Unary Function


Category: functors	Component type: concept

Description

A Unary Function is a kind of function object: an object that is called as if it were an ordinary C++ function. A Unary Function is called with a single argument.

Refinement of

Assignable

Associated types

Argument type	The type of the Unary Function's argument.
Result type	The type returned when the Unary Function is called

Notation

`F`	A type that is a model of Unary Function
`X`	The argument type of `F`
`Result`	The result type of `F`
`f`	Object of type `F`
`x`	Object of type `X`

Definitions

The domain of a Unary Function is the set of all permissible values for its argument.

The range of a Unary Function is the set of all possible values that it may return.

Valid expressions

Name	Expression	Type requirements	Return type
Function call	`f(x)`		`Result`

Expression semantics

Name	Expression	Precondition	Semantics	Postcondition
Function call	`f(x)`	`x` is in `f`'s domain	Calls `f` with `x` as an argument, and returns a value of type `Result` [1]	The return value is in `f`'s range

Complexity guarantees

Invariants

Models

Result (*)(X)

Notes

[1] Two different invocations of f may return different results, even if f is called with the same arguments both times. A Unary Function may refer to local state, perform I/O, and so on. The expression f(x) is permitted to change f's state.