|purpose||filter the input by fundamental category|
|input||a selection of titles|
|output||those input tiddlers that belong to category |
|those input tiddlers that do not belong to category |
C is one of the following fundamental categories:
|Category||Matches any tiddler title that...|
|is the current tiddler|
|has an image ContentType|
|has a binary ContentType|
|does not exist (other than possibly as a shadow tiddler), regardless of whether there are any links to it|
|has no hard links to it|
|is a shadow tiddler, regardless of whether it has been overridden with a non-shadow tiddler|
|is a system tiddler, i.e. its title starts with |
|is in use as a tag|
|exists as a non-shadow tiddler|
|New in: 5.1.20 exists as a variable (whether or not that variable has a non-blank value)|
|New in: 5.1.20 is blank (i.e. is a zero length string)|
| New in: 5.1.23 is a draft of another tiddler. Synonym for |
C is anything else an error message is returned. New in: 5.1.14 if
C is blank, the output is passed through unchanged (in earlier versions an error message was returned).
!is[tiddler] is a synonym for
is[missing], and vice versa.
is[missing] is the first operator in a run, its output is always empty. And when
is[shadow] comes first, it outputs only those shadow tiddlers that have been overridden. This is because the initial input to a run contains only non-shadow tiddlers.