created: 20221009124003601
modified: 20240422084850412
tags: Concepts [[Core Functions]]
title: Functions
type: text/vnd.tiddlywiki

!! Introduction

<<.from-version "5.3.0">> A <<.def function>> is a named snippet of text containing a [[Filter Expression]]. Functions can have named parameters which are available within the function as variables.

Functions are usually defined with the [[Pragma: \function]]:

```
\function myfun(param:"2")
[<param>multiply[1.5]]
\end
```

Functions can be invoked in several ways:

* Directly transclude functions with the syntax `<<myfun param:"value">>`
* Assign functions to widget attributes with the syntax `<div class=<<myfun param:"value">>>`
* Invoke functions via the [[function Operator]] with the syntax `[function[myfun],[value],...]`
* Directly invoke functions whose names contain a period as custom filter operators with the syntax `[my.fun[value]]` or `[.myfun[value]]`

!! How Functions Work

Functions are implemented as a special kind of [[variable|Variables]]. The only thing that distinguishes them from ordinary variables is the way that the parameters are handled.