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

 

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std::forward_list

Member functions
forward_list::forward_list forward_list::~forward_list forward_list::operator= forward_list::assign forward_list::assign_range (C++23)   forward_list::get_allocator Element access forward_list::front Iterators forward_list::before_beginforward_list::cbefore_begin forward_list::beginforward_list::cbegin forward_list::endforward_list::cend Capacity forward_list::empty forward_list::max_size	Modifiers forward_list::clear forward_list::emplace_front forward_list::push_front forward_list::insert_after forward_list::emplace_after forward_list::erase_after forward_list::insert_range_after (C++23) forward_list::prepend_range (C++23) forward_list::pop_front forward_list::resize forward_list::swap Operations forward_list::merge forward_list::splice_after forward_list::removeforward_list::remove_if forward_list::reverse forward_list::unique forward_list::sort
Non-member functions
operator==operator<=> (C++20) swap(std::forward_list) erase(std::forward_list)erase_if(std::forward_list) (C++20)(C++20)	operator!=operator<operator>operator<=operator>= (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides (C++17)

 

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)