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Filter Run

 29th January 2015 at 1:37pm
[step]anything but [ ] or whitespace"anything but ""'anything but ''

A run consists of steps, and it outputs a selection that contributes to a larger filter expression.

The steps are processed from left to right. The input to the first step is same as the input to the run. For each subsequent step, the input is the output of the previous step.

The output of a Filter Step depends on its operator:

  • Most operators derive their output from their input. For example, many of them output a subset of their input, and thus truly live up to the name of "filters", narrowing down the overall output of the containing run. These operators are called selection modifiers.
  • A few operators ignore their input and generate an independent output instead. These are called selection constructors: they construct an entirely new selection.

A good example of a constructor is title. The output of [title[A]title[B]] is just B. But the field operator is a modifier, so [title[A]field:title[B] outputs nothing at all.

The lower three options in the diagram match syntax like HelloThere, "HelloThere", 'HelloThere' and "Filter Operators". They are short for [title[...]].

The quoted options exist to support titles that contain square brackets, as in "An [[[[Unusual]]]] Tiddler".