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81 lines
2.1 KiB
Plaintext
81 lines
2.1 KiB
Plaintext
created: 20140210141217955
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modified: 20150102174633890
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tags: Filters
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title: Filter Syntax
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type: text/vnd.tiddlywiki
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[[Filter expressions|Filters]] follow a grammar that is presented here, using [[RailroadDiagrams]], for those who find formal syntax descriptions helpful. However, you can write your own filter expressions without needing to understand this tiddler.
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---
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;filter
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: <$railroad text="""
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{ [:whitespace] ("+" | :- | "-") run }
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"""/>
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A sequence of runs is evaluated from left to right, as follows:
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|!Sequence |!Interpretation |
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|`run1 run2` |union of the sets, i.e. the tiddlers in //either// run1 //or// run2 |
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|`run1 -run2` |difference of the sets, i.e. run1 but excluding any tiddlers in run2 |
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|`run1 +run2` |run2 takes run1 as its input |
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The first run takes `[all[tiddlers]]` as its input, i.e. the set of all non-missing tiddlers.
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---
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;run
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: <$railroad text="""
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( "[" {step} "]"
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'"' [{/'any character except "'/}] '"'
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"'" [{/"any character except '"/}] '"'
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[{/"any character except [ ] or whitespace"/}]
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)
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"""/>
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* The last three options are short for `[title[text]]`
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* A run evaluates each of its steps and returns the intersection of the results
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---
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;step
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: <$railroad text="""
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[:"!"] operator parameter
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"""/>
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* A step returns a set of tiddlers, in the form of a TitleList
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---
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;operator
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: <$railroad text="""
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( keyword [:":" fieldname] | fieldname )
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"""/>
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* Keywords are reserved names (<code>[[is|FilterOperator: is]]</code>, <code>[[has|FilterOperator: has]]</code>, <code>[[tag|FilterOperator: tag]]</code>, etc) of specific filtering functions
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* A fieldname on its own implies the keyword `field`
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* An entirely omitted operator defaults to `title`
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---
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;parameter
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: <$railroad text="""
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( "[" [{/"any character except ]"/}] "]"
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"{" [{/"any character except }"/}] "}"
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"<" [{/"any character except >"/}] ">"
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)
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"""/>
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* `[`...`]` encloses a literal parameter
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* `{`...`}` encloses a TextReference parameter
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* `<`...`>` encloses a [[variable|Variables]] parameter
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---
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;whitespace
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: <$railroad text="""
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{( "space" | "tab" | "linefeed" | "return" | "vertical tab" | "formfeed" )}
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"""/>
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* A match for the JavaScript regular expression `\s+`
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