std::stack<T,Container>::empty

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

inplace_vector (C++26)

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Iterator invalidation

Member function table

Non-member function table

 

std::stack

Member functions

stack::stack

stack::~stack

stack::operator=

Element access

stack::top

Capacity

stack::empty

stack::size

Modifiers

stack::push

stack::push_range (C++23)

stack::emplace (C++11)

stack::pop

stack::swap (C++11)

Non-member functions

swap(std::stack) (C++11)

operator==operator!=operator<operator>operator<=operator>=operator<=> (C++20)

Helper classes

uses_allocator<std::stack> (C++11)

formatter<std::stack> (C++23)

Deduction guides(C++17)

 

bool empty() const;

Checks if the underlying container has no elements. Equivalent to return c.empty();.

Parameters

(none)

Return value

true if the underlying container is empty, false otherwise.

Complexity

Constant.

Example

Run this code

#include <algorithm>
#include <iostream>
#include <stack>
 
int main()
{
    std::cout << std::boolalpha;
 
    std::stack<int> stack;
 
    std::cout << "Initially, stack.empty(): " << stack.empty() << '\n';
 
    stack.push(42);
    std::cout << "After adding elements, stack.empty(): " << stack.empty() << '\n';
}

Output:

Initially, stack.empty(): true
After adding elements, stack.empty(): false

See also

size	returns the number of elements (public member function)
empty (C++17)	checks whether the container is empty (function template)