TiddlyWiki5/editions/tw5.com/tiddlers/pragmas/Pragma_ _define.tid

created: 20220917112233317
modified: 20230419103154328
tags: Pragmas
title: Pragma: \define
type: text/vnd.tiddlywiki

The ''\define'' [[pragma|Pragmas]] is used to [[define macros|Macro Definitions]]. It is a shortcut syntax for the SetVariableWidget.

The usual form allows macros to span multiple lines.

```
\define <macro-name>(<param-name>[:<param-default-value>],<param-name>[:<param-default-value>]...)
<multiple-line-definition-text>
\end [<macro-name>]
```

Note that the `\end` marker can optionally specify the name of the macro to which it relates which allows macro definitions to be nested.

There is also a single line form for shorter macros:

```
\define <macro-name>(<param-name>[:<param-default-value>],<param-name>[:<param-default-value>]...) <single-line-definition-text>
```

The first line of the definition specifies the macro name and any parameters. Each parameter has a name and, optionally, a default value that is used if no value is supplied on a particular call to the macro.

The lines that follow contain the text of the macro text (i.e. the snippet represented by the macro name), until `\end` appears on a line by itself:

<$codeblock code={{$:/editions/tw5.com/macro-examples/say-hi}}/>

Alternatively, the entire definition can be presented on a single line without an `\end` marker:

```
\define sayhi(name:"Bugs Bunny") Hi, I'm $name$.
```

Macro definitions can be nested by specifying the name of the macro in the `\end` marker. For example:

<<wikitext-example-without-html src:"""\define special-button(caption:"Click me")
\define actions()
<$action-sendmessage $message="tm-notify" $param="HelloThere"/>
\end actions
<$button actions=<<actions>>>
$caption$
</$button>
\end special-button

<<special-button>>
""">>

A more formal [[presentation|Macro Definition Syntax]] of this syntax is also available.