# Adaptable Unary Function

Category: functors | Component type: concept

### Description

An Adaptable Unary Function is a Unary Function with nested `typedef`s 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

- `negate`
- `identity`
- `pointer_to_unary_function`

### 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 `typedef`s. 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.

### See also

Unary Function, Adaptable Generator, Adaptable Binary Function

Copyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation