cpp/named req/SequenceContainer

A SequenceContainer is a Template:concept that stores objects of the same type in a linear arrangement.

Requirements

The type X satisfies SequenceContainer if

• The type X satisfies Template:concept, and

Given

• T, the element type of X
• A, the allocator type of X: X::allocator_type if it exists, otherwise std::allocator<T>
• a, rvalue expression of type X
• p, a valid const iterator into a
• q, a valid dereferenceable const iterator into a
• q1 and q2, two const iterators into a such that [q1, q2) is a valid range
• i and j, Template:concepts such that [i, j) is a valid range and that the iterators refer to elements implicitly convertible to value_type
• il, an object of type std::initializer_list<value_type>
• n, a value of type X::size_type
• t, an lvalue or const rvalue of type X::value_type
• rv, a non-const rvalue of type X::value_type
• Args: a template parameter pack
• args: a function parameter pack with the pattern Arg&&

The following expressions must be valid and have their specified effects for all sequence containers except std::array:

expression	return type	effects	precondition	postcondition
X(n, t) X a(n, t)		Constructs the sequence container holding n copies of t	T Template:concept into X	std::distance(begin(),end()) == n
X(i, j) X a(i, j)		Constructs the sequence container equal, element-wise, to the range [i,j)	T is Template:concept from *i into X (only for std::vector) If the iterators are not Template:concepts, T must be Template:concept	std::distance(begin(),end()) == std::distance(i,j)
X(il)		X(il.begin(), il.end())
a = il	X&	Assigns the range represented by il into a	T Template:concept and Template:concept	Existing elements of a are destroyed or assigned to
a.emplace(p,args)	iterator	Insert an object of type T, constructed with std::forward<Args>(args) before p	T Template:concept (for std::vector and std::deque) T Template:concept and Template:concept	Returned iterator points at the element constructed from args into a
a.insert(p,t)	iterator	Inserts a copy of t before p	T Template:concept (for std::vector and std::deque) T Template:concept or Template:concept	Returned iterator points at the copy of t inserted into a
a.insert(p,rv)	iterator	Inserts a copy of rv before p, possibly using move semantics	T Template:concept (for std::vector and std::deque) T Template:concept	Returned iterator points at the copy of rv inserted into a
a.insert(p,n,t)	iterator	Inserts n copies of t before p	T Template:concept and Template:concept	Returned iterator points at the copy of the first element inserted into a or is p for n==0
a.insert(p,i,j)	iterator	Inserts copies of elements in [i, j) before p	T Template:concept and i and j are not in a (only for std::vector) If the iterators are not Template:concepts, T must be Template:concept and Template:concept	Each iterator in [i,j) is dereferenced once. Returned iterator points at the copy of the first element inserted into a or is p for i==j
a.insert(p, il)	iterator	a.insert(p,il.begin(),il.end())		Returned iterator points at the copy of the first element inserted into a or is p if il is empty.
a.erase(q)	iterator	Erases the element pointed to by q	(std::deque, std::vector) T Template:concept	Returned iterator points at the element that was immediately following q prior to erasure, or a.end() if no such element exists.
a.erase(q1,q2)	iterator	Erases elements in [q1,q2)	(std::deque, std::vector) T Template:concept	Returned iterator points at the element that was pointed by q2 prior to any erasure, or a.end() if no such element exists.
a.clear()	void	Destroys all elements in a		All references, pointers, and iterators are invalidated, including the end iterator. a.empty() == true.
a.assign(i,j)	void	Replaces elements in a with a copy of [i, j)	T Template:concept and i, j not in a (std::vector) If not Template:concept. T Template:concept	Each iterator in [i,j) is dereferenced once
a.assign(il)	void	a.assign(il.begin(),il.end())
a.assign(n,t)	void	Replaces elements in a with n copies of t	T Template:concept and Template:concept
notes

The following expressions must be valid and have their specified effects for the sequence containers named:

expression	return type	effects	preconditions	containers
a.front()	reference const_reference for const a	Equivalent to *a.begin()		(all)
a.back()	reference const_reference for const a	Equivalent to { auto tmp = a.end(); --tmp; return *tmp; }		std::basic_string std::array std::deque std::list std::vector
a.emplace_front(args)	void	Prepends a T constructed with std::forward<Args>(args)...	T Template:concept into X from args	std::deque std::forward_list std::list
a.emplace_back(args)	void	Appends a T constructed with std::forward<Args>(args)...	T Template:concept into X from args (std::vector only) T Template:concept into X	std::deque std::list std::vector
a.push_front(t)	void	Prepends a copy of t	T Template:concept into X	std::deque std::forward_list std::list
a.push_front(rv)	void	Prepends a copy of rv, possibly using move semantics	T Template:concept into X	std::deque std::forward_list std::list
a.push_back(t)	void	Appends a copy of t	T Template:concept into X	std::basic_string std::deque std::list std::vector
a.push_back(rv)	void	Appends a copy of rv, possibly using move semantics	T Template:concept into X	std::basic_string std::deque std::list std::vector
a.pop_front()	void	Destroys the first element.	a.empty() == false	std::deque std::forward_list std::list
a.pop_back()	void	Destroys the last element	a.empty() == false	std::basic_string std::deque std::list std::vector
a[n]	reference const_reference for const a	Equivalent to *(n + a.begin())		std::basic_string std::array std::deque std::vector
a.at(n)	reference const_reference for const a	Equivalent to *(n + a.begin()), except that out_of_range is thrown if n>=size()		std::basic_string std::array std::deque std::vector

Additionally, for every sequence container, the constructor template that takes two input iterators and the member function template overloads of insert(), append(), assign(), replace() that take two input iterators do not participate in overload resolution if the corresponding template argument does not satisfy Template:concept.

SequenceContainers in the standard library

basic_string	stores and manipulates sequences of characters (class template)
array (C++11)	fixed-sized inplace contiguous array (class template)
vector	dynamic contiguous array (class template)
deque	double-ended queue (class template)
forward_list (C++11)	singly-linked list (class template)
list	doubly-linked list (class template)

Trade-offs / usage notes

std::array	Fast access but fixed number of elements
std::vector	Fast access but mostly inefficient insertions/deletions
std::list std::forward_list	Efficient insertion/deletion in the middle of the sequence
std::deque	Efficient insertion/deletion at the beginning and at the end of the sequence