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std::forward_list<T,Allocator>::insert_after - cppreference.com

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iterator insert_after( const_iterator pos, const T& value );

 (1) (since C++11)

iterator insert_after( const_iterator pos, T&& value );

 (2) (since C++11)

iterator insert_after( const_iterator pos, size_type count, const T& value );

 (3) (since C++11)

template< class InputIt > iterator insert_after( const_iterator pos, InputIt first, InputIt last );

 (4) (since C++11)

iterator insert_after( const_iterator pos, std::initializer_list<T> ilist );

 (5) (since C++11)

Inserts elements after the specified position in the container.

1,2) Inserts value after the element pointed to by pos.

3) Inserts count copies of the value after the element pointed to by pos.

4) Inserts elements from range [first, last) after the element pointed to by pos. The behavior is undefined if first and last are iterators into *this.

5) Inserts elements from initializer list ilist.

No iterators or references are invalidated.

Parameters

pos - iterator after which the content will be inserted
value - element value to insert
count - number of copies to insert
first, last - the pair of iterators defining the source range of elements to insert
ilist - initializer list to insert the values from
Type requirements
-InputIt must meet the requirements of LegacyInputIterator.

Return value

1,2) Iterator to the inserted element.

3) Iterator to the last element inserted, or pos if count == 0.

4) Iterator to the last element inserted, or pos if first == last.

5) Iterator to the last element inserted, or pos if ilist is empty.

Exceptions

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

Complexity

1,2) Constant.

3) Linear in count.

4) Linear in std::distance(first, last).

5) Linear in ilist.size().

Example

#include <forward_list>
#include <iostream>
#include <string>
#include <vector>
                                                                                
void print(const std::forward_list<int>& list)
{
    std::cout << "list: {";
    for (char comma[3] = {'\0', ' ', '\0'}; int i : list)
    {
        std::cout << comma << i;
        comma[0] = ',';
    }
    std::cout << "}\n";
}
                                                                                
int main()
{
    std::forward_list<int> ints{1, 2, 3, 4, 5};
    print(ints);
                                                                                
    // insert_after (2)
    auto beginIt = ints.begin();
    ints.insert_after(beginIt, -6);
    print(ints);

    // insert_after (3)
    auto anotherIt = beginIt;
    ++anotherIt;
    anotherIt = ints.insert_after(anotherIt, 2, -7);
    print(ints);

    // insert_after (4)
    const std::vector<int> v = {-8, -9, -10};
    anotherIt = ints.insert_after(anotherIt, v.cbegin(), v.cend());
    print(ints);
                       
    // insert_after (5)
    ints.insert_after(anotherIt, {-11, -12, -13, -14});
    print(ints);
}

Output: 

list: {1, 2, 3, 4, 5}
list: {1, -6, 2, 3, 4, 5}
list: {1, -6, -7, -7, 2, 3, 4, 5}
list: {1, -6, -7, -7, -8, -9, -10, 2, 3, 4, 5}
list: {1, -6, -7, -7, -8, -9, -10, -11, -12, -13, -14, 2, 3, 4, 5}

See also