TiddlyWiki5/editions/test/tiddlers/tests/data/globals/ProceduresWithConditionalDefinitions.tid

title: Globals/ProceduresWithConditionalDefinitions
description: Global procedures with conditional definitions to allow overriding
type: text/vnd.tiddlywiki-multiple
tags: [[$:/tags/wiki-test-spec]]

title: Output

\whitespace trim

<<this-is-one>>|<<this-is-one blah>>~
<$let example="TWO"><<this-is-one>>|<<this-is-one blah>></$let>
+
title: $:/global/this-is-one

\whitespace trim

\?procedure example()
ONE
\end

\parameters (foo:"nothing")
<<example>>-<$text text=<<foo>>/>
+
title: ExpectedResult

<p>ONE-nothing|ONE-blah~TWO-nothing|TWO-blah</p>
Introduce true global variables The basic idea is that if we don't find a variable `foo` then we fallback to retrieving the value from the tiddler `$:/global/foo`, if it exists. This allows us to replace the usual importvariables-based mechanism for global definitions, avoiding cluttering up the variable namespace with every macro. In order to permit subprocedures to be overridden, we also introduce a mechanism for conditional definitions: preceding the word definition\|procedure\|function\|widget with a + causes the definition only to occur if the specified variable doesn't already exist. In the next commit we'll apply this mechanism to the tabs macro 2022-05-28 11:23:50 +00:00			`title: Globals/ProceduresWithConditionalDefinitions`
			`description: Global procedures with conditional definitions to allow overriding`
			`type: text/vnd.tiddlywiki-multiple`
			`tags: [[$:/tags/wiki-test-spec]]`

			`title: Output`

			`\whitespace trim`

			`<<this-is-one>>\|<<this-is-one blah>>~`
			`<$let example="TWO"><<this-is-one>>\|<<this-is-one blah>></$let>`
			`+`
			`title: $:/global/this-is-one`

			`\whitespace trim`

Change to `?` for conditional definitions 2022-05-28 12:49:02 +00:00			`\?procedure example()`
Introduce true global variables The basic idea is that if we don't find a variable `foo` then we fallback to retrieving the value from the tiddler `$:/global/foo`, if it exists. This allows us to replace the usual importvariables-based mechanism for global definitions, avoiding cluttering up the variable namespace with every macro. In order to permit subprocedures to be overridden, we also introduce a mechanism for conditional definitions: preceding the word definition\|procedure\|function\|widget with a + causes the definition only to occur if the specified variable doesn't already exist. In the next commit we'll apply this mechanism to the tabs macro 2022-05-28 11:23:50 +00:00			`ONE`
			`\end`

			`\parameters (foo:"nothing")`
			`<<example>>-<$text text=<<foo>>/>`
			`+`
			`title: ExpectedResult`

			`<p>ONE-nothing\|ONE-blah~TWO-nothing\|TWO-blah</p>`