Difference between revisions of "Template:cpp/container/begin"
From cppreference.com
m (~) |
(Fixed std::set::begin.) |
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===Complexity=== | ===Complexity=== | ||
Constant. | Constant. | ||
| − | {{cpp/container/if c++98|{{{1|}}}|<!- | + | |
| − | ---> | + | {{#if:{{#pos:{{{1|}}}|set}}| |
| + | {{cpp/container/constant iterator note}} | ||
| + | | | ||
| + | {{cpp/container/if c++98|{{{1|}}}| | ||
| + | <!----> | ||
===Notes=== | ===Notes=== | ||
libc++ backports {{tt|cbegin()}} to C++98 mode. | libc++ backports {{tt|cbegin()}} to C++98 mode. | ||
| − | + | }}}} | |
| − | + | <!----> | |
===Example=== | ===Example=== | ||
{{#switch:{{{1|list}}} | {{#switch:{{{1|list}}} | ||
Revision as of 22:14, 10 January 2024
| iterator begin() noexcept; |
(1) | (since {std}) |
| const_iterator begin() const noexcept; |
(2) | (since {std}) |
| const_iterator cbegin() const noexcept; |
(3) | (since {std}) |
Returns an iterator to the first element of the {{{1}}}.
If the {{{1}}} is empty, the returned iterator will be equal to end().
Contents |
Parameters
(none)
Return value
Iterator to the first element.
Complexity
Constant.
Example
Run this code
#include <algorithm> #include <iostream> #include <numeric> #include <string> #include <list> int main() { std::list<int> nums{1, 2, 4, 8, 16}; std::list<std::string> fruits{"orange", "apple", "raspberry"}; std::list<char> empty; // Print list. std::for_each(nums.begin(), nums.end(), [](const int n) { std::cout << n << ' '; }); std::cout << '\n'; // Sums all integers in the 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 list fruits, checking if there is any. if (!fruits.empty()) std::cout << "First fruit: " << *fruits.begin() << '\n'; if (empty.begin() == empty.end()) std::cout << "list 'empty' is indeed empty.\n"; }
Output:
1 2 4 8 16 Sum of nums: 31 First fruit: orange list 'empty' is indeed empty.
See also
| returns an iterator to the end (public member function of std::{{{1}}})
| |
| (C++11)(C++14) |
returns an iterator to the beginning of a container or array (function template) |
