created: 20140410103123179
modified: 20210830010231559
tags: Filters
title: Filter Operators
type: text/vnd.tiddlywiki

\define .operator-rows(filter)
<$list filter="$filter$"><tr>
<td><$link>{{!!caption}}</$link></td>
<td>{{!!op-purpose}}</td>
<td align="center"><$list filter="[all[current]tag[Common Operators]]">✓</$list></td>
<td align="center"><$list filter="[all[current]tag[Negatable Operators]]">`!`</$list></td>
</tr></$list>
\end

\define .group-heading(_)
<tr class="doc-table-subheading"><th colspan="4" align="center">$_$</th></tr>
\end

A <<.def "filter operator">> is a predefined keyword attached to an individual [[step|Filter Step]] of a [[filter|Filters]]. It defines the particular action of that step.

''Important:'' Each first [[step|Filter Step]] of a [[filter run|Filter Run]] not given any input titles receives the output of <$link to="all Operator">[all[tiddlers]]</$link> as its input.

The following table lists all core operators, the most common ones marked ✓. The last column indicates whether an operator allows ''negation'' using the <$link to="Filter Step"><code>!</code> prefix</$link>. For specifics as to each operator's negated output please refer to its documentation.

<table>
<tr>
<th align="left">Operator</th>
<th align="left">Purpose</th>
<th align="center">✓</th>
<th align="center">`!`</th>
</tr>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]!tag[Mathematics Operators]!tag[String Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Order Operators">>
<<.operator-rows "[tag[Filter Operators]tag[Order Operators]!tag[Listops Operators]!tag[Mathematics Operators]!tag[String Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Listops Operators">>
<<.operator-rows "[tag[Filter Operators]tag[Listops Operators]tag[Order Operators]!tag[Mathematics Operators]!tag[String Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "String Operators">>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]tag[String Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Mathematics Operators">>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]tag[Mathematics Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Tag Operators">>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]!tag[Mathematics Operators]!tag[String Operators]tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Special Operators">>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]!tag[Mathematics Operators]!tag[String Operators]!tag[Tag Operators]tag[Special Operators]sort[]]">>
</table>

A typical step is written as `[operator[parameter]]`, although not all of the operators need a [[parameter|Filter Parameter]].

Most steps process the [[selection of titles|Title Selection]] that are supplied as their input, but a few [[construct an entirely new selection|Selection Constructors]] instead. For the exact rules, see [[Filter Syntax]].