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

From cppreference.net

C++
Containers library
std::list
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 T is not CopyInsertable into list , the behavior is undefined.

(since C++11)
2) Inserts value before pos , possibly using move semantics.
If T is not MoveInsertable into list , 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 ( ) ) .


No iterators or references are 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.

Exceptions

If an exception is thrown for any reason, these functions have no effect ( strong exception safety guarantee ).

Example

Run this code 
#include <iostream>
#include <iterator>
#include <string_view>
#include <list>
namespace stq
{
    void println(std::string_view rem, const std::list<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::list<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::list<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

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)