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

From cppreference.net

C++
Containers library
std::deque
Member types
Member functions
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++26)
iterator insert ( const_iterator pos, T && value ) ;
(2) (since C++11)
(constexpr since C++26)
iterator insert ( const_iterator pos,
size_type count, const T & value ) ;
(3) (constexpr since C++26)
template < class InputIt >
iterator insert ( const_iterator pos, InputIt first, InputIt last ) ;
(4) (constexpr since C++26)
iterator insert ( const_iterator pos, std:: initializer_list < T > ilist ) ;
(5) (since C++11)
(constexpr since C++26)

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 ( ) ) .


All iterators (including the end() iterator) are invalidated. References are invalidated too, unless pos == begin() or pos == end() , in which case they are not invalidated.

Contents

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

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.

Complexity

Linear in the number of elements inserted plus std:: min ( std:: distance ( begin ( ) , pos ) , std:: distance ( pos, end ( ) ) ) .

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)

this function has no effect (strong exception guarantee).

If an exception is thrown when inserting a single element at either end, 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)

Example

Run this code 
#include <iostream>
#include <iterator>
#include <string_view>
#include <deque>
namespace stq
{
    void println(std::string_view rem, const std::deque<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::deque<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);
    // reset pos to the begin:
    pos = c1.begin();
    std::deque<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]

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 inserting a single element 		also specified for inserting
multiple elements

See also

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