W3cubDocs

/C++

std::vector<T,Allocator>::front

	(1)
reference front();		(until C++20)
constexpr reference front();		(since C++20)
	(2)
const_reference front() const;		(until C++20)
constexpr const_reference front() const;		(since C++20)

Returns a reference to the first element in the container.

Calling front on an empty container causes undefined behavior.

Parameters

(none).

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::vector<char>:

#include <vector>
#include <iostream>
 
int main()
{
    std::vector<char> letters {'a', 'b', 'c', 'd', 'e', 'f'};
 
    if (!letters.empty())
        std::cout << "The first character is '" << letters.front() << "'.\n";
}

Output: