Standard Template Library Programmer's Guide

Public base classes

unary_function<T, bool>

Members

Member	Where defined	Description
argument_type	Adaptable Unary Function	The type of the second argument: T
result_type	Adaptable Unary Function	The type of the result: bool
bool operator()(const T& x) const	Unary Function Function call operator.	The return value is !x.
logical_not()	Default Constructible	The default constructor.

See also

The function object overview, logical_or, logical_and.

Generalized identity operations

identity<T>

Category: functors

Component type: type

Description

Identity is a Unary Function that represents the identity function: it takes a single argument x, and returns x.

Example

int main() {
 int x = 137;
 identity<int> id;
 assert(x == id(x));
}

Definition

Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h. This class is an SGI extension; it is not part of the C++ standard.

Template parameters

Parameter	Description
T	The function object's argument type, and return type. [1]

Model of

Adaptable Unary Function

Type requirements

None.

Public base classes

unary_function<T, T>

Members

Member	Where defined	Description
argument_type	Adaptable Unary Function	The type of identity's argument: T.
result_type	Adaptable Unary Function	The type of the result: T. [1]
const T& operator()(const T&) const	Adaptable Unary Function	Function call. The return value is simply the argument.

New members

All of identity's members are defined in the Adaptable Unary Function