# (Function | Operator | Map | Mapping | Transformation | Method | Rule | Task | Subroutine)

### Table of Contents

## About

Section about computable function.

A function is a callable unit that may be called:

- a procedure,
- a subrontine
- a routine,
- a method (belong to an object)
- a subprogram
- a task
- a map
- a mapping
- a transformation
- a macro

A function is computable if there exists an algorithm that can do the job of the function.

A function is a reusable block (section|chunk) of code written that:

- accepts arguments as input,
- performs a specific task,
- and returns some other information as output.

Catalog and type of function that you can meet in any development language.

See also:

In real life, all functions are continuous and smooth.

The clarity of examples, and the software’s decipherability and debuggability in the real world, are likely far more important. Form must communicate function.

Functions that take many arguments are obviously bad design. Named properties can be enhanced by using method chaining and single-argument getter-setter methods.

Function property. See (Function|Operator) - Algebraic (Laws|properties) - Axioms

The concept of function is defined as a special kind of binary relation.

## Articles Related

## Syntax

`input -> Rule -> Output`

where rule:

## Declaration

A function declaration has generally:

- a name,
- a list of parameters called a signature,
- an optional list of results,
- and the function body, which contains the statements that define what the function does.

## Execution

Execution of the function begins with the first statement and continues until it encounters a return statement or reaches the end of a function that has no results. Control and any results are then returned to the caller.

## Parallel

## Type

### User Defined Functions (UDF)

### Analytics Function

### Time serie function

### Aggregate functions

Aggregate functions return a single value, calculated from values in a column.

### Scalar functions

### Deterministic function

Did they return always the same result ? deterministic properties