[deque.modifiers]

# 23 Containers library [[containers]](./#containers)

## 23.3 Sequence containers [[sequences]](sequences#deque.modifiers)

### 23.3.5 Class template deque [[deque]](deque#modifiers)

#### 23.3.5.4 Modifiers [deque.modifiers]

[ð](#lib:insert,deque)

`constexpr iterator insert(const_iterator position, const T& x);
constexpr iterator insert(const_iterator position, T&& x);
constexpr iterator insert(const_iterator position, size_type n, const T& x);
template<class InputIterator>
  constexpr iterator insert(const_iterator position,
                            InputIterator first, InputIterator last);
template<[container-compatible-range](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R>
  constexpr iterator insert_range(const_iterator position, R&& rg);
constexpr iterator insert(const_iterator position, initializer_list<T>);

template<class... Args> constexpr reference emplace_front(Args&&... args);
template<class... Args> constexpr reference emplace_back(Args&&... args);
template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args);
constexpr void push_front(const T& x);
constexpr void push_front(T&& x);
template<[container-compatible-range](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R>
  constexpr void prepend_range(R&& rg);
constexpr void push_back(const T& x);
constexpr void push_back(T&& x);
template<[container-compatible-range](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R>
  constexpr void append_range(R&& rg);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6818)

*Effects*: An insertion in the middle of the deque invalidates all the iterators and
references to elements of the deque[.](#1.sentence-1)

An insertion at either end of the
deque invalidates all the iterators to the deque, but has no effect on
the validity of references to elements of the deque[.](#1.sentence-2)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6826)

*Complexity*: The complexity is linear in the number of elements inserted plus the lesser
of the distances to the beginning and end of the deque[.](#2.sentence-1)

Inserting a single element at either the beginning or end of a deque always takes constant time
and causes a single call to a constructor ofT[.](#2.sentence-2)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6834)

*Remarks*: If an exception is thrown other than by the
copy constructor, move constructor,
assignment operator, or move assignment operator ofT,
there are no effects[.](#3.sentence-1)

If an exception is thrown while inserting a single element at either end,
there are no effects[.](#3.sentence-2)

Otherwise, if an exception is thrown by the move constructor of a
non-*Cpp17CopyInsertable*T, the effects are unspecified[.](#3.sentence-3)

[ð](#lib:erase,deque)

`constexpr iterator erase(const_iterator position);
constexpr iterator erase(const_iterator first, const_iterator last);
constexpr void pop_front();
constexpr void pop_back();
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6857)

*Effects*: An erase operation that erases the last element of a deque invalidates only the past-the-end iterator
and all iterators and references to the erased elements[.](#4.sentence-1)

An erase operation that erases the first
element of a deque but not the last element invalidates only iterators
and references to the erased elements[.](#4.sentence-2)

An erase operation
that erases neither the first element nor the last element of a deque invalidates the past-the-end
iterator and all iterators and references to all the elements of the deque[.](#4.sentence-3)

[*Note [1](#note-1)*:

pop_front and pop_back are erase operations[.](#4.sentence-4)

â *end note*]

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6869)

*Throws*: Nothing unless an exception is thrown by the assignment operator ofT[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6874)

*Complexity*: The number of calls to the destructor of T is the same as the
number of elements erased, but the number of calls to the assignment operator of T is
no more than the lesser of the number of elements before the erased elements and the number of elements after the erased elements[.](#6.sentence-1)
