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Standard Template Library Programmer's Guide
(document number: 007-3426-004 / published: 1999-05-21) table of contents | additional info | download
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Adaptable Unary Function


Category: functors	Component type: concept

Description

An Adaptable Unary Function is a Unary Function with nested typedefs that define its argument type and result type. [1] [2] These nested typedef make it possible to use function object adaptors.

Refinement of

Unary Function

Associated types

Argument type	`F::argument_type`	The type of `F`'s argument
Result type	`F::result_type`	The type returned when the Unary Function is called

Notation

`F`	A type that is a model of Unary Function

Definitions

Valid expressions

None, except for those defined by Unary Function

Expression semantics

Complexity guarantees

Invariants

Models

Notes

[1] Note the implication of this: a function pointer T (*f)(X) is a Unary Function, but not an Adaptable Unary Function: the expressions f::argument_type and f::result_type are nonsensical.

[2] When you define a class that is a model of Adaptable Unary Function, you must provide these typedefs. The easiest way to do this is to derive the class from the base class unary_function. This is an empty class, with no member functions or member variables; the only reason it exists is to make defining Adaptable Unary Functions more convenient. Unary_function is very similar to the base classes used by the iterator tag functions.