std::vector front() method

since C++20

// prism-push-types:reference,const_reference
// Non const version
constexpr reference       front();

// Const version
constexpr const_reference front() const;

until C++20

// prism-push-types:reference,const_reference
// Non const version
reference       front();

// Const version
const_reference front() const;

Returns a reference

to the first element in the container.

Undefined Behavior

Calling front() on an empty container is undefined behavior

.

Parameters

(none)

Return value

Reference to the first element.

Complexity

Constant - O(1).

Notes

For a container c, the expression c.front() is equivalent to *c.begin() and c[0].

Example

Main.cpp

#include <array>
#include <iostream>
 
int main()
{
    std::vector<char> letters {'o', 'm', 'g', 'w', 't', 'f'};
 
    if (!letters.empty()) {
        std::cout << "The first character is '" << letters.front() << "'.\n";
    }  
}

Output

The first character is 'o'.