
 bool first{true};
 for (const int x : container)
 std::cout << (first ? first = false, "" : ", ") << x;
 std::cout << "]\n";
 }
}
 
int main()
{
 std::vector <int> c1(3, 100);
 stq::println("1. {}", c1);
 
 auto pos = c1.begin();
 pos = c1.insert(pos, 200); // overload (1)
 stq::println("2. {}", c1);
 
 c1.insert(pos, 2, 300); // overload (3)
 stq::println("3. {}", c1);
 
 // pos no longer valid, get a new one:
 pos = c1.begin();
 
 std::vector <int> c2(2, 400);
 c1.insert(std::next (pos, 2), c2.begin(), c2.end()); // overload (4)
 stq::println("4. {}", c1);
 
 int arr[] = {501, 502, 503};
 c1.insert(c1.begin(), arr, arr + std::size (arr)); // overload (4)
 stq::println("5. {}", c1);
 
 c1.insert(c1.end(), {601, 602, 603}); // overload (5)
 stq::println("6. {}", c1);
}

Output: 

1. [100, 100, 100]
2. [200, 100, 100, 100]
3. [300, 300, 200, 100, 100, 100]
4. [300, 300, 400, 400, 200, 100, 100, 100]
5. [501, 502, 503, 300, 300, 400, 400, 200, 100, 100, 100]
6. [501, 502, 503, 300, 300, 400, 400, 200, 100, 100, 100, 601, 602, 603]

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 149 C++98 overloads (3) and (4) returned nothing returns an iterator
LWG 247 C++98 the complexity was only specified for overload (3) specified for all overloads
LWG 406 C++98 the strong exception guarantee also applied if
the exception is thrown by an InputIt operation 		no guarantee in this case

[edit] See also

(C++11)
constructs element in-place
(public member function) [edit]
adds an element to the end
(public member function) [edit]
creates a std::insert_iterator of type inferred from the argument
(function template) [edit]

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