---
name: "std::set"
section: "3cxx"
platform: "linux"
package: "libstdc++-12-doc"
version: "12.4.0-5"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/std::set/3cxx"
---

# std::set(3cxx)

A standard container made up of unique keys, which can be retrieved in logarithmic time.

## NAME

std::set\< \_Key, \_Compare, \_Alloc \> - A standard container made up of unique keys, which can be retrieved in logarithmic time.

## SYNOPSIS

`#include <set>`

### Public Types

**using** **insert\_return\_type** = **typename** **\_Rep\_type::insert\_return\_type**\
 **using** **node\_type** = **typename** **\_Rep\_type::node\_type**\

**typedef** **\_Key** **key\_type**\
 Public typedefs.  **typedef** **\_Key** **value\_type**\
 Public typedefs.  **typedef** \_Compare **key\_compare**\
 Public typedefs.  **typedef** \_Compare **value\_compare**\
 Public typedefs.  **typedef** \_Alloc **allocator\_type**\
 Public typedefs.

**typedef** **\_Alloc\_traits::pointer** **pointer**\
 Iterator-related typedefs.  **typedef** \_Alloc\_traits::const\_pointer **const\_pointer**\
 Iterator-related typedefs.  **typedef** \_Alloc\_traits::reference **reference**\
 Iterator-related typedefs.  **typedef** \_Alloc\_traits::const\_reference **const\_reference**\
 Iterator-related typedefs.  **typedef** **\_Rep\_type::const\_iterator** **iterator**\
 Iterator-related typedefs.  **typedef** **\_Rep\_type::const\_iterator** **const\_iterator**\
 Iterator-related typedefs.  **typedef** **\_Rep\_type::const\_reverse\_iterator** **reverse\_iterator**\
 Iterator-related typedefs.  **typedef** **\_Rep\_type::const\_reverse\_iterator** **const\_reverse\_iterator**\
 Iterator-related typedefs.  **typedef** \_Rep\_type::size\_type **size\_type**\
 Iterator-related typedefs.  **typedef** \_Rep\_type::difference\_type **difference\_type**\
 Iterator-related typedefs.

### Public Member Functions

**set** ()=**default**\
 Default constructor creates no elements.  template\<**typename** **\_InputIterator** \> **set** (**\_InputIterator** \_\_first, **\_InputIterator** \_\_last)\
 Builds a set from a range.  template\<**typename** **\_InputIterator** \> **set** (**\_InputIterator** \_\_first, **\_InputIterator** \_\_last, const \_Compare &\_\_comp, const **allocator\_type** &\_\_a=**allocator\_type**())\
 Builds a set from a range.  template\<**typename** **\_InputIterator** \> **set** (**\_InputIterator** \_\_first, **\_InputIterator** \_\_last, const **allocator\_type** &\_\_a)\
 Allocator-extended range constructor.  **set** (const \_Compare &\_\_comp, const **allocator\_type** &\_\_a=**allocator\_type**())\
 Creates a set with no elements.  **set** (const **allocator\_type** &\_\_a)\
 Allocator-extended default constructor.  **set** (const **set** &)=**default**\
 Set copy constructor.  **set** (const **set** &\_\_x, const **\_\_type\_identity\_t**\< **allocator\_type** \> &\_\_a)\
 Allocator-extended copy constructor.  **set** (**initializer\_list**\< **value\_type** \> **\_\_l**, const \_Compare &\_\_comp=\_Compare(), const **allocator\_type** &\_\_a=**allocator\_type**())\
 Builds a set from an initializer\_list.  **set** (**initializer\_list**\< **value\_type** \> **\_\_l**, const **allocator\_type** &\_\_a)\
 Allocator-extended initialier-list constructor.  **set** (**set** &&)=**default**\
 Set move constructor  **set** (**set** &&\_\_x, const **\_\_type\_identity\_t**\< **allocator\_type** \> &\_\_a) noexcept(**is\_nothrow\_copy\_constructible**\< \_Compare \>::value &&\_Alloc\_traits::\_S\_always\_equal())\
 Allocator-extended move constructor.  **~set** ()=**default**\
 **iterator** **begin** () const noexcept\
 **iterator** **cbegin** () const noexcept\
 **iterator** **cend** () const noexcept\
 **void** **clear** () noexcept\
 **reverse\_iterator** **crbegin** () const noexcept\
 **reverse\_iterator** **crend** () const noexcept\
 template\<typename... \_Args\> **std::pair**\< **iterator**, bool \> **emplace** (**\_Args** &&... **\_\_args**)\
 Attempts to build and insert an element into the set.  template\<typename... \_Args\> **iterator** **emplace\_hint** (**const\_iterator** **\_\_pos**, **\_Args** &&... **\_\_args**)\
 Attempts to insert an element into the set.  bool **empty** () const noexcept\
 Returns true if the set is empty.  **iterator** **end** () const noexcept\
 **size\_type** **erase** (const **key\_type** &\_\_x)\
 Erases elements according to the provided key.  \_GLIBCXX\_ABI\_TAG\_CXX11 **iterator** **erase** (**const\_iterator** \_\_first, **const\_iterator** \_\_last)\
 Erases a \[\_\_first,\_\_last) range of elements from a set.  \_GLIBCXX\_ABI\_TAG\_CXX11 **iterator** **erase** (**const\_iterator** **\_\_position**)\
 Erases an element from a set.  node\_type **extract** (const **key\_type** &\_\_x)\
 Extract a node.  node\_type **extract** (**const\_iterator** **\_\_pos**)\
 Extract a node.  **allocator\_type** **get\_allocator** () const noexcept\
 Returns the allocator object with which the set was constructed.  template\<**typename** **\_InputIterator** \> **void** **insert** (**\_InputIterator** \_\_first, **\_InputIterator** \_\_last)\
 A template function that attempts to insert a range of elements.  **std::pair**\< **iterator**, bool \> **insert** (const **value\_type** &\_\_x)\
 Attempts to insert an element into the set.  **iterator** **insert** (**const\_iterator** **\_\_hint**, node\_type &&**\_\_nh**)\
 Re-insert an extracted node.  **iterator** **insert** (**const\_iterator** **\_\_position**, const **value\_type** &\_\_x)\
 Attempts to insert an element into the set.  **iterator** **insert** (**const\_iterator** **\_\_position**, **value\_type** &&\_\_x)\
 **void** **insert** (**initializer\_list**\< **value\_type** \> **\_\_l**)\
 Attempts to insert a list of elements into the set.  insert\_return\_type **insert** (node\_type &&**\_\_nh**)\
 Re-insert an extracted node.  **std::pair**\< **iterator**, bool \> **insert** (**value\_type** &&\_\_x)\
 **key\_compare** **key\_comp** () const\
 Returns the comparison object with which the set was constructed.  **size\_type** **max\_size** () const noexcept\
 Returns the maximum size of the set.  template\<**typename** **\_Compare1** \> **void** **merge** (**multiset**\< **\_Key**, **\_Compare1**, \_Alloc \> &&**\_\_source**)\
 template\<**typename** **\_Compare1** \> **void** **merge** (**multiset**\< **\_Key**, **\_Compare1**, \_Alloc \> &**\_\_source**)\
 template\<**typename** **\_Compare1** \> **void** **merge** (**set**\< **\_Key**, **\_Compare1**, \_Alloc \> &&**\_\_source**)\
 template\<**typename** **\_Compare1** \> **void** **merge** (**set**\< **\_Key**, **\_Compare1**, \_Alloc \> &**\_\_source**)\
 **set** & **operator=** (const **set** &)=**default**\
 Set assignment operator.  **set** & **operator=** (**initializer\_list**\< **value\_type** \> **\_\_l**)\
 Set list assignment operator.  **set** & **operator=** (**set** &&)=**default**\
 Move assignment operator.  **reverse\_iterator** **rbegin** () const noexcept\
 **reverse\_iterator** **rend** () const noexcept\
 **size\_type** **size** () const noexcept\
 Returns the size of the set.  **void** **swap** (**set** &\_\_x) noexcept(/\***conditional** \*/)\
 Swaps data with another set.  **value\_compare** **value\_comp** () const\
 Returns the comparison object with which the set was constructed.

**size\_type** **count** (const **key\_type** &\_\_x) const\
 Finds the number of elements.  template\<**typename** **\_Kt** \> **auto** **count** (const **\_Kt** &\_\_x) const -\> **decltype**(\_M\_t.\_M\_count\_tr(\_\_x))\
 Finds the number of elements.

bool **contains** (const **key\_type** &\_\_x) const\
 Finds whether an element with the given key exists.  template\<**typename** **\_Kt** \> **auto** **contains** (const **\_Kt** &\_\_x) const -\> **decltype**(\_M\_t.\_M\_find\_tr(\_\_x), **void**(), **true**)\
 Finds whether an element with the given key exists.

**iterator** **find** (const **key\_type** &\_\_x)\
 Tries to locate an element in a set.  **const\_iterator** **find** (const **key\_type** &\_\_x) const\
 Tries to locate an element in a set.  template\<**typename** **\_Kt** \> **auto** **find** (const **\_Kt** &\_\_x) -\> **decltype**(**iterator**{\_M\_t.\_M\_find\_tr(\_\_x)})\
 Tries to locate an element in a set.  template\<**typename** **\_Kt** \> **auto** **find** (const **\_Kt** &\_\_x) const -\> **decltype**(**const\_iterator**{\_M\_t.\_M\_find\_tr(\_\_x)})\
 Tries to locate an element in a set.

**iterator** **lower\_bound** (const **key\_type** &\_\_x)\
 Finds the beginning of a subsequence matching given key.  **const\_iterator** **lower\_bound** (const **key\_type** &\_\_x) const\
 Finds the beginning of a subsequence matching given key.  template\<**typename** **\_Kt** \> **auto** **lower\_bound** (const **\_Kt** &\_\_x) -\> **decltype**(**iterator**(\_M\_t.\_M\_lower\_bound\_tr(\_\_x)))\
 Finds the beginning of a subsequence matching given key.  template\<**typename** **\_Kt** \> **auto** **lower\_bound** (const **\_Kt** &\_\_x) const -\> **decltype**(**const\_iterator**(\_M\_t.\_M\_lower\_bound\_tr(\_\_x)))\
 Finds the beginning of a subsequence matching given key.

**iterator** **upper\_bound** (const **key\_type** &\_\_x)\
 Finds the end of a subsequence matching given key.  **const\_iterator** **upper\_bound** (const **key\_type** &\_\_x) const\
 Finds the end of a subsequence matching given key.  template\<**typename** **\_Kt** \> **auto** **upper\_bound** (const **\_Kt** &\_\_x) -\> **decltype**(**iterator**(\_M\_t.\_M\_upper\_bound\_tr(\_\_x)))\
 Finds the end of a subsequence matching given key.  template\<**typename** **\_Kt** \> **auto** **upper\_bound** (const **\_Kt** &\_\_x) const -\> **decltype**(**iterator**(\_M\_t.\_M\_upper\_bound\_tr(\_\_x)))\
 Finds the end of a subsequence matching given key.

**std::pair**\< **iterator**, **iterator** \> **equal\_range** (const **key\_type** &\_\_x)\
 Finds a subsequence matching given key.  **std::pair**\< **const\_iterator**, **const\_iterator** \> **equal\_range** (const **key\_type** &\_\_x) const\
 Finds a subsequence matching given key.  template\<**typename** **\_Kt** \> **auto** **equal\_range** (const **\_Kt** &\_\_x) -\> **decltype**(**pair**\< **iterator**, **iterator** \>(\_M\_t.\_M\_equal\_range\_tr(\_\_x)))\
 Finds a subsequence matching given key.  template\<**typename** **\_Kt** \> **auto** **equal\_range** (const **\_Kt** &\_\_x) const -\> **decltype**(**pair**\< **iterator**, **iterator** \>(\_M\_t.\_M\_equal\_range\_tr(\_\_x)))\
 Finds a subsequence matching given key.

### Friends

template\<**typename** **\_K1** , **typename** **\_C1** , **typename** **\_A1** \> bool **operator\<** (const **set**\< **\_K1**, **\_C1**, **\_A1** \> &, const **set**\< **\_K1**, **\_C1**, **\_A1** \> &)\
 template\<**typename** **\_K1** , **typename** **\_C1** , **typename** **\_A1** \> bool **operator==** (const **set**\< **\_K1**, **\_C1**, **\_A1** \> &, const **set**\< **\_K1**, **\_C1**, **\_A1** \> &)\
 template\<**typename** , **typename** \> **struct** **std::\_Rb\_tree\_merge\_helper**\

## Detailed Description

### template\<typename \_Key, typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\>

class std::set\< \_Key, \_Compare, \_Alloc \>"A standard container made up of unique keys, which can be retrieved in logarithmic time.

**Since**

C++98

**Template Parameters**

*\_Key* Type of key objects. \
 *\_Compare* Comparison function object type, defaults to less\<\_Key\>. \
 *\_Alloc* Allocator type, defaults to allocator\<\_Key\>.

Meets the requirements of a `container`, a `reversible container`, and an `associative container` (using unique keys).

Sets support bidirectional iterators.

The private tree data is declared exactly the same way for set and multiset; the distinction is made entirely in how the tree functions are called (\*\_unique versus \*\_equal, same as the standard).

## Member Typedef Documentation

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Alloc std::set\< \_Key, \_Compare, \_Alloc \>::allocator\_type

Public typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Rep\_type::const\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::const\_iterator

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Alloc\_traits::const\_pointer std::set\< \_Key, \_Compare, \_Alloc \>::const\_pointer

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Alloc\_traits::const\_reference std::set\< \_Key, \_Compare, \_Alloc \>::const\_reference

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Rep\_type::const\_reverse\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::const\_reverse\_iterator

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Rep\_type::difference\_type std::set\< \_Key, \_Compare, \_Alloc \>::difference\_type

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Rep\_type::const\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::iterator

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Compare std::set\< \_Key, \_Compare, \_Alloc \>::key\_compare

Public typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Key std::set\< \_Key, \_Compare, \_Alloc \>::key\_type

Public typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Alloc\_traits::pointer std::set\< \_Key, \_Compare, \_Alloc \>::pointer

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Alloc\_traits::reference std::set\< \_Key, \_Compare, \_Alloc \>::reference

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Rep\_type::const\_reverse\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::reverse\_iterator

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Rep\_type::size\_type std::set\< \_Key, \_Compare, \_Alloc \>::size\_type

Iterator-related typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Compare std::set\< \_Key, \_Compare, \_Alloc \>::value\_compare

Public typedefs.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> typedef \_Key std::set\< \_Key, \_Compare, \_Alloc \>::value\_type

Public typedefs.

## Constructor & Destructor Documentation

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set ()` [default]`

Default constructor creates no elements.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set (const \_Compare & \_\_comp, const allocator\_type & \_\_a = allocator\_type`()`)` [inline]`, ` [explicit]`

Creates a set with no elements.

**Parameters**

*\_\_comp* Comparator to use. \
 *\_\_a* An allocator object.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_InputIterator \> std::set\< \_Key, \_Compare, \_Alloc \>::set (\_InputIterator \_\_first, \_InputIterator \_\_last)` [inline]`

Builds a set from a range.

**Parameters**

*\_\_first* An input iterator. \
 *\_\_last* An input iterator.

Create a set consisting of copies of the elements from \[\_\_first,\_\_last). This is linear in N if the range is already sorted, and NlogN otherwise (where N is distance(\_\_first,\_\_last)).

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_InputIterator \> std::set\< \_Key, \_Compare, \_Alloc \>::set (\_InputIterator \_\_first, \_InputIterator \_\_last, const \_Compare & \_\_comp, const allocator\_type & \_\_a = allocator\_type`()`)` [inline]`

Builds a set from a range.

**Parameters**

*\_\_first* An input iterator. \
 *\_\_last* An input iterator. \
 *\_\_comp* A comparison functor. \
 *\_\_a* An allocator object.

Create a set consisting of copies of the elements from \[\_\_first,\_\_last). This is linear in N if the range is already sorted, and NlogN otherwise (where N is distance(\_\_first,\_\_last)).

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set (const set\< \_Key, \_Compare, \_Alloc \> &)` [default]`

Set copy constructor. Whether the allocator is copied depends on the allocator traits.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set (set\< \_Key, \_Compare, \_Alloc \> &&)` [default]`

Set move constructor The newly-created set contains the exact contents of the moved instance. The moved instance is a valid, but unspecified, set.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set (initializer\_list\< value\_type \> \_\_l, const \_Compare & \_\_comp = `_Compare()`, const allocator\_type & \_\_a = allocator\_type`()`)` [inline]`

Builds a set from an initializer\_list.

**Parameters**

*\_\_l* An initializer\_list. \
 *\_\_comp* A comparison functor. \
 *\_\_a* An allocator object.

Create a set consisting of copies of the elements in the list. This is linear in N if the list is already sorted, and NlogN otherwise (where N is *\_\_l.size()*).

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set (const allocator\_type & \_\_a)` [inline]`, ` [explicit]`

Allocator-extended default constructor.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set (const set\< \_Key, \_Compare, \_Alloc \> & \_\_x, const \_\_type\_identity\_t\< allocator\_type \> & \_\_a)` [inline]`

Allocator-extended copy constructor.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set (set\< \_Key, \_Compare, \_Alloc \> && \_\_x, const \_\_type\_identity\_t\< allocator\_type \> & \_\_a)` [inline]`, ` [noexcept]`

Allocator-extended move constructor.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::set (initializer\_list\< value\_type \> \_\_l, const allocator\_type & \_\_a)` [inline]`

Allocator-extended initialier-list constructor.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_InputIterator \> std::set\< \_Key, \_Compare, \_Alloc \>::set (\_InputIterator \_\_first, \_InputIterator \_\_last, const allocator\_type & \_\_a)` [inline]`

Allocator-extended range constructor.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::set\< \_Key, \_Compare, \_Alloc \>::~set ()` [default]`

The dtor only erases the elements, and note that if the elements themselves are pointers, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

## Member Function Documentation

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::begin () const` [inline]`, ` [noexcept]`

Returns a read-only (constant) iterator that points to the first element in the set. Iteration is done in ascending order according to the keys.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::cbegin () const` [inline]`, ` [noexcept]`

Returns a read-only (constant) iterator that points to the first element in the set. Iteration is done in ascending order according to the keys.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::cend () const` [inline]`, ` [noexcept]`

Returns a read-only (constant) iterator that points one past the last element in the set. Iteration is done in ascending order according to the keys.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> void std::set\< \_Key, \_Compare, \_Alloc \>::clear ()` [inline]`, ` [noexcept]`

Erases all elements in a set. Note that this function only erases the elements, and that if the elements themselves are pointers, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::contains (const \_Kt & \_\_x) const -\> decltype(\_M\_t.\_M\_find\_tr(\_\_x), void(), true)

	` [inline]`"

Finds whether an element with the given key exists.

**Parameters**

*\_\_x* Key of elements to be located.

**Returns**

True if there is an element with the specified key.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> bool std::set\< \_Key, \_Compare, \_Alloc \>::contains (const key\_type & \_\_x) const` [inline]`

Finds whether an element with the given key exists.

**Parameters**

*\_\_x* Key of elements to be located.

**Returns**

True if there is an element with the specified key.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::count (const \_Kt & \_\_x) const -\> decltype(\_M\_t.\_M\_count\_tr(\_\_x))

	` [inline]`"

Finds the number of elements.

**Parameters**

*\_\_x* Element to located.

**Returns**

Number of elements with specified key.

This function only makes sense for multisets; for set the result will either be 0 (not present) or 1 (present).

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> size\_type std::set\< \_Key, \_Compare, \_Alloc \>::count (const key\_type & \_\_x) const` [inline]`

Finds the number of elements.

**Parameters**

*\_\_x* Element to located.

**Returns**

Number of elements with specified key.

This function only makes sense for multisets; for set the result will either be 0 (not present) or 1 (present).

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> reverse\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::crbegin () const` [inline]`, ` [noexcept]`

Returns a read-only (constant) iterator that points to the last element in the set. Iteration is done in descending order according to the keys.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> reverse\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::crend () const` [inline]`, ` [noexcept]`

Returns a read-only (constant) reverse iterator that points to the last pair in the set. Iteration is done in descending order according to the keys.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename... \_Args\> std::pair\< iterator, bool \> std::set\< \_Key, \_Compare, \_Alloc \>::emplace (\_Args &&... \_\_args)` [inline]`

Attempts to build and insert an element into the set.

**Parameters**

*\_\_args* Arguments used to generate an element.

**Returns**

A pair, of which the first element is an iterator that points to the possibly inserted element, and the second is a bool that is true if the element was actually inserted.

This function attempts to build and insert an element into the set. A set relies on unique keys and thus an element is only inserted if it is not already present in the set.

Insertion requires logarithmic time.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename... \_Args\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::emplace\_hint (const\_iterator \_\_pos, \_Args &&... \_\_args)` [inline]`

Attempts to insert an element into the set.

**Parameters**

*\_\_pos* An iterator that serves as a hint as to where the element should be inserted. \
 *\_\_args* Arguments used to generate the element to be inserted.

**Returns**

An iterator that points to the element with key equivalent to the one generated from *\_\_args* (may or may not be the element itself).

This function is not concerned about whether the insertion took place, and thus does not return a boolean like the single-argument emplace() does. Note that the first parameter is only a hint and can potentially improve the performance of the insertion process. A bad hint would cause no gains in efficiency.

For more on *hinting*, see: https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert\_hints

Insertion requires logarithmic time (if the hint is not taken).

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> bool std::set\< \_Key, \_Compare, \_Alloc \>::empty () const` [inline]`, ` [noexcept]`

Returns true if the set is empty.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::end () const` [inline]`, ` [noexcept]`

Returns a read-only (constant) iterator that points one past the last element in the set. Iteration is done in ascending order according to the keys.

Referenced by **std::set\< \_Key, \_Compare, \_Alloc \>::extract()**.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::equal\_range (const \_Kt & \_\_x) -\> decltype(pair\<iterator, iterator\>(\_M\_t.\_M\_equal\_range\_tr(\_\_x)))

	` [inline]`"

Finds a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Pair of iterators that possibly points to the subsequence matching given key.

This function is equivalent to

```
std::make_pair(c.lower_bound(val),
               c.upper_bound(val))
```

 (but is faster than making the calls separately).

This function probably only makes sense for multisets.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::equal\_range (const \_Kt & \_\_x) const -\> decltype(pair\<iterator, iterator\>(\_M\_t.\_M\_equal\_range\_tr(\_\_x)))

	` [inline]`"

Finds a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Pair of iterators that possibly points to the subsequence matching given key.

This function is equivalent to

```
std::make_pair(c.lower_bound(val),
               c.upper_bound(val))
```

 (but is faster than making the calls separately).

This function probably only makes sense for multisets.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::pair\< iterator, iterator \> std::set\< \_Key, \_Compare, \_Alloc \>::equal\_range (const key\_type & \_\_x)` [inline]`

Finds a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Pair of iterators that possibly points to the subsequence matching given key.

This function is equivalent to

```
std::make_pair(c.lower_bound(val),
               c.upper_bound(val))
```

 (but is faster than making the calls separately).

This function probably only makes sense for multisets.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::pair\< const\_iterator, const\_iterator \> std::set\< \_Key, \_Compare, \_Alloc \>::equal\_range (const key\_type & \_\_x) const` [inline]`

Finds a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Pair of iterators that possibly points to the subsequence matching given key.

This function is equivalent to

```
std::make_pair(c.lower_bound(val),
               c.upper_bound(val))
```

 (but is faster than making the calls separately).

This function probably only makes sense for multisets.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> size\_type std::set\< \_Key, \_Compare, \_Alloc \>::erase (const key\_type & \_\_x)` [inline]`

Erases elements according to the provided key.

**Parameters**

*\_\_x* Key of element to be erased.

**Returns**

The number of elements erased.

This function erases all the elements located by the given key from a set. Note that this function only erases the element, and that if the element is itself a pointer, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> \_GLIBCXX\_ABI\_TAG\_CXX11 iterator std::set\< \_Key, \_Compare, \_Alloc \>::erase (const\_iterator \_\_first, const\_iterator \_\_last)` [inline]`

Erases a \[\_\_first,\_\_last) range of elements from a set.

**Parameters**

*\_\_first* Iterator pointing to the start of the range to be erased.\
 *\_\_last* Iterator pointing to the end of the range to be erased.

**Returns**

The iterator *\_\_last*.

This function erases a sequence of elements from a set. Note that this function only erases the element, and that if the element is itself a pointer, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> \_GLIBCXX\_ABI\_TAG\_CXX11 iterator std::set\< \_Key, \_Compare, \_Alloc \>::erase (const\_iterator \_\_position)` [inline]`

Erases an element from a set.

**Parameters**

*\_\_position* An iterator pointing to the element to be erased.

**Returns**

An iterator pointing to the element immediately following *\_\_position* prior to the element being erased. If no such element exists, end() is returned.

This function erases an element, pointed to by the given iterator, from a set. Note that this function only erases the element, and that if the element is itself a pointer, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> node\_type std::set\< \_Key, \_Compare, \_Alloc \>::extract (const key\_type & \_\_x)` [inline]`

Extract a node.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> node\_type std::set\< \_Key, \_Compare, \_Alloc \>::extract (const\_iterator \_\_pos)` [inline]`

Extract a node.

References **std::set\< \_Key, \_Compare, \_Alloc \>::end()**.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::find (const \_Kt & \_\_x) -\> decltype(iterator{\_M\_t.\_M\_find\_tr(\_\_x)})

	` [inline]`"

Tries to locate an element in a set.

**Parameters**

*\_\_x* Element to be located.

**Returns**

Iterator pointing to sought-after element, or end() if not found.

This function takes a key and tries to locate the element with which the key matches. If successful the function returns an iterator pointing to the sought after element. If unsuccessful it returns the past-the-end ( `end()` ) iterator.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::find (const \_Kt & \_\_x) const -\> decltype(const\_iterator{\_M\_t.\_M\_find\_tr(\_\_x)})

	` [inline]`"

Tries to locate an element in a set.

**Parameters**

*\_\_x* Element to be located.

**Returns**

Iterator pointing to sought-after element, or end() if not found.

This function takes a key and tries to locate the element with which the key matches. If successful the function returns an iterator pointing to the sought after element. If unsuccessful it returns the past-the-end ( `end()` ) iterator.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::find (const key\_type & \_\_x)` [inline]`

Tries to locate an element in a set.

**Parameters**

*\_\_x* Element to be located.

**Returns**

Iterator pointing to sought-after element, or end() if not found.

This function takes a key and tries to locate the element with which the key matches. If successful the function returns an iterator pointing to the sought after element. If unsuccessful it returns the past-the-end ( `end()` ) iterator.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> const\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::find (const key\_type & \_\_x) const` [inline]`

Tries to locate an element in a set.

**Parameters**

*\_\_x* Element to be located.

**Returns**

Iterator pointing to sought-after element, or end() if not found.

This function takes a key and tries to locate the element with which the key matches. If successful the function returns an iterator pointing to the sought after element. If unsuccessful it returns the past-the-end ( `end()` ) iterator.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> allocator\_type std::set\< \_Key, \_Compare, \_Alloc \>::get\_allocator () const` [inline]`, ` [noexcept]`

Returns the allocator object with which the set was constructed.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_InputIterator \> void std::set\< \_Key, \_Compare, \_Alloc \>::insert (\_InputIterator \_\_first, \_InputIterator \_\_last)` [inline]`

A template function that attempts to insert a range of elements.

**Parameters**

*\_\_first* Iterator pointing to the start of the range to be inserted. \
 *\_\_last* Iterator pointing to the end of the range.

Complexity similar to that of the range constructor.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> std::pair\< iterator, bool \> std::set\< \_Key, \_Compare, \_Alloc \>::insert (const value\_type & \_\_x)` [inline]`

Attempts to insert an element into the set.

**Parameters**

*\_\_x* Element to be inserted.

**Returns**

A pair, of which the first element is an iterator that points to the possibly inserted element, and the second is a bool that is true if the element was actually inserted.

This function attempts to insert an element into the set. A set relies on unique keys and thus an element is only inserted if it is not already present in the set.

Insertion requires logarithmic time.

Referenced by **std::set\< \_Key, \_Compare, \_Alloc \>::insert()**.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::insert (const\_iterator \_\_hint, node\_type && \_\_nh)` [inline]`

Re-insert an extracted node.

References **std::move()**.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::insert (const\_iterator \_\_position, const value\_type & \_\_x)` [inline]`

Attempts to insert an element into the set.

**Parameters**

*\_\_position* An iterator that serves as a hint as to where the element should be inserted. \
 *\_\_x* Element to be inserted.

**Returns**

An iterator that points to the element with key of *\_\_x* (may or may not be the element passed in).

This function is not concerned about whether the insertion took place, and thus does not return a boolean like the single-argument insert() does. Note that the first parameter is only a hint and can potentially improve the performance of the insertion process. A bad hint would cause no gains in efficiency.

For more on *hinting*, see: https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert\_hints

Insertion requires logarithmic time (if the hint is not taken).

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> void std::set\< \_Key, \_Compare, \_Alloc \>::insert (initializer\_list\< value\_type \> \_\_l)` [inline]`

Attempts to insert a list of elements into the set.

**Parameters**

*\_\_l* A std::initializer\_list\<value\_type\> of elements to be inserted.

Complexity similar to that of the range constructor.

References **std::set\< \_Key, \_Compare, \_Alloc \>::insert()**.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> insert\_return\_type std::set\< \_Key, \_Compare, \_Alloc \>::insert (node\_type && \_\_nh)` [inline]`

Re-insert an extracted node.

References **std::move()**.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> key\_compare std::set\< \_Key, \_Compare, \_Alloc \>::key\_comp () const` [inline]`

Returns the comparison object with which the set was constructed.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::lower\_bound (const \_Kt & \_\_x) -\> decltype(iterator(\_M\_t.\_M\_lower\_bound\_tr(\_\_x)))

	` [inline]`"

Finds the beginning of a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Iterator pointing to first element equal to or greater than key, or end().

This function returns the first element of a subsequence of elements that matches the given key. If unsuccessful it returns an iterator pointing to the first element that has a greater value than given key or end() if no such element exists.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::lower\_bound (const \_Kt & \_\_x) const -\> decltype(const\_iterator(\_M\_t.\_M\_lower\_bound\_tr(\_\_x)))

	` [inline]`"

Finds the beginning of a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Iterator pointing to first element equal to or greater than key, or end().

This function returns the first element of a subsequence of elements that matches the given key. If unsuccessful it returns an iterator pointing to the first element that has a greater value than given key or end() if no such element exists.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::lower\_bound (const key\_type & \_\_x)` [inline]`

Finds the beginning of a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Iterator pointing to first element equal to or greater than key, or end().

This function returns the first element of a subsequence of elements that matches the given key. If unsuccessful it returns an iterator pointing to the first element that has a greater value than given key or end() if no such element exists.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> const\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::lower\_bound (const key\_type & \_\_x) const` [inline]`

Finds the beginning of a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Iterator pointing to first element equal to or greater than key, or end().

This function returns the first element of a subsequence of elements that matches the given key. If unsuccessful it returns an iterator pointing to the first element that has a greater value than given key or end() if no such element exists.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> size\_type std::set\< \_Key, \_Compare, \_Alloc \>::max\_size () const` [inline]`, ` [noexcept]`

Returns the maximum size of the set.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> set & std::set\< \_Key, \_Compare, \_Alloc \>::operator= (const set\< \_Key, \_Compare, \_Alloc \> &)` [default]`

Set assignment operator. Whether the allocator is copied depends on the allocator traits.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> set & std::set\< \_Key, \_Compare, \_Alloc \>::operator= (initializer\_list\< value\_type \> \_\_l)` [inline]`

Set list assignment operator.

**Parameters**

*\_\_l* An initializer\_list.

This function fills a set with copies of the elements in the initializer list *\_\_l*.

Note that the assignment completely changes the set and that the resulting set's size is the same as the number of elements assigned.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> set & std::set\< \_Key, \_Compare, \_Alloc \>::operator= (set\< \_Key, \_Compare, \_Alloc \> &&)` [default]`

Move assignment operator.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> reverse\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::rbegin () const` [inline]`, ` [noexcept]`

Returns a read-only (constant) iterator that points to the last element in the set. Iteration is done in descending order according to the keys.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> reverse\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::rend () const` [inline]`, ` [noexcept]`

Returns a read-only (constant) reverse iterator that points to the last pair in the set. Iteration is done in descending order according to the keys.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> size\_type std::set\< \_Key, \_Compare, \_Alloc \>::size () const` [inline]`, ` [noexcept]`

Returns the size of the set.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> void std::set\< \_Key, \_Compare, \_Alloc \>::swap (set\< \_Key, \_Compare, \_Alloc \> & \_\_x)` [inline]`, ` [noexcept]`

Swaps data with another set.

**Parameters**

*\_\_x* A set of the same element and allocator types.

This exchanges the elements between two sets in constant time. (It is only swapping a pointer, an integer, and an instance of the `Compare` type (which itself is often stateless and empty), so it should be quite fast.) Note that the global std::swap() function is specialized such that std::swap(s1,s2) will feed to this function.

Whether the allocators are swapped depends on the allocator traits.

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::upper\_bound (const \_Kt & \_\_x) -\> decltype(iterator(\_M\_t.\_M\_upper\_bound\_tr(\_\_x)))

	` [inline]`"

Finds the end of a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Iterator pointing to the first element greater than key, or end().

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> template\<typename \_Kt \> auto std::set\< \_Key, \_Compare, \_Alloc \>::upper\_bound (const \_Kt & \_\_x) const -\> decltype(iterator(\_M\_t.\_M\_upper\_bound\_tr(\_\_x)))

	` [inline]`"

Finds the end of a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Iterator pointing to the first element greater than key, or end().

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> iterator std::set\< \_Key, \_Compare, \_Alloc \>::upper\_bound (const key\_type & \_\_x)` [inline]`

Finds the end of a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Iterator pointing to the first element greater than key, or end().

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> const\_iterator std::set\< \_Key, \_Compare, \_Alloc \>::upper\_bound (const key\_type & \_\_x) const` [inline]`

Finds the end of a subsequence matching given key.

**Parameters**

*\_\_x* Key to be located.

**Returns**

Iterator pointing to the first element greater than key, or end().

### template\<typename \_Key , typename \_Compare = std::less\<\_Key\>, typename \_Alloc = std::allocator\<\_Key\>\> value\_compare std::set\< \_Key, \_Compare, \_Alloc \>::value\_comp () const` [inline]`

Returns the comparison object with which the set was constructed.

## Author

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