caption: each
created: 20140410103123179
modified: 20241204090042816
op-input: a [[selection of titles|Title Selection]]
op-output: a selection containing the first input title encountered for each distinct value of field <<.place F>>
op-parameter: the name of a [[field|TiddlerFields]], defaulting to <<.field title>>
op-parameter-name: F
op-purpose: select one of each group of input titles by field
op-suffix: optionally, `list-item` or `value`
tags: [[Filter Operators]] [[Group Operators]]
title: each Operator
type: text/vnd.tiddlywiki

Each input title is processed in turn. The value of field <<.place F>> in the corresponding tiddler is examined.

;each
:As long as the value of the field is unique (i.e. has not been encountered before), the title is appended to the output.
;each:list-item
: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.
;each:value
:As long as the title is unique it is appended to the output whether or not the corresponding tiddler exists.

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]]`.

<<.note"""For an example of using the <<.op each>> operator to generate a two-tier list of groups and members, see [[GroupedLists]].""">>

<<.operator-examples "each">>