W3cubDocs

/C++

std::deque<T,Allocator>::begin, std::deque<T,Allocator>::cbegin

iterator begin();
 (until C++11) 
iterator begin() noexcept;
 (since C++11) 
const_iterator begin() const;
 (until C++11) 
const_iterator begin() const noexcept;
 (since C++11) 
const_iterator cbegin() const noexcept;
 (since C++11)

Returns an iterator to the first element of the container.

If the container is empty, the returned iterator will be equal to end().

range-begin-end.svg

Parameters

(none).

Return value

Iterator to the first element.

Complexity

Constant.

Example

#include <iostream>
#include <deque>
#include <string>
 
int main()
{
        std::deque<int> ints {1, 2, 4, 8, 16};
        std::deque<std::string> fruits {"orange", "apple", "raspberry"};
        std::deque<char> empty;
 
        // Sums all integers in the deque ints (if any), printing only the result.
        int sum = 0;
        for (auto it = ints.cbegin(); it != ints.cend(); it++)
                sum += *it;
        std::cout << "Sum of ints: " << sum << "\n";
 
        // Prints the first fruit in the deque fruits, without checking if there is one.
        std::cout << "First fruit: " << *fruits.begin() << "\n";
 
        if (empty.begin() == empty.end())
                std::cout << "deque 'empty' is indeed empty.\n";
}

Output:

Sum of ints: 31
First fruit: orange
deque 'empty' is indeed empty.

See also

returns an iterator to the end
(public member function)

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/container/deque/begin