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std::list<T,Allocator>::front - cppreference.com

From cppreference.com

reference front();

 (1)

const_reference front() const;

 (2)

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)

Return value

Reference to the first element.

Complexity

Constant.

Notes

For a container c, the expression c.front() is equivalent to *c.begin().

Example

The following code uses front to display the first element of a std::list<char>:

#include <cassert>
#include <list>
 
int main()
{
    std::list<char> letters{'a', 'b', 'c', 'd'};
    assert(letters.front() == 'a');
}

See also

access the last element
(public member function) [edit]
returns a reverse iterator to the end
(public member function) [edit]
returns an iterator to the beginning
(public member function) [edit]