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      std::forward_list

      From cppreference.com
      <cpp‎ |container
       
       
       
      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 tostd::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 (viaerase_after) from the list.

      std::forward_list meets the requirements ofContainer (except for thesize member function and thatoperator=='s complexity is always linear),AllocatorAwareContainer andSequenceContainer.

      All member functions ofstd::forward_list areconstexpr: it is possible to create and usestd::forward_list objects in the evaluation of a constant expression.

      However,std::forward_list objects generally cannot beconstexpr, because any dynamically allocated storage must be released in the same evaluation of constant expression.

      		(since C++26)

      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 ofErasable, 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 ofErasable, 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 theallocator completeness requirements.

      Feature-test macroValueStdFeature
      __cpp_lib_incomplete_container_elements201505L(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 ofAllocator.The behavior is undefined(until C++20)The program is ill-formed(since C++20) ifAllocator::value_type is not the same asT.[edit]

      [edit]Member types

      Member type Definition
      value_typeT[edit]
      allocator_typeAllocator[edit]
      size_type Unsigned integer type (usuallystd::size_t)[edit]
      difference_type Signed integer type (usuallystd::ptrdiff_t)[edit]
      referencevalue_type&[edit]
      const_referenceconst value_type&[edit]
      pointerstd::allocator_traits<Allocator>::pointer[edit]
      const_pointerstd::allocator_traits<Allocator>::const_pointer[edit]
      iteratorLegacyForwardIterator andConstexprIterator(since C++26) tovalue_type[edit]
      const_iteratorLegacyForwardIterator andConstexprIterator(since C++26) toconst value_type[edit]

      [edit]Member functions

      constructs theforward_list
      (public member function)[edit]
      destructs theforward_list
      (public member function)[edit]
      assigns values to the container
      (public member function)[edit]
      assigns values to the container
      (public member function)[edit]
      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]
      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]
      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]
      transfers elements from anotherforward_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 twoforward_lists
      (function template)[edit]
      specializes thestd::swap algorithm
      (function template)[edit]
      erases all elements satisfying specific criteria
      (function template)[edit]

      Deduction guides

      		(since C++17)

      [edit]Notes

      Feature-test macroValueStdFeature
      __cpp_lib_containers_ranges202202L(C++23)Ranges construction and insertion for containers
      __cpp_lib_constexpr_forward_list202502L(C++26)constexprstd::forward_list

      [edit]Example

      This section is incomplete
      Reason: no example

      [edit]See also

      doubly-linked list
      (class template)[edit]
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