created: 20201214044413473
modified: 20230711090833212
tags: [[Filter Run Prefix]]
title: Named Filter Run Prefix
type: text/vnd.tiddlywiki

In <<.from-version "5.1.23">> the named filter run prefixes where implemented. `:cascade`, `:map` and `:sort` have been added later as shown in the diagrams.

A named filter run prefix can precede any [[run|Filter Run]] of a [[filter expression|Filter Expression]] in place of a [[shortcut run prefix|Shortcut Filter Run Prefix]].

<$railroad text="""
\start none
\end none
(
[[<":all"> |"All Filter Run Prefix"]] |
[[<":and"> |"And Filter Run Prefix"]] |
[[<":cascade">  /"v5.2.1"/  |"Cascade Filter Run Prefix"]] |
[[<":else"> |"Else Filter Run Prefix"]] |
[[<":except"> |"Except Filter Run Prefix"]] |
[[<":filter"> |"Filter Filter Run Prefix"]] |
[[<":intersection"> |"Intersection Filter Run Prefix"]] |
[[<":map">  /"v5.2.0"/ |"Map Filter Run Prefix"]] |
[[<":or"> |"Or Filter Run Prefix"]] |
[[<":reduce"> |"Reduce Filter Run Prefix"]] |
[[<":sort">  /"v5.2.0"/ |"Sort Filter Run Prefix"]] |
[[<":then">  /"v5.3.0"/ |"Then Filter Run Prefix"]]) [[run|"Filter Run"]]
"""/>


<<.tip "Compare named filter run prefix `:filter` with [[filter Operator]] which applies a subfilter to every input title, removing the titles that return an empty result from the subfilter">>

<<.tip "Compare named filter run prefix `:reduce` with [[reduce Operator]] which is used to used to flatten a list of items down to a single item by repeatedly applying a subfilter">> 

<<.tip """Within the filter runs prefixed with `:reduce`, `:sort`, `:map` and `:filter`, the <<.var currentTiddler>> variable is set to the title of the tiddler being processed.<br>The value of currentTiddler outside the subfilter is available in the variable <<.var "..currentTiddler">> <<.from-version "5.2.0">>""" >>

Also see: [[Interchangeable Filter Run Prefixes]]