26 lines
1.5 KiB
Plaintext
26 lines
1.5 KiB
Plaintext
created: 20140410103123179
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modified: 20191209085901849
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tags: [[Filter Operators]] [[Group Operators]]
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title: each Operator
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type: text/vnd.tiddlywiki
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caption: each
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op-purpose: select one of each group of input titles by field
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op-input: a [[selection of titles|Title Selection]]
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op-suffix: optionally, `list-item` or `value`
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op-parameter: the name of a [[field|TiddlerFields]], defaulting to <<.field title>>
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op-parameter-name: F
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op-output: a selection containing the first input title encountered for each distinct value of field <<.place F>>
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Each input title is processed in turn. The value of field <<.place F>> in the corresponding tiddler is examined.
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;each
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:As long as the value of the field is unique (i.e. has not been encountered before), the title is appended to the output.
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;each:list-item
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:The value is treated as a [[title list|Title List]]. Each title in the list considered in turn. If it has not been encountered before, it is appended to the output.
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;each:value
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:As long as the title is unique it is appended to the output whether or not the corresponding tiddler exists.
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Note that if a tiddler does not contain field <<.place F>>, it is treated as if the value of the field were empty. Thus, a filter expression such as `[each[motovun]]` will return one tiddler that doesn't have a `motovun` field, as well as one tiddler with each distinct value of that field, if any. To obtain just the tiddlers that have a non-blank value for the `motovun` field one can use `[each[motovun]has[motovun]]`.
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<<.operator-examples "each">>
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