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Difference between revisions of "cpp/container/list"

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< cpp‎ | container
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Revision as of 06:56, 17 March 2023

 
C++
 
Containers library
 
std::list
Member functions
Non-member functions
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides(C++17)
 
Defined in header <list>
template<

    class T,
    class Allocator = std::allocator<T>

> class list;
 (1)
namespace pmr {

    template <class T>
    using list = std::list<T, std::pmr::polymorphic_allocator<T>>;

}
 (2) (since C++17)

std::list is a container that supports constant time insertion and removal of elements from anywhere in the container. Fast random access is not supported. It is usually implemented as a doubly-linked list. Compared to std::forward_list this container provides bidirectional iteration capability while being less space efficient.

Adding, removing and moving the elements within the list or across several lists does not invalidate the iterators or references. An iterator is invalidated only when the corresponding element is deleted.

std::list meets the requirements of Container, AllocatorAwareContainer, SequenceContainer and ReversibleContainer.

Contents

Template parameters

T - The type of the elements.
T must meet the requirements of CopyConstructible. T must meet the requirements of CopyAssignable if list::operator= or list::assign is instantiated with T. (until C++11)
The requirements that are imposed on the elements depend on the actual operations performed on the container. Generally, it is required that element type is a complete type and meets the requirements of Erasable, but many member functions impose stricter requirements. (since C++11)
(until C++17)

The requirements that are imposed on the elements depend on the actual operations performed on the container. Generally, it is required that element type meets the requirements of Erasable, but many member functions impose stricter requirements. This container (but not its members) can be instantiated with an incomplete element type if the allocator satisfies the allocator completeness requirements.

Feature-test macro Value Std Feature
__cpp_lib_incomplete_container_elements 201505L (C++17) Minimal incomplete type support
(since C++17)

[edit]

Allocator - An allocator that is used to acquire/release memory and to construct/destroy the elements in that memory. The type must meet the requirements of Allocator. The behavior is undefined(until C++20)The program is ill-formed(since C++20) if Allocator::value_type is not the same as T.[edit]

Member types

Member type Definition
value_type T[edit]
allocator_type Allocator[edit]
size_type Unsigned integer type (usually std::size_t)[edit]
difference_type Signed integer type (usually std::ptrdiff_t)[edit]
reference value_type&[edit]
const_reference const value_type&[edit]
pointer

Allocator::pointer

(until C++11)

std::allocator_traits<Allocator>::pointer

(since C++11)
[edit]
const_pointer

Allocator::const_pointer

(until C++11)

std::allocator_traits<Allocator>::const_pointer

(since C++11)
[edit]
iterator LegacyBidirectionalIterator to value_type[edit]
const_iterator LegacyBidirectionalIterator to const value_type[edit]
reverse_iterator std::reverse_iterator<iterator>[edit]
const_reverse_iterator std::reverse_iterator<const_iterator>[edit]

Member functions

 constructs the list
(public member function) [edit]
destructs the list
(public member function) [edit]
assigns values to the container
(public member function) [edit]
assigns values to the container
(public member function) [edit]
(C++23)
 assigns a range of values to the container
(public member function) [edit]
returns the associated allocator
(public member function) [edit]
Element access
access the first element
(public member function) [edit]
access the last element
(public member function) [edit]
Iterators
(C++11)
 returns an iterator to the beginning
(public member function) [edit]
(C++11)
 returns an iterator to the end
(public member function) [edit]
(C++11)
 returns a reverse iterator to the beginning
(public member function) [edit]
(C++11)
 returns a reverse iterator to the end
(public member function) [edit]
Capacity
checks whether the container is empty
(public member function) [edit]
returns the number of elements
(public member function) [edit]
returns the maximum possible number of elements
(public member function) [edit]
Modifiers
clears the contents
(public member function) [edit]
inserts elements
(public member function) [edit]
(C++23)
 inserts a range of elements
(public member function) [edit]
(C++11)
 constructs element in-place
(public member function) [edit]
erases elements
(public member function) [edit]
adds an element to the end
(public member function) [edit]
(C++11)
 constructs an element in-place at the end
(public member function) [edit]
(C++23)
 adds a range of elements to the end
(public member function) [edit]
removes the last element
(public member function) [edit]
inserts an element to the beginning
(public member function) [edit]
(C++11)
 constructs an element in-place at the beginning
(public member function) [edit]
(C++23)
 adds a range of elements to the beginning
(public member function) [edit]
removes the first element
(public member function) [edit]
changes the number of elements stored
(public member function) [edit]
swaps the contents
(public member function) [edit]
Operations
merges two sorted lists
(public member function) [edit]
moves elements from another list
(public member function) [edit]
removes elements satisfying specific criteria
(public member function) [edit]
reverses the order of the elements
(public member function) [edit]
removes consecutive duplicate elements
(public member function) [edit]
sorts the elements
(public member function) [edit]

Non-member functions

(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20)
 lexicographically compares the values of two lists
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
(C++20)
 erases all elements satisfying specific criteria
(function template) [edit]

Deduction guides

 (since C++17)

Example

Run this code
#include <algorithm>
#include <iostream>
#include <list>
 
int main()
{
    // Create a list containing integers
    std::list<int> l = {7, 5, 16, 8};
 
    // Add an integer to the front of the list
    l.push_front(25);
    // Add an integer to the back of the list
    l.push_back(13);
 
    // Insert an integer before 16 by searching
    auto it = std::find(l.begin(), l.end(), 16);
    if (it != l.end())
        l.insert(it, 42);
 
    // Print out the list
    std::cout << "l = { ";
    for (int n : l)
        std::cout << n << ", ";
    std::cout << "};\n";
}

Output: 

l = { 25, 7, 5, 42, 16, 8, 13, };

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 230 C++98 T was not required to be CopyConstructible
(an element of type T might not be able to be constructed) 		T is also required to
be CopyConstructible
LWG 276 C++98 T was always required to be CopyAssignable only required if operator= or
assign is instantiated with T
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