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# std::forward_list::insert_after

From cppreference.com
< cpp‎ | container‎ | forward list

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.

### [edit] Parameters

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

### [edit] 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.

### [edit] Exceptions

If an exception is thrown during `insert_after` there are no effects (strong exception guarantee).

### [edit] Complexity

1-2) Constant.
3) Linear in count
4) Linear in std::distance(first, last)
5) Linear in ilist.size()

### [edit] Example

Run this code

    #include <forward_list>
    #include <string>
    #include <iostream>
    #include <vector>

    template<typename T>
    std::ostream& operator<<(std::ostream& s, const std::forward_list<T>& v) {
        s.put('[');
        char comma[3] = {'\0', ' ', '\0'};
        for (const auto& e : v) {
            s << comma << e;
            comma[0] = ',';
        }
        return s << ']';
    }

    int main()
    {
        std::forward_list<std::string> words {"the", "frogurt", "is", "also", "cursed"};
        std::cout << "words: " << words << '\n';

        // insert_after (2)
        auto beginIt = words.begin();
        words.insert_after(beginIt, "strawberry");
        std::cout << "words: " << words << '\n';

        // insert_after (3)
        auto anotherIt = beginIt;
        ++anotherIt;
        anotherIt = words.insert_after(anotherIt, 2, "strawberry");
        std::cout << "words: " << words << '\n';

        // insert_after (4)
        std::vector<std::string> V = { "apple", "banana", "cherry"};
        anotherIt = words.insert_after(anotherIt, V.begin(), V.end());
        std::cout << "words: " << words << '\n';

        // insert_after (5)
        words.insert_after(anotherIt, {"jackfruit", "kiwifruit", "lime", "mango"});
        std::cout << "words: " << words << '\n';
    }

Output:

    words: [the, frogurt, is, also, cursed]
    words: [the, strawberry, frogurt, is, also, cursed]
    words: [the, strawberry, strawberry, strawberry, frogurt, is, also, cursed]
    words: [the, strawberry, strawberry, strawberry, apple, banana, cherry, frogurt, is, also, cursed]
    words: [the, strawberry, strawberry, strawberry, apple, banana, cherry, jackfruit, kiwifruit, lime, mango, frogurt, is, also, cursed]

### [edit] See also

emplace_after | constructs elements in-place after an element (public member function) [edit]
push_front | inserts an element to the beginning (public member function) [edit]

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