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Difference between revisions of "cpp/container/forward list"

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< cpp‎ | container
(fix template parameters description)
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{{cpp/title|forward_list}}
 
{{cpp/title|forward_list}}
 
{{cpp/container/forward_list/navbar}}
 
{{cpp/container/forward_list/navbar}}
−
{{ddcl | header=forward_list | since=c++11 |
+
{{dcl begin}}
 +
{{dcl header|forward_list}}
 +
{{dcl|since=c++11|num=1|1=
 
template<
 
template<
 
     class T,
 
     class T,
−
     class Allocator {{=}} std::allocator<T>
+
     class Allocator = std::allocator<T>
 
> class forward_list;
 
> class forward_list;
−
}}  
+
}}
 +
{{dcl|since=c++17|num=2|1=
 +
namespace pmr {
 +
    template< class T >
 +
    using forward_list = std::forward_list<T, std::pmr::polymorphic_allocator<T>>;
 +
}
 +
}}
 +
{{dcl end}}
  
−
{{tt|std::forward_list}} is a container that supports fast insertion and removal of elements from anywhere in the container. Fast random access is not supported. It is implemented as a singly-linked list and essentially does not have any overhead compared to its implementation in C. Compared to {{lc|std::list}} this container provides more space efficient storage when bidirectional iteration is not needed.  
+
{{tt|std::forward_list}} is a container that supports fast insertion and removal of elements from anywhere in the container. Fast random access is not supported. It is implemented as a singly-linked list. Compared to {{lc|std::list}} this container provides more space efficient storage when bidirectional iteration is not needed.
  
−
Addition, removal and moving the elements within the list or across several lists does not invalidate the iterators. An iterator is invalidated only when the corresponding element is deleted.
+
Adding, removing and moving the elements within the list, or across several lists, does not invalidate the iterators currently referring to other elements in the list. However, an iterator or reference referring to an element is invalidated when the corresponding element is removed (via {{lc|erase_after}}) from the list.
  
−
{{tt|std::forward_list}} meets the requirements of {{concept|Container}} (except for the {{tt|size()}} member function), {{concept|AllocatorAwareContainer}} and {{concept|SequenceContainer}}.
+
{{tt|std::forward_list}} meets the requirements of {{named req|Container}} (except for the {{lc|size}} member function and that {{tt|1=operator==}}'s complexity is always linear), {{named req|AllocatorAwareContainer}} and {{named req|SequenceContainer}}.
  
 
===Template parameters===
 
===Template parameters===
 
{{par begin}}
 
{{par begin}}
−
{{par | T | The type of the elements. <br/>
+
{{par inc|cpp/container/param list T|forward_list}}
−
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 {{concept|MoveConstructible}} and {{concept|MoveAssignable}}, but many member functions impose stricter requirements.
+
{{par inc|cpp/container/param list Allocator|forward_list}}
−
}}
+
−
{{par inc | cpp/container/param list T | forward_list}}
+
−
{{par inc | cpp/container/param list Allocator | forward_list}}
+
 
{{par end}}
 
{{par end}}
  
 
===Member types===
 
===Member types===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc hitem | Member type | Definition}}
+
{{dsc hitem|Member type|Definition}}
−
{{dsc inc | cpp/container/dsc value_type | forward_list}}
+
{{dsc inc|cpp/container/dsc value_type|forward_list}}
−
{{dsc inc | cpp/container/dsc allocator_type | forward_list}}
+
{{dsc inc|cpp/container/dsc allocator_type|forward_list}}
−
{{dsc inc | cpp/container/dsc size_type | forward_list}}
+
{{dsc inc|cpp/container/dsc size_type|forward_list}}
−
{{dsc inc | cpp/container/dsc difference_type | forward_list}}
+
{{dsc inc|cpp/container/dsc difference_type|forward_list}}
−
{{dsc inc | cpp/container/dsc reference | forward_list}}
+
{{dsc inc|cpp/container/dsc reference|forward_list}}
−
{{dsc inc | cpp/container/dsc const_reference | forward_list}}
+
{{dsc inc|cpp/container/dsc const_reference|forward_list}}
−
{{dsc inc | cpp/container/dsc pointer | forward_list}}
+
{{dsc inc|cpp/container/dsc pointer|forward_list}}
−
{{dsc inc | cpp/container/dsc const_pointer | forward_list}}
+
{{dsc inc|cpp/container/dsc const_pointer|forward_list}}
−
{{dsc inc | cpp/container/dsc iterator | forward_list}}
+
{{dsc inc|cpp/container/dsc iterator|forward_list}}
−
{{dsc inc | cpp/container/dsc const_iterator | forward_list}}
+
{{dsc inc|cpp/container/dsc const_iterator|forward_list}}
 
{{dsc end}}
 
{{dsc end}}
  
 
===Member functions===
 
===Member functions===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc inc | cpp/container/dsc constructor | forward_list}}
+
{{dsc inc|cpp/container/dsc constructor|forward_list}}
−
{{dsc inc | cpp/container/dsc destructor | forward_list}}
+
{{dsc inc|cpp/container/dsc destructor|forward_list}}
−
{{dsc inc | cpp/container/dsc operator{{=}} | forward_list}}
+
{{dsc inc|cpp/container/dsc operator{{=}}|forward_list}}
−
{{dsc inc | cpp/container/dsc assign | forward_list}}
+
{{dsc inc|cpp/container/dsc assign|forward_list}}
−
{{dsc inc | cpp/container/dsc get_allocator | forward_list}}
+
{{dsc inc|cpp/container/dsc assign_range|forward_list}}
 +
{{dsc inc|cpp/container/dsc get_allocator|forward_list}}
  
−
{{dsc h2 | Element access}}
+
{{dsc h2|Element access}}
−
{{dsc inc | cpp/container/dsc front | forward_list}}
+
{{dsc inc|cpp/container/dsc front|forward_list}}
  
−
{{dsc h2 | Iterators}}
+
{{dsc h2|Iterators}}
−
{{dsc inc | cpp/container/dsc before_begin | forward_list}}
+
{{dsc inc|cpp/container/dsc before_begin|forward_list}}
−
{{dsc inc | cpp/container/dsc begin | forward_list}}
+
{{dsc inc|cpp/container/dsc begin|forward_list}}
−
{{dsc inc | cpp/container/dsc end | forward_list}}
+
{{dsc inc|cpp/container/dsc end|forward_list}}
  
−
{{dsc h2 | Capacity}}
+
{{dsc h2|Capacity}}
−
{{dsc inc | cpp/container/dsc empty | forward_list}}
+
{{dsc inc|cpp/container/dsc empty|forward_list}}
−
{{dsc inc | cpp/container/dsc max_size | forward_list}}
+
{{dsc inc|cpp/container/dsc max_size|forward_list}}
  
−
{{dsc h2 | Modifiers}}
+
{{dsc h2|Modifiers}}
−
{{dsc inc | cpp/container/dsc clear | forward_list}}
+
{{dsc inc|cpp/container/dsc clear|forward_list}}
−
{{dsc inc | cpp/container/dsc insert_after | forward_list}}
+
{{dsc inc|cpp/container/dsc insert_after|forward_list}}
−
{{dsc inc | cpp/container/dsc emplace_after | forward_list}}
+
{{dsc inc|cpp/container/dsc emplace_after|forward_list}}
−
{{dsc inc | cpp/container/dsc erase_after | forward_list}}
+
{{dsc inc|cpp/container/dsc insert_range_after|forward_list}}
−
{{dsc inc | cpp/container/dsc push_front | forward_list}}
+
{{dsc inc|cpp/container/dsc erase_after|forward_list}}
−
{{dsc inc | cpp/container/dsc emplace_front | forward_list}}
+
{{dsc inc|cpp/container/dsc push_front|forward_list}}
−
{{dsc inc | cpp/container/dsc pop_front | forward_list}}
+
{{dsc inc|cpp/container/dsc emplace_front|forward_list}}
−
{{dsc inc | cpp/container/dsc resize | forward_list}}
+
{{dsc inc|cpp/container/dsc prepend_range|forward_list}}
−
{{dsc inc | cpp/container/dsc swap | forward_list}}
+
{{dsc inc|cpp/container/dsc pop_front|forward_list}}
 +
{{dsc inc|cpp/container/dsc resize|forward_list}}
 +
{{dsc inc|cpp/container/dsc swap|forward_list}}
  
−
{{dsc h2 | Operations}}
+
{{dsc h2|Operations}}
−
{{dsc inc | cpp/container/dsc merge | forward_list}}
+
{{dsc inc|cpp/container/dsc merge|forward_list}}
−
{{dsc inc | cpp/container/dsc splice_after | forward_list}}
+
{{dsc inc|cpp/container/dsc splice_after|forward_list}}
−
{{dsc inc | cpp/container/dsc remove | forward_list}}
+
{{dsc inc|cpp/container/dsc remove|forward_list}}
−
{{dsc inc | cpp/container/dsc reverse | forward_list}}
+
{{dsc inc|cpp/container/dsc reverse|forward_list}}
−
{{dsc inc | cpp/container/dsc unique | forward_list}}
+
{{dsc inc|cpp/container/dsc unique|forward_list}}
−
{{dsc inc | cpp/container/dsc sort | forward_list}}
+
{{dsc inc|cpp/container/dsc sort|forward_list}}
 
{{dsc end}}
 
{{dsc end}}
  
 
===Non-member functions===
 
===Non-member functions===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc inc | cpp/container/dsc operator_cmp | forward_list}}
+
{{dsc inc|cpp/container/dsc operator_cmp|forward_list}}
−
{{dsc inc | cpp/container/dsc swap2 | forward_list}}
+
{{dsc inc|cpp/container/dsc swap2|forward_list}}
 +
{{dsc inc|cpp/container/dsc erase seq|forward_list}}
 +
{{dsc end}}
 +
 
 +
{{rrev|since=c++17|
 +
==={{rl|deduction guides|Deduction guides}}===
 +
}}
 +
 
 +
===Notes===
 +
{{ftm begin|std=1|comment=1}}
 +
{{ftm|__cpp_lib_containers_ranges|value=202202L|std=C++23|Ranges construction and insertion for containers}}
 +
{{ftm end}}
 +
 
 +
===Example===
 +
{{example}}
 +
 
 +
===See also===
 +
{{dsc begin}}
 +
{{dsc inc|cpp/container/dsc list}}
 
{{dsc end}}
 
{{dsc end}}
  
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[[de:cpp/container/forward list]]
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{{langlinks|de|es|fr|it|ja|pl|pt|ru|zh}}
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[[es:cpp/container/forward list]]
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[[fr:cpp/container/forward list]]
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[[it:cpp/container/forward list]]
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[[ja:cpp/container/forward list]]
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[[pt:cpp/container/forward list]]
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[[ru:cpp/container/forward list]]
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[[zh:cpp/container/forward list]]
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Latest revision as of 20:53, 2 August 2024

 
C++
 
Containers library
 
std::forward_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 <forward_list>
template<

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

> class forward_list;
 (1) (since C++11)
namespace pmr {

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

}
 (2) (since C++17)

std::forward_list is a container that supports fast insertion and removal of elements from anywhere in the container. Fast random access is not supported. It is implemented as a singly-linked list. Compared to std::list this container provides more space efficient storage when bidirectional iteration is not needed.

Adding, removing and moving the elements within the list, or across several lists, does not invalidate the iterators currently referring to other elements in the list. However, an iterator or reference referring to an element is invalidated when the corresponding element is removed (via erase_after) from the list.

std::forward_list meets the requirements of Container (except for the size member function and that operator=='s complexity is always linear), AllocatorAwareContainer and SequenceContainer.

Contents

[edit] Template parameters

T - The type of the elements.
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. (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]

[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 std::allocator_traits<Allocator>::pointer[edit]
const_pointer std::allocator_traits<Allocator>::const_pointer[edit]
iterator LegacyForwardIterator to value_type[edit]
const_iterator LegacyForwardIterator to const value_type[edit]

[edit] Member functions

 constructs the forward_list
(public member function) [edit]
destructs the forward_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]
Iterators
returns an iterator to the element before beginning
(public member function) [edit]
returns an iterator to the beginning
(public member function) [edit]
returns an iterator to the end
(public member function) [edit]
Capacity
checks whether the container is empty
(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 after an element
(public member function) [edit]
constructs elements in-place after an element
(public member function) [edit]
(C++23)
 inserts a range of elements after an element
(public member function) [edit]
erases an element after an element
(public member function) [edit]
inserts an element to the beginning
(public member function) [edit]
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 forward_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]

[edit] Non-member functions

(C++11)(C++11)(removed in C++20)(C++11)(removed in C++20)(C++11)(removed in C++20)(C++11)(removed in C++20)(C++11)(removed in C++20)(C++20)
 lexicographically compares the values of two forward_lists
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++20)
 erases all elements satisfying specific criteria
(function template) [edit]

Deduction guides

 (since C++17)

[edit] Notes

Feature-test macro Value Std Feature
__cpp_lib_containers_ranges 202202L (C++23) Ranges construction and insertion for containers

[edit] Example

This section is incomplete
Reason: no example

[edit] See also

 doubly-linked list
(class template) [edit]
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