Add support for `=` prefix for filter runs that doesn't remove duplicates

core/modules/filters.js

@@ -119,7 +119,7 @@ exports.parseFilter = function(filterString) {
 		p = 0, // Current position in the filter string
 		match;
 	var whitespaceRegExp = /(\s+)/mg,
-		operandRegExp = /((?:\+|\-|~)?)(?:(\[)|(?:"([^"]*)")|(?:'([^']*)')|([^\s\[\]]+))/mg;
+		operandRegExp = /((?:\+|\-|~|=)?)(?:(\[)|(?:"([^"]*)")|(?:'([^']*)')|([^\s\[\]]+))/mg;
 	while(p < filterString.length) {
 		// Skip any whitespace
 		whitespaceRegExp.lastIndex = p;
@@ -248,6 +248,10 @@ exports.compileFilter = function(filterString) {
 					return function(results,source,widget) {
 						$tw.utils.pushTop(results,operationSubFunction(source,widget));
 					};
+				case "=": // The results of the operation are pushed into the result without deduplication
+					return function(results,source,widget) {
+						Array.prototype.push.apply(results,operationSubFunction(source,widget));
+					};
 				case "-": // The results of this operation are removed from the main result
 					return function(results,source,widget) {
 						$tw.utils.removeArrayEntries(results,operationSubFunction(source,widget));

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

@@ -1,5 +1,5 @@
 created: 20150123220223000
-modified: 20150917193646675
+modified: 20190610165255223
 tags: Filters
 title: Dominant Append
 type: text/vnd.tiddlywiki
@@ -9,3 +9,7 @@ type: text/vnd.tiddlywiki
 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[]]`.

editions/tw5.com/tiddlers/filters/syntax/Filter Expression.tid

@@ -1,5 +1,5 @@
 created: 20150124182421000
-modified: 20181120125803533
+modified: 20190610165329062
 tags: [[Filter Syntax]]
 title: Filter Expression
 type: text/vnd.tiddlywiki
@@ -7,7 +7,7 @@ type: text/vnd.tiddlywiki
 <$railroad text="""
 [{:
   [: [[whitespace|"Filter Whitespace"]] ]
-  ("+"|"~"|:-|"-")
+  ("+"|"~"|:-|"-"|"=")
   [[run|"Filter Run"]]
 }]
 """/>
@@ -17,6 +17,7 @@ A <<.def "filter expression">> is the outermost level of the [[filter syntax|Fil
 If a run has:
 
 * no prefix, its output titles are [[dominantly appended|Dominant Append]] to the filter's output
+* <<.from-version "5.1.20">> the prefix `=`, output titles are appended to the filter's output without de-duplication
 * the prefix `-`, output titles are <<.em removed>> from the filter's output (if such tiddlers exist)
 * the prefix `+`, it receives the filter output so far as its input; its output then <<.em "replaces">> all filter ouput so far and forms the input for the next run
 * <<.from-version "5.1.18">> the prefix `~`, if the filter output so far is an empty list then the output titles of the run are [[dominantly appended|Dominant Append]] to the filter's output. If the filter output so far is not an empty list then the run is ignored
@@ -24,7 +25,8 @@ If a run has:
 In technical / logical terms:
 
 |!Run |!Interpretation |!Output |
-|`run` |union of sets |... OR run |
+|`run` |de-duplicated union of sets |... OR run |
+|`=run` |union of sets without de-duplication |... OR run |
 |`+run` |intersection of sets |... AND run |
 |`-run` |difference of sets |... AND NOT run |
 |`~run` |else |... ELSE run |
@@ -32,7 +34,7 @@ In technical / logical terms:
 The input of a run is normally a list of all the non-[[shadow|ShadowTiddlers]] tiddler titles in the wiki (in no particular order). But the `+` prefix can change this:
 
 |Prefix|Input|h
-|`-`, `~` or none| <$link to="all Operator">`[all[]]`</$link> tiddler titles, unless otherwise determined by the first [[filter operator|Filter Operators]]|
+|`-`, `~`, `=` or none| <$link to="all Operator">`[all[]]`</$link> tiddler titles, unless otherwise determined by the first [[filter operator|Filter Operators]]|
 |`+`|the filter output of all previous runs so far|
 
 Precisely because of varying inputs, be aware that both prefixes `-` and `+` do not behave inverse to one another!