C++ std::list::pop_back

The std::list::pop_back function removes the last element from a std::list. This operation reduces the size of the list by one but does not return the removed element. The function is commonly used when managing elements in LIFO (Last In, First Out) operations.

Syntax of std::list::pop_back

</>

Copy

void pop_back();

Parameters

This function does not accept any parameters.

Return Value

This function does not return a value. It modifies the list by removing the last element.

Exceptions

The std::list::pop_back function does not throw exceptions itself. However, calling it on an empty list results in undefined behavior. To avoid this, always ensure the list is not empty before calling pop_back. This can be done using the empty() method.

Examples for std::list::pop_back

Example 1: Removing Elements from the End of a List

This example demonstrates how to use pop_back to remove elements from the end of a list:

Program

</>

Copy

#include <iostream>
#include <list>

int main() {
    std::list<int> myList = {10, 20, 30, 40};

    myList.pop_back(); // Remove the last element (40)

    std::cout << "List contents after pop_back: ";
    for (const auto& elem : myList) {
        std::cout << elem << " ";
    }
    std::cout << std::endl;

    return 0;
}

Explanation:

A std::list named myList is initialized with the elements {10, 20, 30, 40}.
The pop_back function is called, removing the last element 40.
The remaining elements of the list are printed using a range-based for loop.

Output:

List contents after pop_back: 10 20 30

Example 2: Handling Empty List

This example demonstrates how to safely call pop_back on a list to avoid undefined behavior:

Program

</>

Copy

#include <iostream>
#include <list>

int main() {
    std::list<int> myList;

    if (!myList.empty()) {
        myList.pop_back();
    } else {
        std::cout << "List is empty, cannot call pop_back." << std::endl;
    }

    return 0;
}

Explanation:

A std::list named myList is created and is initially empty.
The empty() method is used to check if the list contains elements before calling pop_back.
If the list is empty, a message is printed to indicate that the operation cannot be performed.

Output:

List is empty, cannot call pop_back.

Example 3: Removing Complex Objects

This example demonstrates how to use pop_back with a list of complex objects:

Program

</>

Copy

#include <iostream>
#include <list>
#include <string>

struct Person {
    std::string name;
    int age;

    Person(const std::string& name, int age) : name(name), age(age) {}
};

int main() {
    std::list<Person> people;

    people.push_back(Person("Arjun", 30));
    people.push_back(Person("Ram", 25));

    people.pop_back(); // Remove the last element ("Bob")

    for (const auto& person : people) {
        std::cout << person.name << " (" << person.age << " years old)" << std::endl;
    }

    return 0;
}

Explanation:

A Person struct is defined with two members: name (a string) and age (an integer).
A std::list of Person objects named people is created, and two objects (“Arjun” and “Ram”) are added using push_back.
The pop_back function is called, removing the last object (“Ram”).
A range-based for loop iterates through the list and prints the details of the remaining Person objects.

Output:

Arjun (30 years old)

TutorialKart

C++ std::list::pop_back