`<utility>`

Article
12/07/2021

Defines C++ Standard Library types, functions, and operators that help to construct and manage pairs of objects, which are useful whenever two objects need to be treated as if they were one.

Requirements

Header: <utility>

Namespace: std

Remarks

Pairs are widely used in the C++ Standard Library. They are required both as the arguments and return values for various functions and as element types for containers such as map class and multimap class. The <utility> header is automatically included by <map> to assist in managing their key/value pair type elements.

Note

The <utility> header uses the statement #include <initializer_list>. It also refers to class tuple as defined in <tuple>.

Members

Classes

Type	Description
chars_format	Floating-point format for primitive numerical conversion.
tuple_element	A class that wraps the type of a `pair` element.
tuple_size	A class that wraps `pair` element count.

Objects

Template	Description
index_sequence	An alias template defined for the common case where `T` is `std::size_t`
index_sequence_for	Helper alias template to convert any type parameter pack into an index sequence of the same length
make_index_sequence	Helper alias template to simplify the creation of a `std::index_sequence` type.
make_integer_sequence	Helper alias template to simplify the creation of a `std::integer_sequence` type.

Functions

Function	Description
as_const	Returns type.
declval	Shorthand expression evaluation.
exchange	Assigns a new value to an object and returns its old value.
forward	Preserves the reference type (either `lvalue` or `rvalue`) of the argument from being obscured by perfect forwarding.
from_chars
get	A function that gets an element from a `pair` object.
make_pair	A template helper function used to construct objects of type `pair`, where the component types are based on the data types passed as parameters.
move	Returns the passed in argument as an `rvalue` reference.
move_if_noexcept
swap	Exchanges the elements of two `pair` objects.
to_chars	Converts value into a character string.

Operators

Operator	Description
operator!=	Tests if the pair object on the left side of the operator is not equal to the pair object on the right side.
operator==	Tests if the pair object on the left side of the operator is equal to the pair object on the right side.
operator<	Tests if the pair object on the left side of the operator is less than the pair object on the right side.
operator<=	Tests if the pair object on the left side of the operator is less than or equal to the pair object on the right side.
operator>	Tests if the pair object on the left side of the operator is greater than the pair object on the right side.
operator>=	Tests if the pair object on the left side of the operator is greater than or equal to the pair object on the right side.

Structs

Struct	Description
from_chars_result	A struct used for `from_chars`.
identity	A struct that provides a type definition as the template parameter.
in_place_t	Also includes structs `in_place_type_t` and `in_place_index_t`.
integer_sequence	Represents an integer sequence.
pair	A type that provides for the ability to treat two objects as a single object.
piecewise_construct_t	A type used to keep separate constructor and function overloading.
to_chars_result	A struct used for `to_chars`.