[set.modifiers]

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

## 23.4 Associative containers [[associative]](associative#set.modifiers)

### 23.4.6 Class template set [[set]](set#modifiers)

#### 23.4.6.4 Modifiers [set.modifiers]

[🔗](#lib:insert,set)

`template<class K> constexpr pair<iterator, bool> insert(K&& x);
template<class K> constexpr iterator insert(const_iterator hint, K&& x);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L12955)

*Constraints*: The [*qualified-id*](expr.prim.id.qual#nt:qualified-id "7.5.5.3 Qualified names [expr.prim.id.qual]") Compare​::​is_transparent is valid and denotes a type[.](#1.sentence-1)

For the second overload,is_convertible_v<K&&, const_iterator> andis_convertible_v<K&&, iterator> are both false[.](#1.sentence-2)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L12963)

*Preconditions*: value_type is *Cpp17EmplaceConstructible* into set fromstd​::​forward<K>(x)[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L12968)

*Effects*: If the set already contains an element that is equivalent to x,
there is no effect[.](#3.sentence-1)

Otherwise, let r be equal_range(x)[.](#3.sentence-2)

Constructs an object u of type value_type with std​::​forward<K>(x)[.](#3.sentence-3)

If equal_range(u) == r is false, the behavior is undefined[.](#3.sentence-4)

Inserts u into *this[.](#3.sentence-5)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L12978)

*Returns*: For the first overload,
the bool component of the returned pair is true if and only if the insertion took place[.](#4.sentence-1)

The returned iterator points to the set element that is equivalent to x[.](#4.sentence-2)

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L12985)

*Complexity*: Logarithmic[.](#5.sentence-1)