36 lines
1.5 KiB
Plaintext
36 lines
1.5 KiB
Plaintext
created: 20150124182127000
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modified: 20230710074414361
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tags: [[Filter Run]]
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title: Filter Step
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type: text/vnd.tiddlywiki
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A <<.def "filter step">> represents a single operation within a <<.def "filter run">>.
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In programming terms, it is akin to a function call to which the step's input is passed as a parameter. A step's output is a [[title selection|Title Selection]] that contributes to a [[filter run|Filter Run]] and hence to the entire [[filter expression|Filter Expression]] that contains it.
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<$railroad text="""
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\start none
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\end none
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[:"!"]
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( / "if omitted, defaults to: title" /|:
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( - | :[[operator|"Filter Operators"]] )
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{ [:":" [[suffix|"Filter Operators"]] ] } )
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{ [[parameter|"Filter Parameter"]] + "," }
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"""/>
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The step's <<.def operator>> is drawn from a list of predefined keywoards which are known as [[filter operators|Filter Operators]].
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Many steps require an explicit <<.def parameter>>, that further defines what the step is to do.
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The <<.def suffix>> is additional text, often the name of a [[field|TiddlerFields]], that extends the meaning of certain operators.
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If a step's <<.def operator>> and <<.def suffix>> are //omitted// altogether, it defaults to the [[title|title Operator]] operator.
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<<.from-version "5.1.23">> Some steps accept multiple <<.def parameter>>s which are separated by a `,` character.
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Any unrecognised operator is treated as if it was the suffix to the <<.olink field>> operator.
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Filter operators can be extended by plugins.
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{{Selection Constructors}}
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