Ways to define variables and parameters

Examples

These examples are meant to provide insight into the various ways of defining and using parameters. In many cases they do not illustrate best practices.

\define

\define mp1(a1)  $a1$ - <<__a1__>>

\define mp2() <$parameters a1><<a1>></$parameters>

\define mp3()
\parameters(a1)
<<a1>>
\end

|<<mp1 foo>>|<<mp2 foo>>|<<mp3 foo>>|

$set, $let, $vars

<$set name="sp1" value="<$parameters a1><<a1>></$parameters>">
<$set name="sp2" value="""
\parameters(a1)
<$parameters a1><<a1>></$parameters>
""">
<$vars vp1="<$parameters a1><<a1>></$parameters>" vp2="""
\parameters(a1)
<$parameters a1><<a1>></$parameters>
""">
<$let lp1="<$parameters a1><<a1>></$parameters>" lp2="""
\parameters(a1)
<$parameters a1><<a1>></$parameters>
""">

|<<sp1 foo>>|<<sp2 foo>>|
|<<vp1 foo>>|<<vp2 foo>>|
|<<lp1 foo>>|<<lp2 foo>>|
</$let>
</$vars>
</$set>
</$set>

\procedure, \widget

\procedure pp1(a1)  <<a1>>

\procedure pp2() <$parameters a1><<a1>></$parameters>

\procedure pp3()
\parameters(a1)
<<a1>>
\end

\procedure wp1(a1)  <<a1>>

\widget wp2() <$parameters a1><<a1>></$parameters>

\widget wp3()
\parameters(a1)
<<a1>>
\end

|<<pp1 foo>>|<<pp2 foo>>|<<pp3 foo>>|
|<<wp1 foo>>|<<wp2 foo>>|<<wp3 foo>>|

\function

\function fp1(a1)  [<a1>]
|<<fp1 foo>>|

Behaviour of invoked variables depends on how the variable was declared

Namespaces

• tiddler titles - tiddlers are uniquely identified by their title. The namespace for tiddler titles and variable names are completely separate.
• variables - \define, $set, $let, $vars, \procedure, \widget, \function all create variables. If the same name is used, then later define will overwrite earlier defined
• function filter operator parameter - only variables defined using \function can be called using the function operator
• filter operators - only the javascript defined filter operators and variables defined using \function with name containing a dot can be called
• widgets - variables defined using \widget can be invoked using <$widget/> syntax ONLY if the name starts a dollar sign. Without the dollar sign prefix, defining variables using \widget is no different than using \procedure.