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Clarify opposite handling of de-duplication order for unique Operator vs Dominant Append (#8357)

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springerspandrel 2024-07-09 11:34:18 -04:00 committed by GitHub
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editions/tw5.com/tiddlers/concepts/Dominant Append.tid
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@ -1,5 +1,5 @@
created: 20150123220223000 created: 20150123220223000
modified: 20190610165255223 modified: 20240709151004998
tags: Filters tags: Filters
title: Dominant Append title: Dominant Append
type: text/vnd.tiddlywiki type: text/vnd.tiddlywiki
@ -13,3 +13,5 @@ For example, if a selection contains `Andrew Becky Clara Daniel` and `Andrew Bar
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. 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[]]`. 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[]]`.
<<.tip """To build a list of unique values that retains only the <<.em earliest>> copy of each value (the opposite behavior from <<.link "Dominant Append" "Dominant Append">>), first use the <<.link `:all` "All Filter Run Prefix">> filter run prefix (or its short form `=`) to retain all duplicate values while building your list. Then finish your filter run with the <<.olink unique>> operator" to remove later duplicates.""">>

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editions/tw5.com/tiddlers/filters/unique.tid
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@ -1,4 +1,6 @@
caption: unique caption: unique
created: 20240709151018238
modified: 20240709151336906
op-input: a list of items op-input: a list of items
op-output: a list of unique items op-output: a list of unique items
op-parameter: ignored op-parameter: ignored
@ -7,4 +9,6 @@ tags: [[Filter Operators]] [[Order Operators]] [[Listops Operators]]
title: unique Operator title: unique Operator
type: text/vnd.tiddlywiki type: text/vnd.tiddlywiki
<<.note """Unlike the default <<.link "Dominant Append" "Dominant Append">> handling of duplication, the effect of <<.op unique>> is to retain only the <<.em earliest>> instance among duplicated values.""">>
<<.operator-examples "unique">> <<.operator-examples "unique">>