std::forward_list<T,Allocator>::front
From cppreference.com
< cpp | container | forward list
C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Containers library
(C++17)
(C++11)
(C++26)
(C++26)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++23)
(C++23)
(C++23)
(C++23)
(C++20)
(C++23)
Tables
std::forward_list
(C++23)
forward_list::front
(C++23)
(C++23)
(C++20)
(C++20)(C++20)
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides (C++17)
reference front();
(1)
(since C++11) (constexpr since C++26)
const_reference front() const;
(2)
(since C++11) (constexpr since C++26)
Returns a reference to the first element in the container.
If empty() is true, the behavior is undefined.
(until C++26)If empty() is true:
- If the implementation is hardened, a contract violation occurs. Moreover, if the contract-violation handler returns under "observe" evaluation semantic, the behavior is undefined.
- If the implementation is not hardened, the behavior is undefined.
Contents
[edit] Return value
Reference to the first element.
[edit] Complexity
Constant.
[edit] Notes
For a container c, the expression c.front() is equivalent to *c.begin().
[edit] Example
The following code uses front to display the first element of a std::forward_list <char>:
Run this code
#include <cassert> #include <forward_list> int main() { std::forward_list <char> letters{'a', 'b', 'c', 'd'}; assert (letters.front() == 'a'); }