Binary Function


Category: functors	Component type: concept

Description

A Binary Function is a kind of function object: an object that is called as if it were an ordinary C++ function. A Binary Function is called with two arguments.

Refinement of

Assignable

Associated types

First argument type	The type of the Binary Function's first argument.
Second argument type	The type of the Binary Function's second argument.
Result type	The type returned when the Binary Function is called

Notation

`F`	A type that is a model of BinaryFunction
`X`	The first argument type of `F`
`Y`	The second argument type of `F`
`Result`	The result type of `F`
`f`	Object of type `F`
`x`	Object of type `X`
`y`	Object of type `Y`

Definitions

The domain of a Binary Function is the set of all ordered pairs (x, y) that are permissible values for its arguments.

The range of a Binary Function is the set of all possible value that it may return.

Valid expressions

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

Expression semantics

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

Complexity guarantees

Invariants

Models

Result (*)(X,Y)

Notes

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