std::deque<T,Allocator>::begin, std::deque<T,Allocator>::cbegin
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iterator begin();
(1)
(noexcept since C++11) (constexpr since C++26)
const_iterator begin() const;
(2)
(noexcept since C++11) (constexpr since C++26)
const_iterator cbegin() const noexcept;
(3)
(since C++11) (constexpr since C++26)
Returns an iterator to the first element of *this.
If *this is empty, the returned iterator will be equal to end() .
Contents
[edit] Return value
Iterator to the first element.
[edit] Complexity
Constant.
Notes
libc++ backports cbegin() to C++98 mode.
[edit] Example
Run this code
#include <algorithm> #include <iostream> #include <numeric> #include <string> #include <deque> int main() { std::deque <int> nums{1, 2, 4, 8, 16}; std::deque <std::string > fruits{"orange", "apple", "raspberry"}; std::deque <char> empty; // Print deque. std::for_each (nums.begin(), nums.end(), [](const int n) { std::cout << n << ' '; }); std::cout << '\n'; // Sums all integers in the deque 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 deque fruits, checking if there is any. if (!fruits.empty()) std::cout << "First fruit: " << *fruits.begin() << '\n'; if (empty.begin() == empty.end()) std::cout << "deque 'empty' is indeed empty.\n"; }
Output:
1 2 4 8 16 Sum of nums: 31 First fruit: orange deque 'empty' is indeed empty.
[edit] See also
(C++11)(C++14)
(function template) [edit]