# std::forward_list<T,Allocator>::assign

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< cpp‎ | container‎ | forward list

void assign( size_type count, const T& value ); | (1) | (since C++11)
template< class InputIt > void assign( InputIt first, InputIt last ); | (2) | (since C++11)
void assign( std::initializer_list <T> ilist ); | (3) | (since C++11)

Replaces the contents of the container.

1) Replaces the contents with count copies of value value.
2) Replaces the contents with copies of those in the range `[`first`,` last`)`.
If either argument is an iterator into *this, the behavior is undefined.

This overload has the same effect as overload (1) if `InputIt` is an integral type. | (until C++11)
This overload participates in overload resolution only if `InputIt` satisfies LegacyInputIterator. | (since C++11)

3) Replaces the contents with the elements from ilist.

All iterators, pointers and references to the elements of the container are invalidated.

### Parameters

count | - | the new size of the container
value | - | the value to initialize elements of the container with
first, last | - | the range to copy the elements from
ilist | - | std::initializer_list to copy the values from

### Complexity

1) Linear in count.
2) Linear in distance between first and last.
3) Linear in ilist.size().

### Example

The following code uses `assign` to add several characters to a std::forward_list <char>:

Run this code

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

    int main()
    {
        std::forward_list<char> characters;

        auto print_forward_list = [&]()
        {
            for (char c : characters)
                std::cout << c << ' ';
            std::cout << '\n';
        };

        characters.assign(5, 'a');
        print_forward_list();

        const std::string extra(6, 'b');
        characters.assign(extra.begin(), extra.end());
        print_forward_list();

        characters.assign({'C', '+', '+', '1', '1'});
        print_forward_list();
    }

Output:

    a a a a a
    b b b b b b
    C + + 1 1

### 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 2209 | C++11 | the replacement operation was required to be implemented as erasing all existing elements followed by inserting the given elements | removed the requirement

### See also

assign_range (C++23) | assigns a range of values to the container (public member function)
operator= | assigns values to the container (public member function)

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