std::forward_list<T,Allocator>::begin, std::forward_list<T,Allocator>::cbegin
From cppreference.com
iterator begin() noexcept;
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(1) | (since C++11) |
const_iterator begin() const noexcept;
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(2) | (since C++11) |
const_iterator cbegin() const noexcept;
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(3) | (since C++11) |
Returns an iterator to the first element of the forward_list.
If the forward_list is empty, the returned iterator will be equal to end().
Return value
Iterator to the first element.
Complexity
Constant.
Example
Run this code
#include <algorithm>
#include <cassert>
#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 nums.
std::for_each(nums.cbegin(), nums.cend(),
[](const int n) { std::cout << n << ' '; });
std::cout << '\n';
// Sum all integers in the forward_list nums, printing only the result.
std::cout << "Sum of nums: "
<< std::accumulate(nums.cbegin(), nums.cend(), 0) << '\n';
// Print the first fruit in the forward_list fruits, checking if there is any.
if (!fruits.empty())
std::cout << "First fruit: " << *fruits.cbegin() << '\n';
if (empty.cbegin() == empty.cend())
std::cout << "forward_list ‘empty’ is indeed empty.\n";
// Modify the first element in nums.
*nums.begin() = 32;
assert(*nums.cbegin() == 32);
}
Output:
1 2 4 8 16
Sum of nums: 31
First fruit: orange
forward_list ‘empty’ is indeed empty.
See also
| returns an iterator to the end (public member function) | |
(C++11)(C++14) |
returns an iterator to the beginning of a container or array (function template) |