std::forward_list end() method

since C++11

// Non-const version
iterator end() noexcept;

// Const version
const_iterator end() const noexcept;
const_iterator cend() const noexcept;

Returns an iterator

to the element past-the-end of the array.

note

If the array is empty, the returned iterator will be equal to begin().

Undefined Behavior

Attempting to dereference a past-the-end iterator is undefined behaviour

.

Parameters

(none)

Return value

Iterator to the first element.

Complexity

Constant - **O(1)*8.

Notes

For a container c, the expression *c.begin() is equivalent to c.front().

Difference between end and cend

For a const container c, end and cend are the same - c.end() == c.cend()

For non-const container of type c they return different iterators:

Non const container

end

#include <forward_list>

int main()
{
    std::forward_list<int> arr = {1, 2, 3, 4, 5};
    auto it = arr.end(); // Type: std::forward_list<int>::iterator
    *std::prev(it) = 5; // ✔ Ok
}

cend

#include <forward_list>

int main()
{
    std::forward_list<int> arr = {1, 2, 3, 4, 5};
    auto it = arr.cend(); // Type: std::forward_list<int>::const_iterator
    *std::prev(it) = 5; // ❌ Error!
}

Const container

end

#include <forward_list>

int main()
{
    const std::forward_list<int> arr = {1, 2, 3, 4, 5};
    auto it = arr.end(); // Type: std::forward_list<int>::const_iterator
    *std::prev(it) = 5; // ❌ Error!
}

cend

#include <forward_list>

int main()
{
    const std::forward_list<int> arr = {1, 2, 3, 4, 5};
    auto it = arr.cend(); // Type: std::forward_list<int>::const_iterator
    *std::prev(it) = 5; // ❌ Error!
}

Example

Main.cpp

#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>
#include <forward_list>
 
int main()
{
    std::forward_list<int> nums {1, 2, 4, 8, 16};
    std::forward_list<std::string> fruits {"orange", "apple", "raspberry"};
    std::forward_list<char> empty;
 
    // Print forward_list.
    std::for_each(nums.begin(), nums.end(), [](const int n) { std::cout << n << ' '; });
    std::cout << '\n';
 
    // Sums all integers in the forward_list nums (if any), printing only the result.
    std::cout << "Sum of nums: "
              << std::accumulate(nums.begin(), nums.end(), 0) << '\n';
 
    // Prints the first fruit in the forward_list fruits, checking if there is any.
    if (!fruits.empty())
        std::cout << "First fruit: " << *fruits.begin() << '\n';
 
    if (empty.begin() == empty.end())
        std::cout << "forward_list 'empty' is indeed empty.\n";
}

Output

1 2 4 8 16
Sum of nums: 31
First fruit: orange
forward_list 'empty' is indeed empty.