TiddlyWiki5/editions/tw5.com/tiddlers/wikitext/Conditional Shortcut Syntax.tid

created: 20230901122740573
modified: 20230901123102263
tags: WikiText
title: Conditional Shortcut Syntax
type: text/vnd.tiddlywiki

<<.from-version "5.3.2">> The conditional shortcut syntax provides a convenient way to express if-then-else logic within WikiText. It evaluates a [[filter expression|Filter Expression]] and considers the condition to be true if there is at least one result (regardless of the value of that result).

Within an "if" or "elseif" clause, the variable `condition` contains the value of the first result of evaluating the filter condition.

A simple example:

<$macrocall $name='wikitext-example-without-html'
src='<% if [{$:/info/url/protocol}match[file:]] %>
  Loaded from a file URI
<% else %>
  Not loaded from a file URI
<% endif %>
'/>

One or more `<% elseif %>` clauses may be included before the `<% else %>` clause:

<$macrocall $name='wikitext-example-without-html'
src='<% if [{$:/info/url/protocol}match[file:]] %>
  Loaded from a file URI
<% elseif [{$:/info/url/protocol}match[https:]] %>
  Loaded from an HTTPS URI
<% elseif [{$:/info/url/protocol}match[http:]] %>
  Loaded from an HTTP URI
<% else %>
  Loaded from an unknown protocol
<% endif %>
'/>

The conditional shortcut syntax can be nested:

<$macrocall $name='wikitext-example-without-html'
src='\procedure test(animal)
<% if [<animal>match[Elephant]] %>
  It is an elephant
<% else %>
  <% if [<animal>match[Giraffe]] %>
    It is a giraffe
  <% else %>
    It is completely unknown
  <% endif %>
<% endif %>
\end

<<test "Giraffe">>

<<test "Elephant">>

<<test "Antelope">>
'/>

Notes:

* Clauses are parsed in inline mode by default. Force block mode parsing by following the opening `<% if %>`, `<% elseif %>` or `<% else %>` with two line breaks
* Widgets and HTML elements must be within a single conditional clause; it is not possible to start an element in one conditional clause and end it in another
* The conditional shortcut syntax cannot contain pragmas such as procedure definitions