std::forward_list<T,Allocator>::front - cppreference.com (original) (raw)
| 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. | (since C++26) |
[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>:
#include #include int main() { std::forward_list letters{'a', 'b', 'c', 'd'}; assert(letters.front() == 'a'); }