TiddlyWiki5/editions/tw5.com/tiddlers/concepts/Dominant Append.tid

created: 20150123220223000
modified: 20190610165255223
tags: Filters
title: Dominant Append
type: text/vnd.tiddlywiki

[[Filters]] manipulate [[sets of titles|Title Selection]] in which no title may appear more than once. Furthermore, they often need to append one such set to another.

This is done in such a way that, if a title would be duplicated, the earlier copy of that title is discarded. The titles being appended are dominant.

For example, if a selection contains `Andrew Becky Clara Daniel` and `Andrew Barney Clara Daisy` is then appended to it, the result is `Becky Daniel Andrew Barney Clara Daisy`.

This behaviour can cause unexpected results when working with [[Mathematics Operators]]. For example, `1 2 3 +[sum[]]` evaluates to `6`, as expected. But `1 1 1 +[sum[]]` evaluates to `1`. Removing the `+[sum[]]` from each filter reveals the problem: `1 2 3` evaluates to the list `1`, `2`, `3`, while `1 1 1` evaluates to the single item `1` due to de-duplication.

In such situations, the `=` prefix can be used to disable the de-duplication. For example, `=1 =1 =1 +[sum[]]` evaluates to `3` as expected. Alternatively, the [[split Operator]] can be used: `[[1,1,1]split[,]sum[]]`.
Overhaul the filter operator documentation: part 2 2015-01-24 21:18:44 +00:00			`created: 20150123220223000`
Add support for `=` prefix for filter runs that doesn't remove duplicates 2019-06-10 16:54:20 +00:00			`modified: 20190610165255223`
Documentation updates Adding “Story River” to the “Concepts” category, and doing some clean-up of other entries in the category by moving some concepts to become sub-concepts in the TOC 2015-09-18 08:19:21 +00:00			`tags: Filters`
Overhaul the filter operator documentation: part 1 2015-01-18 18:39:00 +00:00			`title: Dominant Append`
			`type: text/vnd.tiddlywiki`

Overhaul the filter operator documentation: part 2 2015-01-24 21:18:44 +00:00			`[[Filters]] manipulate [[sets of titles\|Title Selection]] in which no title may appear more than once. Furthermore, they often need to append one such set to another.`
Overhaul the filter operator documentation: part 1 2015-01-18 18:39:00 +00:00
Overhaul the filter operator documentation: part 2 2015-01-24 21:18:44 +00:00			`This is done in such a way that, if a title would be duplicated, the earlier copy of that title is discarded. The titles being appended are dominant.`
Overhaul the filter operator documentation: part 1 2015-01-18 18:39:00 +00:00
Overhaul the filter operator documentation: part 2 2015-01-24 21:18:44 +00:00			For example, if a selection contains `Andrew Becky Clara Daniel` and `Andrew Barney Clara Daisy` is then appended to it, the result is `Becky Daniel Andrew Barney Clara Daisy`.
Add support for `=` prefix for filter runs that doesn't remove duplicates 2019-06-10 16:54:20 +00:00
			This behaviour can cause unexpected results when working with [[Mathematics Operators]]. For example, `1 2 3 +[sum[]]` evaluates to `6`, as expected. But `1 1 1 +[sum[]]` evaluates to `1`. Removing the `+[sum[]]` from each filter reveals the problem: `1 2 3` evaluates to the list `1`, `2`, `3`, while `1 1 1` evaluates to the single item `1` due to de-duplication.

			In such situations, the `=` prefix can be used to disable the de-duplication. For example, `=1 =1 =1 +[sum[]]` evaluates to `3` as expected. Alternatively, the [[split Operator]] can be used: `[[1,1,1]split[,]sum[]]`.