#### 1.3.5.1 A Sample Function Description

In a function description, the name of the function being described appears first. It is followed on the same line by a list of parameters. The names used for the parameters are also used in the body of the description.

After all of the calling forms have been enumerated, the next line is a concise one-sentence summary of the function.

After the summary there may be documentation on the inputs and outputs, examples of function usage, notes about the algorithm used, and references to related functions.

Here is a description of an imaginary function `foo`:

Function File: foo (x)
Function File: foo (x, y)
Function File: foo (x, y, …)

The function `foo` subtracts x from y, then adds the remaining arguments to the result.

If y is not supplied, then the number 19 is used by default.

Example:

```foo (1, [3, 5], 3, 9)
⇒ [ 14, 16 ]
foo (5)
⇒ 14
```

More generally,

```foo (w, x, y, …)
≡
x - w + y + …
```

Any parameter whose name contains the name of a type (e.g., integer or matrix) is expected to be of that type. Parameters named object may be of any type. Parameters with other sorts of names (e.g., new_file) are discussed specifically in the description of the function. In some sections, features common to parameters of several functions are described at the beginning.

Functions in Octave may be defined in several different ways. The category name for functions may include a tag that indicates the way that the function is defined. These additional tags include

Function File

The function described is defined using Octave commands stored in a text file. See Function Files.

Built-in Function

The function described is written in a language like C++, C, or Fortran, and is part of the compiled Octave binary.

The function described is written in a language like C++, C, or Fortran. On systems that support dynamic linking of user-supplied functions, it may be automatically linked while Octave is running, but only if it is needed. See External Code Interface.

Mapping Function

The function described works element-by-element for matrix and vector arguments.