`<utility>`

Article
11/15/2024

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

Requirements

Header: <utility>

Namespace: std

Remarks

Pairs are widely used in the C++ Standard Library. They're required both as the arguments and return values for various functions and as element types for associative containers like map and multimap.

Members

Classes

Type	Description
`chars_format`	Floating-point format for primitive numerical conversion.
`tuple_element`	Wraps the type of a `pair` element.
`tuple_size`	Wraps a `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 isn't 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`, `in_place_type_t`, `in_place_index_t`	Indicates how to create an object in place.
`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`.

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